JP2009094317A - Surface-emitting laser - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a surface-emitting laser that is capable of high-speed operation and has a narrow radial angle. <P>SOLUTION: The surface-emitting laser includes a first reflecting mirror 111, a second reflecting mirror 102, an active layer 104 and a current constriction structure 106 that are formed between the first reflecting mirror 111 and the second reflecting mirror 102, and an electrode 110, which has transparency and is formed between the first reflecting mirror 111 and the active layer 104. The electrode 110 has the periodicity of a refractive index in the direction of the surface where it is formed. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a surface emitting laser.

  Since optical communication is capable of long-distance and large-capacity transmission, long-distance communication has been widely used practically from early on. In general, a semiconductor laser is used as a light source in an optical communication transmitter. As a light source for short-distance communication, a surface emitting laser (VCSEL) having advantages such as small size and low power consumption is used. As the current confinement mechanism of the surface emitting laser, there are an air post type, a proton injection type, an oxidation constriction type, and the like. Among them, the oxidation confinement type is not affected by side surface recombination, and has advantages such as greatly reducing diffraction loss due to light collection caused by the difference in refractive index between the oxide layer and the semiconductor layer. Has become mainstream.

  FIG. 6 shows a structural diagram of an oxide confined surface emitting laser. A semiconductor substrate 1, a lower DBR (Distributed Bragg reflector) 2, an active layer 3, an oxide layer 4, an upper DBR 5, an upper electrode 6 and a lower electrode 7 are sequentially stacked. The oxide layer 4 is formed by partially oxidizing a semiconductor layer made of AlAs. Thereby, a current confinement structure is formed. Since the oxide layer 4 is an insulator, a current can be intensively applied to a region of the active layer 3 having a diameter substantially the same as that of the non-oxidized region 8 of the semiconductor layer. In the structure of FIG. 6, the active layer volume is defined by the diameter of the current confinement portion, and the transverse mode is controlled. In order to increase the modulation band of this laser, the current density is often increased by reducing the resistance and capacitance of the element (CR limiting rate-limiting relaxation) and reducing the opening diameter of the current confinement portion. Generally, in order to obtain a modulation band of 10 Gbps, it is necessary to narrow the aperture diameter to about 15 μm or less.

  However, since the element resistance increases due to the narrowing of the current confinement portion opening diameter, the high speed is saturated by self-heating. For this reason, the relaxation oscillation frequency, which is an index of high-speed performance, remains at a maximum of about 16 GHz. Further, in the multi-mode oscillation surface emitting laser, the narrowing of the current confinement portion opening diameter increases the emission angle of the emitted light and also decreases the coupling efficiency with the optical fiber.

  In order to solve the above problems, the inventors have developed a buried tunnel junction type surface emitting laser disclosed in Non-Patent Document 1. This surface emitting laser is characterized in that it is not current confinement due to an oxide layer but current confinement due to a tunnel junction. In addition to reducing the resistance of the tunnel junction, it is possible to reduce the p-type region having high resistance in the element structure. Therefore, the element resistance can be greatly reduced and the high speed is excellent.

  As shown in FIG. 7, the buried tunnel junction type surface emitting laser disclosed in Non-Patent Document 1 has a lower DBR 12, an active layer 13, a p-type spacer layer 14, a tunnel junction layer 15, an n-type semiconductor substrate 11. A mold spacer layer 16, an upper DBR 17, an upper electrode 18 and a lower electrode 19 are provided. With this configuration, a low-resistance surface-emitting laser that oscillates at a threshold current of 1 mA and a wavelength of 1090 nm and has an element resistance of 50Ω can be obtained.

ただし、ｄｇ／ｄｎが微分利得、Ｖｐがモード体積である。上述の素子抵抗低減による自己発熱抑制は、この微分利得の増大を利用した解決方法である。一方、式からモード体積Ｖｐの低減も有効であることが分かる。 Here, the relaxation oscillation frequency fr, which is one guideline for high speed, is given by the following equation.

However, dg / dn is a differential gain, and Vp is a mode volume. The suppression of self-heating by reducing the element resistance described above is a solution method utilizing the increase in differential gain. On the other hand, it can be seen from the equation that reduction of the mode volume Vp is also effective.

  In order to reduce the mode volume, it is important to shorten the effective resonance length of light in the element. The inventors have found that the effective resonance length is significantly shortened by replacing the upper DBR with the semiconductor multilayer DBR from the dielectric multilayer DBR. Since the dielectric multilayer DBR has a large refractive index difference, a reflectance of 99% or more can be obtained by stacking several pairs. For this reason, it is possible to suppress the leakage of light to the dielectric multilayer DBR side, and as a result, it is possible to shorten the effective resonator length.

  This dielectric multilayer DBR can also be applied to an oxide confined surface emitting laser. However, in this case, the current path has a so-called intracavity structure that bypasses the upper DBR. Here, since the distance between the upper electrode and the opening portion of the current confinement structure is increased and the region between them is a relatively high-resistance p-type semiconductor layer, the element resistance increases. In addition, holes that are heavier than electrons travel, causing non-uniform injection in which the current path concentrates around the opening, leading to problems such as mode instability of the emitted light and an increase in the emission angle. There is.

  On the other hand, the buried type tunnel junction surface emitting laser originally has an intracavity structure, and electrons travel from the upper electrode and are converted into holes in the tunnel portion and injected into the active region. Therefore, the electron transit region can be an n-type semiconductor layer, and the problem of device resistance can be greatly reduced as compared with the oxidized constriction structure.

  However, in the buried tunnel junction type surface emitting laser, a convex portion 20 is formed on the n-type spacer layer 16 as shown in FIG. That is, the resonance wavelength varies depending on the thickness of the n-type spacer layer 16. As a result, light confinement occurs due to the difference in equivalent refractive index. In general, the greater the unevenness, the greater the equivalent refractive index difference. If the equivalent refractive index at the center is smaller, a so-called reverse waveguide structure is formed, which causes problems such as an increase in threshold current and, consequently, oscillation inability. Conversely, when the equivalent refractive index at the center is larger, the light confinement becomes stronger. In this case, there is a problem that a high-order mode is likely to occur, and it cannot be used for applications that require a single mode.

  As described above, when the optical confinement becomes strong and the stability of the oscillation mode is lost, the radiation angle becomes widened or unstable, and the coupling efficiency with the optical fiber or the optical waveguide decreases. On the other hand, it is possible to use a lens, but this is not preferable from the viewpoint of high density integration and cost reduction.

  Further, if the buried layer is made sufficiently thick, the surface can be flattened as shown in FIG. 8 (a), or the uneven portion as shown in FIG. 8 (b) can be moved away to a region where light does not reach. Become. Therefore, the problem due to the unevenness can be avoided. However, the thicker the buried layer, the longer the cavity length of the laser and the larger the mode volume, thereby sacrificing high speed.

By the way, in patent documents 1 and 2, a transparent electrode is used for a surface emitting laser.
JP 2006-216816 A JP 2000-196189 A Yashiki et al., “1.1um-Range Low-Resistance InGaAs Quantum-Well Vertical-Cavity Surface-Emitting Lasers with a Buried Type-II Tunnel Junction”, Jpn. J. Appl. Phys., 2007, pp. L512-514

  The present invention has been made to solve the above problems, and an object of the present invention is to provide a surface emitting laser capable of high-speed operation and having a narrow emission angle.

  The surface emitting laser according to the present invention includes a first reflecting mirror, a second reflecting mirror, an active layer and a current confinement structure formed between the first and second reflecting mirrors, and the first reflecting mirror. A transparent electrode is formed between the reflecting mirror and the active layer, and the electrode has a periodicity of refractive index in the formed surface direction.

  According to the present invention, it is possible to provide a surface emitting laser capable of high speed operation and having a narrow emission angle.

  Hereinafter, specific embodiments to which the present invention is applied will be described in detail with reference to the drawings. However, the present invention is not limited to the following embodiment. In addition, for clarity of explanation, the following description and drawings are simplified as appropriate.

First Embodiment A configuration of a surface emitting laser according to a first embodiment of the present invention will be described with reference to FIG. Here, an example in which the present invention is applied to an oxidized confined surface emitting laser having an oscillation wavelength of 1.1 μm will be described.

FIG. 1A is a cross-sectional view of the surface emitting laser element according to the first embodiment of the present invention. This surface emitting laser is formed on an n-type semiconductor substrate 101 with a lower DBR 102, an n-type cladding layer 103, an active layer 104, a p-type cladding layer 105, an oxide layer 106, a p-type semiconductor layer 107, a p ⁺ -type semiconductor layer 108, A transparent electrode 110 and an upper DBR 111 are included. FIG. 1B is a plan view of the transparent electrode 110. FIG. 1A is a cross-sectional view taken along the line IA-IA in FIG.

The lower DBR 102 is formed on an n-type semiconductor substrate 101 made of, for example, GaAs. The lower DBR 102 has a structure in which, for example, a low refractive index layer made of n-type Al _0.9 Ga _0.1 As and a high refractive index layer made of n-type GaAs are sequentially stacked. The optical film thickness of each layer is preferably λ / 4 (λ is an oscillation wavelength in each medium).

The n-type cladding layer 103 is formed on the lower DBR 102 and is made of, for example, Al _0.3 Ga _0.7 As.
The active layer 104 is formed on the n-type cladding layer 103, and includes, for example, a non-doped Ga _0.7 In _0.3 As quantum well and a GaAs barrier layer. The optical film thickness of the entire active layer 104 is preferably 1λ (one wavelength within the medium).
The p-type cladding layer 105 is formed on the active layer 104 and is made of, for example, Al _0.3 Ga _0.7 As.
The oxide layer 106 is formed on the p-type cladding layer 105, and is formed, for example, by oxidizing p-type Al _x Ga _1-x As (where 0 <x <1). This oxide layer 106 forms a current constriction. The diameter of the current path of the current confinement part is preferably 4 to 15 μm.

The p-type semiconductor layer 107 is formed on the oxide layer 106 and is made of, for example, Al _0.3 Ga _0.7 As. The p ⁺ type semiconductor layer 108 is formed on the p type semiconductor layer 107 and is made of, for example, GaAs. On the upper surface of the p ⁺ type semiconductor layer 108, periodic and fine irregularities are formed based on the design of the Frennel lens. A transparent electrode 110 made of ITO or the like is formed in the recess. Specifically, as shown in FIG. 1B, the transparent electrode 110 is intermittently formed concentrically around the center of the current confinement structure as viewed from the laser emission direction. Then, all the circular transparent electrodes are connected in a cross shape. In the present embodiment, the transparent electrode 110 is formed in contact with the upper DBR 111. Here, although not necessarily in contact, the transparent electrode 110 is preferably formed at a distance within 0.5 μm from the lower surface of the upper DBR 111.

  The transparent electrode 110 can reduce the resistance of the conventional intracavity type device to 250Ω, which is about 1/3, compared to 250Ω. Further, the FFP can be narrowed from 30 degrees to 15 degrees due to the diffraction effect of the transparent electrode 110. Further, in an element having an opening diameter of 6 μm in the oxidized constriction portion, the thickness of the diffraction grating is set to 0.3 μm and the period is 0.4 μm, and only the width is uniformly reduced from the center, whereby a single mode can be achieved.

The upper DBR 111 is formed on the transparent electrode 110. The upper DBR 111 has, for example, a structure in which an SiO ₂ low refractive index layer having an optical film thickness λ / 4 and an amorphous Si (a-Si) high refractive index layer having an optical film thickness λ / 4 are sequentially stacked.

Next, a method of manufacturing the surface emitting laser according to the first embodiment will be described with reference to FIG. First, as shown in FIG _. 4A, a lower DBR 102, Al ₀ ..., A plurality of stacked layers of a pair of n-type GaAs layers and n-type Al _0.9 Ga _0.1 As layers on an n-type semiconductor substrate 101 _. N-type cladding layer 103 made of ₃ Ga _0.7 As, active layer 104 made of non-doped Ga _0.7 In _0.3 As quantum well and GaAs barrier layer, p-type cladding made of Al _0.3 Ga _0.7 As Layer 105, p-type Al _x Ga _1-x As (where 0 <x <1) layer 106a for forming oxide layer 106, p-type semiconductor layer 107 made of Al _0.3 Ga _0.7 As, and GaAs. The p ⁺ type semiconductor layer 108 is sequentially stacked by a metal-organic vapor phase deposition (MOVPE) method. Of course, other crystal growth methods such as molecular beam epitaxy (MBE) may be used.

Next, as shown in FIG. 4B, a photoresist is applied onto the p ⁺ type semiconductor layer 108 to form a circular resist mask having a diameter of about 30 μm. Next, etching is performed by dry etching until the surface of the lower DBR 102 is exposed, and a mesa (columnar structure) 109 having a diameter of about 30 μm is formed.

Then, heating is performed at a temperature of about 400 ° C. for about 10 minutes in a furnace in a steam atmosphere. As a result, as shown in FIG. 4C, the p-type Al _x Ga _1-x As (where 0 <x <1) layer 106a is selectively oxidized in an annular shape, and the oxide layer 106 is formed. . As a result, a current path (opening) is formed in the non-oxidized region at the center.

Further, periodic irregularities are formed in the p ⁺ type semiconductor layer 108 based on the design of the Frennel lens. A transparent conductive film made of ITO or the like is formed in the recess, and a transparent electrode 110 having a periodic refractive index change in the horizontal direction is formed as shown in FIG. Specifically, a photoresist is applied onto the p ⁺ type semiconductor layer 108, and a resist mask for forming periodic unevenness is formed by a photolithography technique. Here, a region to be a recess is not covered with the resist mask, and the p ⁺ type semiconductor layer 108 in the region is removed by etching to form a recess. Further, using this resist mask, a transparent conductive film is formed so as to fill the recess. Then, by removing the resist mask, the transparent electrode 110 having a periodic refractive index change is formed.

Next, the upper DBR 111 in which a plurality of pairs of SiO ₂ and amorphous Si (a-Si) are stacked is formed on the columnar structure by sputtering as shown in FIG.

  Next, the mesa 109 is filled with the polyimide 112, the p-type electrode 113 is formed so as to pull out the transparent electrode 110, and the n-type electrode 114 is formed on the lower surface of the lower DBR layer 102, thereby completing the device of FIG. .

Second Embodiment Next, a configuration of a surface emitting laser according to a second embodiment of the present invention will be described with reference to FIG. Here, an example in which the present invention is applied to a buried tunnel junction type surface emitting laser having an oscillation wavelength of 1.1 μm will be described.

FIG. 2 is a cross-sectional view of a surface emitting laser element according to the second embodiment of the present invention. This surface-emitting laser has a lower DBR 202, an n-type cladding layer 203, an active layer 204, a p-type cladding layer 205, a p-type spacer layer 206, a p ⁺ -type semiconductor layer 207, and an n ⁺ -type semiconductor on an n-type semiconductor substrate 201. A layer 208, an n-type spacer layer 209, a transparent electrode 210, and an upper DBR 211 are included.

The lower DBR 202 is formed on an n-type semiconductor substrate 201 made of, for example, GaAs. The lower DBR 202 has a structure in which, for example, a low refractive index layer made of n-type Al _0.9 Ga _0.1 As and a high refractive index layer made of n-type GaAs are sequentially stacked. The optical film thickness of each layer is preferably λ / 4 (λ is an oscillation wavelength in each medium).

The n-type cladding layer 203 is formed on the lower DBR 202 and is made of, for example, Al _0.3 Ga _0.7 As.
The active layer 204 is formed on the n-type cladding layer 203, and includes, for example, a non-doped Ga _0.7 In _0.3 As quantum well and a GaAs barrier layer. The optical film thickness of the entire active layer 204 is preferably 1λ (one wavelength within the medium).
The p-type cladding layer 205 is formed on the active layer 204 and is made of, for example, Al _0.3 Ga _0.7 As.
The p-type spacer layer 206 is formed on the p-type cladding layer 205 and is made of, for example, GaAs.

The p ⁺ type semiconductor layer 207 is formed on the p type spacer layer 206 and is made of, for example, GaAs _0.9 Sb _0.1 . On the other hand, the n ⁺ type semiconductor layer 208 is formed on the p ⁺ type semiconductor layer 207 and is made of, for example, In _0.15 Ga _0.85 As. The p ⁺ type semiconductor layer 207 and the n ⁺ type semiconductor layer 208 constitute a tunnel junction layer. Here, C (concentration 1 × 10 ²⁰ cm ⁻³ ) can be used as the p-type dopant of the p ⁺ -type semiconductor layer 207. On the other hand, Si (concentration 2 × 10 ¹⁹ cm ⁻³ ) can be used as the n-type dopant of the n ⁺ -type semiconductor layer 208. Further, the p ⁺ type semiconductor layer 207 can have a thickness of 5 nm, and the n ⁺ type semiconductor layer 208 can have a thickness of 10 nm. Further, the tunnel junction layer composed of the p ⁺ type semiconductor layer 207 and the n ⁺ type semiconductor layer 208 leaves only the portion that will eventually become a current injection region in the substrate plane, and the periphery is removed. As a result, a current confinement portion is formed. The diameter of the current path of the current confinement part is preferably 4 to 15 μm.

The n-type spacer layer 209 is formed so as to cover the tunnel junction layer composed of the p ⁺ -type semiconductor layer 207 and the n ⁺ -type semiconductor layer 208. The n-type spacer layer 209 is made of, for example, GaAs. In FIG. 2, the upper surface of the n-type spacer layer 209 is drawn flat, but actually, a convex portion is formed in the same manner as shown in FIG.

  On the upper surface of the n-type spacer layer 209, periodic and fine irregularities are formed based on the design of the Frennel lens. A transparent electrode 210 made of ITO or the like is formed in the recess. Specifically, as in FIG. 1B, the transparent electrode 210 is intermittently formed concentrically with the center of the current confinement structure as the center when viewed from the laser emission direction. Furthermore, all circular transparent electrodes are connected in a cross shape. In the present embodiment, the transparent electrode 110 is formed in contact with the upper DBR 111. Here, although not necessarily in contact, the transparent electrode 110 is preferably formed at a distance within 0.5 μm from the lower surface of the upper DBR 111. The transparent electrode 210 can reduce the resistance of the conventional intracavity type device resistance to 50Ω, compared with 50Ω. Further, the FFP can be narrowed from 45 degrees to 20 degrees due to the diffraction effect of the transparent electrode 210.

The upper DBR 211 is formed on the transparent electrode 210. The upper DBR 211 has, for example, a structure in which an SiO ₂ low refractive index layer having an optical film thickness λ / 4 and an amorphous Si (a-Si) high refractive index layer having an optical film thickness λ / 4 are sequentially stacked.

Next, a method for manufacturing the surface emitting laser according to the second embodiment will be described with reference to FIG. First, as shown in FIG. 5A, a lower DBR 202 in which a plurality of pairs of n-type GaAs layers and n-type Al _0.9 Ga _0.1 As layers are stacked on an n-type semiconductor substrate 201 made of GaAs. n-type cladding layer 203 made of Al _0.3 Ga _0.7 as, made of undoped _Ga 0.7 _{In 0.3} as active layer ₂₀₄ made of quantum wells and GaAs barrier _layer, Al 0.3 _{Ga 0.7} as A p-type cladding layer 205, a p-type spacer layer 206 made of GaAs, a p ⁺ -type semiconductor layer 207 made of GaAs _0.9 Sb _0.1 , and an n ⁺ -type semiconductor layer 208 made of In _0.15 Ga _0.85 As. The layers are sequentially deposited by metal organic chemical vapor deposition (MOCVD).

Next, after forming a circular resist mask having a diameter of about 6 μm by photolithography, the p ⁺ type semiconductor layer 207 and the n ⁺ type semiconductor layer 208 are removed by etching. Thereby, a cylindrical tunnel junction layer having a diameter of about 6 μm is formed. Thereafter, the photoresist is removed. Next, as shown in FIG. 5B, an n-type spacer layer 209 is laminated again using the MOCVD method.

In this structure, the p ⁺ type semiconductor layer 207 and the n ⁺ type semiconductor layer 208 form a tunnel junction. After removing this part, it is embedded with a semiconductor. A current flows only through the remaining tunnel junction. The tunnel junction is disposed at a node of a standing wave whose interface is between the lower DBR 202 and the upper DBR 211 described later, and reduces light absorption.

Further, periodic irregularities are formed on the upper surface of the n-type spacer layer 209 based on the design of the Frennel lens. A transparent conductive film made of ITO or the like is formed in the recess, and a transparent electrode 210 having a periodic refractive index change in the horizontal direction is formed as shown in FIG. Specifically, a photoresist is applied onto the p ⁺ type semiconductor layer 108, and a resist mask for forming periodic unevenness is formed by a photolithography technique. Here, a region to be a recess is not covered with the resist mask, and the p ⁺ type semiconductor layer 108 in the region is removed by etching to form a recess. Further, using this resist mask, a transparent conductive film is formed so as to fill the recess. Then, by removing the resist mask, the transparent electrode 110 having a periodic refractive index change is formed.

Next, the inner diameter region of the upper electrode 215 is left by a photolithography technique for forming an upper DBR 211 in which a plurality of pairs of SiO ₂ and amorphous Si (a-Si) are stacked on the wafer by sputtering. The upper DBR 211 in the outer peripheral region is removed.

  Next, a resist is applied to the upper surface of the wafer, a circular resist mask having a diameter of about 30 μm is formed by photolithography, and then etching is performed until the surface of the lower DBR 202 is exposed. ) 212 is formed. Thereafter, the resist is removed to obtain the structure of FIG.

  Next, an electrode is formed on the lower DBR 202 exposed by the mesa etching. First, after applying a photoresist on the front surface, only a portion of the photoresist where an electrode is to be formed is removed by photolithography. After depositing Ti / Pt / Au, the photoresist is removed and lifted off to form a lower electrode 213 on a part of the lower DBR 202. Next, after filling the mesa 212 with polyimide, the polyimide on the lower electrode 213 is removed by photolithography.

  Finally, the electrode 215 is formed. First, after applying a photoresist and patterning by mask exposure, Ti / Pt / Au is vapor-deposited. Then, the photoresist is removed and lifted off to form the upper electrode 215 on the polyimide layer 214, thereby completing the surface emitting laser shown in FIG.

  As described above, in the surface emitting laser according to the present invention, the diffraction grating type transparent electrode is disposed under the upper dielectric DBR. Since this transparent electrode has a periodic structure in the direction of its formation surface, it functions as a diffraction grating. In addition, since the contact area with the semiconductor layer is large, the element resistance can be reduced. Furthermore, although the light transmittance of the transparent electrode remains at about 90% at a wavelength of 1.1 μm, the effective light transmittance can be increased by employing an intermittent structure such as the concentric structure shown in the embodiment. Can do.

  Furthermore, due to the diffraction effect of the transparent electrode, the radiation angle can be narrowed, the higher-order mode of the laser emission light can be suppressed, or the single mode can be achieved. This diffraction effect is more effective as the electric field strength of light is higher. FIG. 3 shows the electric field intensity distribution of the element of the present invention. The maximum intensity region is immediately below the upper dielectric multilayer DBR (interface with the semiconductor layer). Therefore, by arranging the diffraction grating type transparent electrode in this portion, both a large diffraction effect and low resistance were realized.

  The implementation method of the present invention is not limited to the various forms described above, and various modifications can be made without departing from the scope of the present invention. The wavelength and material of the light-emitting element can be selected other than those described in the embodiment. Further, the diffraction grating type transparent electrode can form a periodic structure having a refractive index, and various shapes such as a radial shape and a mesh shape can be applied as long as it has a desired diffraction effect with respect to light of an arbitrary wavelength.

It is sectional drawing and a top view of the surface emitting laser which is the 1st Embodiment of this invention. It is sectional drawing of the surface emitting laser which is the 2nd Embodiment of this invention. It is a graph explaining electric field strength distribution in the element of this invention. It is sectional drawing which shows the manufacturing method of the surface emitting laser which is the 1st Embodiment of this invention. It is sectional drawing which shows the manufacturing method of the surface emitting laser which is the 2nd Embodiment of this invention. It is sectional drawing of the related oxidation confinement type | mold surface emitting laser. It is sectional drawing of a related tunnel junction type | mold surface emitting laser. It is sectional drawing of a related tunnel junction type | mold surface emitting laser.

Explanation of symbols

101 n-type semiconductor substrate 102 lower DBR
103 n-type cladding layer 104 active layer 105 p-type cladding layer 106 oxide layer 106a p-type Al _x Ga _1-x As layer 107 p-type semiconductor layer 108 p ⁺ -type semiconductor layer 109 mesa 110 transparent electrode 111 upper DBR
112 polyimide layer 113 p-type electrode 114 n-type electrode 201 n-type semiconductor substrate 202 first DBR
203 n-type cladding layer 204 active layer 205 p-type cladding layer 206 p-type spacer layer 207 p ⁺ -type semiconductor layer 208 n ⁺ -type semiconductor layer 209 n-type spacer layer 210 transparent electrode 211 upper DBR
212 Mesa 213 Lower electrode 214 Polyimide layer 215 Upper electrode

Claims (11)

A first reflector;
A second reflector;
An active layer and a current confinement structure formed between the first and second reflectors;
An electrode formed between the first reflecting mirror and the active layer and having transparency;
The electrode is a surface emitting laser having a periodicity of a refractive index in a formed surface direction.   2. The surface emitting laser according to claim 1, wherein the surface emitting laser is an intracavity type.   3. The surface emitting laser according to claim 1, wherein the electrode is formed at a distance of 0.5 μm or less from the surface of the first reflecting mirror on the active layer side. 4.   The surface emitting laser according to claim 1, wherein the electrode has the periodicity by being formed intermittently.   5. The surface emitting laser according to claim 4, wherein the electrode is formed concentrically around the center of the current confinement structure as viewed from the laser emission direction.   The surface-emitting laser according to claim 1, wherein the electrode includes ITO.   The surface emitting laser according to any one of claims 1 to 6, wherein the current confinement structure is formed by oxidation confinement.   The surface emitting laser according to any one of claims 1 to 6, wherein the current confinement structure is formed by a tunnel junction.   The surface emitting laser according to claim 1, wherein the first reflecting mirror is a dielectric distributed Bragg reflecting mirror. The dielectric distributed Bragg reflector, a surface emitting laser according to claim 9, featuring that it has a multilayer structure composed of a Si layer and the SiO ₂ layer.   11. The surface emitting laser according to claim 1, wherein a current path of the current confinement structure has a diameter of 4 μm or more and a single-mode light output is obtained.

Images