JP5721422B2 - Surface emitting laser and array light source - Google Patents

Description

  The present invention relates to a two-dimensional photonic crystal surface emitting laser.

In recent years, many examples in which a photonic crystal is applied to a semiconductor laser have been proposed. For example, Patent Document 1 discloses a surface emitting laser in which a two-dimensional photonic crystal is formed in the vicinity of an active layer.
In this two-dimensional photonic crystal, cylindrical holes and the like are periodically provided in the semiconductor layer, and has a two-dimensional periodic refractive index distribution. Due to the periodic refractive index distribution, the light generated in the active layer resonates, forms a standing wave, and oscillates.

Also, a structure has been proposed in which the direction of the emitted beam can be controlled using such a two-dimensional photonic crystal surface emitting laser.
Patent Document 2 discloses that a tilted beam is emitted using a plurality of photonic crystals that generate standing waves having different wave numbers.
It is also known that a tilted beam is emitted by using a non-Γ point oscillation mode even in a single photonic crystal.
A light source whose emission beam is controlled is expected to be applied as a light source for electrophotography or laser display, for example.

JP 2000-332351 A JP 2009-076900

When a two-dimensional photonic crystal surface emitting laser is used as a light source for electrophotography or the like, it is used for a laser that emits a tilted beam with equal intensity in both directions from the viewpoint of light utilization efficiency and suppression of stray light generation. On the other hand, it is preferable that the ratio of the emitted beam intensity can be controlled.
However, in the case of using a plurality of photonic crystals of Patent Document 2 or in the case of using non-Γ point oscillation, the tilted beam is two symmetrical with respect to the normal line of the laser light emission surface. It has the subject that it will radiate | emit with the intensity | strength equal to a direction (bidirectional).
Hereinafter, these reasons will be described.
First, a case where a plurality of photonic crystals are used as in Patent Document 2 will be described.
The surface emitting laser disclosed in Patent Document 2 has two two-dimensional photonic crystals with different periods.
In the two two-dimensional photonic crystals, standing waves having different wave numbers are formed, and the two standing waves are superimposed to generate a standing wave having a wave number in the in-plane direction.
Since a standing wave having a wave number in the in-plane direction of the two-dimensional photonic crystal is emitted with an inclination from the normal line of the two-dimensional photonic crystal, an inclined beam is obtained.
Here, due to the symmetry of the two-dimensional photonic crystal, the standing wave is line symmetric with respect to the normal line.
Therefore, the inclined beam is emitted with equal intensity in two directions (bidirectional) that are line-symmetric with respect to the normal line.

Next, a case where a non-Γ point oscillation mode is used will be described.
A standing wave oscillating at a non-Γ point has a wave number in the in-plane direction of the two-dimensional photonic crystal.
Light having a wave number in the in-plane direction is emitted with the beam tilted from the normal line of the two-dimensional photonic crystal, so that a tilted beam is obtained.
Due to the symmetry of the two-dimensional photonic crystal, the standing wave oscillating at the non-Γ point is line symmetric with respect to the normal line.
Therefore, also in this case, the tilted beam is emitted in a direction (bidirectional) symmetrical with respect to the normal line, and is emitted with equal intensity.

When a two-dimensional photonic crystal surface emitting laser is used as a light source for, for example, electrophotography or laser display, a beam mainly used (referred to as a main beam) is either one of the beams. Therefore, if the same power is emitted in both directions, high light utilization efficiency cannot be obtained.
Further, if a beam that is not mainly used (referred to as a secondary beam) is too strong, stray light may be caused.

  In view of the above-described problems, the present invention can control the intensity ratio of laser light emitted in two directions that are oblique directions that are line-symmetric with respect to the normal line of the laser light emission surface. An object is to provide a nick crystal surface emitting laser.

The two-dimensional photonic crystal surface emitting laser of the present invention has a two-dimensional photonic crystal having a resonance mode in the in-plane direction, and has at least two oblique directions that are line-symmetric with respect to the normal line of the laser light emission surface. A two-dimensional photonic crystal surface emitting laser emitting the laser light in one direction,
The two-dimensional photonic crystal is
The depth of the medium constituting the lattice points of the two-dimensional photonic crystal along the direction perpendicular to the projection direction of the laser beam emitted in the two directions projected onto the laser beam emission surface. Or the height is constant,
The depth or height of the medium constituting the lattice point of the two-dimensional photonic crystal changes asymmetrically with respect to an arbitrary plane having a direction parallel to the projection direction as a normal along the projection direction. It is characterized by being.

  According to the present invention, the two-dimensional photonic crystal surface that can control the intensity ratio of the laser light emitted in two directions that are obliquely symmetrical with respect to the normal line of the laser light emission surface. A light emitting laser can be realized.

FIG. 2 is a schematic diagram for explaining the outline of a two-dimensional photonic crystal surface emitting laser according to Embodiment 1. FIG. 3 is a diagram illustrating a state of generation of diffracted light at a lattice point for explaining the first embodiment. FIG. 3 is a diagram illustrating an intensity difference between two inclined beams for explaining the first embodiment. The figure which showed the range which the main beam for demonstrating Embodiment 1 strengthens. The figure which showed the range where the sub beam for describing Embodiment 1 weakens. The figure which showed the range where the main beam for demonstrating Embodiment 1 strengthens and the sub beam weakens. The figure which showed the mode of the depth change of the lattice point for demonstrating Embodiment 1. FIG. FIG. 5 is a diagram illustrating a modification of the two-dimensional photonic crystal surface emitting laser according to the first embodiment. FIG. 5 is a schematic diagram for explaining an outline of a two-dimensional photonic crystal surface emitting laser according to Embodiment 2. FIG. 6 is a diagram showing a modification of the two-dimensional photonic crystal surface emitting laser in the second embodiment. FIG. 6 is a schematic diagram of a two-dimensional photonic crystal surface emitting laser according to Embodiment 3. FIG. 3 is a cross-sectional view illustrating an outline of a two-dimensional photonic crystal surface emitting laser in Example 1. FIG. 3 is a diagram showing a band structure and an oscillation mode of a two-dimensional photonic crystal in Example 1. FIG. 3 is a diagram showing a method for manufacturing a two-dimensional photonic crystal in Example 1. FIG. 6 is a diagram showing another method for manufacturing a two-dimensional photonic crystal in Example 1. 4 is a schematic diagram of a two-dimensional photonic crystal in Example 2. FIG. FIG. 5 shows a band structure and an oscillation mode of a two-dimensional photonic crystal in Example 3.

Hereinafter, embodiments of the present invention will be described.
In the following drawings, the same symbols are assigned to components having the same function.
[Embodiment 1]
As Embodiment 1, a configuration example of a two-dimensional photonic crystal surface emitting laser (distributed feedback surface emitting laser) having a two-dimensional photonic crystal having a resonance mode in the in-plane direction will be described with reference to FIGS. To do.
FIG. 1A is a plan view of the two-dimensional photonic crystal 101, and FIG. 1B is a cross-sectional view taken along the AA ′ plane.
The two-dimensional photonic crystal surface emitting laser of the present embodiment has a configuration in which laser light is emitted in at least two directions which are oblique directions that are line-symmetric with respect to the normal line of the laser light emission surface.
Specifically, the two-dimensional photonic crystal surface emitting laser of the present embodiment is x with respect to the direction (z direction) of the normal line (normal line of the laser beam emission surface) 102 of the two-dimensional photonic crystal 101. Laser light is emitted in two line-symmetric directions inclined in the direction.
Here, the x direction means a projection direction obtained by projecting the emission direction vector of the laser light emitted in the two directions onto the emission surface of the laser light.
FIG. 1B shows a state in which the emission direction vectors of light are 103 and 104, and the angle between the emission direction vector 103 (104) and the normal line 102 (z axis) is θ.
The two-dimensional photonic crystal 101 in the present embodiment has a structure in which the medium constituting the lattice points is arranged in a lattice shape in the medium made of the host material 105.
The two-dimensional photonic crystal 101 in the present embodiment is a direction in which the depth of the medium constituting the lattice point, that is, the depth of the hole 106 as the medium constituting the lattice point is perpendicular to the projection direction (y direction). ) Along the x direction and changing at a constant rate.
However, the present invention is constant along the y direction and changes at a constant rate along the x direction, but is not limited to the depth of the medium constituting the lattice points. .
For example, the present invention is also applicable to a case where a so-called rod array type two-dimensional photonic crystal is formed, for example, where the host material 105 is air and the medium constituting the lattice point is made of a material having a refractive index different from that of air. . That is, in the case of such a rod arrangement type two-dimensional photonic crystal, the height of the medium constituting the lattice point (the height of the rod portion) is constant along the y direction, and the x direction. It is configured to change at a constant rate along.

FIG. 2 shows how the emitted light is generated in the two-dimensional photonic crystal 101.
The diffracted light at each lattice point reflects the wave number in the x direction of the standing wave of the two-dimensional photonic crystal 101 and is emitted with the same intensity in the 103 direction and the 104 direction.
The generated diffracted light interferes with each other, and light emitted from the entire two-dimensional photonic crystal surface emitting laser is obtained.
The thing of this embodiment utilizes the interference of this diffracted light.
Attention is paid to the diffracted light generated at the adjacent lattice points 110 and 120.
The diffracted light 111 and the diffracted light 121 generated at the lattice point 110 and emitted in the 103 direction have an optical path length difference represented by the following equation (1).
However, α is an angle formed by a line connecting the bottoms of the holes in the change region where the depth of the holes 106 changes at a constant rate and the projection direction (x direction).
Further, θ is an angle formed between the normal line of the laser beam emission surface and the emission direction of the laser beam emitted in a direction symmetrical to the normal line.

On the other hand, the diffracted beams 112 and 122 emitted in the 104 direction have an optical path length difference expressed by the following equation (2).

  If there is a difference between the two optical path lengths, there will be a difference in intensity between the light emitted in the 103 direction as the interference light of 111 and 121 and the light emitted in the 104 direction as the interference light of 112 and 122. Accordingly, the ratio of the beam intensity emitted in the 103 direction and the 104 direction (bidirectional) can be controlled.

FIG. 3 shows the result of calculating the difference in light intensity between the 103 direction and the 104 direction when the angle θ and the angle α are changed.
The white portion indicates that light in the 103 direction is large, and the black portion indicates that light in the 104 direction is large.
FIG. 3 shows that there is a difference in the bidirectional light intensity regardless of the angle θ and the angle α.
Although FIG. 1 shows an example in which the rate changes along the x direction at a constant rate (angle α), it does not necessarily have to change at a constant rate.
This is because when considering two adjacent lattice points from FIG. 3, if the depth of the hole is different between the two lattice points, a difference occurs in the bidirectional light intensity.
Specifically, the depth of the lattice point (hole 106) is constant along the direction (y direction) perpendicular to the projection direction of the light emission direction onto the two-dimensional photonic crystal 101,
If the light emission direction changes asymmetrically along the projection direction (x direction) onto the photonic crystal, it is possible to make a difference in the intensity in both directions.
Here, asymmetric means that when the two-dimensional photonic crystal 101 is folded back with respect to a plane passing through the center of the two-dimensional photonic crystal 101 and having a normal line in the x direction, the original structure is not matched. That is, the depth of the holes constituting the lattice points of the two-dimensional photonic crystal changes asymmetrically with respect to an arbitrary plane having a direction parallel to the projection direction as a normal along the projection direction. Means.
However, it is preferable that the depth of the lattice points change at a constant rate in the x direction because the interference conditions are the same between adjacent lattice points and the intensity unevenness of the emitted light can be reduced.

Further, there are more preferable conditions for satisfying the angle θ and the angle α.
Below, the conditions and the preferable reason are demonstrated.
For convenience of explanation, it is assumed that a beam with a high light intensity (referred to as a main beam) is emitted in the 103 direction and a beam with a weak direction (referred to as a sub beam) is emitted in the 104 direction. Obviously, the direction of the secondary beam may be reversed.
First, the conditions under which the light intensity of the main beam becomes stronger than when the depth of the lattice points is constant will be described. This is preferable because the light use efficiency to the main beam is increased.
Since the optical path length difference in the main beam direction (103 direction) is described by equation (1), if the following equation (3) is satisfied, the light intensity of the main beam is greater than when the depth of the lattice points is constant. Become stronger. However, n in this formula (3) is an integer.

FIG. 4 shows the magnitude of the light intensity in the main beam direction, and the white part is the range of the angle θ and the angle α satisfying the expression (3).
From the above, it can be seen that it is preferable to change the depth of the lattice points asymmetrically so as to satisfy the expression (3), since the light utilization efficiency to the main beam becomes high.
In particular, it is more preferable that the following expression (4) is satisfied, because the diffracted light generated from each lattice point is completely strengthened. However, n in this formula (4) is an integer.

Next, the conditions under which the light intensity of the sub beam becomes weaker than when the depth of the lattice point is constant will be described. In this case, the light intensity of the sub beam that can cause stray light becomes weak, which is preferable. Since the optical path length difference in the sub beam direction (104 direction) is described by equation (2), if the following equation (5) is satisfied, the light intensity of the sub beam is higher than that when the depth of the lattice point is constant. become weak. However, n in this formula (5) is an integer.

FIG. 5 shows the magnitude of the light intensity in the sub-beam direction, and the black part is the range of the angle θ and the angle α that satisfy the equation (5). From the above, it can be seen that it is preferable to change the depth of the lattice points asymmetrically so as to satisfy the expression (5) because stray light caused by the sub beam can be reduced. In particular, it is more preferable that the following expression (6) is satisfied, because diffracted light generated from each lattice point is completely weakened. However, n in this formula (6) is an integer.

It is more preferable to satisfy the expressions (3) and (5) at the same time because the light use efficiency is high and stray light can be reduced.
FIG. 6 shows a range in which the expressions (3) and (5) are simultaneously satisfied.
A white part is the range of angle (theta) and angle (alpha) which satisfy | fills Formula (3) and Formula (5) simultaneously.
In particular, if both the angle θ and the angle α are smaller than 30 degrees, the expression (3) and the expression (5) are satisfied at the same time, and the amount of change in the depth of the hole 106 may be small, so that the two-dimensional photonic crystal 101 It is easier to produce and is more preferable.

Further, as shown in FIG. 7A, it is more preferable that the uniform change regions 107 in which the depths of the lattice points change at a constant rate are arranged periodically.
This is because, as shown in FIG. 7B, the required depth of the hole 106 is shallower than that in the case where the depth of the lattice points is changed at a constant rate over the entire area of the two-dimensional photonic crystal 101. This is because the two-dimensional photonic crystal 101 can be easily manufactured.
The difference in the depth of the hole 106 between two adjacent uniformly changing regions is d, and the period of the uniformly changing region 107 is P.

A more desirable condition for the difference P between the period P and the depth will be described below. In FIG. 7A, the hole on the right side of the portion where the difference in depth d occurs is 130, and the hole corresponding to the hole 130 in FIG.
The main beam generated at the hole 130 is 131, the sub beam is 132, the main beam generated at the hole 140 is 141, and the sub beam is 142.
First, focusing on the main beam, it is preferable to satisfy the following expression (7).

This is because the phase difference between the main beam 131 and the main beam 141 is an integral multiple of 2π, and therefore the role of the deep hole 140 can be substituted by the shallow hole 130 for the main beam.
Next, focusing on the sub beam, it is preferable to satisfy the following expression (8). This is because the phase difference between the sub beam 132 and the sub beam 142 is an integral multiple of 2π, so that the role of the deep hole 140 can be substituted for the sub beam by the shallow hole 130.

In the present embodiment, the depth of the hole 106 is constant within each lattice point, but the depth of the hole 106 may change within the lattice point.
In particular, as shown in FIG. 8, when the depth of the hole 106 at each lattice point changes asymmetrically in the direction in which the depth of the lattice point changes asymmetrically (x direction), interference also occurs inside the lattice point. Since conditions are the same, it is preferable.
In this embodiment, the photonic crystal 101 in which the holes 106 are arranged in a lattice pattern in the host material 105 is used. However, the holes 106 are filled with another material having a refractive index different from that of the host material 105. Also good.
The host material 105 described above may be air, and the medium constituting the lattice point may be a so-called rod arrangement type two-dimensional photonic crystal made of a material having a refractive index different from that of air.
The shape of the lattice points is not necessarily circular, and may be a polygon such as a triangle or a quadrangle, or may be composed of a plurality of figures.
In the present embodiment, the direction of the periodic arrangement of the two-dimensional photonic crystal coincides with the projection direction of the light onto the two-dimensional photonic crystal 101 (x direction) and the direction perpendicular to the direction (y direction). Although the case where it does is shown in figure, of course, these do not necessarily need to correspond.
Furthermore, in the present embodiment, an example of a square lattice in which two basic translation vectors are equal in size is shown as a two-dimensional photonic crystal. However, the lattice is not necessarily a square lattice, and may be a triangular lattice or a face-centered rectangular lattice. A rectangular lattice or an oblique lattice may be used.
Moreover, the active layer in the surface emitting laser of this embodiment can use what is used for a general semiconductor laser.
For example, a multiple quantum well structure using a material such as GaAs / AlGaAs, GaInP / AlGaInP, or GaN / InGaN.
Further, the surface emitting laser according to the present embodiment can be driven by an optical excitation method or a current injection method.

[Embodiment 2]
As a second embodiment, a configuration example of a two-dimensional photonic crystal surface emitting laser having a different form from the first embodiment will be described with reference to FIGS.
In the two-dimensional photonic crystal surface emitting laser of this embodiment, the area of the hole 206 of the two-dimensional photonic crystal 201 is different from the two-dimensional photonic crystal surface emitting laser in the direction (x The point is changing along the direction.
As shown in FIG. 9, in the two-dimensional photonic crystal 201 of the present embodiment, the area of the hole 206 increases as the depth of the hole 206 decreases.
The use of the two-dimensional photonic crystal 201 has a single wavelength compared with the case of using the two-dimensional photonic crystal 101 in which the size of the hole 106 is a constant area regardless of the depth of the lattice point. It is preferable because it easily oscillates. The reason will be explained below.

The oscillation wavelength of the two-dimensional photonic crystal surface emitting laser is determined by the resonance wavelength of the two-dimensional photonic crystal 201.
In the case of a two-dimensional photonic crystal having the same structure when viewed in plan, the resonance wavelength is determined by the effective refractive index neff of the two-dimensional photonic crystal.
The larger the hole filling rate of the two-dimensional photonic crystal, the lower the effective refractive index neff of the two-dimensional photonic crystal.
As the depth of the hole 206 is shallower, the two-dimensional photonic crystal 201 having a larger area of the hole 206 has a smaller difference in hole filling rate depending on the location than the two-dimensional photonic crystal 101 having the same size of the hole 106. .
Therefore, the two-dimensional photonic crystal 201 has a smaller difference in effective refractive index neff depending on the location and a smaller difference in resonance wavelength depending on the location than the two-dimensional photonic crystal 101.
Therefore, the two-dimensional photonic crystal surface emitting laser 200 is more likely to oscillate at a single wavelength than the two-dimensional photonic crystal surface emitting laser 100.

As described above, the two-dimensional photonic crystal surface emitting laser 200 is more likely to oscillate at a single wavelength when the two-dimensional photonic crystal 201 having a large area of the hole 206 is used as the depth of the hole 206 is shallow. preferable.
Changing the depth of the hole 206 and the product of the hole 206 to be constant is more preferable because the filling rate of the holes matches and the resonance wavelength shift is eliminated.
FIG. 9 shows the case where the area of the hole changes symmetrically with respect to the x direction and the y direction along the x direction. Does not matter.
For example, as shown in FIGS. 10A and 10B, only the length of the hole in the y direction may be changed, or as shown in FIGS. 10C and 10D, the length of the hole in the x direction may be changed. Only the length may change. Further, both the lengths in the x direction and the y direction may be changed, and the ratio may be asymmetric.

[Embodiment 3]
As a third embodiment, a two-dimensional photonic crystal surface emitting laser having a different form from the above embodiments will be described with reference to FIG.
As shown in FIG. 11, the two-dimensional photonic crystal surface emitting laser 300 of this embodiment includes a detection unit 307 that detects the sub beam 304 and a control unit 308 that feeds back the detection result to the main beam 303.
By detecting the secondary beam 304 and feeding it back to the main beam, the state of the main beam is controlled in real time.
The detection means 307 may use, for example, a photodetector, and the amount to be detected includes, for example, intensity and emission wavelength. Examples of the control means 308 include a power source and a heater.
If the intensity of the sub beam 304 is detected and fed back to the power source 308 to control the injection current, the two-dimensional photonic crystal surface emitting laser 300 capable of auto power control can be provided.
If the emission wavelength of the sub beam 304 is detected and fed back to the heater 308 to control the temperature, the two-dimensional photonic crystal surface emitting laser 300 that stably oscillates at the same wavelength can be provided.

Examples of the present invention will be described below.
The following example specifically shows the structure of the two-dimensional photonic crystal surface emitting laser described in the first, second, and third embodiments.
[Example 1]
The two-dimensional photonic crystal surface emitting laser in Example 1 will be described with reference to FIGS.
As shown in FIG. 12, the two-dimensional photonic crystal surface emitting laser 400 of this example includes an n-GaN layer 402, an n-AlGaN cladding layer 403, an n-GaN guide layer 404, an active layer 405 on a GaN substrate 401. Are sequentially stacked.
Further, on the active layer 405, a ud-GaN guide layer 406, a p-AlGaN electron blocking layer 407, a p-GaN layer 408, a p-AlGaN cladding layer 409, and a p ⁺ -GaN layer 410 are sequentially stacked.
A two-dimensional photonic crystal 411 is embedded in the p-GaN layer 408. The two-dimensional photonic crystal 411 is designed to oscillate at a wavelength λ of 405 nm.
The two-dimensional photonic crystal 411 is formed by arranging circular holes 412 two-dimensionally in the p-GaN layer 408.
The lattice structure is a rectangular lattice, the lattice constant in the x direction is 138 nm, and the lattice constant in the y direction is 165 nm.
In addition, uniform change regions 413 in which the depth of the circular hole 412 decreases at a constant rate along the + x direction and the size of the circular hole 412 increases along the + x direction are arranged every period P.
As shown in FIG. 12, the depth and area of the circular hole are changed so that the product of the depth of the circular hole and the area of the circular hole is constant.
In the uniform change region 413, the angle α between the line connecting the bottoms of the circular holes 412 and the x axis is 15 degrees.
Further, the difference in the depth of the circular hole 412 between adjacent uniform change regions is d.

The band structure of the two-dimensional photonic crystal 411 is shown in FIG.
FIG. 13 shows a band structure of only a mode having a wave number in the x direction.
Reflecting that the lengths of the two basic translation vectors extending in different directions of the two-dimensional photonic crystal 411 are different, the resonance mode 420 having a wave number in the direction (x direction) of the relatively short basic translation vector. Oscillates and a tilted beam is emitted.
Of the tilted beams, a beam that is tilted and emitted toward the −x side is a main beam 421, and a beam that is tilted and emitted to the + x side is a sub beam 422. The angle θ formed by the normal of the tilted beam and the two-dimensional photonic crystal is 15 degrees.
When both the angle θ and the angle α are 15 degrees, the equations (4) and (6) are satisfied at the same time. Therefore, in the uniform change region 413, the main beam 421 is completely strengthened and the sub beam 422 is completely weakened. Yes.
That is, it is possible to provide a two-dimensional photonic crystal surface emitting laser that has high light utilization efficiency and can prevent stray light from being generated. Further, since both the angle θ and the angle α are smaller than 30 degrees, the manufacturing is easy.

Next, the difference d between the period P and the depth will be described.
When the period P is 4 and the depth difference d is 103 nm as shown in FIG. 12A, the main beam 421 is completely strengthened across a plurality of uniform change regions 413 to satisfy the equation (7). Yes.
Further, as shown in FIG. 12B, when the period P is 2 and the depth difference d is 108 nm, the sub beam 422 is completely spread over a plurality of uniform change regions 413 to satisfy the equation (8). We are weakened by.
In either case, the role of a deep hole can be substituted by a shallow hole.
Further, since the product of the depth of the circular hole 412 and the area of the circular hole 412 is constant, the filling rate of the circular hole 412 is equal depending on the place.
Therefore, a two-dimensional photonic crystal surface emitting laser that can easily oscillate at a single wavelength can be provided.

The two-dimensional photonic crystal 411 was formed by being embedded in the p-GaN layer using patterning using electron beam lithography and dry etching, and a re-growth technique.
In order to control the depth of the circular hole 412, each circular hole may be dry-etched one by one using masks 430 and 431 as shown in FIG.
Further, as shown in FIG. 15, dry etching may be performed collectively using a mask 432 and a sacrificial layer 433 having different thicknesses in the x direction.
The active layer 405 is composed of three periods of In _0.08 Ga _0.92 N / In _0.01 Ga _0.99 N multiple quantum wells.
A p-electrode 414 made of Ni and Au is arranged on the p-GaN side of the laser structure, and an n-electrode 415 made of Ti and Al is arranged on the n-GaN side, from which current is injected. As a result, laser oscillation occurs.

As described above, in the two-dimensional photonic crystal surface emitting laser according to the present embodiment, the depth of the hole 412 is along the projection direction of the inclined beams 421 and 422 to the two-dimensional photonic crystal. It changes asymmetrically.
Therefore, it can control so that the intensity ratios of the inclined beams 421 and 422 are different. In the present embodiment, the case where the two-dimensional photonic crystal 411 is a rectangular lattice is shown, but the present invention can be applied if the two basic translation vectors have different sizes. That is, the two-dimensional photonic crystal 411 may be an orthorhombic lattice.

[Example 2]
A two-dimensional photonic crystal surface emitting laser in Example 2 will be described with reference to FIG.
The two-dimensional photonic crystal surface emitting laser 500 in this embodiment differs from the two-dimensional photonic crystal surface emitting laser 400 shown in FIG. 14 in the first embodiment only in the structure of the two-dimensional photonic crystal.
As shown in FIG. 16, the two-dimensional photonic crystal 511 in this embodiment has a structure in which a first two-dimensional photonic crystal 551 and a second two-dimensional photonic crystal 552 overlap.
Both the two-dimensional photonic crystal 551 and the two-dimensional photonic crystal 552 have a structure in which circular holes are two-dimensionally arranged, and the radius of the circle is 32 nm.
The two-dimensional photonic crystal 551 has a square lattice and a lattice constant of 160 nm. The two-dimensional photonic crystal 552 has a rectangular lattice with a lattice constant in the x direction of 192 nm and a lattice constant in the y direction of 160 nm.
That is, two photonic crystals having different lattice constants in the x direction are arranged so as to overlap each other.
In the two-dimensional photonic crystal in this embodiment, standing waves having different wave numbers in the x direction are formed in the two-dimensional photonic crystals 551 and 552, and these two lights are superimposed.
Therefore, a resonance mode having a wave number in the direction (x direction) in which the length of the basic translation vector is different oscillates, and the tilted beam 521 and the tilted beam 522 are emitted. The resonance wavelength λ of the resonance mode is 405 nm.
The angle formed between the tilted beams 521 and 522 and the normal line of the two-dimensional photonic crystal 511 is determined by the wave number in the x direction of the resonance mode, and is 15 degrees in this embodiment.
The depth of the circular hole 512 of the photonic crystal 511 changes asymmetrically along the direction of projection of the inclined beams 521 and 522 onto the two-dimensional photonic crystal (x direction).
Therefore, as in the case of the first embodiment, the intensity ratio between the inclined beam 521 and the inclined beam 522 can be controlled to be different.

In the configuration of this embodiment shown in FIG. 16, the two-dimensional photonic crystal 551 and the two-dimensional photonic crystal 552 are completely overlapped, but the two-dimensional photonic crystal 551 and the two-dimensional photonic crystal 552 are It suffices if they overlap in plan view (viewed from the z direction).
In this case, the depth of at least one of the two-dimensional photonic crystal 551 and the two-dimensional photonic crystal 552 may be changed.
In the configuration of this embodiment shown in FIG. 16, an example in which the photonic crystal 551 is a square lattice and the photonic crystal 552 is a rectangular lattice is shown. However, at least one basic of two photonic crystals is shown. The present invention can be applied if the magnitudes of the translation vectors are different.
For example, both the photonic crystal 551 and the photonic crystal 552 may have a rectangular lattice, or an oblique lattice.

[Example 3]
The two-dimensional photonic crystal surface emitting laser in Example 3 will be described with reference to FIG.
The two-dimensional photonic crystal surface emitting laser in this example differs from the two-dimensional photonic crystal surface emitting laser 400 shown in FIG. 14 only in the structure of the two-dimensional photonic crystal.
The two-dimensional photonic crystal in this example is a square lattice in which circular holes having a radius of 41 nm are two-dimensionally arranged, and the lattice constant is 206 nm.
The two-dimensional photonic crystal of this example has a band structure shown in FIG.
In this embodiment, a resonance mode in the Γ-X direction is used. Since the resonance mode is a resonance mode having a wave number in the in-plane direction, two inclined beams inclined in the x direction can be obtained.
The oscillation wavelength of the resonance mode is 405 nm, and the angle formed by the two inclined beams and the normal line of the two-dimensional photonic crystal is 21 degrees.
The depth of the circular hole of the photonic crystal changes asymmetrically along the direction of projection of the two inclined beams onto the two-dimensional photonic crystal.
Therefore, as in the case of the first embodiment, it is possible to control the intensity ratio of one of the two inclined beams and the other inclined beam to be different.
In this embodiment, the resonance mode in the Γ-X direction is used. However, the present invention can be applied as long as the oscillation is in the resonance mode having a wave number in the in-plane direction.
Although the emission direction varies depending on the resonance mode, the depth of the hole may be changed asymmetrically along the projection direction of the emission direction of the inclined beam onto the two-dimensional photonic crystal.

Although each embodiment has been described above, the surface emitting laser of the present invention is not limited to the configuration of each embodiment described above.
The shape and material of the photonic crystal, the material constituting the active layer, the clad layer, and the electrode can be appropriately changed within the scope of the present invention.
In the above embodiment, a laser oscillation wavelength of 405 nm is shown, but operation at an arbitrary wavelength is possible by selecting an appropriate material and structure.
A plurality of surface emitting lasers of the present invention may be arranged on the same plane and used as an array light source.

101: Two-dimensional photonic crystal 102: Normal line of two-dimensional photonic crystal 103: Main beam 104: Sub beam 105: Medium by host material 106: Hole α: Change in which the depth of the hole changes at a constant rate The angle formed by the line connecting the bottoms of these holes in the region and the projection direction (x direction) θ: the laser beam emitted in a direction symmetrical to the normal line of the laser beam emission surface and the normal line Angle with the exit direction of

Claims (16)

Has a 2-dimensional photonic crystal having a resonant mode in the plane direction, in at least two directions are line symmetrical oblique direction with respect to the normal line of the exit surface of the laser light, it shines that surface emission exits the laser beam A laser,
The two-dimensional photonic crystal is
The depth of the medium constituting the lattice points of the two-dimensional photonic crystal along the direction perpendicular to the projection direction of the laser beam emitted in the two directions projected onto the laser beam emission surface. Or the height is constant,
The depth or height of the medium constituting the lattice point of the two-dimensional photonic crystal changes asymmetrically with respect to an arbitrary surface having a direction parallel to the projection direction as a normal along the projection direction ,
A change region in which the depth or height of the medium constituting the lattice points changes at a constant rate along the projection direction;
The angle formed by the projection direction and the line connecting the depth region or the height region in the change region is α, and the direction normal to the laser beam emission surface and the normal line The angle α and the angle θ are configured to satisfy at least one of the following formula 3 and formula 5 where θ is an angle formed with the emission direction of the laser beam emitted to be that the surface-emitting laser with.

The surface emitting laser according to claim 1, wherein the two-dimensional photonic crystal has two basic translation vectors having different lengths extending in different directions. 3. The surface emitting laser according to claim 2, wherein the projection direction coincides with a direction of a basic translation vector having a relatively short length among the basic translation vectors having different lengths. The two-dimensional photonic crystal comprises two two-dimensional photonic crystals having different lengths of at least one basic translation vector,
The two two-dimensional photonic crystals are arranged so as to overlap each other in plan view so that directions of the basic translation vectors having different lengths coincide with each other. The surface emitting laser according to item. 5. The surface emitting laser according to claim 4, wherein the projection direction coincides with directions of basic translation vectors having different lengths. The surface emitting laser according to any one of claims 1 to 5, characterized in that meet both the above formula 5 in the formula 3. The surface emitting laser according to any one of claims 1 to 6 , wherein both the angle α and the angle θ are smaller than 30 degrees. The two-dimensional photonic crystal surface emitting laser according to any one of claims 1 to 7, wherein a plurality of the change area that periodically aligned along the projection directions. Among the plurality of change regions arranged periodically along the projection direction, a difference in depth or height constituting the lattice point between two adjacent change regions is d,
When the period of the plurality of change regions arranged periodically is P,
The surface emitting laser according to claim 8 , wherein the following expression is satisfied.

Among the plurality of change regions arranged periodically along the projection direction, a difference in depth or height constituting the lattice point between two adjacent change regions is d,
When the period of the plurality of change regions arranged periodically is P,
The surface emitting laser according to claim 8 , wherein the following expression is satisfied.

The two-dimensional photonic crystal, the more shallow the depth or height of the medium constituting the grid points, any one of claims 1 to 10, characterized in that the area of the lattice point is increased A surface emitting laser according to claim 1. 12. The surface emitting laser according to claim 11 , wherein the product of the depth or height of the medium constituting the lattice points and the area of the lattice points is constant. A detecting means for detecting a sub-beam which is a relatively weak light of the laser light emitted in the two directions, and a control means for feeding back a detection result by the detecting means,
The surface emitting laser according to any one of claims 1 to 12 , wherein a state of a main beam which is light having a relatively strong intensity is controlled based on the detection result. 14. The surface emitting laser according to claim 13 , wherein the light intensity of the main beam is controlled by detecting the intensity of the sub beam by the detecting means and controlling the injection current by the control means. The surface emitting laser according to claim 13 or 14 , wherein the wavelength of the main beam is controlled by detecting the wavelength of the sub-beam by the detecting means and controlling the temperature by the control means. . An array light source in which a plurality of surface emitting devices according to any one of claims 1 to 15 are arranged.

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