JP2006210429A - Surface emitting semiconductor laser - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a surface emitting semiconductor laser which can be easily manufactured and can suppress high order transverse mode oscillation without reducing optical output of a basic transverse mode. <P>SOLUTION: A lower DBR mirror layer 11 and an upper DBR mirror layer 15 are provided with an active layer 13 sandwiched, and a laser beam is emitted in a vertical direction through the layer 15. A laminate structure of a first insulating film 17 and a second insulating film 18 is provided on the center region of light emitting regions of the surface of the layer 15, and a third insulating region 19 is provided on a region (peripheral region) surrounding the center region, and the reflectivity of the peripheral region is lower than the reflectivity of the center region. Thus, the high order transverse oscillation can be suppressed without reducing the optical output of the basic transverse mode. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a surface emitting semiconductor laser having a laser light emitting region on its upper surface, and more particularly to a surface emitting semiconductor laser that can be suitably applied to applications requiring a low-order transverse mode light output.

  Unlike the conventional Fabry-Perot resonator type, the surface-emitting semiconductor laser emits light in a direction perpendicular to the substrate, and a large number of elements are arranged in a two-dimensional array on the same substrate. In recent years, it has attracted attention in the data communication field.

  Conventionally, this type of surface-emitting type semiconductor laser has a pair of multilayer reflectors formed on a semiconductor substrate, and has an active layer serving as a light emitting region between the pair of multilayer reflectors. One multilayer reflector is provided with a current confinement layer having a structure in which the current injection region is narrowed in order to increase the current injection efficiency into the active layer and reduce the threshold current. In addition, an n-side electrode is provided on the lower surface side, and a p-side electrode is provided on the upper surface side, and an opening is provided in the p-side electrode for emitting laser light. In this surface emitting semiconductor laser, the current is constricted by the current confinement layer and then injected into the active layer, where it emits light, and this is reflected by the pair of multilayer reflectors, and is reflected as laser light in the opening of the p-side electrode. It is emitted from.

  By the way, in the surface emitting semiconductor laser described above, it is known that fundamental transverse mode oscillation mainly occurs in the central region of the laser light emission region, while high-order transverse mode oscillation mainly occurs in the peripheral region. Many techniques relating to the control of transverse mode oscillation utilizing this property have been reported.

  For example, Patent Document 1 discloses a technique in which a loss determining element is provided with respect to an emission region of a laser beam, starting from a central portion of the region, and a reflection loss gradually increasing as the distance from the origin is increased. Yes. Patent Document 2 discloses a technique in which a second adjustment layer and a first adjustment layer for reducing the reflectance of a peripheral region surrounding a laser light emission region are provided on the light emission surface in this order.

JP-A-10-56233 JP 2000-22271 A

  However, the technique described in Patent Document 1 is not practical because the surface of the loss determining element needs to be a specific curved surface, and it is not easy to manufacture such a curved surface. Further, in the technique described in Patent Document 2, the second adjustment layer is placed on the low refractive index layer having a large aluminum (Al) composition in the multilayer reflector in order to reduce the reflectance of the region other than the laser light emitting region. And a high refractive index layer having an Al composition smaller than that of the low refractive index layer. However, it is very difficult to selectively etch the second adjustment layer to expose the low refractive index layer. Further, even if the second adjustment layer can be selectively etched, the low refractive index layer with a large Al composition is easily oxidized, and in order to prevent a change in the refractive index due to oxidation, an oxide layer or It is necessary to provide a high refractive index layer with a small Al composition. However, when such a layer is provided on the surface, the reflectance of the laser light emission region is lowered, and thus there is a problem that the light output in the fundamental transverse mode is lowered.

  The present invention has been made in view of such problems, and an object thereof is to easily manufacture a light adjustment layer and to suppress higher-order transverse mode oscillation without reducing the light output of the fundamental transverse mode. An object of the present invention is to provide a surface-emitting type semiconductor laser that can be used.

  The surface emitting semiconductor laser according to the present invention includes an active layer having a light emission center region, a pair of multilayer reflectors having a light emission region on one side, and a light emission region corresponding to the light emission region. An electrode having an opening and a light emitting region are provided so as to correspond to the light emitting region, and the reflectance of the peripheral region surrounding the central region corresponding to the light emitting central region is lower than that of the central region. And an insulating film formed.

  In the surface emitting semiconductor laser of the present invention, the reflectance of the peripheral region surrounding the central region in the light emitting region is relatively lower than that of the central region. Here, in the light emission region, the central region mainly corresponds to a region in which fundamental transverse mode oscillation occurs (light emission central region), and the peripheral region surrounding the central region corresponds to a region in which high-order transverse mode oscillation mainly occurs. . It is preferable that the difference in reflectance between the central region and the periphery is large. The insulating film is made of a high resistance material such as oxide or nitride, and may include a plurality of layers made of different materials. Note that a contact layer or the like may be interposed between the electrode and the multilayer reflector on the emission side.

  According to the surface emitting semiconductor laser of the present invention, the reflectance of the peripheral region surrounding the central region of the insulating film provided in the light emitting region is relatively lower than that of the central region. Higher-order transverse mode oscillation can be suppressed without reducing the optical output of. Moreover, the light adjustment layer by this insulating film can be manufactured easily.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

[First Embodiment]
FIG. 1 shows a cross-sectional structure of a surface emitting semiconductor laser 1 according to an embodiment of the present invention. 2A and 2B show the structure near the opening 23 of the surface-emitting type semiconductor laser 1 and the reflectance distribution in the opening 23. FIG.

  The surface-emitting type semiconductor laser 1 includes a lower DBR mirror layer 11 (a multilayer reflector having no light emission region), a lower cladding layer 12, an active layer 13, an upper cladding layer 14, and an upper DBR on one surface side of a substrate 10. A laser structure portion in which a mirror layer 15 (multilayer film reflecting mirror having a light emitting region) and a p-side contact layer 16 are stacked in this order is provided. Here, a part of the lower cladding layer 12, the active layer 13, the upper cladding layer 14, the upper DBR mirror layer 15 and the p-side contact layer 16 are formed up to the p-side contact layer 16, and then selectively etched from the upper surface. Thus, a convex mesa post 30 is formed.

  A first insulating film 17, a second insulating film 18, a third insulating film 19, a protective film 20, and a p-side electrode 21 (electrode) are stacked on an upper portion or a peripheral portion of the mesa post 30. An n-side electrode 24 is formed on the back surface of the substrate 10.

  The substrate 10, the lower DBR mirror layer 11, the lower cladding layer 12, the active layer 13, the upper cladding layer 14, the upper DBR mirror layer 15 and the p-side contact layer 16 are each composed of, for example, a GaAs (gallium arsenide) based compound semiconductor. Has been. The GaAs compound semiconductor is a compound semiconductor containing at least gallium (Ga) among the 3B group elements in the short periodic table and at least arsenic (As) among the 5B elements in the short periodic table. Say.

The substrate 10 is made of, for example, n-type GaAs. The lower DBR mirror layer 11 is formed by stacking m sets of low refractive index layers 11Ai and high refractive index layers 11Bi (1 ≦ i ≦ m, where m is an integer of 1 or more). is there. The low refractive index layer 11Ai is, for example, an n-type Al _x1 Ga _1-x1 As (0 <x1 <1) having a thickness of λ / 4n ₄ (where λ is an oscillation wavelength and n ₄ is a refractive index), and a high refractive index layer 11Bi. Are formed of n-type Al _x2 Ga _{1 -x2} As (0 <x2 <x1) having a thickness of λ / 4n ₅ (n ₅ is a refractive index), for example. Examples of the n-type impurity include silicon (Si) and selenium (Se).

The lower cladding layer 12 is made of, for example, Al _x3 Ga _1-x3 As (0 <x3 <1). The active layer 13 is made of, for example, a GaAs material. In the active layer 13, a region facing a later-described current injection region 15C-1 is a light emitting region, and a central region (light emitting center region 13A) of the light emitting region is a region in which fundamental transverse mode oscillation mainly occurs. Of the regions, the region surrounding the light emission center region 13A is a region where high-order transverse mode oscillation mainly occurs. The upper cladding layer 14 is made of, for example, Al _x4 Ga _{1 -x4} As (0 <x4 <1). The lower cladding layer 12, the active layer 13, and the upper cladding layer 14 are preferably undoped, but may contain p-type or n-type impurities.

The upper DBR mirror layer 15 is configured by laminating a low refractive index layer 15Aj and a high refractive index layer 15Bj (1 ≦ j ≦ n, where n is an integer of 1 or more) as a set, and n sets thereof. is there. The low refractive index layer 15Aj is, for example, a p-type Al _x5 Ga _1-x5 As (0 <x5 <1) having a thickness of λ / 4n ₆ (λ is an oscillation wavelength and n ₆ is a refractive index), and a high refractive index layer. For example, 15Bj is formed of p-type Al _x6 Ga _1-x6 As (0 <x6 <x5) having a thickness of λ / 4n ₇ (n ₇ is a refractive index). Examples of the p-type impurity include zinc (Zn), magnesium (Mg), and beryllium (Be).

However, in the upper DBR mirror layer 15, a current confinement layer 15 </ b> C is formed instead of the low refractive index layer 15 </ b> Bj in a portion of the low refractive index layer 15 </ b> Bj that is j sets apart from the active layer 13 side. In the current confinement layer 15C, the central region is the current injection region 15C-1, and the peripheral region surrounding the current injection region 15C-1 is the current confinement region 15C-2. The current injection region 15C-1 is made of, for example, Al _x7 Ga _1-x7 As (x5 <x7 ≦ 1), and the current confinement region 15C-2 is made of Al ₂ O obtained by oxidizing it. ₃ (aluminum oxide).

  The p-side contact layer 16 is made of, for example, p-type GaAs, and has, for example, a circular opening in a region facing the current injection region 15C-1. The upper DBR mirror layer 15 is exposed at the bottom of the opening.

  The p-side electrode 21 is formed by laminating, for example, a titanium (Ti) layer, a platinum (Pt) layer, and a gold (Au) layer in this order, and is electrically connected to the p-side contact layer 16. . In addition, the p-side electrode 21 is provided with an opening to be a laser light emission region 22 in a region corresponding to the opening of the p-side contact layer 16, and when viewed from the optical axis direction of the laser light, It seems that one opening 23 formed by the openings of the p-side contact layer 16 and the p-side electrode 21 is provided on the top of the mesa post 30. However, the openings of the p-side contact layer 16 and the p-side electrode 21 do not have to have the same inner diameter, and the inner diameter of the opening of the p-side electrode 21 is larger than that of the p-side contact layer 16. Also good. Of the opening 23, the central region 23A mainly corresponds to a region where basic transverse mode oscillation occurs, and the region surrounding the central region 23A (peripheral region 23B) mainly corresponds to a region where higher order transverse mode oscillation occurs. . Further, a portion of the p-side electrode 21 formed on the peripheral substrate of the mesa post 30 has a flat plate shape having a sufficient surface area for wire bonding.

The first insulating film 17 is formed in the central region 23A of the opening 23, that is, mainly in a region where fundamental transverse mode oscillation occurs. Specifically, the film thickness is (2a-1) λ / 4n ₁ ( a is an integer of 1 or more, n ₁ is a refractive index), and the refractive index n ₁ is composed of a material, for example, an oxide, lower than the refractive index n _{7 of} the high refractive index layer 15Bn provided on the surface of the upper DBR mirror layer 15. Has been. Examples of the oxide include SiO ₂ (silicon oxide). The width W ₁ of the first insulating film 17 is as follows when the inner diameter of the opening 23 is A ₁ (the inner diameter A ₁ mainly indicates the inner diameter of the opening of the p-side electrode 21 in the opening 23). It is preferable that it is the range which satisfy | fills Formula (1).

_{A 1/3 ≦ W 1 ≦} 2A 1/3 ... Formula (1)

A second insulating film 18 is formed on the first insulating film 17. Specifically, the second insulating film 18 has a thickness of (2b-1) λ / 4n ₂ (b is an integer of 1 or more, n ₂ is a refractive index), and the refractive index n ₂ is the first insulating film 17. It is composed of a lower material such as nitride. A third insulating film 19 is formed in the peripheral region 23B of the opening 23, that is, a region where high-order transverse mode oscillation mainly occurs. Specifically, the third insulating film 19 has a thickness of (2c-1) λ / 4n ₃ (where c is an integer of 1 or more and n ₃ is a refractive index) and a refractive index n ₃ is the first insulating film 17. It is made of a lower material, for example, a nitride such as SiN (silicon nitride).

The reflectance of the central region 23A of the opening 23, that is, the laminated structure of the first insulating film 17 and the second insulating film 18, is R ₁ , and the reflectance of the peripheral region 23B of the opening 23, that is, the third insulating film 19 is defined. When the reflectance of the opening 23 when these insulating films are not provided in R ₂ and the opening 23 is R ₃ , the respective refractive indexes can be adjusted so as to satisfy the relationship of the following formula (2). preferable.

R ₁ ≧ R ₃ > R ₂ Formula (2)

For example, when the refractive index of the first insulating film 17 is 1.6 and the refractive indexes of the second insulating film 18 and the third insulating film 19 are 2.0, the reflectance R ₁ in the central region 23A is 99.6%. The reflectance R ₂ in the peripheral region 23B is 97.2%. R3 is generally 99.5%. Thus, even when the reflectivity is reduced by a slight difference, the gain in the peripheral region 23B is lowered, so that only high-order transverse mode oscillation is suppressed without reducing the light output of the fundamental transverse mode. Is possible.

  Further, the second insulating film 18 and the third insulating film 19 may be made of the same film thickness and material. This is because the manufacturing process can be simplified as will be described later.

  Next, the protective film 20 is made of, for example, oxide or nitride, and is formed so as to cover the peripheral portion of the p-side contact layer 16 to the side surface of the mesa post 30 and the vicinity thereof.

  The n-side electrode 24 has, for example, a structure in which an alloy layer of gold (Au) and germanium (Ge), a nickel (Ni) layer, and a gold (Au) layer are sequentially stacked from the substrate 10 side. It is electrically connected to the substrate 10.

  The surface emitting semiconductor laser 1 according to the present embodiment can be manufactured, for example, as follows.

3A to 3B and FIGS. 4A to 4B show the manufacturing method in the order of steps. Here, the compound semiconductor layer on the substrate 10 made of GaAs is formed by, for example, MOCVD (Metal Organic Chemical Vapor Deposition). At this time, for example, trimethylaluminum (TMA), trimethylgallium (TMG), trimethylindium (TMIn), or arsine (AsH ₃ ) is used as a raw material for the III-V group compound semiconductor. , H ₂ Se, and dimethyl zinc (DMZ), for example, is used as the acceptor impurity material.

  First, as shown in FIG. 3A, a lower DBR mirror layer 11, a lower cladding layer 12, an active layer 13, an upper cladding layer 14, an upper DBR mirror layer 15 and a p-side contact layer 16 are formed on a substrate 10. Laminate in this order.

  Next, as shown in FIG. 3B, for example, a mask layer (not shown) is formed on the p-side contact layer 16, and the reactive ion etching (RIE) method is used to form the p layer. The side contact layer 16, the upper DBR mirror layer 15, the upper cladding layer 14, the active layer 13, and the lower cladding layer 12 are selectively removed and part of the p-side contact layer 16 is etched to form openings. Form.

  Next, as shown in FIG. 4A, oxidation treatment is performed at a high temperature in a steam atmosphere to selectively oxidize Al in the AlAs layer 15D from the outside of the mesa post 30. Thereby, the peripheral region of the AlAs layer 15D becomes an insulating film (aluminum oxide). That is, the current confinement layer 15C is formed in which the peripheral region is the current confinement region 15C-2 and only the central region is the current injection region 15C-1.

  Next, the insulating material is deposited on the mesa post 30 and the peripheral substrate of the mesa post 30 by, for example, a CVD (Chemical Vapor Deposition) method. Thereafter, as shown in FIG. 4B, a region other than the portion corresponding to the central region of the opening of the p-side contact layer 16 in the insulating material is selectively removed by etching. As a result, the first insulating film 17 is formed in the central region 23 </ b> A of the opening 23. Subsequently, after the second insulating film 18 is formed on the first insulating film 17 using the same method as described above, the third insulating film 19 is formed in a region (peripheral region 23B) other than the central region 23A of the opening 23. Form. Subsequently, the protective film 20 is formed on the side surface of the mesa post 30 and the peripheral substrate. Since the insulating material as described above has excellent selectivity with respect to the semiconductor material such as the upper DBR mirror layer 15 and does not need to have a complicated shape, the first insulating film 17 can be easily formed by etching. Can be formed.

  In the case where the second insulating film 18, the third insulating film 19 and the protective film 20 are made of the same film thickness and material, these layers may be formed simultaneously. In this case, after depositing an insulating material on the mesa post 30 and the peripheral substrate of the mesa post 30 by, for example, a CVD method, a region other than the portion corresponding to the p-side contact layer 16 is selectively removed by etching. As a result, the second insulating film 18 is formed in the central region 23A of the opening 23, the third insulating film 19 is formed in a region other than the central region 23A of the opening 23 (peripheral region 23B), the side surface of the mesa post 30 and the peripheral substrate. A protective film 20 is formed on each. In this way, the manufacturing process can be simplified by forming these layers simultaneously.

  Next, as shown in FIG. 1, after laminating the above metal material on the mesa post 30 and the peripheral substrate of the mesa post 30 by, for example, vacuum deposition, the second insulating film 18 and the second insulating film 18 are formed by, for example, selective etching. 3 The insulating film 19 is exposed to form an opening, and a wire bonding pad is formed on the peripheral substrate of the mesa post 30. In this way, the p-side electrode 21 is formed, and the opening 23 is formed in the upper part of the mesa post 30.

  Next, the back surface of the substrate 11 is appropriately polished to adjust its thickness, and then the n-side electrode 24 is formed on the back surface of the substrate 11. In this way, the surface emitting semiconductor laser 1 is manufactured.

  In the surface emitting semiconductor laser 1 having such a configuration, when a predetermined voltage is applied between the n-side electrode 24 and the p-side electrode 21, the active layer 13 is passed through the current injection region 15C-1 in the current confinement layer 15C. An electric current is injected into this, and light is emitted by recombination of electrons and holes. This light is reflected by the pair of the lower DBR mirror layer 11 and the upper DBR mirror layer 15 and causes laser oscillation at a wavelength at which the phase change when it reciprocates once in the element is an integral multiple of 2π. Is emitted.

By the way, in the surface emitting semiconductor laser 1 described above, the light output in the fundamental transverse mode generally has the largest value at the center portion of the opening 23 and tends to decrease as the distance from the center portion of the opening 23 increases. For this reason, when the surface emitting semiconductor laser 1 is used for high-power applications, it is preferable to increase the inner diameter A ₁ of the opening 23 so that as much of the fundamental transverse mode laser light as possible can be extracted. However, the light output in the high-order transverse mode generally has the largest value in a region away from the central portion of the opening 23 by a predetermined distance, and tends to decrease toward the central portion of the opening 23. If the inner diameter A ₁ of the head 23 is made too large, even the higher-order transverse mode laser light may be output at a high output.

For this reason, in the conventional surface-emitting type semiconductor laser, measures such as reducing the inner diameter A ₁ of the opening 23 or providing a structure having a complicated shape in the opening 23 are used. The emission of light was suppressed. Even when the surface-emitting type semiconductor laser 1 is used for low-power applications, it is necessary to take the same measures as described above in order to eliminate as much as possible the high-order transverse mode laser light.

  On the other hand, in the present embodiment, the first insulating film 17 and the second insulating film 18 are stacked in this order on the central region 23A of the opening 23, and the third insulating film 19 is provided on the opening 23. It is provided in a region (peripheral region 23B) other than the central region 23A. As a result, as shown in FIG. 2B, the reflectance of the region (peripheral region 23 </ b> B) other than the central region 23 </ b> A of the opening 23 is lower than that of the central region 23 </ b> A of the opening 23.

  At this time, as described above, by adjusting the respective refractive indexes so as to satisfy the relationship of Expression (2), it is possible to suppress only the higher-order transverse mode oscillation without reducing the light output of the fundamental transverse mode. It becomes possible.

  In the present embodiment, as described above, it is very easy to selectively etch the first insulating film 17, and the first insulating film 17, the second insulating film 18, and the third insulating film 19. Therefore, the surface emitting semiconductor laser 1 can be easily manufactured.

[Second Embodiment]
Next, a second embodiment of the present invention will be described. In this example, the description of the configuration, operation, manufacturing method, and effects common to those of the surface-emitting type semiconductor laser 1 of the first embodiment will be omitted as appropriate.

  5A and 5B show the structure in the vicinity of the opening 23 of the surface-emitting type semiconductor laser 2 according to the present embodiment and the distribution state of the reflectance in the opening 23. FIG. In the surface-emitting type semiconductor laser 2, only the reflectance of the region (peripheral region 23 </ b> B) other than the central region 23 </ b> A of the opening 23 is opened by the fourth insulating film 27 made of a single layer provided in the opening 23. It differs from the surface emitting semiconductor laser 1 according to the first embodiment in that it is lower than the central region 23A of the portion 23. Hereinafter, the fourth insulating film 27 will be described.

As shown in FIG. 5A, the fourth insulating film 27 is provided on the surface of the upper DBR mirror layer 15 that is exposed at the bottom of the opening 23. The film thickness of the central region 23A of the opening 23 in the fourth insulating film 27 is dλ / 2n ₅ (d is an integer of 1 or more, λ is the emission wavelength, and n ₅ is the refractive index). The film thickness of the area other than the central area 23A (the peripheral area 23B) is (2e-1) λ / 4n ₅ (e is an integer of 1 or more). The refractive index n ₅ of the fourth insulating film 27 is made of a material lower than the surface of the upper DBR mirror layer 15, for example, an oxide or a nitride. Examples of the oxide include SiO ₂ , and examples of the nitride include SiN. The width W ₂ of the fourth insulating film 27 is as follows when the inner diameter of the opening 23 is A ₂ (the inner diameter A ₂ mainly indicates the inner diameter of the opening of the p-side electrode 21 in the opening 23). It is preferable that it is the range which satisfy | fills Formula (3).

_{A 2/3 ≦ W 2 ≦} 2A 2/3 ... Equation (3)

The reflectance of the central region 23A of the opening 23 is R ₁ , the reflectance of the region other than the central region 23A of the opening 23 (peripheral region 23B) is R ₂ , and the insulating film is not provided in the opening 23. When the reflectance is R ₃ , it is preferable to adjust the refractive index so as to satisfy the relationship of the following formula (4). By adopting such a reflectance distribution, higher-order transverse mode oscillation can be suppressed without reducing the light output of the fundamental transverse mode.

R ₁ ≧ R ₃ > R ₂ Formula (4)

For example, when the refractive index of the fourth insulating film 27 is 2.0, the reflectance R ₁ at the central region 23A of the opening 23 is 99.2%, and the region other than the central region 23A of the opening 23 (the peripheral region 23B). ) reflectance R ₂ in becomes 97.2%. As described above, even when a slight difference in reflectance is provided, only high-order transverse mode oscillation is performed without reducing the light output in the fundamental transverse mode, as in the case of the first embodiment. Can be suppressed.

  The fourth insulating film 27 can be manufactured, for example, as follows. The insulating material is deposited on the mesa post 30 and the peripheral substrate of the mesa post 30 by, for example, a CVD method. After that, as shown in FIG. 5B, the insulating material is selectively removed from the insulating material other than the portion corresponding to the opening of the p-side contact layer 16, and the opening of the p-side contact layer 16 is removed. A region other than the central region (peripheral region) is shaved to a predetermined thickness, and a fourth insulating film 27 is formed. Since the insulating film has excellent selectivity with respect to the semiconductor material such as the upper DBR mirror layer 15 and does not need to have a more complicated shape, the fourth insulating film 27 is easily formed by etching. be able to.

  The present invention has been described with reference to the embodiment. However, the present invention is not limited to the above embodiment, and various modifications can be made.

  For example, in the above embodiment, the light adjustment layer is configured by the first insulating film 17 to the third insulating film 19 or the fourth insulating film 27. However, the light adjustment layer may have other configurations. In short, what is necessary is that the configuration is such that the reflectance of the peripheral region is relatively low with respect to the central region in the light emitting region.

1 is a cross-sectional configuration diagram of a surface emitting semiconductor laser according to a first embodiment of the present invention. It is a figure showing the principal part of the laser of FIG. 1 with the distribution of reflectance. It is sectional drawing for demonstrating the manufacturing process of the laser shown in FIG. It is sectional drawing for demonstrating the process following FIG. It is a figure showing the principal part of the surface emitting semiconductor laser which concerns on the 2nd Embodiment of this invention with distribution of reflectance.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1, 2 ... Surface emitting semiconductor laser, 10 ... Substrate, 11 ... Lower DBR mirror layer, 11Ai, 15Aj ... Low refractive index layer, 11Bi, 15Bj ... High refractive index layer, 12 ... Lower clad layer, 13 ... Active layer, 13A ... emission center region, 14 ... upper cladding layer, 15 ... upper DBR mirror layer, 15C ... current confinement layer, 15C-1 ... current injection region, 15C-2 ... current confinement region, 15D ... AlAs layer, 16 ... p side Contact layer, 17 ... first insulating film, 18 ... second insulating film, 19 ... third insulating film, 20 ... protective film, 21 ... p-side electrode, 22 ... light emitting region, 23 ... opening, 23A ... central region , 23B ... peripheral region, 24 ... n-side electrode, 27 ... fourth insulating film, 30 ... mesa post

Claims (9)

An active layer having an emission center region;
A pair of multilayer reflectors provided with the active layer in between and having a light output region on one side;
An electrode having an opening corresponding to the light emitting region;
Insulation provided so as to correspond to the light emitting region and configured such that the reflectance of the peripheral region surrounding the central region corresponding to the light emission central region of the light emitting region is lower than that of the central region. A surface emitting semiconductor laser comprising: a film; The portion of the insulating film corresponding to the central region of the light emission region has a film thickness of (2a-1) λ / 4n ₁ (a is an integer of 1 or more, λ is an emission wavelength, and n ₁ is a refractive index). , A first insulating film having a refractive index n ₁ lower than that of the surface of the multilayer reflector on the exit side, and a film thickness of (2b-1) λ / 4n ₂ (b is an integer greater than or equal to 1, n ₂ is a refractive index), and a second insulating film having a refractive index n ₂ having a value lower than that of the first insulating film is laminated in this order, and corresponds to the peripheral region of the light emitting region. The portion has a thickness of (2c-1) λ / 4n ₃ (c is an integer of 1 or more, n ₃ is a refractive index), and a refractive index n ₃ is a third value lower than that of the first insulating film. The surface emitting semiconductor laser according to claim 1, wherein the surface emitting semiconductor laser is an insulating film. 3. The surface emitting semiconductor laser according to claim 2, wherein the first insulating film is made of an oxide, and the second insulating film and the third insulating film are made of a nitride. 3. The surface-emitting type semiconductor laser according to claim 2, wherein a width of the first insulating film is W ₁ and an inner diameter of the opening is A ₁ , the following formula is satisfied.
_{A 1/3 ≦ W 1 ≦} 2A 1/3 ... Formula (1) The reflectance of the insulating region in the central region of the light emitting region is R ₁ , the reflectance of the insulating region in the peripheral region of the light emitting region is R ₂ , and the reflectance when there is no insulating film in the light emitting region. The surface emitting semiconductor laser according to claim 2, wherein R ₃ satisfies the following formula.
R ₁ ≧ R ₃ > R ₂ Formula (2) The insulating film has a thickness corresponding to the central region of the light emitting region of dλ / 2n ₅ (d is an integer of 1 or more, λ is an emission wavelength, and n ₅ is a refractive index), Among these, the film thickness of the portion corresponding to the peripheral region is a fourth insulating film whose thickness is (2e-1) λ / 4n ₅ (e is an integer greater than or equal to 1), and the refractive index n ₅ is the multilayer film reflecting mirror on the exit side. The surface emitting semiconductor laser according to claim 1, wherein the surface emitting semiconductor laser has a value lower than that of the surface of the surface. The surface emitting semiconductor laser according to claim 6, wherein the fourth insulating film is made of an oxide or a nitride. 7. The surface according to claim 6, wherein a width of a region having a film thickness of dλ / 2n ₅ in the fourth insulating film is W ₂ , and an inner diameter of the opening is A _2. Light emitting semiconductor laser.
_{A 2/3 ≦ W 2 ≦} 2A 2/3 ... Equation (3) Of the fourth insulating film, the reflectance of the portion corresponding to the central region of the light emitting region is R ₁ , and the reflectance of the portion corresponding to the peripheral region of the light emitting region is R _2. The surface emitting semiconductor laser according to claim 6, wherein the following expression is satisfied, where R ₃ is a reflectance when the insulating film is not provided.
R ₁ ≧ R ₃ > R ₂ Formula (4)

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