JP2016151623A - Thermal lens forming element and method for manufacturing the same - Google Patents

Abstract

An inorganic dye which is difficult to be made into a solution and easily settles even when colloidally dispersed in a liquid is made available for a thermal lens forming element. SOLUTION: The inorganic porous particles and the refractive index are formed on an inorganic porous particle layer 6 made of inorganic porous particles including a dye that does not absorb light having a signal light wavelength but absorbs light having a control light wavelength. Is a thermal lens forming element 100 having a control light absorption region impregnated with a mixed organic solvent 10 adjusted to be the same. [Selection] Figure 2c

Description

  The present invention relates to an optical path switching device and a thermal lens forming element used in an optical path switching method useful in the fields of optoelectronics and photonics such as optical communication and optical information processing, and a manufacturing method thereof.

  As an optical path switching method and apparatus based on a completely new principle, the inventors of the present invention have a control light absorption region in a thermal lens forming element, a control light in a wavelength band absorbed by the control light absorption region, and a control light absorption region. The signal light in the wavelength band that is not absorbed is converged and irradiated so that the optical axes coincide with each other. When the control light is not irradiated, the signal light travels straight through the hole in the mirror, while the control light is irradiated. In this case, the inventors invented a method of polarizing an optical path by reflecting using a mirror with a hole provided to be inclined with respect to the traveling direction of the signal light (see Patent Document 1). The background art prior to the present invention is described in detail in Patent Document 1.

  The inventors have also invented an optical control type optical path switching type optical signal transmission device and an optical signal optical path switching method using a combination of a plurality of thermal lens forming elements and mirrors with holes (see Patent Document 2). When the control light is irradiated in the optical path switching methods described in Patent Document 1 and Patent Document 2, the beam cross-sectional shape of the signal light becomes a ring shape due to the thermal lens effect. Therefore, this method is hereinafter referred to as “ring beam method”.

  The inventors have also filed the invention described below. The control light in the wavelength band that is absorbed by the control light absorption region and the signal light in the wavelength band that is not absorbed by the control light absorption region are incident on the control light absorption region in the thermal lens forming optical element. The light and the signal light are irradiated so as to converge in the control light absorption region, and the control light and the signal light are irradiated such that the positions of the convergence points of the control light and the signal light are different from each other. The signal light is diffused after converging at or near the incident surface of the control light absorption region in the light traveling direction. Thereby, a thermal lens is formed reversibly due to the temperature rise occurring in the control light absorption region and the peripheral region thereof, and the refractive index is changed by the formed thermal lens, An optical polarization method and an optical path switching device characterized by changing the traveling direction of the signal light have been disclosed (see Patent Documents 3 to 5). In Patent Documents 3 to 5, the control light absorption region of the thermal lens forming optical element is disclosed in which a pigment is dissolved in a solvent and sealed in a glass container, and as the solvent, at least the pigment to be used is dissolved. Suitable when the temperature rises at the time of forming the thermal lens without being thermally decomposed and having a boiling temperature (boiling point) of 100 ° C. or higher, preferably 200 ° C. or higher, more preferably 300 ° C. or higher. It is described that it can be used. In the optical path switching methods described in Patent Documents 3 to 5, the beam cross-sectional shape of the signal light is kept substantially circular even when the control light is irradiated. Therefore, this method is hereinafter referred to as “round beam method”.

  The present inventors refer to an optical cell filled with a liquid photoresponsive composition as a thermal lens forming element, and as a solvent for a dye solution that absorbs control light having a wavelength to which the photoresponsive composition is sensitive, 160 ° C. Using a solvent having a viscosity of 0 to 3 mPa · s as described above, a viscosity value at 160 ° C., and a value obtained by dividing the viscosity value at 40 ° C. of 1 or more and 6 or less; As a control light absorption region, the dye solution is filled into a first space in the shape of a cylinder having an optical axis of incident signal light as a central axis or an N prism (N is an integer of 4 or more) circumscribing the cylinder. A structure is disclosed in which the first space is connected to the second space via a solution introduction path and a weir, and the second space is filled with the dye solution and an inert gas bubble 14 ( (See Patent Document 6).

  The present inventors also do not absorb light of the wavelength of signal light as a thermal lens forming element for the purpose of forming and extinguishing a thermal lens at high speed in a wide use temperature range without depending on the direction of the element. A container containing a dye solution in which a dye that absorbs light of control light is dissolved in a solvent has two outer planes and two inner planes that are parallel to each other for a total of four planes. A sealed rectangular cross-section hollow tube, wherein the two outer planes and the two inner planes that are parallel to each other are both perpendicular to the optical axis when signal light travels straight without being irradiated with control light The two outer planes and the two inner planes that are parallel to each other have a size that is a plane in a region where the control light and the signal light are incident and a region where the signal light that goes straight or is switched by an optical path passes. And Close to the iodine solution portion was disclosed a structure in which one bubbles exist (see Patent Document 7).

  In Patent Documents 6 and 7, it is effective to thoroughly remove oxygen and water from a dye solution in order to prevent decomposition by light and heat of an organic dye that absorbs control light, Patent Document 7 describes that the dye solution can be prevented from being decomposed by melt-sealing the dye solution together with an inert gas, for example, in a quartz glass cell.

  The present inventors also irradiate the control light and the signal light having different wavelengths by converging the light absorption layer film in the thin film optical element including at least the light absorption layer film, and the wavelength of the control light is The light absorption layer film is selected from the wavelength band to be absorbed, at least the control light is focused in the light absorption layer film, and the light absorption layer film absorbs the control light and its peripheral area In the thin-film optical element that performs intensity modulation and / or light beam density modulation of the signal light by using a thermal lens based on a refractive index distribution that occurs reversibly due to a temperature rise occurring in the light absorption layer film, It has been found that it is preferable that the thickness of the light does not exceed twice the confocal distance of the converged control light (see Patent Document 8).

  On the other hand, Patent Document 9 has a pore diameter of 0.5 nm to 10 nm as a means for providing photo-semiconductor fine particles that exhibit sufficient photocatalytic performance, are resistant to deterioration of a medium such as an organic binder, and have excellent weather resistance. A method for producing photo-semiconductor fine particles coated with a porous silica film, comprising at least a surfactant aqueous solution and a water-soluble organic solvent mixed at 1 to 10 ° C. to prepare a mixed solution; The step of forming a film on the surface of the photo-semiconductor fine particles by adding the photo-semiconductor fine particles and the alkoxysilane to the mixed solution and stirring at 1 to 10 ° C., and firing the photo-semiconductor fine particles coated with the film A process for forming a porous silica film, and a method for producing the optical semiconductor fine particle, wherein the thickness of the porous silica film is 1 nm to 300 nm. A manufacturing method is disclosed.

Japanese Patent No. 3809908 Japanese Patent No. 3906926 Japanese Patent No. 4822113 Japanese Patent No. 4822114 Japanese Patent No. 4822115 Japanese Patent No. 5370711 Japanese Patent No. 5453656 Japanese Patent No. 4196019 Japanese Patent No. 5065636

Sato Fujiaki "Solar Cell Kihon" SB Creative (issued in April 2011) [ISBN Code: 9784797360844]

  The present invention avoids the phenomenon that infrared absorbing organic dyes obtained by solubilizing giant aromatic compounds used in thermal lens forming elements are crystallized and deposited over a period of several years, and manufacture of thermal lens forming elements The purpose is to avoid the phenomenon that organic dyes deteriorate over time due to oxygen or water mixed in due to process defects. Another object of the present invention is to make it possible to use, for a thermal lens-forming element, an inorganic dye that is excellent in durability but is difficult to be made into a solution and easily settles even when colloidally dispersed in a liquid.

The present invention has the following features.
(1) A porous layer composed of inorganic porous particles that do not absorb light of the wavelength of signal light and that contains a dye that absorbs light of the wavelength of control light has the same refractive index as that of the inorganic porous particles. This is a thermal lens forming element having a control light absorption region impregnated with a mixed organic solvent adjusted to be.

  (2) The control light absorption region is formed on one surface of the inner wall of the square cross-section hollow tube, and the control light absorption region is formed with an air gap between the opposite surface of the inner wall. Features.

  (3) One end of the rectangular cross-section hollow tube in which the control light absorption region is formed is melt-sealed, one end of the empty chamber is filled with the mixed organic solvent, and the other end of the empty chamber is 1 atm. The mixed organic solvent vapor and inert gas are filled at the following pressure, and the other end of the square cross-section hollow tube is melt-sealed.

  (4) A cross-sectional shape of the square cross-section hollow tube in which the control light absorption region is formed is a square cross-section hollow tube having two outer planes and two inner planes parallel to each other with respect to four planes. The two outer planes parallel to each other and the two inner planes are both perpendicular to the optical axis when the control light is not irradiated and the signal light travels straight, and the two outer planes parallel to each other and The size of the two inner planes is a size that is a plane in a region where the control light and the signal light are incident and a region where the signal light that goes straight or whose optical path is switched passes, and the rectangular cross-section hollow tube Both ends of the substrate are melt-sealed at the melting point of the material, and the control light absorption region absorbs the control light having a wavelength selected from the wavelength band absorbed by the control light absorption region and the control light absorption region. Na The signal light having a wavelength selected from a wavelength band is converged and irradiated, and the control light and the signal light are irradiated such that the positions of the convergence points of the control light and the signal light are the same or different, and the control light absorption region is A thermal lens is formed based on a refractive index distribution formed reversibly due to a temperature rise that occurs in the control light-absorbing region and its surrounding region, and the thermal lens is not irradiated with the control light. If not, the converged signal light is emitted in the normal opening angle and straight direction, and the control light is irradiated so that the positions of the convergence points of the control light and the signal light are the same, and the thermal lens In the state where the converged signal light is emitted at an opening angle larger than a normal opening angle, or the control light and the signal light have different convergence points. When a thermal lens is formed by irradiation, a state in which the converged signal light is emitted in an opening angle different from a normal opening angle and in a direction different from the straight traveling direction is made to correspond to the presence or absence of the control light irradiation. It is characterized by being realized.

  (5) A polymer of inorganic porous particles in which a dye that absorbs light of the wavelength of the control light and does not absorb the light of the wavelength of the signal light is contained inside the horizontally mounted square cross-section hollow tube After injecting the liquid dispersed in the binder solution, a gas having a temperature of 100 ° C. or less is blown into the square cross-section hollow tube and dried, and the inorganic porous material is formed on the bottom of the square cross-section hollow tube. Steps of forming a water-soluble polymer binder coating film of particles and the coating film forming step are repeated, and the coating film having a desired thickness is formed with vacancies between the opposing surface of the bottom surface A step of blowing dry gas to the square cross-section hollow tube to remove moisture in the coating film, and heating the square cross-section hollow tube to 500 to 600 ° C. Blowing and removing the water-soluble polymer binder by blowing air at 500 to 600 ° C. to the tube, the inorganic A step of forming a porous layer made of porous particles, a step of melt-sealing one end of the square cross-section hollow tube, and the inorganic porous structure leaving the vacancies in the vacancies of the square cross-section hollow tube Filling the porous layer with a mixed organic solvent adjusted to have the same refractive index as that of the particles, impregnating the porous organic layer with the mixed organic solvent, decompressing the vacancies and filling the vacancies with the vapor of the mixed organic solvent And a step of melt-sealing the other end of the square cross-section hollow tube in a state where the vapor of the mixed organic solvent and an inert gas are filled at less than 1 atm in the empty chamber. To do.

  According to the present invention, the porous layer composed of inorganic porous particles contains a pigment that absorbs light of the control light wavelength without absorbing the signal light wavelength, so that it can be crystallized and deposited over time. Therefore, it is possible to avoid the use of infrared absorbing organic dyes which are soluble solubilized macroaromatic compounds. In addition, it is possible to avoid the use of an organic dye that may deteriorate over time due to the influence of oxygen or water mixed due to incomplete manufacturing process of the thermal lens forming element. Furthermore, although it is excellent in terms of durability, it is possible to use an inorganic dye that is difficult to be made into a solution and easily settles even when colloidally dispersed as a control light absorbing layer of a thermal lens forming element.

In the manufacturing method of the thermal lens formation element of Embodiment 1 of the present invention, it is a side view of a square section hollow tube placed horizontally. In the manufacturing method of the thermal lens forming element according to the first embodiment of the present invention, the wavelength of the control light is not absorbed in the rectangular cross-section hollow tube placed horizontally without absorbing the light of the wavelength of the signal light. It is a side view showing the state which inject | poured the liquid which disperse | distributed the porous particle which included the pigment | dye which absorbs light in the polymer binder solution. In the method for manufacturing a thermal lens forming element according to the first embodiment of the present invention, after removing most of the dispersion liquid of porous particles injected into the inside of a horizontally mounted square-shaped hollow tube FIG. 3 is a side view showing a state in which a dispersion liquid remains on the bottom surface of a horizontally mounted square section hollow tube. The side view showing the process of drying the dispersion liquid of the porous particle which remained on the bottom face of the square cross-section hollow tube mounted horizontally in the manufacturing method of the thermal lens formation element of Embodiment 1 of this invention. It is. In the method for manufacturing a thermal lens forming element according to the first embodiment of the present invention, the step of firing the polymer binder of the porous particle coating layer deposited on the bottom surface of the horizontally mounted square cross-section hollow tube It is a side view showing. In the method for manufacturing a thermal lens forming element according to the first embodiment of the present invention, after forming a fired layer of porous particles on the bottom surface of a horizontally mounted square section hollow tube, the square section hollow It is a side view showing the state which melt-sealed one end of the pipe | tube. In the manufacturing method of the thermal lens forming element according to the first embodiment of the present invention, a side view showing a state in which a mixed organic solvent is injected while leaving vacancies in a square cross-section hollow tube whose one end is melt-sealed. is there. It is a conceptual diagram showing the thermal lens formation element of this invention produced by the manufacturing method of the thermal lens formation element of Embodiment 1 of this invention. It is sectional drawing showing the aa 'cross section of the square cross-section hollow tube of FIG. It is sectional drawing showing the bb 'cross section of the square cross-section hollow pipe of FIG. 2a. It is sectional drawing showing the cc 'cross section of the square cross-section hollow tube of FIG. 2b. It is a schematic block diagram of an example of the ring beam type optical path switching apparatus using the thermal lens formation element of this invention. It is a schematic block diagram of an example of the round beam type optical path switching device using the thermal lens formation element of this invention. It is a figure which shows the response | compatibility of the cross-sectional shape of the signal light beam radiate | emitted from the thermal lens formation element of this invention, and control light power, Comprising: It is a signal light beam (round beam of Gaussian distribution) when not irradiating control light. It is a figure which shows the response | compatibility of the cross-sectional shape of the signal light beam radiate | emitted from the thermal lens formation element of this invention, and control light power, Comprising: It is a signal light beam cross section at the time of irradiating control light power 2.0mW. It is a figure which shows the correspondence of the cross-sectional shape of the signal light beam radiate | emitted from the thermal lens formation element of this invention, and control light power, Comprising: It is a signal light beam cross section at the time of irradiating control light power 4.0mW. It is a figure which shows the correspondence of the cross-sectional shape of the signal light beam radiate | emitted from the thermal lens formation element of this invention, and control light power, Comprising: It is a signal light beam cross section at the time of irradiating control light power 8.0mW. It is a figure showing the relationship between the polarization angle and control light power in the round beam type optical path switching device using the thermal lens forming element of the present invention.

Embodiments of the present invention will be described below with reference to the drawings of FIGS.
(Embodiment 1)
Configuration of thermal lens forming element:
First, a schematic configuration of the thermal lens forming element 100 will be described, and then each component constituting the thermal lens forming element 100 and a manufacturing method thereof will be described in detail. As shown in FIG. 2c, the thermal lens forming element 100 is a rectangular parallelepiped hollow tube 1 having a hollow rectangular parallelepiped shape and including four planes including inner planes 16 and 17, and one of the planes. The inorganic porous particle layer 6 formed on the inner flat surface 16, the mixed organic solvent 10 with the refractive index adjusted to be filled in the square cross-section hollow tube 1 by a predetermined amount, and the square cross-section hollow tube 1 and one bubble 11 made of an inert gas sealed inside. The inside of the square cross-section hollow tube 1 is filled with the mixed organic solvent 10 and the bubbles 11. After one end 7 of the square cross-section hollow tube 1 is melt-sealed, the mixed organic solvent 10 is filled, and after the bubbles 11 are sealed, the other end 12 of the square cross-section hollow tube 1 is melt-sealed. Is done. Further, a non-reflective coating is applied to the outer flat surfaces 14 and 15 corresponding to the inner flat surfaces 16 and 17 of the square cross-section hollow tube 1.

[Square cross-section hollow tube]
As shown in FIG. 2c, FIG. 3a, etc., there are two outer planes 14, 15 and two inner planes 16, 17 that are used in the thermal lens forming element 100 of the present invention and are parallel to each other for a total of four planes. Quartz glass is preferably used as the material of the square cross-section hollow tube 1.

  The thickness S of the quartz glass plate constituting the tube wall of the square cross-section hollow tube 1 is preferably 100 μm to 500 μm. If the thickness S of the quartz glass plate material is thinner than 100 μm, the quartz glass plate is easily damaged due to insufficient strength. On the other hand, if the thickness of the quartz glass plate is greater than 500 μm, the degree to which the beam shape of the signal light that is incident while converging or the signal light that is emitted while being diffused and polarized is deteriorated due to refraction, that is, the beam cross-sectional shape The deviation from the circle becomes large, which is not preferable.

The dimensions of the rectangular cross-section hollow tube 1 are optimal in relation to processing restrictions, restrictions on the length of the liquid column of the mixed organic solvent 10 injected into the inside, and the thermal lens effect. Is determined.
First, as a processing restriction, when the end of a square cross-section hollow tube 1 having a width of 1 mm or less on the outer plane is sealed by heating and melting at a melting point of quartz glass of about 1700 ° C., the end of the internal dye solution and the melt The distance H of the sealing portion is a minimum of 10 mm, the upper limit is not limited in processing, and is preferably as short as possible from the viewpoint of industrial use, and is preferably within 15 mm. On the other hand, it is preferable that the dimensions of the square cross-section hollow tube 1 are processing restrictions, and the length M of the liquid column of the dye solution injected into the interior is a minimum of about 1 mm and a maximum of about 15 mm. When the length M of the liquid column is shorter than 1 mm, the plane portion through which the signal light and the control light pass may be affected by the shape of the end face of the melt-sealed hollow tube 1. There is no particular upper limit on the length M of the liquid column, but it is preferably shorter than 15 mm at the longest in the dye solution filling operation. Accordingly, when the liquid column of the dye solution is brought to one end of the square cross-section hollow tube 1 and filled with a length of 5 to 10 mm, the total length of the square cross-section hollow tube 1 is 20 to 25 mm. .

  On the other hand, the refractive index is adjusted to the distance between the two inner planes (inner planes 16 and 17) of the square cross-section hollow tube 1 used in the thermal lens forming element 100, that is, the thickness d1 of the inorganic porous particle layer 6. The optical path length d0 to which the thickness d2 of the mixed organic solvent is added is determined to be optimal from the viewpoint of the response speed of thermal lens formation and extinction (see FIG. 2c). That is, in order to form the thermal lens in the control light absorption region as effectively as possible, a certain amount of thermal energy needs to be accumulated in a specific region. For example, as an example, when a dye thin film is directly formed on a glass substrate by vacuum deposition, the generated heat is diffused instantaneously even when the control light is convergently irradiated, so that a detectable thermal lens effect does not occur. Absent. The thickness d1 of the inorganic porous particle layer 6 and the thickness d2 of the mixed organic solvent 10 in which the refractive index was adjusted were changed to examine the magnitude of the thermal lens effect. As a result, the thickness of the inorganic porous particle layer 6 was determined. d1 is preferably 100 μm to 200 μm, and the thickness d2 of the mixed organic solvent 10 whose refractive index has been adjusted is greater than the thickness of the thermal lens effect, and the thickness of the empty chamber 4 when the inorganic porous particle layer 6 is produced. However, from the viewpoint of work, it is preferable that the thickness is 200 μm to 500 μm. Therefore, it was found that the optical path length d obtained by adding d2 to the thickness d1 is preferably 400 μm to 700 μm. When the thickness d1 of the inorganic porous particle layer 6 is less than 100 μm, the heat when the inorganic dye contained in the inorganic porous particles constituting the inorganic porous particle layer 6 absorbs the control light is in the square cross section. It escapes to the inner plane 16 of the empty tube 1, and the formation of the thermal lens is hindered. On the other hand, when the thickness d1 of the inorganic porous particle layer 6 exceeds 200 μm, the heat when the dye absorbs the control light stops at the inorganic porous particle layer 6 and is effective for forming a thermal lens in the adjacent mixed organic solvent 10. Not used for. The thickness d2 of the mixed organic solvent 10 with the adjusted refractive index corresponds to the thickness of the vacancies 4 when the inorganic porous particle layer 6 is produced. If this is less than 200 μm, the dispersion of the porous particles The injection resistance increases, which hinders work. On the other hand, when the thickness d2 exceeds 500 μm, the optical path length d obtained by adding d2 to the thickness d1 exceeds 700 μm. Considering the deflection angle of the signal light whose optical path is polarized by the thermal lens effect, the square cross section The widths of the signal light incident surface and the output surface of the hollow tube 1 need to be increased accordingly. As a result, the cross-sectional size of the square cross-section hollow tube 1 is 1.2 mm or more in outer dimension, and a large flame is required for melt sealing after injecting the organic solvent, which increases the possibility of failure of melt sealing. End up.

  Further, the width D of the inner flat surfaces 16 and 17 of the square cross-section hollow tube 1 used for the thermal lens forming element 100 is converged on the plane portion and incident on the beam diameters of the control light and the signal light, and is emitted while spreading. The beam diameter of the signal light to be transmitted, the beam diameter of the signal light that is output after the optical path is polarized, and the emission position are defined. It is assumed that the signal light passes through the center of a circle (its diameter Q = D) inscribed in the inner plane 16 or 17 of the square cross-section hollow tube 1. Specifically, the minimum value of the width D of the inner planes 16, 17 of the square cross-section hollow tube 1, where R is the larger beam diameter of the signal light and control light incident on the thermal lens forming element 100. May be about twice the larger beam diameter R. When the minimum value of the width D or the minimum value of the length M is smaller than 2R, the signal light emitted while spreading spreads on the inner side surfaces 16 and 17 orthogonal to the inner planes 16 and 17 of the rectangular cross-section hollow tube 1. There is a possibility that. The beam diameter R is the largest when collimated collimated light from the multimode fiber is incident as signal light or control light, and R is around 100 μm. That is, the minimum value of 2R, that is, D is 200 μm.

  The width D of the inner flat surfaces 16 and 17 of the square cross-section hollow tube 1 is limited by the strength of the quartz glass constituting the tube wall of the square cross-section hollow tube 1, and the thickness S of the quartz glass plate material When it exceeds 2 times, it becomes easy to break. When the thickness S is 100 μm, the restriction of the signal light or the control light beam, that is, D is 200 μm, the two restrictions are satisfied simultaneously. When the thickness S is 200 to 250 μm, the maximum value of D is 400 to 700 μm, which is suitable in terms of intensity and transmission of signal light or control light beam.

  In summary, the preferred embodiments of the dimensions of the square cross-section hollow tube 1 used for the thermal lens forming element 100 are as follows.

  (1) The tube wall thickness S of the square cross-section hollow tube 1 is 200 to 250 μm.

  (2) The width D of the inner plane of the square cross-section hollow tube 1 is 500 to 700 μm.

  (3) The width D of the outer plane of the square cross-section hollow tube 1 is 1000 to 1200 μm.

  (4) The distance d0 between the two inner planes of the square cross-section hollow tube 1: 500 to 700 μm.

  (5) The length M of the liquid column of the mixed organic solvent injected into one end inside the square cross-section hollow tube 1: 1 to 15 mm.

  (6) Distance H between the end portion of the mixed organic solvent 10 inside and the melt-sealed portion: 10 to 15 mm.

[Manufacture of square cross-section hollow tubes]
A square cross-section hollow tube 1 used in the thermal lens forming element 100 of the present invention is manufactured by melt-drawing and cooling a preform of the square cross-section hollow tube 1 manufactured by a known method by a known method. can do. A preferred embodiment in terms of the dimensions of the square cross-section hollow tube 1 is as described above.

  The parallelism and smoothness of the four surfaces (two outer planes 14 and 15 and two inner planes 16 and 17) of the rectangular cross-section hollow tube 1 through which the signal light passes satisfy the following tolerances. It is preferable. The X, Y, and Z axes are defined as follows.

  X axis: Long axis direction of the square cross-section hollow tube 1.

  Y axis: parallel to the four surfaces 14 to 17 of the rectangular cross-section hollow tube 1 through which signal light passes, and perpendicular to the long axis of the square cross-section hollow tube.

  Z-axis: direction of signal light passing perpendicularly through the four surfaces 14 to 17 of the square cross-section hollow tube 1.

  (1) Smoothness: λ / 4 for light having a wavelength (λ) of 400 to 1600 nm.

  (2) Angular deviation in the X axis direction with respect to the Z axis: 1 degree or less, preferably 0.5 degrees or less.

  (3) Angular deviation in the Y-axis direction with respect to the Z-axis: 1 degree or less, preferably 0.5 degrees or less.

[Cutting and cleaning of square cross-section hollow tube 1]
The length (H + M) in the major axis direction of the thermal lens forming element 100 is, for example, 20 to 25 mm when the length M of the liquid column of the mixed organic solvent 10 is 10 mm. In order to manufacture the thermal lens forming element 100 having this length, a length (specifically, two to three times as long as the length (H + M) is compensated in advance by making up for the length of a portion lost in a process described later. It is preferable to cut the square cross-section hollow tube 1 at 50 to 80 mm). The square cross-section hollow tube 1 can be cut by a known method.

[Organic dyes cannot be used]
Since the inorganic porous particles encapsulating the dye constituting the porous layer in the thermal lens element of the present invention are exposed to a high temperature during the firing process at 500 to 600 ° C., it is difficult to use an organic dye.

[Inorganic dye]
Inorganic lenses suitable for inclusion in the inorganic porous particles constituting the porous layer in the thermal lens element of the present invention are listed below.

  [A] Metal salt (eg, cobalt chloride, copper bromide, etc.)

  [B] Metal oxides and composite oxide pigments (eg, Daiichi Seika Kogyo Co., Ltd., various types of Dipyroxide (registered trademark))

  [C] Metal sulfides (eg, cadmium sulfide, copper sulfide)

  [D] Metal fine particles and colloids (eg, gold, silver, silicon, germanium)

  [E] Compound semiconductor (eg, cadmium telluride, gallium arsenide, indium phosphide, copper indium selenide)

  In addition, since the absorption wavelength of inorganic pigments listed in Table 1 varies depending on the particle diameter and the surrounding environment when fine particles are used, the wavelength described in Table 1 is merely an example.

[Creation of an inorganic porous particle layer composed of inorganic porous particles]
As shown in FIGS. 1b to 1e, the inorganic porous particle layer 6 of the thermal lens forming element 100 of the present invention is composed of inorganic porous particles containing an inorganic dye, and is a square section hollow tube placed horizontally. After injecting the inorganic porous particle dispersion 2 dispersed in the polymer binder solution into 1, the majority of the inorganic porous particle dispersion 2 is poured out, and then the inner flat surface 16 of the square cross-section hollow tube 1 is poured. The residual inorganic porous particle dispersion 3 remaining on the top is repeatedly subjected to an operation of blowing the air 8 at a temperature of 100 ° C. or less into the hollow tube 1 and drying it to obtain a desired thickness. The inorganic porous particle coating film 5 is formed, dried completely, and then baked with blown air 9 at 500 to 600 ° C. to remove the polymer binder.

[Inorganic porous particles]
As the inorganic porous particles forming the inorganic porous particle layer 6 of the thermal lens forming element 100 of the present invention, silicon oxide (silica gel; at a wavelength of 588 nm) from the viewpoint of compatibility of the refractive index with the mixed organic solvent 10 described later. An example of the refractive index of quartz glass, 1.5168) is preferred. Porous particles made of silicon oxide can be suitably produced by a known sol-gel method, and inorganic pigment fine particles are included in the production process.

  By controlling the particle size distribution of the inorganic porous particles forming the inorganic porous particle layer 6 of the thermal lens forming element 100 of the present invention, the shape of the absorption spectrum of the encapsulated dye, particularly the longest absorption wavelength (absorption edge) can be obtained. Can be sharpened. This is important when the control light wavelength and the signal light wavelength need to be as close as possible.

  The average particle diameter of the inorganic porous particles forming the inorganic porous particle layer 6 of the thermal lens forming element 100 of the present invention is preferably 1 to 100 nm as primary particles and 10 to 1000 nm as aggregates of primary particles. . When these particle diameters are deviated, it may be difficult to sharply control the particle size distribution.

[Dispersion of inorganic porous particles]
When silica gel is used as the inorganic porous particles, water is suitable as a solvent for the dispersion. Polyvinyl alcohol is preferable as the polymer binder, and a stable and low-viscosity dispersion liquid (coating liquid) can be prepared without using a dispersant.

  A preferred specific embodiment of the dispersion when silica gel is used as the inorganic porous particles is, for example, that the primary particle diameter of silica gel is 7 nm and the particle diameter of 100 nm as an aggregate is ultrasonically dispersed in water at 8 wt%. A liquid and an 8% by weight aqueous solution of polyvinyl alcohol are mixed at 1: 4 parts by weight.

[Creation of inorganic porous particle coating film]
As shown in FIG. 1 a, the rectangular cross-section hollow tube 1 is cut into, for example, a length of 300 mm, and one end thereof is inserted into the insertion hole 21 of the injection header 20 placed inside the heat insulation / heating furnace 35. The air introduction valve 22 attached to the injection header 20 is closed, the dispersion introduction valve 23 is opened, the inorganic porous dispersion 25 is injected into the square cross-section hollow tube 1, and the excess dispersion flows out to the waste liquid receiver 30. Then, the dispersion introduction valve 23 is closed. Next, the air introduction valve 22 is opened, and the air heated to the room temperature or higher and lower than 100 ° C. by the air residual heater 26 is gently injected into the horizontally disposed square section hollow tube 1. The flow rate is controlled so that the air flow rate is 10 to 30 mm per second. In this way, the inorganic porous particle coating film 5 is formed on the upper surface of the inner flat surface 16 of the square cross-section hollow tube 1. This procedure of pouring and drying the dispersion is repeated to form an inorganic porous particle coating film 5 having a desired thickness on the upper surface of the inner wall 17 of the square cross-section hollow tube 1. Water is removed by injecting heated air to completely dry the inorganic porous particle coating film 5. Next, the internal temperature of the heat retaining / heating furnace 35 is heated to 500 to 600 ° C., the air introduction valve 22 is opened, and the air heated to 500 to 600 ° C. by heating the blown air 24 with the air residual heater 26 is square. Injection into the cross-section hollow tube 1. The flow rate is controlled so that the air flow rate is 100 to 500 mm per second. In this way, the polymer binder contained in the inorganic porous particle coating film 5 is burned and removed, and the inorganic porous particle layer 6 is formed on the upper surface of the inner flat surface 16 of the square cross-section hollow tube 1. In the above process, if the air injection speed is too high, the inorganic porous particle layer 6 is cracked or the surface is wavy. On the other hand, if the firing temperature exceeds 600 ° C., the silica gel holes may be fused.

[Preparation of inorganic porous particles containing inorganic pigment]
In the manufacturing process of the thermal lens forming element 100 of the present invention, the procedure for encapsulating the inorganic dye in the inorganic porous particles constituting the inorganic porous particle layer 6 is performed before the firing step of the inorganic porous particle layer 6. preferable. As a method for encapsulating an inorganic dye in the inorganic porous particles constituting the inorganic porous particle layer 6, the methods listed below can be suitably used.

  [A] If necessary, a surfactant is used, and a solution containing water, a water-soluble organic solvent, inorganic pigment fine particles, and alkoxysilane is stirred on the surface of the inorganic pigment fine particles by adjusting the temperature. A silica gel film is formed, and inorganic porous particles containing inorganic pigment fine particles are prepared.

  [B] If necessary, a surfactant is used, and a solution containing water, a water-soluble organic solvent, and an alkoxysilane is stirred under temperature adjustment to form nuclei of silica gel fine particles. By adding a dispersion of fine particles and continuing stirring under temperature adjustment, inorganic porous particles containing inorganic pigment fine particles are prepared.

  In any case, the reaction temperature of the alkoxysilane is preferably kept at 20 ° C. or lower, preferably 0 ° C. to 10 ° C. Below the above temperature range, water may freeze. On the other hand, when the reaction temperature is high, coarse silica gel particles are formed, which is inappropriate as the inorganic porous particles constituting the inorganic porous particle layer 6.

[Preferable dye concentration]
In the thermal lens forming element 100 of the present invention, the thickness d1 of the inorganic porous particle layer 6 and the thickness d2 of the mixed organic solvent 10 to be described later in which the refractive index is adjusted are changed to investigate the magnitude of the thermal lens effect. As a result, it was found that the thickness d1 of the inorganic porous particle layer 6 is preferably 100 μm to 200 μm. Here, the density | concentration of the pigment | dye included in the inorganic porous particle which comprises the inorganic porous particle layer 6 is adjusted so that the transmittance | permeability may be 0.1 to 10% in the wavelength of the control light used. It is preferable. When the concentration of the dye is increased so that the transmittance is less than 0.1%, the influence of absorption or scattering that extends to the wavelength region of the signal light is increased, and the signal transmitted through the thermal lens forming element 100 is increased. There is a risk that light attenuation will increase. On the other hand, if the transmittance exceeds 10%, it may be difficult to form a sufficiently large thermal lens during control light irradiation.

  Needless to say, the greater the absorption coefficient of the dye used, the easier it is to adjust the dye concentration when encapsulated in the inorganic porous particles.

[Mixed organic solvent]
General physical properties of the organic solvent suitably used for the thermal lens forming element 100 are described in detail in Patent Document 7. The mixed organic solvent 10 used in the thermal lens forming element 100 of the present invention satisfies these various properties, and in addition, maximizes the signal light transmittance when the control light is not irradiated. And the refractive index should be equivalent.

The refractive index of quartz glass or silica gel varies depending on the composition of quartz glass, particularly the hydroxyl group content, but as an example, it is 1.51680 at a wavelength of 588 nm and 1.50669 at a wavelength of 1060 nm. On the other hand, the refractive index at a wavelength of 588 nm of a commercial product of the following four-component mixed solvent (referred to as “solvent # 1”) is 1.563, which is slightly larger than that of quartz glass. Incidentally, the refractive index increases as the content of an aromatic residue such as a phenyl group in the organic solvent molecule increases. On the other hand, the refractive index of the aliphatic organic solvent is relatively low.
First component: 1-phenyl-1- (2,5-xylyl) ethane Second component: 1-phenyl-1- (2,4-xylyl) ethane Third component: 1-phenyl-1- ( 3,4-Xylyl) ethane Fourth component: 1-phenyl-1- (4-ethylphenyl) ethane

Various physical properties of the solvent # 1 are as follows.
Appearance: colorless and transparent liquid Odor: weak aromatic odor Boiling point: 290-305 ° C
Melting point: -47.5 ° C
・ Vapor pressure: 0.067Pa (25 ℃)
Vapor density: 7.2 (air = 1)
Specific gravity (water = 1): 0.987
-Water solubility (20 ° C): Insoluble in water.
Volume thermal expansion coefficient (25 ° C to 85 ° C): about 5%

  By mixing n-paraffin as an aliphatic organic solvent having a low refractive index as the fifth component in the solvent # 1, various physical properties as a mixed organic solvent, in particular, viscosity-temperature characteristics can be obtained. It is possible to make the value of the refractive index close to that of quartz glass or silica gel while suitably maintaining as a solvent.

  As n-paraffin, n-heptadecane can be suitably used as its boiling point is close to that of solvent # 1.

Various physical properties of n-heptadecane are as follows.
・ Appearance: Colorless transparent liquid ・ Odor: Weak kerosene odor ・ Boiling point: 302 ℃
Melting point: 22-24 ° C
Refractive index: 1.436 (20 ° C., wavelength 588 nm)
Specific gravity (water = 1): 0.77
-Water solubility (20 ° C): Insoluble in water.

  Table 2 lists measurement examples of the refractive index and the signal light transmittance when n-heptadecane is mixed with the solvent # 1 at various ratios. The refractive index was measured using an Abbe refractometer using sodium D-line (wavelength 588 nm) as the light source, and the signal wavelength transmittance of infrared wavelength was measured with an outer dimension of 1 mm square (square) and an inner dimension of 500 μm square. (Square) square cross-section hollow tube 1 is provided with a 200 μm thick silica gel fired layer (silica gel apparent particle diameter of 100 nm) on the inner flat surface 16, and a mixed organic solvent sample in the thermal lens forming element 100 sealed only at one end. After the silica gel fired layer is sufficiently impregnated with a mixed organic solvent, it is attached to a thermal lens effect measurement test bench (FIG. 4), irradiated with an infrared laser as signal light at an intensity of 1 mW, and only the mixed organic solvent is applied. This was carried out by a method of comparing the intensity of transmitted signal light using the injected square-section hollow tube / element tube without a silica gel fired layer as a reference sample. In the case of transmittance measurement, a sensor of an optical power meter was installed instead of the straight output side signal light / optical fiber 420 in FIG. In the case of this measurement, the AR coating is not performed on the outer plane of the thermal lens forming element that is sealed only at one end, so that the signal light transmittance is about 90% at the best.

[One-end sealing and vacuum drying of square cross-section hollow tube]
As shown in FIGS. 2a to 3c, one end 7 of the square cross-section hollow tube 1 is heated and melted with a burner and sealed. It is preferable to confirm that the pinhole does not remain by magnifying and observing the sealed portion with an optical microscope. Since moisture in the combustion gas of the burner may condense inside the melted and sealed square cross-section hollow tube 1, the square cross-section hollow tube 1 that has been sealed once is sealed in a suitable vacuum container ( (Not shown) and vacuum-dried while heating to 80 ° C. or higher, for example. If the pressure inside the vacuum drying chamber reaches less than 3 × 10 ⁻⁴ Pa, the drying is sufficient.

[Solution injection into hollow tube with square cross section]
In order to avoid the adverse effects of moisture and oxygen on the mixed organic solvent 10, the adjustment of the mixed organic solvent 10 and the following injection process are preferably performed in a glove box (not shown) that satisfies the following conditions. .

  (1) Oxygen concentration less than 0.5 ppm

  (2) Moisture concentration less than 0.5 ppm (dew point temperature -80 ° C or less)

  The sealable vacuum vessel (not shown) is put into the glove box through a pass box, and then the square-shaped hollow tube 1 with one end sealed after vacuum drying is taken out. As shown in FIG. 2b, the mixed organic solvent injection pipe 19 is inserted into the inside of the square cross-section hollow tube 1 that has been sealed at one end, and the tip of the mixed organic solvent injection pipe 19 is sealed at the end of the square cross-section hollow tube 1 that has been sealed at one end The mixed organic solvent 10 is injected through the mixed organic solvent injection tube 19 until it reaches. The injection amount of the mixed organic solvent 10 is adjusted so that the length of the liquid column of the mixed organic solvent 10 becomes 1 to 15 mm after the mixed organic solvent injection tube 19 is pulled out.

[Temporal sealing of the other end of the square tube]
An adhesive that requires one hour or more for curing the square cross-section hollow tube 1 that has been mixed with the mixed organic solvent 10 on the melt-sealed end side, and is volatilized when the pressure is reduced to the pressure described later. Put in a container with adhesive that does not contain ingredients, put it in a suitable vacuum chamber (eg, the pass box), for example, keep the pressure at 0.01 atm and wait for the adhesive to cure . As the adhesive, for example, an epoxy adhesive having no volatile component can be suitably used. The amount of the adhesive used is preferably a minimum amount for temporarily sealing the open end (the other end) of the square cross-section hollow tube 1 that has been sealed at one end, for example, 50 to 100 mg. The height is, for example, 10 to 20 mm in height and is large enough to vertically support the square cross-section hollow tube 1 that has been sealed at one end. What is necessary is just to be the minimum size necessary for inserting the tube 1, for example, a circle having a diameter of 2 to 3 mm.

[Inert gas bubbles]
Before temporarily sealing the other end of the square cross-section hollow tube 1, one bubble 11 is formed by filling the inside of the square cross-section hollow tube 1 already sealed with one end. In the thermal lens forming element 100 of the present invention, as shown in FIG. 2C, the mixed organic solvent 10 is present as one liquid column without bubbles at one end of the square cross-section hollow tube 1 and at the other end. Is characterized in that one bubble 11 made of an inert gas described later exists in contact with the liquid column of the mixed organic solvent 10. Since the mixed organic solvent 10 exists as a single liquid, even if the thermal lens forming element 100 is impacted from the outside by the frictional force of the wall of the rectangular cross-section hollow tube 1 and the solution, It is hard to be divided. A suitable length H of one bubble 11 made of an inert gas is 10 to 15 mm as described above. Nitrogen, argon, and helium can be suitably used as the inert gas. The preferable pressure of the bubbles 11 is described in detail in Patent Document 7.

[Sealing the other end of the square tube]
After the adhesive is cured and temporary sealing of the square cross-section hollow tube 1 that has been sealed once is completed, the square cross-section hollow tube 1 that has been sealed once is taken out of the glove box and the vacuum chamber, The portion filled with the mixed organic solvent is suspended and the portion where the mixed organic solvent 10 does not exist is melt-sealed with a gas burner. By using a burner flame of the minimum size necessary for melting and sealing within 1 second, melting and sealing of quartz glass can be completed without affecting the mixed organic solvent 10 inside. . In order to confirm the completeness of the sealed state of the thermal lens forming element 100 of the present invention completed by sealing both ends, the weight (10 to several tens of milligrams) of the thermal lens forming element 100 was precisely measured in μg units. Thereafter, for example, after heating was continued at 85 ° C. for 1000 hours, the weight was accurately measured. As a result, it was confirmed that the weight change was within ± 2 μg, and it was found that the sealing was complete.

[Non-reflective coating]
The refractive index of quartz glass, which is the material of the square cross-section hollow tube 1 of the thermal lens forming element 100 of the present invention, is 1.56 to 1.56 in the infrared region with a wavelength of 1.5 μm from the refractive index of air of 1.00. 1.50. Therefore, if the non-reflective coating is not performed, a reflection loss of 4 to 5% occurs with respect to the signal light or control light perpendicularly incident on the flat portion 14 or 15, and therefore no reflection corresponding to the wavelength of the signal light and control light to be used. It is recommended to apply a reflective (AR) coat. As the AR coat, a known one can be used. For example, a dielectric multilayer film corresponding to the wavelength of signal light and control light to be used, or a transparent organic polymer film having a refractive index intermediate between the refractive indices of air and quartz glass can be used. However, the vacuum process for forming the transparent organic polymer film on the surface of the thermal lens forming element 100 is usually low in productivity by batch processing and exposed to high temperature, so that the AR before filling with the mixed organic solvent 10 is performed. In order to prevent the inside of the square cross-section hollow tube 1 of the thermal lens forming element 100 from being contaminated, for example, both ends of the square cross-section hollow tube 1 are temporarily melt-sealed and mixed organically. It is necessary to add a process such as opening one end before injecting the solvent 10. On the other hand, a method in which a solution in which a transparent organic polymer is dissolved in an appropriate volatile solvent is applied to the surface of the thermal lens forming element 100 by dipping or the like and dried to form an AR coating layer includes a thermal lens forming element. AR coating is possible after injecting mixed organic solvent 10 into 100 square cross-section hollow tubes 1 and melting and sealing both ends, and the manufacturing process can be streamlined. The refractive index of the transparent organic polymer is preferably 1.2 to 1.4 in the infrared region having a wavelength of 1.5 μm from the visible light region. A refractive index of about 1.35 is more preferable. Even if the refractive index is smaller or larger than the above range, the effect of reducing the reflection loss is small. As a specific example of the transparent organic polymer solution, a solution obtained by dissolving an organic fluororesin “CYTOP” (registered trademark) (manufactured by Asahi Glass Co., Ltd.) in a fluorine-based solvent can be preferably used. The refractive index of this polymer film is 1.34. The thickness of the AR coating film by coating is preferably 10 nm to 200 μm. If it is thinner than this, a pinhole may be formed in the coating film. Moreover, when a film thicker than this is formed by a coating method, unevenness in film thickness tends to occur. If the thickness of the AR coating film is 100 μm to 200 μm, the planar portion of the thermal lens forming element 100 of the present invention made of very thin quartz glass can be reinforced to improve impact resistance.

[Application to ring beam optical path switching]
FIG. 4 is a schematic configuration diagram of an example of a ring beam type optical path switching device using the thermal lens forming element 100 of the present invention. As the thermal lens forming element 100 of the present embodiment of the present embodiment, a silica gel fired layer having a thickness of 200 μm is formed on the inner plane 16 of the square cross-section hollow tube 1 having an outer dimension of 1 mm square and an inner dimension of 500 μm square (square). As the apparent particle diameter of silica gel (100 nm), an inorganic porous particle layer 6 prepared by firing silica gel particles encapsulating indium phosphide particles manufactured by applying a known solar cell manufacturing method is used. In addition, the mixed organic solvent sample was sufficiently impregnated between the pores of the silica gel fine particles constituting the inorganic porous particle layer 6 and in the pores, and then the argon was sealed in the air chamber 4 at 0.01 atm and hermetically sealed. . When the laser having a wavelength of 1550 nm is used as the signal light source and the laser having a wavelength of 850 nm is used as the control light source, the transmittance of the thermal lens forming element 100 of the present embodiment of the present embodiment is 90% or more and 5% or less, respectively. It was.

  The details of the ring beam type optical path switching device are described in Patent Document 1. As an outline, the input signal light / incident signal light emitted from the optical fiber 400 is converted into a substantially parallel beam 401 by the collimator lens 40, transmitted through the dichroic mirror 42, and further converged by the condenser lens 43. The light is incident on the thermal lens forming element 100 as light. On the other hand, the control light emitted from the control light / optical fiber 410 is reflected by the dichroic mirror 42 as a substantially parallel beam 411 by the collimator lens 41, and the optical axis of the signal light beam 401 is made coincident. And converged to enter the thermal lens forming element 100 as convergent light. In the ring beam type optical path switching device and method, the control light and the signal light are converged and incident on the control light absorption area of the thermal lens forming element with the same optical axis, and the convergence areas of both the control light and the signal light overlap, The optical system is finely adjusted so as to be positioned near the signal light incident side of the control light absorption region. In this way, the control light that converges and enters the vicinity of the signal light incident side of the thermal lens forming element / control light absorption region travels while being absorbed in the control light absorption region, and the absorbed light energy is changed to heat, and mixed. A density decrease and a refractive index decrease due to the thermal expansion of the organic solvent cause a thermal lens having a specific shape in the light traveling direction. Thus, when the signal light converged and incident inside the thermal lens formed in the control light absorption region travels while spreading, the energy distribution of the beam cross section of the signal light that was Gaussian at the time of incidence is converted into a ring shape. Then, the light is emitted from the thermal lens forming element 100 at an opening angle larger than the angle when the control light is not irradiated. The outgoing signal light is received by a light receiving lens 44 having a numerical aperture larger than that of the condenser lens 43, converted into a substantially parallel beam, and then is sent to a signal light / optical path 45 when traveling straight without being irradiated with control light. When the light is incident on the mirror 45 with a hole provided with a hole of a size large enough to allow the signal light beam to travel straight without being irradiated with the control light, the control light is irradiated. If not, the signal light 421 goes straight, enters the coupling lens 46, is converged, and enters the straight output-side signal light / optical fiber 420. On the other hand, when the control light is irradiated, the signal light converted into the ring beam by the thermal lens effect is reflected around the hole of the holed mirror 45, converged by the coupling lens 47, and the optical path switching signal light 431. Then, it enters the optical path switching output side signal light / optical fiber 430.

  6a to 6d, the laser light having a wavelength of 1550 nm as the signal light source and the laser light having a wavelength of 850 nm as the control light source are used to irradiate the thermal lens forming element 100 of the present embodiment, and the cross-sectional shape and control light power of the emitted signal light beam The correspondence of is shown. In addition, it replaced with the mirror 45 with a hole in FIG. 4, and the light-receiving surface of the beam profiler was mounted. When the control light is not irradiated, the beam cross section of the signal light is a round beam having a Gaussian distribution as shown in FIG. When the control light power is increased to 2.0, 4.0 mw, and 8.0 mW, the beam cross section of the signal light changes as shown in FIGS. 6b, 6c, and 6d, respectively. In this case, when the control light power is 4.0 mW, the shape and size of the ring are optimal. When 2.0 mw is the same, the power is insufficient and the “opening degree of the ring” is insufficient. The control light is too strong, the shape of the thermal lens is disturbed, and multiple rings are formed.

  The ring beam type optical path switching device using the thermal lens forming element 100 of the present invention is a case where the control light power is as small as 4 to 5 mW and the control light is irradiated with a Gaussian distribution / round beam and no control light. The ring beam can be converted. Absorption of the control light absorption region of the thermal lens forming element 100 of the present invention, that is, in the vicinity of the beam waist of the control light irradiated with convergent porous layers composed of inorganic porous particles containing a dye that absorbs light having the wavelength of the control light. The generated heat is efficiently transferred to the mixed organic solvent 10, and the mixed organic solvent 10 is thermally expanded to form a thermal lens in the vicinity of the beam waist of the control light that has been converged and irradiated. Conversion to a beam could be realized.

  It was confirmed that the ring beam type optical path switching device using the thermal lens forming element 100 of this embodiment can withstand repeated use for 3 years or more.

[Comparative Embodiment 1]
Instead of the thermal lens forming element 100 of the present invention, a conventional thermal lens forming element filled with a solvent # 1 solution of tetra-tertiary butyl copper phthalocyanine (pigment concentration 0.2 wt%) was used, and a control light source As a result, when the laser beam with a wavelength of 660 nm was used and the optical path switching by the thermal lens effect was repeatedly performed with the ring beam type optical path switching apparatus of FIG. 4, the initial performance could be exhibited for two years. However, a blue solid has been deposited in the dye solution of the thermal lens forming element over the course of 3 years. Even if a solid is deposited, the dye solution still works effectively, so it is possible to switch the optical path by the thermal lens effect.However, when the deposited solid crosses the optical path of the signal light, the signal light is temporarily blocked. , Detected as noise. That is, it has been confirmed that the service life for switching optical paths in optical communication is about two years.

[Application to round beam optical path switching]
FIG. 5 is a schematic configuration diagram of an example of a round beam type optical path switching device using the thermal lens forming element 100 of the present invention. Details of the round beam type optical path switching device are described in Patent Documents 3 to 5. As the thermal lens forming element 100 of the present embodiment of the present embodiment, a silica gel fired layer having a thickness of 200 μm is formed on the inner plane 16 of the square cross-section hollow tube 1 having an outer dimension of 1 mm square and an inner dimension of 500 μm square (square). As an apparent particle diameter of silica gel (100 nm), an inorganic porous particle layer 6 prepared by firing silica gel fine particles encapsulating fine particles of copper indium selenide produced by applying a known solar cell production method is provided. Used after thoroughly impregnating the mixed organic solvent sample between the particles of silica gel fine particles constituting the inorganic porous particle layer 6 and in the pores, and sealing the hermetically sealed argon 4 at 0.01 atm. It was. When the laser having a wavelength of 1550 nm is used as the signal light source and the laser having a wavelength of 980 nm is used as the control light source, the transmittance of the thermal lens forming element 100 of the present embodiment of the present embodiment is 90% or more and 5% or less, respectively. It was.

  As an outline, input signal light / incident signal light emitted from the optical fiber 500 is converted into a substantially parallel beam 501 by the collimator lens 50, transmitted through the dichroic mirror 52, further converged by the condenser lens 53, and converged. The light is incident on the thermal lens forming element 100 as light. On the other hand, the control light emitted from the control light / optical fiber 510 is reflected by the dichroic mirror 52 as a substantially parallel beam 511 by the collimator lens 51, further converged by the condenser lens 53, and the thermal lens forming element as convergent light. 100 is incident. In the round beam type optical path switching device and method, the control light and the signal light are converged and incident on the control light absorption region of the thermal lens forming element 100, and the central points of the convergence regions of both the control light and the signal light are separated by about 30 μm. The optical system is finely adjusted so that it overlaps and is positioned in the vicinity of the signal light incident side of the control light absorption region. In this way, the control light that has converged and entered slightly away from the thermal lens forming element / control light absorption region in the vicinity of the signal light incident side proceeds while being absorbed in the control light absorption region, and the absorbed light energy is Instead of heat, it causes a decrease in density and a decrease in refractive index due to thermal expansion of the mixed organic solvent, and a thermal lens having a specific shape is formed in the traveling direction of light. Thus, if the signal light converged and incident at different convergence positions travels inside the thermal lens formed in the control light absorption region, the traveling direction is maintained while maintaining the energy distribution of the cross section of the Gaussian round beam at the time of incidence. Is polarized and the optical path is polarized several degrees from the straight direction when the control light is not irradiated, and is emitted from the thermal lens forming element 100. The outgoing signal light is received by the light receiving lens 54 and converted into a substantially parallel beam. When the control light is not irradiated, the signal light 521 travels straight, enters the coupling lens 56, is converged, and travels straight. The incident light enters the side signal light / optical fiber 520. On the other hand, when the control light is irradiated, the signal light 531 whose optical path is polarized as a round beam by the thermal lens effect is incident on the coupling lens 57 as the signal light 532 via the mirror 58 and is converged, and the optical path. The light enters the switching output side signal light / optical fiber 530.

  When the control light power is 10.0, 20.0, 30.0, and 40.0 mW, the deflection angle of the signal light 531 deflected as a round beam by the thermal lens effect is not irradiated with the control light. FIG. 7 shows the measurement results when the signal light exit direction is “0 degree” when the signal light exits the thermal lens forming element 100 at the origin and the control light is not irradiated. In this measurement, the light receiving surface of the beam profiler is placed in place of the coupling lens 56 and the mirror 58 in the optical apparatus shown in FIG. 5, and the deflection angle of the optical path switching signal light is calculated from the light receiving position of the beam. did. As the control light power was increased, the deflection angles increased to 10.5 degrees, 13.0 degrees, 14.1 and 15.2 degrees. Absorption of the control light absorption region of the thermal lens forming element 100 of the present invention, that is, in the vicinity of the beam waist of the control light irradiated with convergent porous layers composed of inorganic porous particles containing a dye that absorbs light having the wavelength of the control light. The generated heat is efficiently transmitted to the mixed organic solvent 10, and the mixed organic solvent 10 is thermally expanded to form a thermal lens in the vicinity of the beam waist of the control light that is converged and irradiated, and the optical path of the signal light with high efficiency The deflection could be realized.

  It has been confirmed that the thermal lens forming element of the present invention can withstand long-term use for 3 years or more. Currently, we are conducting durability tests under actual use conditions over 10 years.

  The present invention can be effectively used in the fields of optical communication and optical information processing.

  DESCRIPTION OF SYMBOLS 1 Square cross-section hollow tube, 2,25 Inorganic porous particle dispersion liquid, 3 Residual inorganic porous particle dispersion liquid, 4 Air | hole, 5 Inorganic porous particle coating film, 6 Inorganic porous particle layer, 7 One end, 8 , 9, 24 Blowing air, 10 Mixed organic solvent, 11 Bubble, 12 Other end, 14, 15 Outer plane, 16, 17 Inner plane, 19 Mixed organic solvent injection tube, 20 Injection header, 21 Square section hollow tube insertion Hole, 22 Air introduction valve, 23 Dispersion liquid introduction valve, 26 Air residual heater, 30 Waste liquid receiver, 35 Insulation / heating furnace, 40, 41, 50, 51 Collimator lens, 42, 52 Dichroic mirror, 43, 53 Optical lens, 44, 54 Light-receiving lens, 45-hole mirror, 46, 47, 56, 57 Coupled lens, 58 mirror, 100 Thermal lens forming element, 400 Input side signal light / optical fiber, 4 01 Incident signal light (beam), 410 Control light / optical fiber, 411 Incident control light (beam), 420 Linear output signal light / optical fiber, 421 Linear signal light, 430 Optical path switching output signal / optical fiber, 431 Optical path switching signal Light, 500 Input signal light / optical fiber, 501 Incident signal light (beam), 510 Control light / optical fiber, 511 Incident control light (beam), 520 Straight output signal light / optical fiber, 521 Straight signal light, 530 Optical path switching output Side signal light / optical fiber, 531 532 light path switching signal light.

Claims (5)

  Adjustment is made so that the refractive index of the porous layer is the same as that of the inorganic porous particle, which is made of an inorganic porous particle containing a dye that absorbs light of the wavelength of the control light without absorbing the signal light wavelength. A thermal lens forming element having a control light absorption region impregnated with the mixed organic solvent. The control light absorption region is formed on one surface of an inner wall of a square cross-section hollow tube, and the control light absorption region is formed with an air gap between the opposite surface of the inner wall. The thermal lens forming element according to claim 1. One end of the rectangular cross-section hollow tube in which the control light absorption region is formed is melt-sealed, one end of the empty chamber is filled with the mixed organic solvent, and the other end of the empty chamber is 1 atmosphere or less in pressure. The thermal lens forming element according to claim 2, wherein the mixed organic solvent vapor and an inert gas are filled, and the other end of the rectangular cross-section hollow tube is melt-sealed. A cross-sectional shape of the rectangular cross-section hollow tube in which the control light absorption region is formed is a square cross-section hollow tube having two outer planes and two inner planes parallel to each other with respect to four planes. Two parallel outer planes and two inner planes are both perpendicular to the optical axis when the control light is not irradiated and the signal light travels straight, and the two outer planes and two inner planes parallel to each other. The size of the plane is a size that is a plane in the region where the control light and the signal light are incident and the region where the signal light that goes straight or is optically switched passes and the both ends of the square cross-section hollow tube are The control light absorption region is melt-sealed at the melting point of the material, and the control light absorption region has a wavelength selected from the wavelength band absorbed by the control light absorption region and a wavelength that the control light absorption region does not absorb. Signal light having a wavelength selected from a region is converged and irradiated, and the control light and the signal light are irradiated so that the positions of the convergence points of the control light and the signal light are the same or different, and the control light absorption region is the control light A thermal lens is formed based on the refractive index distribution reversibly formed due to the temperature rise occurring in the light absorbing region and the surrounding region,
When the control light is not irradiated and a thermal lens is not formed, the converged signal light is emitted in a normal opening angle and a straight direction, and
When the control light is irradiated so that the positions of the convergence points of the control light and the signal light are the same to form a thermal lens, the converged signal light has an opening angle larger than a normal opening angle. When the control lens is irradiated with the control light and the thermal lens is formed so that the positions of the convergence points of the control light and the signal light are different from each other, the converged signal light has a normal opening angle. A different opening angle and a state of emitting in a direction different from the straight direction,
The thermal lens forming element according to claim 1, wherein the thermal lens forming element is realized corresponding to the presence or absence of irradiation of the control light. Inorganic polymer particles containing a dye that absorbs light of the control light wavelength without absorbing the light of the wavelength of the signal light inside the horizontally mounted square cross-section hollow tube in the polymer binder solution After injecting the dispersed liquid, a gas having a temperature of 100 ° C. or less is blown into the inside of the square cross-section hollow tube and dried, and the water of the inorganic porous particles is added to the bottom of the square cross-section hollow tube. Forming a conductive polymer binder coating film,
Repeatedly performing the coating film forming step, and forming the coating film of a desired thickness sandwiching vacancies between the opposing surface of the bottom surface,
A step of removing moisture in the coating film by blowing dry gas to the square cross-section hollow tube;
The square cross-section hollow tube is heated to 500 to 600 ° C., and air of 500 to 600 ° C. is blown to the square cross-section hollow tube to burn and remove the water-soluble polymer binder. Forming a porous layer of particles,
Melting and sealing one end of the square cross-section hollow tube,
Filled into the vacancies of the square cross-section hollow tube is a mixed organic solvent adjusted to have the same refractive index as that of the inorganic porous particles, leaving the vacancies, and the porous organic layer is filled with the mixed organic solvent. Impregnation step,
Depressurizing the empty chamber and filling the empty chamber with the vapor of the mixed organic solvent;
Melting and sealing the other end of the square cross-section hollow tube in a state where the mixed organic solvent vapor and inert gas are filled at less than 1 atm in the air chamber,
The manufacturing method of the thermal lens formation element characterized by having.