JP2009176970A - Surface emitting laser - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To materialize a stabilization of a wavelength, a reduction of a loss of an optical resonator, and an improvement of a cooling efficiency. <P>SOLUTION: In a surface emitting laser, a first optical multilayer film formed on a diaphragm for controlling a wavelength is opposed to a second optical multilayer film through an active layer, whereby the optical resonator is formed with the first and second optical multilayer films. This surface emitting laser has a space formed between the first optical multilayer film and the active layer, and a liquid intervening in this space. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a surface emitting laser, and more particularly to a method for stabilizing the wavelength of a surface emitting laser.

  FIG. 12 is a cross-sectional view showing an example of a conventional surface emitting laser (see, for example, Patent Document 1). In FIG. 12, the separation layer 19 is newly formed on the surface of the compound semiconductor composed of the lower DBR layer 12 and the active layer 14. The isolation layer 19 performs electrical insulation, and is, for example, a pn junction layer or a high resistance layer.

  A refractive index control unit 20 is newly provided in contact with an air gap AG in the optical resonator formed by the lower DBR layer 12 and the dielectric multilayer mirror 17. The refractive index control unit 20 includes an n-type contact layer 21, a multiple quantum well layer 22, a p-type contact layer 23, an upper electrode 24 for refractive index control, and a lower electrode 25 for refractive index control.

  The n-type contact layer 21 is formed on the separation layer 19. The separation layer 19 electrically insulates the compound semiconductor that emits laser light from the refractive index control unit 20. The multiple quantum well layer 22 is formed on the n-type contact layer 21. Here, the multiple quantum well layer 22 is a refractive index control layer. The absorption wavelength of the multiple quantum well layer 22 is shorter than the absorption edge wavelength of the active layer 14. That is, the multiple quantum well layer 22 has a band gap that becomes transparent with respect to the oscillation wavelength of the active layer 14.

  The p-type contact layer 23 is formed on the multiple quantum well layer 22. The upper electrode 24 for controlling the refractive index is formed on the p-type contact layer 23 by removing the central portion for extracting the laser beam. The lower electrode 25 for controlling the refractive index is formed on the periphery of the n-type contact layer 21 from which the multi-quantum well layer 22 and the p-type contact layer 23 are removed by mesa processing.

Next, the operation of the surface emitting laser will be described.
First, the operation for causing the laser to emit light will be described.
When a voltage is applied between the upper electrode 16 and the lower electrode 25, the upper electrode 16 passes through the upper spacer layer 15, the active layer 14, the lower spacer layer 13, the lower DBR layer 12, and the n-type InP substrate 11. A current flows to the electrode 25.

  At this time, holes and electrons are coupled in the active layer 14 having the narrowest band gap, and light is emitted. The light is amplified by the optical resonator and taken out of the n-type InP substrate 11, that is, the n-type InP substrate. 11 is emitted as laser light from the back side.

  Since the injected current flows from the upper electrode 16 toward the lower electrode 18, the current is injected from the vertical direction of the active layer 14 which is the light emitting region, but the current may be injected from the lateral direction of the light emitting region. Absent.

  As described above, the optical resonator includes the lower DBR layer 12 formed on the compound semiconductor n-type InP substrate 11 and the dielectric multilayer mirror 17 bonded to the upper side of the active layer 14 through the air gap AG. And function as a surface emitting laser.

Next, an operation for changing the oscillation wavelength will be described.
The oscillation wavelength is changed by moving the dielectric multilayer mirror 17 in the vertical direction by MEMS to change the interval between the optical resonators.

Next, a conventional example of a surface emitting laser will be described with reference to FIG. FIG. 13 is a cross-sectional view showing another example of a conventional surface emitting laser.
The insulating layer is formed on the chip 8 by removing the central portion in order to measure the movement amount of the diaphragm 5. Therefore, the insulating layers 7a and 7b from which the central portion is removed on the chip 8 are defined as the lower gap 9, and the insulating layer 7a, the insulating layer 7b, and the lower gap 9 are defined on the chip 8 as the lower gap 9. Through this, a diaphragm 5 is formed, and a first optical multilayer film 4 is formed thereon.
Further, the first optical multilayer film 4 provided on the diaphragm 5 and the second optical multilayer film 2 are opposed to each other through the active layer 3 and the upper gap 10, so that the first optical multilayer film 4 and An optical resonator is formed by the second optical multilayer film 2. Accordingly, the second optical multilayer film 2 and the active layer 3 are formed on the chip 1.

The operation of the conventional example shown in FIG. 13 will be described.
When a voltage is applied to an electrode on the diaphragm 5 (not shown), an electrostatic force is generated. The diaphragm 5 moves downward using this electrostatic force as a driving force, and returns to the original state, so that the distance between the first optical multilayer film 4 and the second optical multilayer film 2 changes, so that the light The resonator length, that is, the interval between the optical resonators changes, and the laser oscillation wavelength changes. That is, the interval between the first optical multilayer film 4 and the second optical multilayer film 2 can be changed.

JP 2005-222968 A

However, such a surface emitting laser has the following problems.

  When the diaphragm is placed in the air, there is a problem that the damping characteristics of the diaphragm vibration are deteriorated.

  Further, when the diaphragm is placed in the air, there is a problem that the diaphragm vibrates and the line width of the laser oscillation spectrum increases.

  There is also a problem that a part of the optical resonator is outside the chip.

In addition, since the laser active layer is in contact with air, the heat dissipation is performed only within the chip, so that there is a problem that the heat dissipation characteristics deteriorate.

  Accordingly, the present invention aims to eliminate the drawbacks of the prior art as described above, and to achieve stabilization of wavelength, reduction of optical resonator loss, and improvement of cooling efficiency.

In order to achieve the above object, according to a first aspect of the present invention, a first optical multilayer film and a second optical multilayer film provided on a wavelength control diaphragm are interposed via an active layer. In the surface emitting laser in which the first and second optical multilayer films form an optical resonator by facing each other, a space formed between the first optical multilayer film and the active layer, and this space And a liquid interposed between the two.

  According to a second aspect of the present invention, in the surface emitting laser according to the first aspect of the present invention, the container includes the container containing the optical resonator and the liquid filled in the container and the space.

According to a third aspect of the present invention, in the surface emitting laser according to the first or second aspect of the present invention, the lead for an electrode is formed so as to penetrate through the container and reach the inside of the container.

  According to a fourth aspect of the present invention, the surface emitting laser according to any one of the first to third aspects further comprises a stabilizing unit that keeps the internal pressure of the container constant.

  According to a fifth aspect of the present invention, in the surface emitting laser according to the fourth aspect, the stabilizing means is an elastic sphere or an elastic hollow sphere disposed in the container.

According to a sixth aspect of the present invention, in the surface emitting laser according to the fourth aspect, the stabilizing means is an air chamber formed in the container.

According to a seventh aspect of the present invention, in the surface emitting laser according to the fourth aspect of the present invention, the stabilizing means has an air pocket in the electrode lead.

According to an eighth aspect of the present invention, in the surface emitting laser according to the fourth aspect, the stabilizing means is an internal pressure stabilizing diaphragm formed on an outer wall of the container.

According to a ninth aspect of the present invention, in the surface emitting laser according to the fourth aspect of the present invention, the stabilizing means is the container having a bellows shape at least at a part of the outer wall.

According to a tenth aspect of the present invention, in the surface emitting laser according to the fifth aspect, the stabilizing means is a bellows protruding inward or outward of the container.

According to an eleventh aspect of the present invention, the surface emitting laser according to the first aspect further includes a holding unit for holding the liquid in the space.

According to a twelfth aspect of the present invention, in the surface emitting laser according to the first aspect, the liquid has a refractive index different from that of air.

According to a thirteenth aspect of the present invention, in the surface emitting laser according to any one of the first to third aspects, the liquid is insulative.

The effects obtained by the typical inventions among those disclosed in the present application will be described as follows.

  By inserting the liquid into the optical path portion of the optical resonator, the wavelength can be stabilized, the loss of the optical resonator can be reduced, and the cooling efficiency can be improved.

  Moreover, the internal pressure fluctuation in the container with respect to the environmental temperature caused by inserting the liquid into the container can be stabilized.

  Hereinafter, the surface emitting laser of the present invention will be described with reference to the drawings.

  FIG. 1 is a block diagram showing an embodiment of the present invention. In the figure, the same components as those in FIG. 13 are denoted by the same reference numerals.

  As shown in FIG. 1, in the surface emitting laser, first, insulating layers 7a and 7b are formed on the chip 8, and the portion shown in the lower gap 9 is removed to extract the laser light, and the insulating layers 7a and 7b are formed. Become.

A diaphragm 5 is formed on the insulating layers 7 a and 7 b, and a first optical multilayer film 4 is formed on the diaphragm 5.

On the other hand, a second optical multilayer film 2 is formed on the chip 1, and an active layer 3 is formed on the second optical multilayer film 2. The second optical multilayer film 2 and the first optical multilayer film 4 are opposed to each other through the active layer 3 and the upper gap 10.

Further, the joining column 6 joins the active layer 3 and the diaphragm 5.

The second optical multilayer film 2 and the first optical multilayer film 4 form an optical resonator.

Oil or other liquid (hereinafter referred to as liquid 30) is inserted into the optical path portion of the optical resonator.

Further, by inserting the liquid 30 into the optical path portion of the optical resonator, the space formed between the active layer 3 and the first optical multilayer film 4 is held by surface tension.

That is, the liquid 30 holds between two chips joined by surface tension.

By inserting the liquid 30 into the optical path portion, the vibration of the diaphragm 5 can be reduced. Since the diaphragm 5 can reduce vibration, the spectral line width can be reduced.

Moreover, since the liquid 30 is inserted into the optical path portion of the optical resonator, the chip 1 and the chip 8 are joined, so that the cooling effect can be improved.

Further, the loss of the optical resonator can be reduced by inserting the liquid 30 into the optical path portion of the optical resonator.

In addition, by inserting the liquid 30 into the optical path portion of the optical resonator, the vibration is suppressed by the liquid 30 even if a shake due to an external impact occurs. That is, the vibration of the diaphragm 5 can be suppressed.

The liquid 30 may be inserted only in the optical path portion.

Next, the liquid sealing structure of the optical resonator optical path portion of the surface emitting laser according to the first embodiment of the present invention will be described with reference to FIG.

FIG. 2 is a configuration diagram including a holding unit for holding the liquid 30 in a space formed between the first optical multilayer film 4 and the active layer 3.

In FIG. 2, the joining column 6 is used as a holding means.

That is, the joining column 6 is used as a holding means for the liquid 30 that joins and inserts the active layer 3 and the diaphragm 5 which are the roles of the joining column 6 of FIG.

Further, when the surface tension of the liquid 30 is taken into consideration, the holding means may surround at least a part of the optical resonator instead of enclosing the entire optical path.

With the holding means, the liquid 30 inserted into the optical resonator optical path portion can be held more than when there is no holding means.

  FIG. 3 is a block diagram showing an embodiment of the present invention. In the figure, the same components as those in FIG.

As shown in FIG. 3, in Example 2, a container 31 and a laser beam extraction port 32 were added to the surface emitting laser of Example 1.

In FIG. 3, a surface emitting laser container 31 contains a surface emitting laser including an optical resonator.

The second optical multilayer film 2 and the first optical multilayer film 4 form an optical resonator.

The liquid 30 is filled in a space formed between the container 31 and the first optical multilayer film 4 and the active layer 3.

It is possible to improve the damping characteristics of the diaphragm 5 vibration by enclosing the surface emitting laser in the container 31 and filling the liquid 30 in the space formed between the first optical multilayer film 4 and the active layer 3. it can.

Further, by filling the optical resonator optical path portion with the liquid 30, vibration of the diaphragm 5 can be reduced. Since the vibration of the diaphragm 5 can be reduced, it is possible to reduce noise on the output light of the laser that causes the vibration of the diaphragm 5.

Further, by opening the lower gap 9 to the atmosphere through the laser light extraction port 32, the heat radiation characteristics of the laser light emitting part are improved. By improving the heat radiation characteristics of the laser light emitting section, the light emission output of the laser can be increased.

Next, a liquid sealing structure in a container 31 containing a surface emitting laser according to a second embodiment of the present invention will be described with reference to FIG.

FIG. 4 shows a lead 33 for an electrode that is penetrated through the container 31 and reaches the inside of the container 31 and a liquid filling port 34 for filling the electrode 30 with the liquid 30. FIG.

The surface emitting laser has a plurality of electrode leads 33. By forming at least one electrode lead 33 into a hollow structure, the inside of the container 31 containing the surface emitting laser from the liquid filling port 34 is provided. The liquid 30 can be inserted into the container.

Further, the inside of the container 31 is evacuated using the electrode lead 33 formed in a hollow shape, and the tip of the electrode lead 33 is attached to the defoamed liquid 30 in the evacuated atmosphere. By breaking the state, the liquid 30 can be inserted into the container 31.

Further, since the liquid filling port 34 makes the existing electrode lead 33 hollow, it is not necessary to make a new liquid filling port 34 separately.

In addition, after inserting the liquid 30 into the container 31, the liquid sealing port 34 mechanically seals or cuts off the tip of the electrode lead 33, or seals it by soldering or the like.

  FIG. 5 is a block diagram showing an embodiment of the present invention. In the figure, the same components as those in FIG.

As shown in FIG. 5, in Example 3, an elastic ball 35 was added as a stabilizing means to the surface emitting lasers of Examples 1 and 2.

In FIG. 5, the elastic sphere 35 is inserted into a container 31 filled with a liquid 30.

The elastic sphere 35 may be a hollow elastic sphere.

Further, the position of the elastic sphere 35 may be anywhere in the container 31.

  By inserting the elastic sphere 35 into the container 31 filled with the liquid 30, the liquid 30 expands when the temperature rises, and the elastic sphere 35 is compressed to absorb the expansion of the liquid 30, thereby suppressing an increase in pressure. it can.

On the other hand, when the temperature decreases, the liquid 30 contracts, and the elastic sphere 35 expands to absorb the contraction of the liquid 30, thereby suppressing a decrease in pressure.

That is, by inserting the elastic sphere 35 into the container 31 filled with the liquid 30, the internal pressure of the container 31 can be stabilized with respect to the environmental temperature.

  As shown in FIG. 6, in Example 3, an air chamber 36 was added to the surface emitting lasers of Examples 1 and 2 as stabilizing means.

In FIG. 6, the air chamber 36 is formed in the container 31.

The position of the air chamber 36 may be anywhere as long as it is connected to the container 31.

By connecting the air chamber 36 to the container 31 filled with the liquid 30, the liquid 30 expands when the temperature rises, the air in the air chamber 36 is compressed to absorb the expansion of the liquid 30, and the increase in pressure is suppressed. be able to.

On the other hand, when the temperature decreases, the liquid 30 contracts, and the air in the air chamber 36 expands to absorb the contraction of the liquid 30, thereby suppressing a decrease in pressure.

That is, by connecting the air chamber 36 to the container 31 filled with the liquid 30, the internal pressure of the container 31 can be stabilized with respect to the environmental temperature.

  As shown in FIG. 7, in Example 3, an air pocket 37 was added as a stabilizing means to the surface emitting lasers of Examples 1 and 2.

In FIG. 7, as described with reference to FIG. 4, a hollow is formed in the electrode lead 33, and after the liquid 30 is inserted into the container 31 from the liquid sealing port 34 of the electrode lead 33, The liquid filling port 34 is sealed.

  By providing the air reservoir 37 on the electrode lead 33, the liquid 30 expands when the temperature rises, and the air in the air reservoir 37 is compressed to absorb the expansion of the liquid 30, thereby suppressing an increase in pressure. it can.

  On the other hand, when the temperature decreases, the liquid 30 contracts, and the air in the air pool 37 expands to absorb the contraction of the liquid 30, thereby suppressing a decrease in pressure.

That is, the container 31 filled with the liquid 30 penetrates through the container 31 and reaches the inside of the container 31, and also connects the air reservoir 37 to the electrode lead 33 formed in the hollow, thereby the container 31. The internal pressure can be stabilized with respect to the environmental temperature.

  As shown in FIG. 8, in Example 3, a center diaphragm 38 was added as a stabilizing means to the surface emitting lasers of Examples 1 and 2.

In FIG. 8, the center diaphragm 38 is formed on the outer wall of the container 31.

Further, the position of the center diaphragm 38 may be set anywhere as long as one side of the center diaphragm 38 is in contact with the outside and the other side is in contact with the liquid 30 in the container 31.

By providing the center diaphragm 38 formed on the outer wall of the container 31 filled with the liquid 30, the liquid 30 expands when the temperature rises, and the center diaphragm 38 expands as the dotted line in FIG. The increase in pressure can be suppressed by absorbing.

On the other hand, when the temperature decreases, the liquid 30 contracts, the center diaphragm 38 bends as shown by the solid line in FIG. 8, and the contraction of the liquid 30 is absorbed.

  That is, by forming the center diaphragm 38 outside the container 31 filled with the liquid 30, the internal pressure of the container 31 can be stabilized with respect to the environmental temperature.

The outer wall of the container 31 includes a container 31 and a plate that closes the container 31.

  As shown in FIG. 9, in Example 3, the can 39 with bellows was added to the surface emitting lasers of Examples 1 and 2 as a stabilizing means.

In FIG. 9, the can 39 with bellows has a part of the container 31 formed in a bellows shape.

The bellows may be anywhere in the container 31 as long as it is in contact with the liquid 30 in the container 31.

By using the bellows can 39 in which a part of the container 31 filled with the liquid 30 is formed in a bellows shape, the liquid 30 expands when the temperature rises, and the bellows of the bellows can 39 expands and the liquid 30 By absorbing the expansion, the increase in pressure can be suppressed.

On the other hand, when the temperature decreases, the liquid 30 contracts, the bellows of the bellows can 39 compresses, and the contraction of the liquid 30 is absorbed, so that a decrease in pressure can be suppressed.

That is, by forming the bellows-equipped can 39 in a part of the container 31 filled with the liquid 30, the internal pressure of the container 31 can be stabilized with respect to the environmental temperature.

  As shown in FIGS. 10 and 11, in Example 3, bellows 40a and 40b were added as stabilizing means to the surface emitting lasers of Examples 1 and 2.

10 and 11, bellows 40 a and 40 b protrude inside or outside the container 31.

The positions of the bellows 40a and 40b may be anywhere.

Further, the bellows 40 a and 40 b may be in contact with the liquid 30 in the container 31.

By using the bellows 40a and 40b protruding inside or outside the container 31 filled with the liquid 30, the liquid 30 expands when the temperature rises, and the bellows of the bellows 40a expands to absorb the expansion of the liquid 30. As a result, an increase in pressure can be suppressed.

On the other hand, when the temperature decreases, the liquid 30 contracts, and the bellows of the bellows 40b compresses to absorb the contraction of the liquid 30, thereby suppressing a decrease in pressure.

  That is, the internal pressure of the container 31 can be stabilized with respect to the environmental temperature by protruding inward or outward of the container 31 filled with the liquid 30.

In the above-described embodiment, the liquid 30 having a refractive index different from that of air is inserted into the optical resonator optical path portion and the container 31 so that the oscillation wavelength of the surface emitting laser can be set regardless of the length of the joining column 6. Can be changed.

  Further, the oscillation wavelength can be finely adjusted by changing the pressure of the liquid 30.

The liquid 30 is insulating.

It is a block diagram which shows one Example of this invention. It is a block diagram which shows one Example of this invention. It is a block diagram which shows one Example of this invention. It is a block diagram which shows one Example of this invention. It is a block diagram which shows one Example of this invention. It is a block diagram which shows one Example of this invention. It is a block diagram which shows one Example of this invention. It is a block diagram which shows one Example of this invention. It is a block diagram which shows one Example of this invention. It is a block diagram which shows one Example of this invention. It is a block diagram which shows one Example of this invention. It is a block diagram which shows an example of the past. It is a block diagram which shows an example of the past.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Chip 2 2nd optical multilayer film 3 Active layer 4 1st optical multilayer film 5 Diaphragm 6 Joining pillars 7a and 7b Insulating layer 8 Chip 9 Lower gap 10 Upper gap 11 n-type InP substrate 12 Lower DBR layer 13 Lower part Spacer layer 14 Active layer 15 Upper spacer layer 16 Upper electrode 17 Dielectric multilayer mirror 18 Lower electrode 19 Separating layer 20 Refractive index controller 21 n-type contact layer 22 Multiple quantum well layer 23 p-type contact layer 24 Upper electrode 25 Lower electrode 30 Liquid 31 Container 32 Laser light extraction port 33 Electrode lead 34 Liquid sealing port 35 Elastic sphere 36 Air chamber 37 Air pool 38 Center diaphragm 39 Cans with bellows 40a, 40b Bellows

Claims (13)

By making the first optical multilayer film and the second optical multilayer film provided on the wavelength control diaphragm face each other through the active layer, an optical resonator is formed by the first and second optical multilayer films. In the surface emitting laser forming
A space formed between the first optical multilayer film and the active layer;
A surface emitting laser comprising: a liquid interposed in the space. A container containing the optical resonator;
The surface-emitting laser according to claim 1, further comprising the liquid filled in the container and the space. Penetrates the container and reaches into the container,
3. The surface emitting laser according to claim 2, further comprising an electrode lead formed in a hollow shape.   4. The surface emitting laser according to claim 2, further comprising a stabilizing unit that keeps the internal pressure of the container constant.   5. The surface emitting laser according to claim 4, wherein the stabilizing means is an elastic sphere or an elastic hollow sphere disposed in the container.   5. The surface emitting laser according to claim 4, wherein the stabilizing means is an air chamber formed in the container.   7. The surface emitting laser according to claim 6, wherein the stabilizing means has an air pocket in the lead for the electrode. The stabilizing means includes
5. The surface emitting laser according to claim 4, wherein the surface emitting laser is an internal pressure stabilizing diaphragm formed on an outer wall of the container.   5. The surface emitting laser according to claim 4, wherein the stabilizing means is the container having a bellows shape at least at a part of the outer wall.   5. The surface emitting laser according to claim 4, wherein the stabilizing means is a bellows protruding inside or outside the container.   2. The surface emitting laser according to claim 1, further comprising holding means for holding the liquid in the space.   The surface emitting laser according to claim 1, wherein the liquid has a refractive index different from that of air.   The surface emitting laser according to claim 1, wherein the liquid is insulative.