JP2011090200A - Optical module - Google Patents

Abstract

A technique capable of further improving the light transmission efficiency is provided.
A core portion is composed of a widened portion having a longer length (width) in the Z-axis direction and a base portion having a smaller width. Further, the lens 13 is configured such that the length Z in the Z-axis direction of the cut surface of the light beam by a plane including the incident surface of the base 21 is equal to or shorter than the length a of the incident surface of the base 21 in the Z-axis direction. The light beam emitted from the base 21 is guided to the incident surface S of the base 21.
[Selection] Figure 5

Description

  The present invention relates to an optical module that transmits or receives an optical signal.

  As an optical module for transmitting or receiving an optical signal, an optical module in which a core portion having a predetermined optical refractive index and a cladding portion having a lower optical refractive index than the core portion are joined is known. First, regarding this type of optical module, the thickness of the light incident side end portion of the core layer is made larger than the thickness of the light emitting side end portion of the core layer, and gradually decreases from the light incident side to the light emitting side. A technique has been proposed ([0070]).

JP 2005-62298 A

  However, the optical module of Patent Document 1 has room for further improving the light transmission efficiency.

  The present invention has been made in view of such circumstances, and an object thereof is to provide a technique capable of further improving the light transmission efficiency.

  The invention according to claim 1 has a lens part for condensing the introduced light, a core part having a predetermined light refractive index, and a clad part having a light refractive index lower than that of the core part. And an internal waveguide that transmits a light beam incident on the core portion from the lens portion, using a boundary surface between the core portion and the clad portion that covers a predetermined portion of the core portion in a close contact state. The core part has a predetermined width in a predetermined direction orthogonal to the optical axis of the light beam emitted from the lens part, and a base part for transmitting the light beam and an incident functioning as an incident surface of the core part And the incident surface has a width larger than the width of the base in the predetermined direction, and the width in the predetermined direction of the cut surface of the light beam by a plane including the incident surface of the base is the base Less than the width of the incident surface in the predetermined direction Sea urchin, an optical module and a widened portion formed by bonding for guiding the light beam emitted from the lens portion on the incident surface of the base.

  According to this invention, it has an incident surface that functions as an incident surface of the core portion, and a predetermined portion including the incident surface includes a widened portion having a length larger than the width of the base portion in the predetermined direction. Therefore, as compared with a configuration in which the predetermined portion including the incident surface of the widened portion is set to have the same length as the width of the base portion, more light flux collected by the lens portion is transferred to the internal waveguide. Can be introduced.

  Further, the widened portion is configured such that the length in the predetermined direction of the cut surface of the light beam by a plane including the incident surface of the base is equal to or less than the length in the predetermined direction of the incident surface of the base. Since the light beam emitted from the lens unit is guided to the incident surface of the base unit, the situation where the light collected by the lens unit and incident on the incident surface of the core unit goes out of the incident surface of the base unit is reduced. The

  As a result, the widened portion as compared with the case where the length in the predetermined direction of the cut surface of the light beam by the plane including the incident surface of the base is larger than the length of the incident surface of the base in the predetermined direction. It is possible to improve the efficiency of guiding the light transmitted through the base to the base.

  According to a second aspect of the present invention, in the optical module according to the first aspect, the lens portion is disposed in close contact with an incident surface of the widened portion.

  According to this invention, since the lens portion is disposed in close contact with the incident surface of the widened portion, space saving in a direction orthogonal to the incident surface of the widened portion can be achieved.

  According to a third aspect of the present invention, in the optical module according to the second aspect of the present invention, the optical module further includes a light emitting element that outputs a light beam to the lens unit, wherein the full width at half maximum of the light beam output from the light emitting element is θ, and the light emitting element When the distance in the optical axis direction from the light emitting position to the incident surface of the widened portion is X, the length of the lens portion in the predetermined direction and the width of the incident surface of the widened portion in the predetermined direction are It is larger than 2X · tan (θ / 2).

  According to this invention, the light beam output from the light emitting element can be introduced into the internal waveguide with almost no loss.

  According to a fourth aspect of the present invention, in the optical module according to any one of the first to third aspects, the width of the widened portion in the predetermined direction is from the incident surface side of the widened portion to the base portion. It becomes smaller toward the coupling surface side.

  According to the present invention, the length of the widened portion in the predetermined direction is reduced from the incident surface side of the widened portion toward the coupling surface side with the base portion. The amount of light incident on the base can be increased by the amount of light reflected toward the surface as compared with the case where such a configuration is not adopted.

According to a fifth aspect of the present invention, in the optical module according to any one of the first to fourth aspects, the optical refractive index of the cladding portion is n ₀ , the optical refractive index of the core portion is n ₁ , and the base portion. The width of the widened portion is b, the width of the incident surface of the widened portion in the predetermined direction is b, and the length in the optical axis direction from the incident surface of the widened portion to the coupling surface of the widened portion and the base is L When this is done, the image-side NA satisfies the following formula (T-1).

  According to this invention, the efficiency which guide | induces the light introduce | transduced into the wide part to the said base part can be improved.

According to a sixth aspect of the present invention, in the optical module according to any one of the first to fourth aspects, the optical refractive index of the cladding portion is n ₀ , the optical refractive index of the core portion is n ₁ , and the base portion. The width of the widened portion is b, the width of the incident surface of the widened portion in the predetermined direction is b, and the length in the optical axis direction from the incident surface of the widened portion to the coupling surface of the widened portion and the base is L When this is done, the image-side NA satisfies the following formula (T-2).

  According to this invention, the efficiency which guide | induces the light introduce | transduced into the wide part to the said base part can be improved.

  According to a seventh aspect of the invention, in the optical module according to the fifth or sixth aspect, the image side NA further satisfies the following formula (T-3).

  According to this invention, the efficiency which guide | induces the light introduce | transduced into the wide part to the said base part can be improved.

  The invention according to claim 8 is the optical module according to any one of claims 1 to 7, further comprising a light emitting element that outputs a light beam to the lens unit, wherein the optical axis of the lens unit is the light emission. This coincides with the optical axis of the light beam output from the element.

  According to the present invention, it is possible to improve the efficiency of guiding the light beam output from the light emitting element to the internal waveguide.

  According to the present invention, it is possible to introduce more light beams collected by the lens unit into the internal waveguide, and to improve the efficiency of guiding the light transmitted through the widened portion to the base, The light transmission efficiency can be further improved.

It is the schematic which shows 1st Embodiment of the optical module which concerns on this invention. It is an expanded sectional view which shows the structure of the light emission part periphery of the light emission side mounting substrate. It is an enlarged plan view which shows the structure of the light emission part periphery of the light emission side mounting substrate. It is a perspective view of an internal waveguide. It is a figure which shows the structure optically equivalent to FIG. It is a figure which shows the structure optically equivalent to FIG. It is a figure for demonstrating the conventional problem. It is a figure for demonstrating the entrance plane of a base. It is a figure for demonstrating the calculation method of image side NA at the time of paying attention to the component parallel to a XZ plane. It is a figure for demonstrating the calculation method of the image side NA which pays its attention to the component parallel to XY plane. It is a figure for demonstrating the effect in 1st Embodiment. It is a figure for demonstrating the modification of the optical module which concerns on this invention. It is a figure for demonstrating the modification of the optical module which concerns on this invention. It is a figure for demonstrating the modification of the optical module which concerns on this invention.

  An embodiment of an optical module according to the present invention will be described. FIG. 1 is a schematic view showing a first embodiment of an optical module according to the present invention.

  As shown in FIG. 1, the optical module 100 includes a light emitting side mounting substrate 1, a light receiving side mounting substrate 2, and an external waveguide substrate 3 that connects these mounting substrates 1 and 2 so as to be optically connectable. Configured. In the following description, the left-right direction of FIG. 1 is referred to as the X-axis direction, the up-down direction is referred to as the Y-axis direction, and the direction perpendicular to the paper surface is referred to as the Z-axis direction. And

  The light emitting side mount substrate 1 is a plate-like member, and is disposed in parallel to the XZ plane. The light emitting side mounting substrate 1 is required to have rigidity in order to avoid the influence of heat and stress due to the use environment when the optical module 100 is mounted, and the light emitting unit 4 is highly accurately arranged and in use. It is made of silicon in consideration of suppression of position fluctuation.

  At an appropriate position on the upper surface 6 of the light-emitting side mounting substrate 1, an IC substrate 5 on which a light-emitting unit 4 for converting an electrical signal into an optical signal and outputting it and an IC circuit for transmitting the electrical signal to the light-emitting unit 4 are configured. Are arranged. The light emitting unit 4 includes a surface emitting laser (VCSEL (Vertical Cavity Surface Emitting Laser)) which is a semiconductor laser, a light emitting element 12 such as an LED (see FIGS. 2 and 3), and a lens 13 (see FIGS. 2 and 3). is doing. The IC substrate 5 is a driver IC that drives the light emitting element 12, and is disposed in the vicinity of the light emitting unit 4. Although not shown, the light emitting unit 4 and the IC substrate 5 are electrically connected by a wiring pattern formed on the upper surface 6 of the light emitting side mount substrate 1 with gold bumps.

  The light emitting side mount substrate 1 is formed with a waveguide forming groove (not shown) extending from a position immediately below the light emitting portion 4 toward the rear end surface 7 of the light emitting side mount substrate 1 toward the external waveguide substrate 3. An internal waveguide 8 that is optically coupled to the light emitting unit 4 (in which light output from the light emitting unit 4 is introduced) is disposed in the waveguide forming groove.

  The light receiving side mount substrate 2 is a plate-like member made of, for example, silicon like the light emitting side mount substrate 1, and is disposed in parallel to the XZ plane. Mounted on the upper surface 9 of the light receiving side mount substrate 2 are a light receiving unit 10 for converting an optical signal into an electric signal and an IC substrate 11 on which an IC circuit for receiving the electric signal from the light receiving unit 10 is formed. ing. A PD (photodiode) is employed as the light receiving unit 10, and the IC substrate 11 is an element such as a TIA (Trans-impedance Amplifier) that performs current / voltage conversion.

  The light receiving side mount substrate 2 is formed with a waveguide forming groove (not shown) extending from the external waveguide substrate 3 to a position directly below the light receiving portion 4, and in the waveguide forming groove, the light receiving portion 10 and An internal waveguide 22 that optically couples (takes in light introduced from the external waveguide substrate 3) is disposed.

  The external waveguide substrate 3 is a flexible film body having a long shape, and can be optically coupled to each of the internal waveguide 8 of the light emitting side mounting substrate 1 and the internal waveguide 22 of the light receiving side mounting substrate 2. An external waveguide is provided.

  In the optical module 100 having such a configuration, the light output from the light emitting unit 4 installed on the light emitting side mount substrate 1 is transmitted to the internal waveguide 8, the external waveguide of the external waveguide substrate 3, and the light receiving side mount substrate. The light is guided to the light receiving unit 10 installed on the light receiving side mount substrate 2 through the two internal waveguides 22.

  2 is an enlarged cross-sectional view showing the structure around the light emitting portion 4 of the light emitting side mount substrate 1, FIG. 3 is an enlarged plan view showing the structure around the light emitting portion 4 of the light emitting side mount substrate 1, and FIG. 3 is a perspective view of a waveguide 8. FIG. For the visibility of the drawing, hatching is not shown in the cross-sectional view of FIG.

  As shown in FIGS. 2 and 3, the light emitting unit 4 includes a lens 13 that condenses light output from the light emitting element 12 in addition to the light emitting element 12 that outputs a light beam downward. The lens 13 condenses the light output from the light emitting element 12 and guides it to the internal waveguide 8. Here, the positional relationship between the lens 13 and the light emitting element 12 is set so that the optical axis of the lens 13 is positioned on the optical axis of the light beam output from the light emitting element 12. Thereby, the efficiency which permeate | transmits the light output from the light emitting element 12 to the lens 13 can be improved.

  The lens 13 is a convex lens in this embodiment, and the full width at half maximum of the light output from the light emitting element 12 is γ, and the distance in the optical axis direction between the light emitting position of the light emitting element 12 and the incident surface of the internal waveguide 8 is Where X is X, the diameter of the lens 13 is set to be larger than 2X · tan (γ / 2). Thereby, the light output from the light emitting element 12 can be transmitted through the lens 13 with almost no loss.

  As shown in FIGS. 2 to 4, the internal waveguide 8 includes a cladding portion 14 having a predetermined refractive index and a core portion 23 having a higher refractive index of light than the cladding portion 14. It is configured.

  The clad portion 14 includes a flat plate portion 15 that is parallel to the XZ plane, and a triangular columnar portion 16 that is provided along the front end surface of the upper surface of the flat plate portion 15 and has a triangular cross section along the XY plane. The triangular prism-shaped portion 16 is provided with an inclined surface 16 a that is inclined by 45 ° with respect to each of the X axis and the Y axis so as to be positioned below the lens 13. And the mirror part 19 is arrange | positioned on this inclined surface 16a. The mirror unit 19 is an optical element for bending the optical axis of light emitted from the light emitting unit 4 (lens 13) in the Y-axis direction by 90 ° in the X-axis direction toward the core unit 23.

  The clad portion 14 includes first and second block body portions 17 and 18. The first and second block body parts 17, 18 have a core part 23 elongated in the X-axis direction installed at the center part in the Z-axis direction on the upper surface of the flat plate part 15, with respect to the core part 23. And provided on the upper surface of the flat plate portion 15 in such a manner as to be sandwiched on both sides in the Z-axis direction.

  The core part 23 has a T-shaped cross section by the XZ plane and has two parts having different lengths in the Z-axis direction (hereinafter referred to as width). That is, the core portion 23 includes the widened portion 20 (width w1) having the larger width and the base portion 21 (width w2 (<w1)) having the smaller width. The width w1 of the widened portion 20 has a length equivalent to the diameter of the lens 13.

  The widened portion 20 is a portion where the cross section taken along the XZ plane has a rectangular shape and the cross section taken along the XY plane has a trapezoidal shape, and the upper surface is an incident surface for light transmitted through the lens 13. The lens 13 is disposed at a position directly below the lens 13 so as to be in close contact with the incident surface of the widened portion 20 in order to save space in a direction orthogonal to the incident surface of the widened portion 20.

  Further, the side surface (front side surface) located on the front side of the side surface of the widened portion 20 is an inclined surface inclined by 45 ° with respect to each of the X axis and the Y axis, and this side surface is reflected by the mirror portion 19. It is in close contact with the surface.

  A side surface (rear side surface) of the widened portion 20 on the external waveguide substrate 3 side (rear side) is a surface parallel to the Y axis, and the base portion 21 is coupled to a central portion in the Z axis direction of the rear side surface. Yes. The base portion 21 extends to the rear end surface of the light emitting side mounting substrate 1 in parallel to the X axis.

  The lower surface of the core portion 23 (the widened portion 20 and the base portion 21) having such a structure is covered in close contact with the flat plate portion 15 of the clad portion 14, and the core portion 23 (the widened portion 20 and the base portion 21). The side surface in the Z-axis direction is covered in close contact with the first and second block body portions 17 and 18 of the cladding portion 14, and the front side surface of the widened portion 20 (widened portion 20) is reflected by the mirror portion 19. The bottom surface of the core portion 23 (the widened portion 20 and the base portion 21) is exposed to the outside.

  As described above, in this embodiment, since the light emitting unit 4 (the optical element 12 and the lens 13) is installed on the upper surface 6 of the light emitting side mount substrate 1, the mirror is used to bend the light beam transmitted through the lens 13 in the X-axis direction. The portion 19, the triangular prism-shaped portion 16, and the like are provided, and accordingly, the shape of the front end side of the widened portion 20 is configured as described above. The function and the like of the internal waveguide 8 will be described with the configuration shown in FIGS. 5 and 6 that is optically equivalent to the above configuration.

  5 and 6, the light emitting unit 4 (the optical element 12 and the lens 13) is not installed on the upper surface 6 of the light emitting side mount substrate 1 but on the front end surface 8 a side of the internal waveguide 8. The triangular prism-shaped portion 16 and the lens 13 are omitted, and a rectangular parallelepiped widened portion 20 ′ having a side surface flush with the front side surface of the flat surface portion 15 is provided. 5 and 6, the lower surface of the core portion 23 (the widened portion 20 ′ and the base portion 21) is covered with the flat plate portion 15 of the clad portion 14 in close contact with the core portion 23. The side surfaces of (the widened portion 20 ′ and the base portion 21) are covered in close contact with the first and second block body portions 17 ′ and 18 ′ of the cladding portion 14.

  Conventionally, as shown in FIG. 7, a core portion 23 ′ having the same width w <b> 2 as the base portion 21 is provided from the entrance surface to the exit surface of the internal waveguide 8. However, in this configuration, when the lens 13 is brought close to the incident surface T of the internal waveguide 8 because the space between the light emitting unit 4 and the internal waveguide 8 has to be reduced due to space limitations, Such a problem occurs.

  That is, when the lens 13 is brought close to the incident surface T of the internal waveguide 8, the length A (width) in the Z-axis direction of the cut surface of the light beam by the plane including the incident surface T of the core portion 23 ′ is the core portion 23. Is larger than the length w2 (width) of the incident surface S in the Z-axis direction, and as shown in FIG. 7, light that does not enter the incident surface S of the core portion 23 ′ out of the light flux that has passed through the lens 13. Will increase. That is, the optical coupling efficiency between the lens 13 and the core portion 23 'is lowered.

  With respect to this problem, in the present embodiment, by providing the widened portion 20 ′ having a length equivalent to the diameter of the lens 13, light transmitted through the lens 13 is cored compared to the configuration shown in FIG. 7. The efficiency introduced into the incident surface of the part 23 is improved.

  Furthermore, in the present embodiment, as shown in FIG. 5, in the Z-axis direction among the cut surfaces of the light beam by a plane including the incident surface S (the coupling surface with the widened portion 20 ′; see FIG. 8) of the base portion 21. The light beam emitted from the lens 13 is guided to the incident surface S of the base 21 so that the length Z is equal to or shorter than the length a in the Z-axis direction of the incident surface S of the base 21. The efficiency with which the light transmitted through the portion 20 ′ is introduced into the base portion 21 is improved. Hereinafter, this point will be described in detail.

Now, as shown in FIG. 9, the optical refractive index of the clad portion 14 is n ₀ , the optical refractive index of the core portion 23 is n ₁ , and the lengths of the widened portion 20 ′ and the base portion 21 in the Z-axis direction are b, a, The length in the X-axis direction of the widened portion 20 ′ is represented as L, and the relationship between the size of the widened portion 20 ′ and the base 21 and the light incident on the base 21 is parallel to the component parallel to the XZ plane and the XY plane. Think of it as a separate ingredient. First, attention is focused on components parallel to the XZ plane.

  In order to improve the efficiency with which the light beam incident on the widened portion 20 ′ enters the base portion 21, the light beam passing through the apex on the incident surface side of the widened portion 20 ′ may be incident on the core portion 23. Now, when attention is paid to the vertex T1 shown in FIG. 9 as the vertex on the incident surface side of the widened portion 20 ′, the light beam passing through the vertex T1 is incident between the intersection P1 and the intersection P2 between the widened portion 20 ′ and the base portion 21. Then, it can be seen that the light beam passing through the vertex T1 enters the core portion 23.

That is, if the intersection angle between the light beam E1 passing through the intersection P1 and the Z axis is θ _min , and the intersection angle between the light beam E2 passing through the intersection P2 and the Z axis is θ _max , the base portion 21 and the cladding portion 14 (here, the first portion) The incident angle θ on the boundary surface T2 with the one block body portion 17) may be a value between the intersection angle θ _min and the intersection angle θ _max .

θ _min <θ <θ _max
In the following description, the intersection angle θ _{min is referred} to as a minimum incident angle θ _min, and the intersection angle θ _{max is referred} to as a maximum incident angle θ _max .

  On the other hand, the distance X1 from the vertex T1 to the intersection T2 is

The minimum incident angle θ _min can be expressed as

It can be expressed as.

  Further, the distance X2 from the vertex T1 to the intersection T3 is

The maximum incident angle θ _max can be expressed as

It can be expressed as.

  Therefore, in order for the light beam passing through the vertex T1 to enter the core portion 23, the incident angle θ of the base portion 21 and the cladding portion 14 with respect to the boundary surface T2 needs to satisfy the following formula (M-5). I understand that.

At this time, the image side NA is
Image side NA = n ₁ × (1-sin ² θ) ^1/2
Therefore, the image side NA is represented by the following formula (M-6) from this formula and the formula (M-5). The image side NA (Numerical Aperture) is the numerical aperture of the lens 13 (an index for obtaining the resolution of the lens 13).

  Up to this point, the conditions for improving the efficiency with which the light beam incident on the widened portion 20 ′ is incident on the base portion 21 have been studied. However, the light incident on the incident surface of the base portion 21 is external waveguide of the external waveguide substrate 3. In order to improve the efficiency guided to the light, the light incident into the base portion 21 is totally reflected at the boundary surface T2 without penetrating from the boundary surface T2 between the base portion 21 and the cladding portion 14 to the cladding portion 14. It is necessary to configure as follows.

In order to totally reflect the incident light on the boundary surface T2 between the base portion 21 and the cladding portion 14 at the boundary surface T2, the incident angle of the incident light with respect to the boundary surface T2 needs to be equal to or greater than the critical angle θ _C. There is. The critical angle θ _C is obtained by using the refractive indexes n ₀ and n ₁ of the cladding part 14 and the core part 23.
θ _C = sin ⁻¹ (n ₀ / n ₁ )
It is expressed.

  Therefore, in this case, it is understood that the incident angle θ on the boundary surface T2 needs to satisfy the following formula (M-7).

  At this time, the image side NA is represented by the following formula (M-8).

As described above, in order to totally reflect the light incident on the incident surface of the base portion 21 on the boundary surface T2 between the base portion 21 and the clad portion 14 on the boundary surface T2, it is necessary to consider the relationship between the incident angle and the critical angle theta _C with respect to the boundary surface T2 of the light incident on.

That is, if the minimum incident angle θ _min is equal to or greater than the critical angle θ _C , the incident angle of the light incident on the incident surface of the base portion 21 with respect to the boundary surface T2 is the light refraction between the core portion 23 and the cladding portion 14. Since the critical angle θ _{C is} equal to or greater than the critical angle θ _C regardless of the rate, when the minimum incident angle θ _min is equal to or greater than the critical angle θ _C , the image-side NA is the value represented by the formula (M-5) Become.

Conversely, if the minimum incident angle θ _min is less than the critical angle θ _C , some of the light incident on the incident surface of the base 21 has an incident angle with respect to the boundary surface T2 that is the critical angle θ. _{Since it is} less than _C , when the minimum incident angle θ _min is smaller than the critical angle θ _C , the image side NA has a value represented by the formula (M-8).

  Next, attention is focused on the component parallel to the XY plane of the light beam transmitted through the lens 13. In this case, when the incident angle φ to the boundary surface T3 between the base portion 21 and the flat plate portion 15 of the cladding portion 14 satisfies the following formula (M-9), all the light incident on the widened portion 20 ′ is incident on the base portion 21. In addition, the light incident on the base 21 is guided to the external waveguide substrate 3.

  At this time, the image side NA is a value represented by the following formula (M-10).

As described above, in the present embodiment, since the widened portion 20 ′ having a length equivalent to the diameter of the lens 13 is provided, the light beam L that does not enter the core portion 23 ′ in the configuration shown in FIG. _As shown in FIG. 11, _N enters the core portion 23 by the widened portion 20 ′, and more light out of the light transmitted through the lens 13 is cored than in the configuration shown in FIG. 7. It can be introduced into the incident surface of the part 23.

  Further, the length Z in the Z-axis direction of the cut surface of the light beam by a plane including the incident surface S (the coupling surface with the widened portion 20 ′; see FIG. 8) of the base portion 21 is the incident surface S of the base portion 21. Since the light beam emitted from the lens 13 is guided to the incident surface S of the base portion 21 so that the length is not more than the length a in the Z-axis direction, the light transmitted through the widened portion 20 ′ is the base portion 21. The efficiency introduced into the inside can be improved.

  In this case, the following modifications may be employed instead of or in addition to the embodiment.

  (1) In the above embodiment, the core 13 and the separate lens 13 are in close contact with the incident surface of the widened portion 20 (20 ′). However, the present invention is not limited to this, and as shown in FIG. 23, a lens portion 13 ′ (for example, a Fresnel lens) having the same function as the lens portion 13 is formed, and the lens portion 13 ′ is integrated with the widened portion 20 (20 ′). Also good.

  (2) In the above-described embodiment, the cross-sectional shape of the widened portion 20 ′ (20) taken along the XZ plane is rectangular. However, the present invention is not limited to this, and as shown in FIG. It is good also as a shape which has the site | part P where the said width becomes small toward the output surface side from the incident surface side. In the widened portion 20 ′ (20) according to the first embodiment, as shown by a dotted line in FIG. 13, it is reflected by the rear end surface of the widened portion 20 ′ (20) and is not incident on the incident surface S of the base portion 21. Even with light, by forming the above-described portion P, light reflected toward the incident surface S of the base 21 is newly generated by the portion P. Therefore, compared with the first embodiment, the amount of light incident on the base 21 is increased by the amount of light newly reflected by the portion P toward the incident surface S of the base 21. can do.

  (3) The widened portion 20 (20 ′) in the core portion 23 of the first embodiment has a shape in which the cross-sectional shape by the XY plane is different from the cross-sectional shape by the XZ plane. However, the shape of the cross section by the XY plane may be a widened portion having the same shape as that of the cross section by the XZ plane.

  (4) In the first embodiment, when the light beam output from the light emitting element 12 is introduced into the internal waveguide 8, the widened portion 20 ′ is provided in the core portion 23 of the internal waveguide 8. Although not limited to this, as shown in FIG. 14, the light beam guided from the external waveguide formed by the external waveguide substrate 3 is introduced into the internal waveguide 22 formed on the light receiving side mount substrate 2. In this case, a widened portion similar to the widened portion 20 ′ may be provided in the core portion of the internal waveguide 22.

DESCRIPTION OF SYMBOLS 100 Optical module 1 Light emission side mount board | substrate 2 Light reception side mount board | substrate 3 External waveguide board | substrate 4 Light emission part 8 Internal waveguide 12 Light emitting element 13 Lens 14 Cladding part 20 Widening part 21 Base part 23 Core part

Claims (8)

A lens unit that collects the introduced light; and
The core part having a predetermined optical refractive index and a cladding part having a lower optical refractive index than the core part, and covering the core part and a predetermined part of the core part in a close contact state And an internal waveguide that transmits a light beam incident on the core part from the lens part, using a boundary surface with
The core part is
A base having a predetermined width in a predetermined direction perpendicular to the optical axis of the light beam emitted from the lens unit, and transmitting the light beam;
An incident surface that functions as an incident surface of the core portion, and the incident surface has a width larger than the width of the base portion in the predetermined direction, and is a cut surface of a light flux by a plane including the incident surface of the base portion A widened portion that couples the light beam emitted from the lens portion to the incident surface of the base portion is coupled so that the width in the predetermined direction is equal to or smaller than the width of the incident surface of the base portion in the predetermined direction. Optical module.   The optical module according to claim 1, wherein the lens unit is disposed in close contact with an incident surface of the widened portion. A light emitting element that outputs a light beam to the lens unit;
When the full width at half maximum of the light beam output from the light emitting element is θ and the distance in the optical axis direction from the light emitting position of the light emitting element to the incident surface of the widened portion is X, the lens portion in the predetermined direction The optical module according to claim 2, wherein a length and a width of the incident surface of the widened portion in the predetermined direction are greater than 2X · tan (θ / 2).   4. The optical module according to claim 1, wherein a width of the widened portion in the predetermined direction decreases from an incident surface side of the widened portion toward a coupling surface side with the base portion. 5. The optical refractive index of the cladding part is n ₀ , the optical refractive index of the core part is n ₁ , the width of the base part is a, the width of the incident surface of the widened part in the predetermined direction is b, and the widened part of the widened part 5. The image-side NA satisfies the following formula (T-1), where L is the length in the optical axis direction from the incident surface to the coupling surface between the widened portion and the base portion. The optical module according to item.

The optical refractive index of the cladding part is n ₀ , the optical refractive index of the core part is n ₁ , the width of the base part is a, the width of the incident surface of the widened part in the predetermined direction is b, and the widened part of the widened part 5. The image side NA satisfies the following formula (T-2), where L is the length in the optical axis direction from the incident surface to the coupling surface between the widened portion and the base portion. The optical module according to item.

The optical module according to claim 5 or 6, wherein the image side NA further satisfies the following formula (T-3).

A light emitting element that outputs a light beam to the lens unit;
The optical module according to claim 1, wherein an optical axis of the lens unit coincides with an optical axis of a light beam output from the light emitting element.

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