JPH07106695A - Semiconductor laser - Google Patents

Abstract

PURPOSE:To provide a self pumping low noise laser excellent in electrical and optical characteristics having sufficiently suppressed astigmatism by a structure wherein the overall thickness of a second laminate is difference between a region at least on one edge of a laser resonator and a central region sandwiched by the opposite edges. CONSTITUTION:A second laminate has the overall thickness different between a region 122a on the edge of a resonator and the central region 322b thereof. The difference of equivalent refractive index of a stripe part 115 between the inner layer direction and the outer layer direction is set larger in the edge region than in the central region. Consequently, the difference of equivalent refractive index in the central part of resonator can be determined to cause self-pumping whereas the difference of refractive index in the edge of resonator can be determined such that the astigmatism of laser is suppressed while increasing the radiation angle in the horizontal direction. When the inventive semiconductor laser is applied to a regenerative laser, a low noise self-pumping laser having sufficiently suppressed astigmatism can be obtained without sacrifice of slope efficiency.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor laser device used in an optical disk device or the like.

[0002]

2. Description of the Related Art Conventionally, semiconductor laser devices have been widely used as light sources for optical disk devices and the like. There are two types of lasers, a reproduction laser dedicated to signal reproduction and a recording / reproduction laser for both recording and reproduction.

(Prior Art 1) When a signal is reproduced from an optical disk device, there is a problem in that noise is induced by the return light from the optical disk and other optical parts to cause a read error. To prevent this, the optical output is 5m
As a reproducing laser of about W, a laser utilizing a self-sustained pulsation phenomenon has been proposed and demonstrated (reference: Hayashi et al. O
QE84-30). FIG. 15 shows a conventional example (Japanese Patent Application No. 2-9).
9012).

In FIG. 15, an n-GaAs semiconductor substrate
N-Al having a layer thickness of 1.0 μm on 901_0.5Ga_0.5As
First cladding layer 902, undoped with a layer thickness of 0.08 μm
Al _0.13Ga_0.87As active layer with a layer thickness of 0.35 μm
p-Al_0.5Ga_0.5As second clad layer 904 is sequentially provided.
The first laminated structure 920 and the p-Al_0.5Ga
_0.5On As second clad layer 904, layer thickness 0.01 μm
P-GaAs epitaxial growth promoting layer 905, layer thickness
0.01 μm p-Al_0.6Ga_0.4As etch stop
Layer 906 and n-Al having a layer thickness of 1.0 μm_0.1Ga_0.9A
Second laminated structure 921 in which the light absorption layer 907 is sequentially provided
To form. This second laminated structure and the second laminated structure
Current / light confinement means in the stripe groove 922 separating the
Is configured. To fill the stripe groove 922,
P-Al with a layer thickness of 2.0 μm_0.5Ga_0.5As 3rd clad
Layer 908 and p-GaAs contact with a layer thickness of 5.0 μm
Layer 909 is formed on the n-GaAs semiconductor substrate 901 side.
Growth of electrode 910 and p-GaAs contact layer 909 on
An electrode 911 is formed on the layer side. Semiconductor laser
The device 923 is completed.

In the laser oscillation spectrum of the semiconductor laser device 923, the longitudinal mode becomes multimode due to the self-excited oscillation phenomenon, and the line width further widens. In this case, since the temporal coherence is lowered, the influence on the return light is reduced and the noise is lowered. This self-sustained pulsation phenomenon is a difference between the equivalent refractive index in the layer direction inside the stripe and the equivalent refractive index in the layer direction outside the stripe (hereinafter, this difference is referred to as Δn).
Has been demonstrated to occur frequently when Δn = 1 to 5 × 10 ⁻³ . FIG. 16 shows the relationship between the maximum output that causes the self-excited oscillation and the Δn of the reproducing laser. However, the value of Δn at which self-excited oscillation occurs is considerably smaller than Δn = 1 to 2 × 10 ^-2 of a laser that oscillates in a normal single longitudinal mode.

(Prior Art 2) Further, in order to record a signal on an optical disk, a high output semiconductor laser having an optical output of 30 mW or more is used, and this high output laser is also used for signal reproduction. As a conventional example of this recording / reproducing (recording / reproducing) laser,
Active layer 903 in semiconductor laser device 923 of FIG.
Of the p-second cladding layer 9 is reduced to 0.05 μm.
It is realized by setting the layer thickness of 04 to 0.20 μm. In this case, Δn becomes 2 × 10 ^-2 , and oscillation occurs in the single longitudinal mode. Therefore, when the recording / reproducing laser is used at the time of reproduction, in order to reduce the noise due to the returning light, a method of superposing a high frequency on the drive current to make the longitudinal mode multi-mode (high frequency superposition method) is used. .

[0007]

(Problem 1) In the conventional self-excited oscillation laser device for reproduction, the equivalent refractive index difference (Δn) inside and outside the stripe is different from that of a normal single oscillation laser. Since it is much smaller than the above, the following problems occur.

FIG. 17 shows the relationship between the astigmatic difference of the laser with respect to the stripe width of the Δn = 3 × 10 ⁻³ self-oscillation type laser and the Δn = 1 × 10 ⁻² single longitudinal mode oscillation type laser. .
In FIG. 17, when Δn = 3 × 10 ⁻³ , the amount of light seeping out to the outside of the stripe increases, so that the absorption of light by the current / optical confinement layer outside the stripe increases and the wavefront of the laser light bends. The astigmatic difference is larger than in the case of Δn = 1 × 10 ^-2 . The astigmatic difference of the laser affects the condensing characteristics, and when the astigmatic difference increases, the spot diameter of the condensed beam increases. Therefore, when this laser is used in an optical disk device, there is a problem that crosstalk increases and an error occurs during reproduction. Therefore, the astigmatic difference of the laser is preferably 5 μm or less. Here, in the case of Δn = 1 × 10 ^-2 , the stripe width may be 4.5 μm in order to set the astigmatic difference to 5 μm. On the other hand, in the case of Δn = 3 × 10 ⁻³ , the stripe width needs to be 2 μm to make the astigmatic difference 5 μm.

Further, in FIG. 18, the optical output with respect to the stripe width of the self-oscillation type laser device of Δn = 3 × 10 ⁻³ and the single longitudinal mode oscillation type laser device of Δn = 1 × 10 ^−2. -Shows the slope efficiency relationship of the current characteristics. An λ / 2-λ / 2 coat of an Al ₂ O ₃ film is applied to the cavity end face of the laser, and the cavity length is 250 μm. In FIG. 18, when the stripe width becomes narrower, the amount of light leaking out of the stripe increases, so that the waveguide loss increases and the efficiency decreases. △ n
= 1 × 10 ^-2, the stripe width at which the astigmatic difference is 5 μm is 4.5 μm, in which case the efficiency is 0.375.
W / A, which is high enough. On the other hand, Δn = 3 ×
In the case of 10 ^−3, the stripe width with an astigmatic difference of 5 μm is 2 μm, and in that case, the efficiency drops to 0.09 W / A. Thus, the Δn of the self-excited oscillation laser for reproduction is
Is small and therefore the astigmatic difference becomes large, and if the stripe width is narrowed to reduce it, there is a problem that the slope efficiency becomes low.

(Problem 2) On the other hand, in the above-mentioned conventional high-power laser device for recording and reproducing, the high-frequency superimposing method was used to reduce the return optical noise during signal reproduction. Circuit is required, the drive circuit is downsized,
There was a problem with low power consumption. Therefore, in the recording / reproducing laser device as well, it has been considered to cause a self-excited oscillation phenomenon during signal reproduction. FIG. 19 shows the relationship between Δn and the maximum optical output at which self-sustained pulsation occurs in the recording / reproducing laser.
In FIG. 19, similar to the reproducing laser, Δn = 1 to 3 ×
Self-oscillation occurs at 10 ^-3 . The structure of the self-excited oscillation type laser for recording / reproduction has a layer thickness of the active layer 903 of FIG.
And the p-second cladding layer 904 has a thickness of 0.45 μm.
In this case, Δn is 2.5 × 10 ⁻³ . In a normal high-power laser, Δn = 2 × 10 ^-2, which is considerably smaller than that. Therefore, the following problems occur. FIG. 20 shows the relation of the astigmatic difference of the laser with respect to the stripe width of the Δn = 2.5 × 10 ⁻³ self-excited oscillation type laser and the Δn = 2 × 10 ⁻² single longitudinal mode oscillation type laser. For the same reason as for the reproducing laser, as shown in FIG. 20, Δn = 2.5 × 1 in order to set the astigmatic difference to 5 μm.
In the case of 0 ^-3 , the stripe width needs to be 2 μm.

Further, in FIG. 21, stripe widths of Δn = 2.5 × 10 ⁻³ self-excited oscillation type semiconductor laser and Δn = 2 × 10 ⁻² single longitudinal mode oscillation type semiconductor laser. 5 shows the relationship of the slope efficiency of the optical output-current characteristic with respect to. Here, the emission end face of the laser beam is adjusted to have a reflectance of 12% by λ / 3 coating of an Al ₂ O ₃ film, and the opposite end face is made of Al ₂ O ₃
The reflectance is adjusted to 75% by the multilayer coating of the film and the Si film. Further, the resonator length is 375 μm. Where △
When n = 2.5 × 10 ⁻³ , even if the stripe width is reduced to 2 μm in order to achieve the astigmatic difference of 5 μm, the slope efficiency is 0.68 W / A, which is a sufficiently good value. .

However, in FIG. 22, Δn = 2.5 × 1
The relationship between the half width of the radiation angle in the horizontal direction with respect to the stripe width of the self-pulsation laser device of 0 ⁻³ and the single longitudinal mode oscillation laser device of Δn = 2 × 10 ⁻² is shown. As the stripe width becomes narrower, when Δn = 2.5 × 10 ⁻³ , the light absorption in the active layer outside the stripe decreases, so that the light confinement inside the stripe decreases. As a result, the horizontal radiation angle is narrowed. Therefore, to make the astigmatic difference 5 μm, the stripe width must be 2 μm, in which case the half-width of the emission angle is reduced to 8 °. As the horizontal radiation angle becomes narrower, the ratio of the horizontal and vertical radiation angle spread increases,
There arises a problem regarding optical characteristics such as a decrease in coupling efficiency with a lens.

As described above, the Δn of the self-excited oscillation type laser for recording / reproducing is small, so that the astigmatic difference becomes large, and if the stripe width is narrowed to reduce it, the horizontal radiation angle becomes narrow. There was a problem of becoming.

The present invention solves the above-mentioned conventional problems, and provides a semiconductor laser device having a self-oscillation type low noise characteristic with a sufficiently small astigmatic difference and good electrical and optical characteristics. The purpose is to do.

[0015]

A semiconductor laser device according to a first aspect of the present invention comprises a first laminated structure formed on a semiconductor substrate and comprising an active layer and a clad layer sandwiching the active layer, and the first laminated structure. A current / light confinement means that is formed on the laminated structure and has one or more second laminated structures and a stripe portion that spatially separates the second laminated structure, and confines current and light inside the stripe portion. In the semiconductor laser device, the difference between the equivalent refractive index in the layer direction inside the stripe portion and the equivalent refractive index in the layer direction outside the stripe portion is at least one end face portion of both end faces of the resonator of the laser. Is larger than at least the central region sandwiched between the both end faces, the total layer thickness of the second laminated structure is equal to at least one end face region of the resonator both end faces of the laser. Both It is obtained by at least the central portion of the region and in different configurations sandwiched by surface, the object is achieved.

The semiconductor laser device according to the second aspect of the present invention includes a first laminated structure formed on a semiconductor substrate and comprising an active layer and a clad layer sandwiching the active layer, and a first laminated structure on the first laminated structure. A semiconductor having a second laminated structure formed of one or more layers, and a stripe portion spatially separating the second laminated structure, and a current / light confinement means for confining current and light inside the stripe portion. In the laser device, the difference between the equivalent refractive index in the layer direction inside the stripe portion and the equivalent refractive index in the layer direction outside the stripe portion is such that at least one end face region of the laser resonator both end faces is The layer thickness from the active layer in the first laminated structure to the second laminated structure is set so as to be larger than at least the central region sandwiched by the both end faces at least in the resonator both end faces of the laser. Towards the region of the square end surface portions are those configured thinner than the region of at least the central portion sandwiched by the both end faces, the objects can be achieved.

Further, the third semiconductor laser device of the present invention comprises a first laminated structure formed on a semiconductor substrate and comprising an active layer and a clad layer sandwiching the active layer, and a first laminated structure on the first laminated structure. A semiconductor having a second laminated structure formed of one or more layers, and a stripe portion spatially separating the second laminated structure, and a current / light confinement means for confining current and light inside the stripe portion. In the laser device, the difference between the equivalent refractive index in the layer direction inside the stripe portion and the equivalent refractive index in the layer direction outside the stripe portion is such that at least one end face region of the laser resonator both end faces is The layered structure from the active layer to the second laminated structure in the first laminated structure is smaller than that of at least the central region sandwiched between the both end faces in the resonator both end faces of the laser. Also it is obtained by configuration different from that in at least the central portion of the region between the region and the both end surface of one end face, the object is achieved.

Further, the width of the stripe portion in the semiconductor laser device of the first and third aspects of the present invention is at least such that at least one end face region of the laser cavity both end faces is sandwiched between the end faces. It is configured to be narrower than the central region, which achieves the above object.

[0019]

With the above structure, the total layer thickness of the second laminated structure is different between the cavity end face region and the central region thereof, or from the active layer in the first laminated structure to the second laminated structure. The layer thickness is configured such that the region at both end face portions of the resonator is thinner than the region at the central portion thereof, or the layer structure from the active layer to the second laminated structure in the first laminated structure has a region at both end face portions of the resonator. The difference between the equivalent refractive index in the layer direction inside the stripe portion and the equivalent refractive index in the layer direction outside the stripe portion is that the resonator end face area is more than the central area. The difference in equivalent refractive index in the central part of the resonator is determined so that self-sustained pulsation occurs, and the astigmatic difference of the laser is small.
It is possible to determine the difference in the equivalent refractive index of the cavity end face so that the horizontal radiation angle becomes large. Further, since the slope efficiency of the optical output-current characteristics is determined in the central part of the resonator, the slope efficiency is set to be sufficiently large. Therefore, when the present invention is applied to a reproducing laser, a self-excited oscillation type low noise laser having a sufficiently small astigmatic difference can be obtained without lowering the slope efficiency, and the present invention is applied to a recording / reproducing laser. Then, a self-excited oscillation type low noise laser having a sufficiently small astigmatic difference can be obtained without narrowing the horizontal radiation angle.

[0020]

The present invention will be described with reference to the following examples.

An embodiment for making Δn of the cavity end face of the semiconductor laser device of the present invention larger than that of the center of the cavity sandwiched between the cavity end faces will be described below.

The first to fourth embodiments of the first invention will be described.

First, the semiconductor laser device of the first embodiment when used as a reproducing laser will be described. In FIG. 1, n-A having a layer thickness of 1.0 μm is formed on an n-GaAs semiconductor substrate 101 by metalorganic vapor phase epitaxy (MOCVD method).
l _0.5 Ga _0.5 As first cladding layer 102, layer thickness 0.08
μm undoped Al _0.13 Ga _0.87 As active layer 103,
P-Al _0.5 Ga _0.5 As second cladding layer 104 having a layer thickness of 0.35 μm, p-GaAs epitaxial growth promoting layer 105 having a layer thickness of 0.003 μm, p-A having a layer thickness of 0.01 μm
l _0.6 Ga _0.4 As etch stop layer 106, layer thickness 0.1
n-Al _{0. 2} Ga _0.8 As the laser light-transmitting layer 107 [mu] m,
N-Al _0.1 Ga _0.9 As laser light absorption layer 108 having a layer thickness of 0.27 μm, n-GaAs epitaxial growth promoting layer 109 having a layer thickness of 0.003 μm, n-A having a layer thickness of 0.01 μm
l _0.6 Ga _0.4 As etch stop layer 110, layer thickness 0.1
0 μm n-Al _0.1 Ga _0.9 As laser light absorption layer 111
Further, an n-GaAs epitaxial growth promoting layer 112 having a layer thickness of 0.003 is sequentially grown.

Here, the laser cavity end faces 113 and 11
Distance from the position corresponding to 4 to the inside of the resonator 20 μm
Up to the position of n-GaAs epitaxial growth promoting layer 1
12 Further, n-Al _0.1 Ga _0.9 As laser light absorption layer 11
1 is removed with an ammonia-based etchant, and n-
The Al _0.6 Ga _0.4 As etch stop layer 110 is removed with a hydrofluoric acid-based etchant.

Further, a stripe groove 115 having a width of 4 μm is formed by photolithography and chemical etching in a direction perpendicular to the cavity end faces 113 and 114. The shape of the stripe groove 115 is an inverted mesa shape due to anisotropy with respect to the substrate surface orientation of chemical etching. At this time, the n-GaAs epitaxial growth promoting layers 112, 1
09, n-Al _0.1 Ga _0.9 As laser light absorption layer 111,
108, and the n-Al _0.2 Ga _0.8 As laser light transmission layer 107 is removed by an ammonia-based etchant, and n-A
The 1 _0.6 Ga _0.4 As etch stop layers 110 and 106 are removed with a hydrofluoric acid-based etchant.

Further, a layer thickness of 2.0 μm is formed by a liquid phase growth method (LPE method) so as to fill the stripe groove 115.
P-Al _0.5 Ga _0.5 As third clad layer 116 is laminated, and a p-GaAs contact layer 117 having a layer thickness of 5.0 μm is further laminated. Then, the n-type electrode 11 is provided on the substrate side.
8. A p-type electrode 119 is formed on the growth layer side. The resonator length is set to 250 μm, and λ / 2− of the Al ₂ O ₃ film is formed on both end faces thereof.
A λ / 2 coat is applied and a solder material is used to mount the package. The semiconductor laser device 120 is completed by the above.

In this embodiment, the first laminated structure 121 is composed of the first cladding layer 102, the active layer 103, the second cladding layer 104 and the epitaxial growth promoting layer 105. The current / light confinement means is composed of the second laminated structures 122a and 122b and the second laminated structures 122a and 122b.
Stripe groove 115 for spatially separating 22b
It is composed of. Further, this second laminated structure is
It consists of two areas. The second laminated structure 12 in the region of the resonator end face portions 123 and 124 from the resonator end faces 113 and 114 to a distance of 20 μm in the resonator inward direction and perpendicular to the end faces.
2a is an etch stop layer 106 and a laser light transmission layer 10
7, a laser light absorption layer 108 and an epitaxial growth promoting layer 109. On the other hand, the second laminated structure 122b in the other region of the resonator central portion 125
Is an etch stop layer 106, a laser light transmitting layer 107, a laser light absorbing layer 108, and an epitaxial growth promoting layer 10.
9, an etch stop layer 110, a laser light absorption layer 111, and an epitaxial growth promoting layer 112.

In the above structure, the difference (Δn) between the equivalent refractive index in the layer direction inside the stripe and the equivalent refractive index in the layer direction outside the stripe having the second laminated structures 122a and 122b.
FIG. 2 shows the relationship of the above with respect to the total layer thickness of the second laminated structures 122a and 122b. Here, n-Al _0.2 Ga _0.8 As
The layer thickness of the laser light transmitting layer 107 is fixed to 0.1 μm, and n
The layer thickness of the laser light absorption layer is changed by the —Al _0.1 Ga _0.9 As laser light absorption layers 108 and 111. As shown in FIG. 2, Δn periodically oscillates with respect to changes in the total layer thickness of the second laminated structures 122a and 122b. From the point where the total layer thickness is thin, the total layer thickness when Δn becomes the maximum is set to d _M1 , d _M2 , d _M3 ... In order, and the total layer thickness when Δn becomes the minimum is d _m1 , d _m2 , d _m3 ...

The reason why Δn changes while oscillating with respect to the total layer thickness of the second laminated structure will be described below. In the case where the total layer thickness is d _M2 , the transverse mode in the layer direction outside the stripe is shown. The light intensity distribution is shown in FIG. In FIG. 3, the first cladding layer 201, the active layer 202, and the second cladding layer 20.
3, laser light transmitting layer 204, laser light absorbing layer 205, third cladding layer 206, and stripe groove 207. Here, the epitaxial growth promoting layer and the etch stop layer are omitted for simplicity. Since the epitaxial growth promoting layer and the etch stop layer are thinner than the other layers, they have little influence on the value of the equivalent refractive index and may be considered without consideration. Total layer thickness is d
_In the case of _M2 , the conditions that light reflected on the laser light transmitting layer 204 and the laser light absorbing layer 205 are strengthened by interference and reflected are satisfied. Therefore, the light intensity distribution curve 208
Has a distribution spread over the first cladding layer 201. here,
Since the value of the refractive index of each layer is inversely proportional to the Al mixed crystal ratio, the magnitude relationship of the refractive index is as follows.

Refractive index of the first, second and third clad layers <refractive index of the laser light transmitting layer <refractive index of the active layer <refractive index of the laser light absorbing layer. As the amount of protrusion increases, the equivalent refractive index of the transverse mode in the layer direction outside the stripe decreases. Since the equivalent refractive index of the transverse mode in the layer direction inside the stripe is constant, as a result, the difference Δn between the equivalent refractive index inside and outside the stripe becomes large. When the total layer thickness of the second laminated structure becomes thicker than d _M2 , the interference condition is not satisfied, so that the amount of light bleeding into the first cladding layer decreases. Further, in this case, the proportion of light in the second laminated structure increases. Since the refractive indices of the laser light transmitting layer and the laser light absorbing layer that form the second laminated structure are relatively high as described above, the equivalent refractive index of the transverse mode in the layer direction outside the stripe becomes large. Since the equivalent refractive index of the transverse mode in the layer direction inside the stripe is constant, Δn becomes small as a result. Δn becomes small until the total layer thickness d _M3 where Δn becomes the next maximum, and Δn becomes minimum at the total layer thickness d _m2 . At this time, FIG. 4 shows the light intensity distribution of the transverse mode in the layer direction outside the stripe when the total layer thickness is d _m2 . In FIG. 4, the first cladding layer 30
1, active layer 302, second cladding layer 303, laser light transmitting layer 304, laser light absorbing layer 305, third cladding layer 3
06 and stripe groove 307. Again, for the same reason as above, the epitaxial growth promoting layer and the etch stop layer are omitted for simplicity. Light intensity distribution curve 30
8 shows a distribution in which a large amount of light is occupied by the second laminated structure.

As described above, by utilizing the phenomenon that Δn oscillates with respect to the total layer thickness of the second laminated structure, Δn is large in the resonator end face and the resonator end face portions 123 and 124 in the vicinity thereof. The total layer thickness of the second laminated structure 122a
In the resonator central portion 125, which is the resonator internal region, the total layer thickness of the second laminated structure 122b is set such that Δn is small so that self-sustained pulsation occurs. In the embodiment shown above, as is clear from FIG. 2, the total thickness of the resonator end face and its vicinity is 0.3.
It is 83 μm and Δn = 9 × 10 ⁻³ . The total layer thickness in the region inside the resonator is 0.496 μm, and Δn = 2.5 × 1
It becomes 0 ^-3 .

In this embodiment, laser oscillation is determined inside the resonator. Therefore, since Δn = 2.5 × 10 ⁻³ inside the resonator, self-excited oscillation occurs in the laser oscillation. Further, the astigmatic difference of the laser is determined by Δn in the cavity facet and its vicinity. The stripe width is 4 μm, which is large at Δn = 9 × 10 ^{−3 in} the cavity end face and its neighboring region.
As shown in FIG. 7, the astigmatic difference is 3 μm, which is 5 μm or less. Further, in this case, as shown in FIG. 18, the slope efficiency is 0.3 W / A, and a high value is obtained. As described above, in the present embodiment, it is possible to realize a self-excited oscillation type semiconductor laser device for reproduction with an astigmatic difference of 5 μm or less and a sufficiently high slope efficiency.

The second laminated structure excluding the epitaxial growth promoting layer and the etch stop layer is formed into n-Al _0.2 Ga _0.8 A.
The reason why the two-layer structure of the s laser light transmitting layer and the n-Al _0.1 Ga _0.9 As laser light absorbing layer is used is to increase the amount of light seeping into the second laminated structure and reduce the light absorption. This is to increase the change in Δn with respect to the total layer thickness of the two-layer structure. However, the same effect can be obtained with only the light absorption layer, although the change in Δn is small.

Next, a semiconductor laser device of the second embodiment when used as a reproducing laser will be described. In FIG. 5, MOCVD is performed on the n-GaAs semiconductor substrate 401.
Method, n-Al _0.5 Ga _0.5 As first cladding layer 402 having a layer thickness of 2.0 μm, undoped Al having a layer thickness of 0.08 μm
_0.13 Ga _0.87 As active layer 403, p of 0.35 μm layer thickness
-Al _0.5 Ga _0.5 As second cladding layer 404, layer thickness 0.
4μm of n-Al _0.1 Ga _{0 .9} As the laser light absorption layer 40
5. n-Al _0.6 Ga _0.4 As etch stop layer 406 having a layer thickness of 0.005 μm and n-Al having a layer thickness of 0.12 μm
_{A 0.1} Ga _0.9 As laser light absorption layer 407 is sequentially grown. From the position corresponding to the resonator end faces 408, 409 of the laser to the position at a distance of 30 μm in the inside of the resonator, n−
The Al _0.1 Ga _{0 .9} As the laser light absorption layer 407 is removed by an etchant of ammonia series, further n-Al _0.6 Ga _0.4
The As etch stop layer 406 is removed with a hydrofluoric acid-based etchant. Then, by photolithography and chemical etching in a direction perpendicular to the cavity end faces 408 and 409, a stripe groove 410a having a width of 3 μm is formed at and near the cavity end face, and a stripe groove 410b having a width of 3.5 μm is formed inside the cavity. Form. This groove shape is a forward mesa shape due to anisotropy with respect to the substrate surface orientation of chemical etching. Here, the n-Al _0.1 Ga _0.9 As laser light absorption layers 407 and 405 are removed by an ammonia-based etchant, and the n-Al _0.6 Ga _0.4 As etch stop layer 4 is formed.
06 is removed with a hydrofluoric acid-based etchant. Then, p-Al _0.5 G having a layer thickness of 2.0 μm is again formed by MOCVD so as to fill the stripe grooves 410a and 410b.
An a _0.5 As third cladding layer 411 is grown, and a p-GaAs contact layer 412 having a layer thickness of 5.0 μm is further grown. After that, an n-type electrode 413 is formed on the substrate side, and a p-type electrode 414 is formed on the growth layer side. The resonator length is 250 μm, and λ / 2−λ of the Al ₂ O ₃ film is formed on both end surfaces 408 and 409.
/ 2 coat is applied, and it is mounted on the package using a solder material. The semiconductor laser device 415 is completed as described above.

In this embodiment, the first laminated structure 416
Is composed of a first cladding layer 402, an active layer 403 and a second cladding layer 404. The second laminated structure is composed of the following two regions. From the resonator end faces 408 and 409, 30 in each direction perpendicular to the end faces toward the inside of the resonator.
The second laminated structure 419a in the cavity end face portions 417 and 418 in the region up to the distance of μm is composed of the laser light absorption layer 405. The other area inside the resonator, that is,
The second laminated structure 419b in the resonator central portion 420 sandwiched between the resonator end face portions 417 and 418 is composed of the laser light absorption layer 405, the etch stop layer 406, and the laser light absorption layer 407.

In the above structure, the difference (Δn) between the equivalent refractive index in the layer direction inside the stripe and the equivalent refractive index of the transverse mode in the layer direction outside the stripe having the second laminated structure is
The relationship of the laminated structure to the total layer thickness is shown in FIG. Here, the sum of the layer thicknesses of the laser light absorption layers 405 and 407 is changed. As described above, in FIG. 6 as well, Δn shows a periodic oscillation change with respect to the total layer thickness of the second laminated structure. As can be seen from FIG. 6, since the total layer thickness of the second laminated structure 419a is 0.4 μm in both the cavity end faces and the cavity end face portions 417 and 418 in the vicinity thereof, Δn = 6 × 1
0 ^-3 , the total layer thickness is 0.
Since it is 525 μm, Δn = 3 × 10 ⁻³ . Since laser oscillation is determined inside the resonator, self-excited oscillation also occurs in this embodiment. Furthermore, since the stripe width inside the resonator is 4 μm, the slope efficiency of the light-current characteristic is 0.3 W / A, which is sufficiently high as shown in FIG. Further, the astigmatic difference of the laser is Δn on the cavity facet and its vicinity.
In this region, Δn = 6 × 10 ⁻³ is large, and the stripe width is as narrow as 3.5 μm. Therefore, the astigmatic difference of 5 μm can be achieved from FIG.

In the second embodiment, the laser light absorption layer is G
The same effect can be obtained when it is aAs. But,
Since GaAs absorbs more light than Al _0.1 Ga _0.9 As, light seeps out less, and the change in Δn with respect to the total layer thickness becomes even smaller. At this time, the change of Δn with respect to the total layer thickness of the second laminated structure is shown in FIG. 7. Here, Ga
The layer thickness of the As laser light absorption layer is changed. As can be seen from FIG. 7, Δn = 4.5 when the total layer thickness is 0.33 μm at both end faces of the resonator and in the vicinity thereof.
× 10 ⁻³ , Δn = 3 × 10 ^{−3 when the} total layer thickness is 0.25 μm at the resonator central portion in the resonator internal region. Even in this case, self-sustained pulsation occurs and the astigmatic difference is 6 μm, which is a value sufficiently smaller than that of the conventional self-sustained pulsation type laser. Further, in the second embodiment, the same effect can be obtained even if the laser light absorption layer has a multi-layer structure having different Al mixed crystal ratios. Further, in the second embodiment, the second excluding the etch stop layer 406
The same effect can be obtained even when the laminated structure is composed of only the laser light transmitting layer.

As the laser light transmitting layer, Al _0.2 Ga was used.
FIG. 8 shows the change in Δn with respect to the total layer thickness of the second laminated structure when _0.8 As was used. Here, Al _0.2 Ga _0.8 A
s The layer thickness of the laser light transmitting layer is changed. As can be seen from FIG. 8, assuming that the total layer thickness is 0.5 μm at the resonator end face and both resonator end face portions in the vicinity thereof, Δn = 8 × 10 ⁻³ ,
The total layer thickness is 0.64 μm at the center of the resonator inside the resonator.
Then, Δn = 2 × 10 ⁻³ . Even in this case, self-excited oscillation occurs in the laser oscillation, and the astigmatic difference is 5 μm.
Becomes Furthermore, the slope efficiency is 0.3W / A,
A sufficiently high value can be obtained. Further, in the second embodiment, the same effect can be obtained even if the laser light transmitting layer has a multi-layer structure having different Al mixed crystal ratios.

Further, although the embodiment of the type in which the stripe groove is embedded and grown has been shown so far, the present embodiment can be applied to an element of the type in which both side surfaces of the ridge stripe are embedded in addition to the above.

Next, a semiconductor laser device of the third embodiment when used as a recording / reproducing laser will be described. In FIG. 9, MOCVD is performed on the n-GaAs semiconductor substrate 501.
N-GaAs buffer layer 50 having a layer thickness of 0.5 μm
2, n-Al _0.5 Ga _0.5 As first cladding layer 503 having a layer thickness of 2.0 μm, undoped Al _{0.13 having a} layer thickness of 0.05 μm
Ga _0.87 As active layer 504, p-A having a layer thickness of 0.45 μm
l _0.5 Ga _0.5 As second cladding layer 505, layer thickness 0.00
A p-GaAs etch stop layer 506 having a thickness of 03 μm and a p-Al _0.5 Ga _0.5 As third cladding layer 507 having a thickness of 1.0 μm are sequentially grown. Both resonator end faces 508, 50
A stripe of SiN having a width of 3 μm is formed by photolithography and lift-off in a direction perpendicular to 9. That S
Using the iN stripe as a mask, the ridge stripe 51
Form 0. Here, the etching of the p-Al _{0. 5} Ga _0.5 As third cladding layer 507 using a hydrofluoric acid etchant. Using the SiN stripe as a mask, M again
The following layers are grown by the OCVD method so as to fill both side surfaces of the ridge stripe 510.

That is, on both side surfaces of the ridge stripe 510 and on the p-GaAs etch stop layer 506, an n-Al _0.2 Ga _0.8 As laser light transmitting layer 511 having a layer thickness of 0.15 μm and an n-GaAs layer having a layer thickness of 0.15 μm are formed. Laser light absorption layer 512, n-Al _0.2 Ga _0.8 As with a layer thickness of 0.07 μm
Laser light transmitting layer 513, n-Al _0.
6 Ga _0.4 As Etch stop layer 514 Further layer thickness 0.1
It is sequentially grown on the n-Al _0.2 Ga _{0 .8} As laser light transmitting layer 515 [mu] m.

Here, the laser cavity end faces 508, 50
A distance of 25μ from the position corresponding to 9 to the inside of the resonator.
n-Al _0.2 Ga _0.8 As laser light transmitting layer 5 up to the position of m
15 is removed with an ammonia-based etchant. Then, the SiN film is removed, and the entire surface is again MOCVD-processed.
P-Al _0.5 Ga _0.5 As fourth cladding layer 5 having a layer thickness of 1 μm
16 Further, a p-GaAs contact layer 51 having a layer thickness of 3 μm
7 is laminated. After that, an n-type electrode 518 is formed on the substrate side and a p-type electrode 519 is formed on the growth layer side. Resonator length 375μ
The Al ₂ O ₃ film and the Si film are formed so that the reflectance of the light emitting end face is 12% and the reflectance of the opposite end face is 90% as m. This element is mounted in a package using a solder material. The semiconductor laser device 520 is completed by the above.

In this embodiment, the first laminated structure 520
Is a buffer layer 502, a first cladding layer 503, an active layer 5
04, the second cladding layer 505 and the etch stop layer 5
It is composed of 06. In addition, the current confinement means is composed of a ridge stripe 510 and a second portion spatially separated by the ridge stripe 510.
It has a laminated structure. This second laminated structure is composed of the following two regions. Both resonator end face portions 522 and 522 in a region from both resonator end faces 508 and 509 to a distance of 25 μm perpendicular to the end faces.
The second laminated structure 524 in 523 is the laser light transmitting layer 5
11, a laser light absorption layer 512, a laser light transmission layer 513, and an etch stop layer 514. The second laminated structure 526 in the other region of the resonator central portion 525.
Is composed of a laser beam transmitting layer 511, a laser beam absorbing layer 512, a laser beam transmitting layer 513, an etch stop layer 514 and a laser beam transmitting layer 515. In the above structure, the difference (Δn) between the transmission refractive index in the layer direction inside the stripe and the transmission refractive index in the layer direction outside the stripe is Δ in the resonator.
n = 2 × 10 ⁻³ , and Δn = 8 × 10 ⁻³ at both resonator end face portions 522 and 523 in the resonator end face and its vicinity region.
Is set to. Therefore, self-sustained pulsation occurs, and the noise with respect to the returning light becomes sufficiently low. Further, since the stripe width is 3 μm, the astigmatic difference is 5 μm from FIG.
As shown in FIG. 21, the slope efficiency of the optical output-current characteristics is 0.58 W / A, which is a sufficiently high value. Further, from FIG. 22, the half value width of the radiation angle in the horizontal direction is 12 °, and a value of 10 ° or more can be obtained.

In the third embodiment, AlGaAs-
I have described GaAs-based materials.
It is also applicable to 1GaInP-GaInP-based materials.

Next, a semiconductor laser device of the fourth embodiment when used as a reproducing laser will be described. In FIG. 10, MOCV is formed on the n-GaAs semiconductor substrate 601.
N- (Al _0.5 Ga _0.5 ) _0.5 In having a layer thickness of 1 μm by the D method
_0.5 P first clad layer 602, undoped Ga _0.5 In _0.5 P active layer 603 having a layer thickness of 0.07 μm, layer thickness 0.3 μm
P- (Al _0.5 Ga _0.5 ) _0.5 In _0.5 P second cladding layer 604, 0.01 μm thick p-Ga _0.5 In _0.5 P etch stop layer 605, 1.0 μm thick p- (Al _0.5
A Ga _0.5 ) _0.5 In _0.5 P third cladding layer 606 and a p-Ga _0.5 In _0.5 P epitaxial growth promoting layer 607 having a layer thickness of 0.01 μm are sequentially grown. Resonator end face 60
A convex stripe of SiN having a width of 4 μm is formed by photolithography and lift-off in a direction perpendicular to 8, 609. A ridge stripe 610 is formed using the SiN stripe as a mask. Using the SiN stripe as a mask, the ridge stripe 6 is formed again by the MOCVD method.
The following layers are grown so as to fill both side surfaces of 10.

[0046] That is, the etch stop layer on the 605, the layer thickness _{0.15μm n- (Al 0.2 Ga 0 .8} ) 0.5 In 0.5 P laser light transmitting layer 611, n-Ga _0.5 layer thickness 0.01μm
An In _{0 .5} P etch stop layer 612, a layer thickness 0.07μm
N- (Al _0.2 Ga _0.8 ) _0.5 In _0.5 P laser light transmitting layer 613 and a layer thickness of 0.01 μm of n-Ga _0.5 In _0.5 P
The epitaxial growth promoting layer 614 is sequentially grown. N-Ga from the position corresponding to the resonator end faces 608 and 609 of the laser toward the position inside the resonator at a distance of 25 μm
_0.5 In _0.5 P epitaxial 614 and n- (Al
_{The 0.2} Ga _0.8 ) _0.5 In _0.5 P laser light transmitting layer 613 is removed. Then, the SiN film is removed, and the MOC is formed on the entire surface again.
P- (Al _0.5 Ga _0.5 ) _0.5 I with a layer thickness of 1 μm by the VD method
n _0.5 P fourth clad layer 615 and p− with a layer thickness of 3 μm
A GaAs contact layer 616 is laminated. After that, an n-type electrode 617 is formed on the substrate side and a p-type electrode 618 is formed on the growth layer side. The resonator length is 250 μm, and both resonator end faces 60
Λ / 2-λ / 2 coat is applied to each of 8, 609. The device is mounted in a package using a solder material. The semiconductor laser device 619 is completed by the above.

In this embodiment, the first laminated structure 620 is used.
Is composed of a first cladding layer 602, an active layer 603, a second cladding layer 604 and an etch stop layer 605.
The current / light confinement means is a ridge stripe 610.
And a second laminated structure that is spatially separated thereby. This second layered structure then consists of two regions. 25 from each of the resonator end faces 608 and 609 perpendicularly to the end face.
The second laminated structure 623 in the cavity end face portions 621 and 622 in the region up to the distance of μm is composed of the laser light transmission layer 611 and the etch stop layer 612. The second laminated structure 625 in the other region of the resonator central portion 624 is composed of the laser light transmission layer 611, the etch stop layer 612, the laser light transmission layer 613, and the epitaxial growth promotion layer 614.

In the above structure, the difference (Δn) between the equivalent refractive index in the layer direction inside the stripe and the equivalent refractive index in the layer direction outside the stripe is Δn = 2 × 1 in the resonator central portion 624.
0 ⁻³ , and Δn = 8 × 10 ⁻³ is set in the resonator end face and the resonator end face portions 621 and 622 in the vicinity thereof. Therefore, self-excited oscillation occurs and the astigmatic difference is 5 μm.
And the slope efficiency of the optical output-current characteristics is 0.3 W /
A is obtained.

Next, a semiconductor laser device according to the second embodiment of the present invention when used as a recording / reproducing laser will be described.
In FIG. 11, on the n-GaAs semiconductor substrate 701,
N-Al _0.5 Ga _0.5 with a layer thickness of 2.0 μm by MOCVD method
As first cladding layer 702, quantum well type active layer 703,
P-Al _0.5 Ga _0.5 As second cladding layer 704 having a layer thickness of 0.20 μm, p-GaAs first etch stop layer 705 having a layer thickness of 0.003 μm, p-Al _{0.5 having} a layer thickness of 0.2 μm.
Ga _0.5 As third cladding layer 706, layer thickness 0.003μ
m p-GaAs second etch stop layer 707 and a p-Al _0.5 Ga _0.5 As fourth clad layer 708 having a layer thickness of 1.0 μm are sequentially grown. Here, the quantum well active layer 7
03 is undoped Al _0.3 Ga with a layer thickness of 0.004 μm
_0.7 As guide layer and undoped Al with a layer thickness of 0.01 μm
It is composed of five guide layers and four quantum well layers alternately with _0.1 Ga _0.9 As quantum well layers.

Further, perpendicular to the resonator end faces 709 and 710.
Width by photolithography and lift-off in different directions
A 3.5 μm SiN stripe is formed. This Si
Use the N stripe as a mask to create a convex ridge stripe
Form. At this time, p-Al _0.5Ga_0.5As 4th Kura
A hydrochloric acid-based etchant is used for etching the dead layer 708.
To use. In addition, the p-GaAs second etch stop layer 70
7 is not removed by hydrochloric acid type etchant, so it is an etch
Ing is stopped and a ridge stripe 711 is formed.
Next, from the positions corresponding to the resonator end faces 709 and 710,
Photolithography up to a distance of 20 μm inside the shaker
The second etch of p-GaAs by graphography and lift-off
Stop layer 707 and p-Al_0.5Ga_0.5As third crack
Etch layer 706. Here, p-GaAs
2 Etch stop layer 707 is an ammonia-based etchant
Etching with p-Al_0.5Ga_0.5As No.
3 Cladding layer 706 is etched by hydrochloric acid type etchant
To go. This etching is the first etch of p-GaAs.
Stop at the top layer 705, and
The ridge stripe 7 is formed on both resonator end face portions 712 and 713.
14 is formed. And mask the SiN stripe
Then, the ridge stripe 7 is formed again by the MOCVD method.
The following layers should be embedded so that both sides of 11,714 are embedded.
Grow sequentially.

That is, the n-GaAs laser light absorption layer 715 having a layer thickness of 1.0 μm is laminated on the p-GaAs first etch stop layer 705, the SiN film is removed, and the entire surface is again formed by the MOCVD method. A p-GaAs contact layer 716 having a thickness of 3 μm is formed. After that, the n-type electrode 71 is provided on the substrate side.
7. A p-type electrode 718 is formed on the growth layer side. The resonator length as 500 [mu] m, reflectance 12% of the light emission end face, and the Al ₂ O ₃ film as a 90% reflectivity of the opposite end face S
An i film is formed. The device is mounted in a package using a solder material. As described above, the semiconductor laser device 71
9 is completed. In the present embodiment, the first laminated structure 720 in the resonator end face and the resonator end face portions 712 and 713 in the vicinity thereof includes the first cladding layer 702, the quantum well active layer 703, the second cladding layer 704, and the first etch stop. It is composed of layer 705. Further, the first laminated structure 722 in the resonator central portion 721 sandwiched between the two resonator end face portions 712 and 713 has the first clad layer 702, the quantum well active layer 703, the second clad layer 704, and the first etch stop. Layer 705, third cladding 706 and second
It is composed of the etch stop layer 707. On the contrary,
The second laminated structures 723a and 723b are the laser light absorption layer 71.
It is composed of 5. First laminated structures 720, 723a,
723b from the active layer 703 to the second stacked structure 722
FIG. 12 shows changes in equivalent refractive index difference (Δn) in the layer direction inside and outside the stripe with respect to the total layer thickness up to. As can be seen from FIG. 12, when the total layer thickness from the active layer to the second laminated structure is thicker, the influence of the second laminated structure is less likely to occur, so that the refractive index difference (Δn) inside and outside the stripe tends to become smaller. is there. In this embodiment, the total thickness of the resonator end faces and the both resonator end face portions 712 and 713 in the vicinity thereof are set to 0.
Since it is set to 203 μm, Δn = 1.5 × 10 ^-2
And the total layer thickness is 0.4 in the resonator central portion 721.
Since it is 53 μm, Δn = 2.5 × 10 ⁻³ .

With the above structure, self-sustained pulsation occurs, and the noise with respect to the returning light is sufficiently reduced. Since the stripe width is 3.5 μm, the astigmatic difference is 3 μm from FIG.
And the slope efficiency of the optical output-current characteristics is 0.6.
A sufficiently high value of W / A can be obtained. Further, from FIG. 22, the half value width of the radiation angle in the horizontal direction is 11 °, and a value of 10 ° or more can be obtained.

In this embodiment, the n-GaAs laser light absorption layer 715 is shown as the second laminated structure.
Similar effects can be obtained in the case of other laser light absorption layers or laser light transmission layers. Particularly, as the laser light transmitting layer, n-A having a higher Al mixed crystal ratio than the cladding layer is used.
It may be used l _0.6 Ga _0.4 As layer.

Next, a semiconductor laser device of the third embodiment of the present invention when used as a reproducing laser will be described.
In FIG. 13, on the n-GaAs semiconductor substrate 801,
N-Al _0.5 Ga _0.5 with a layer thickness of 1.0 μm by MOCVD method
As first cladding layer 802, undoped Al _0.13 Ga _0.87 As active layer 803 having a layer thickness of 0.08 μm, layer thickness of 0.35
μm p-Al _0.5 Ga _0.5 As second cladding layer 804,
P-GaAs first etch stop layer 805 having a layer thickness of 0.0003 μm, p-Al _0.5 Ga _0.5 A having a layer thickness of 0.01 μm
s First etch stop layer 806, p with a layer thickness of 0.02 μm
-GaAs second etch stop layer 807, layer thickness 0.01
μm p-Al _0.5 Ga _0.5 As third etch stop layer 8
08, an n-GaAs laser light absorption layer 809 having a layer thickness of 1.0 μm is sequentially grown.

Here, the laser cavity end faces 810, 81
Stripe groove 812 having a width of 3.5 μm and reaching the p-GaAs second etch stop layer 807 in the direction perpendicular to 1
Are formed by photolithography and chemical etching. At this time, the n-GaAs laser light absorption layer 809 is removed with an ammonia-based etchant, and p-Al is used.
_{The 0.5} Ga _0.5 As third etch stop layer 808 is removed with a hydrofluoric acid-based etchant. Further, the stripe groove 812 is again formed in the resonator region having a distance of 25 μm or more from the position corresponding to the resonator end face 810 on the light output side toward the inside of the resonator.
Toward the bottom of the p-GaAs first etch stop layer 80
Etching up to 5 and deep stripe groove 8
13 is formed. At this time, the p-GaAs second etch stop layer 807 is removed with an ammonia-based etchant, and the p-Al _0.5 Ga _0.5 As first etch stop layer 806 is removed with a hydrofluoric acid-based etchant.

Further, the laser light absorption layer 809 is formed by the LPE method so as to fill the stripe grooves 812 and 813.
A p-Al _0.5 Ga _0.5 As third cladding layer 814 having a layer thickness of 2.0 μm is stacked on the p-Al _0.5 Ga _0.5 As third clad layer 814, and further a p-Ga layer having a layer thickness of 50 μm is formed.
The As contact layer 815 is laminated. Then, an n-type electrode 816 is formed on the substrate side and a p-type electrode 817 is formed on the growth layer side. The cavity length is set to 250 μm, and both cavity end faces 8
Λ / 2-λ / 2 coat of Al ₂ O ₃ film is applied to 10,811 and mounted on a package using a solder material. The semiconductor laser device 818 is completed by the above.

In this embodiment, the first laminated structure 820 in the cavity end facet 819 on the light output side has the first clad layer 802, the active layer 803, the second clad layer 804, the etch stop layer 805, and the first etch stop. Layer 806 and second etch stop layer 807. Further, the first laminated structure 822 in the resonator central portion 821 in the resonator region having a distance of 25 μm or more from the position corresponding to the resonator end face 810 on the light output side toward the inside of the resonator has the first cladding layer 802 and the active layer 803. , The second cladding layer 804 and the etch stop layer 805. Further, the second laminated structure 823 in the cavity end face portion 819 is composed of the third etch stop layer 808 and the laser light absorption layer 809. In addition, the second laminated structure 8 in the resonator central portion 821
24 is composed of a first etch stop layer 806, a second etch stop layer 807, a third etch stop layer 808 and a laser light absorption layer 809. Therefore, the resonator end face 81
0 and the resonator end face portion 819 in the vicinity thereof, the active layer 803 in the first laminated structure 821 inside the stripe.
From the second laminated structure to the resonator central portion 820.
In comparison with the layer structure from the active layer 803 to the second laminated structure in FIG. Here, the cavity end face 810 and the GaAs etch stop layer 80 inside the stripe in the vicinity thereof are
It is composed of 5 layers. Thus, the resonator end face 810
The total thickness of the GaAs etch stop layer in and around it is thicker than the inside of the resonator. FIG. 14 shows Δ for the total thickness of the GaAs etch stop layer inside the stripe.
The relationship of n is shown. As can be seen from FIG. 14, the thicker the GaAs etch stop layer, the larger the refractive index inside the stripe, so Δn tends to increase. In this embodiment, the thickness of the GaAs etch stop layer inside the resonator is 0.
Since it is set to 003 μm, Δn = 2.5 × 10 ⁻³
Since the thickness of the GaAs etch stop layer on the resonator end face and its vicinity is set to 0.023 μm,
Δn = 9 × 10 ⁻³ .

Therefore, also in this embodiment, self-excited oscillation occurs, and the noise with respect to the returning light becomes sufficiently low. Further, since the stripe width is 3.5 μm, the astigmatic difference is as narrow as 3 μm from FIG. 18, and the slope efficiency of optical output-current magnetism is 0.3 W / A, which is a sufficiently high value, as shown in FIG.

In each of the above examples, the difference (Δn) in the equivalent refractive index in the layer direction inside and outside the stripe
^Is set to Δn = 1 to 5 × 10 ⁻³ in the resonator internal region,
At the resonator end face and the resonator end face region in the vicinity thereof, Δn =
It is set to 5 to 10 × 10 ⁻³ , and Δn of the end face of the resonator is set to be larger than that inside the resonator. This is because laser oscillation is determined by Δn inside the resonator, so Δn inside the resonator is set to 1 to 5 × 10 ⁻³ so that self-excited oscillation occurs. On the other hand, since the optical characteristics of the emitted light, that is, the astigmatic difference and the horizontal radiation angle are determined by Δn of the end face of the resonator, the astigmatic difference is about 5 μm or sufficiently small. , And Δn = 5 to 10 × 10 ⁻³ so that the radiation angle in the horizontal direction becomes larger than 10 °. Also, since the slope efficiency is determined inside the resonator, the stripe width inside the resonator should be 3μ so that the slope efficiency is sufficiently large.
Set to m or more. In this way, the stripe width is 3 μm
Since the above setting is made, the slope efficiency of the optical output-current characteristic does not decrease in the case of the reproducing laser. Further, since the horizontal radiation angle of the laser is determined by Δn of the end face of the resonator, the radiation angle of 10 ° or more is obtained in the case of the recording / reproducing laser, and the coupling rate to the lens is not lowered.

The layer thicknesses and layer structures other than those in the above embodiments are applicable as long as the claims of the present invention are satisfied. Further, a region having a larger Δn than the inside of the resonator may be provided only on one light output side end face of the resonator and in the vicinity thereof. Further, the stripe width is preferably narrower in the resonator end face and in the region in the vicinity thereof than in the resonator, and the stripe width may gradually change (tapered) from a wide portion to a narrow portion. . Furthermore, MOC is used as a growth method.
Although the VD method and the LPE method are shown, the molecular beam epitaxial growth method (MBE method), the MONBE method, the atomic layer epitaxial growth method (ALE method), and the like can be applied.

[0061]

As described above, according to the semiconductor laser device of the present invention, the total layer thickness of the second laminated structure is different between the cavity end face region and the central region, or
The layer thickness from the active layer to the second laminated structure in the laminated structure is configured such that the region at both end face portions of the resonator is thinner than the region at the central portion thereof, or from the active layer to the second laminated structure in the first laminated structure. The layer structure up to is different between the region at both end faces of the resonator and the region at the center, and the difference between the equivalent refractive index in the layer direction inside the stripe part and the equivalent refractive index in the layer direction outside the stripe part is Since the region of the end face of the cavity is made larger than the region of the center, the difference in the equivalent refractive index at the center of the resonator can be determined so that self-sustained pulsation occurs, and the laser non- It is possible to determine the difference in the equivalent refractive index of the resonator end face so that the point difference is small and the horizontal radiation angle is large. Further, since the width of the stripe portion is configured such that the end facet of the laser is narrower than the center part, the slope efficiency of the optical output-current characteristics is determined by the center part of the resonator, so that the slope efficiency is sufficiently large. The stripe width in the central part of the resonator can be set wide. Therefore, in the self-excited oscillation laser for reproduction, the astigmatic difference can be reduced without lowering the slope efficiency, and in the self-excited oscillation laser for recording and reproduction, the horizontal radiation angle can be narrowed. And a semiconductor laser device having a self-oscillation type low noise characteristic in which the astigmatic difference is sufficiently small, and the electrical characteristics and the optical characteristics are good. be able to.

[Brief description of drawings]

FIG. 1 is a perspective view of a semiconductor laser device showing a first embodiment of the first invention.

FIG. 2 is a diagram showing the relationship between Δn and the total layer thickness of the second laminated structure in the semiconductor laser device of FIG.

FIG. 3 is a light intensity distribution diagram outside the stripe when the total layer thickness = d _{M2 in} FIG. 2;

FIG. 4 is a light intensity distribution diagram outside the stripe when the total layer thickness = d _{m2 in} FIG. 2;

FIG. 5 is a perspective view of a semiconductor laser device showing a second embodiment of the first present invention.

6 is a diagram showing the relationship between Δn and the total layer thickness of the second laminated structure in the semiconductor laser device of FIG. 5 (where the light absorption layer is Al.
_0.1 Ga _0.9 As).

FIG. 7 is a diagram showing the relationship between Δn and the total layer thickness of the second laminated structure in the semiconductor laser device (when the light absorption layer is GaAs).

FIG. 8 is a diagram showing the relationship between Δn and the total layer thickness of the second laminated structure in the semiconductor laser device (the light transmission layer is Al _0.2 G).
a _0.8 As).

FIG. 9 is a perspective view of a semiconductor laser device showing a third embodiment of the first present invention.

FIG. 10 is a perspective view of a semiconductor laser device showing a fourth embodiment of the first present invention.

FIG. 11 is a perspective view of a semiconductor laser device showing an embodiment of the second invention.

12 is a diagram showing the relationship between Δn and the total layer thickness from the active layer to the second laminated structure in the semiconductor laser device of FIG.

FIG. 13 is a perspective view of a semiconductor laser device showing an embodiment of the third invention.

14 is a diagram showing the relationship between Δn and the total thickness of the GaAs etch stop layer inside the stripe in the semiconductor laser device of FIG.

FIG. 15 is a perspective view of a conventional semiconductor laser device.

FIG. 16 is a diagram showing the relationship between the maximum self-pulsation oscillation optical output and Δn in the case of a reproducing laser.

FIG. 17 is a diagram showing the relationship between astigmatic difference and stripe width in the case of a reproducing laser.

FIG. 18 is a diagram showing the relationship between slope efficiency and stripe width in the case of a reproducing laser.

FIG. 19 is a diagram showing the relationship between the self-oscillation maximum light output and Δn in the case of a recording / reproducing laser.

FIG. 20 is a diagram showing the relationship between the astigmatic difference and the stripe width in the case of a recording / reproducing laser.

FIG. 21 is a diagram showing the relationship between slope efficiency and stripe width in the case of a recording / reproducing laser.

FIG. 22 is a diagram showing a relationship between a half value width of a horizontal radiation angle and a stripe width in the case of a recording / reproducing laser.

[Explanation of symbols]

101, 401, 501, 601, 701, 801
Semiconductor substrate 102, 402, 503, 602, 702, 802
First cladding layer 103, 403, 504, 603, 703, 803
Active layer 104, 404, 505, 604, 704, 804
Second clad layer 113, 114, 408, 409, 508, 509, 6
08,609,709,710,810,811 Resonator end face 115,410a, 410b, 507,610,71
1,714,812,813 Stripe groove 120,415,520,619,719,818
Semiconductor laser device 121, 416, 521, 620 First laminated structure 122a, 419a, 524, 623, 723a, 82
3 Second laminated structure of resonator end face 122b, 419b, 526, 625, 723b, 82
4 Second laminated structure in central part of resonator 123, 124, 417, 418, 522, 523, 6
21, 622, 712, 713 Resonator end face portion 125, 420, 525, 624, 721, 821
Resonator central portion 720,820 Resonator end face first laminated structure 722,822 Resonator central portion first laminated structure

Claims (4)

[Claims] 1. A first laminated structure formed on a semiconductor substrate and comprising an active layer and a clad layer sandwiching the active layer,
A current / light which is formed on the first laminated structure and has one or more second laminated structures and a stripe portion which spatially separates the second laminated structure, and confines current and light inside the stripe portion. A semiconductor laser device including confinement means, wherein a difference between an equivalent refractive index in a layer direction inside the stripe portion and an equivalent refractive index in a layer direction outside the stripe portion is at least one of both end face portions of a laser cavity. So that the region of the end face portion of the second laminated structure is larger than at least the region of the central portion sandwiched between the end face portions of the second laminated structure. The semiconductor laser device is configured so as to have a different structure in the region of (1) and at least the region of the central portion sandwiched by the both end faces. 2. A first laminated structure which is formed on a semiconductor substrate and is composed of an active layer and a clad layer sandwiching the active layer,
A current / light which is formed on the first laminated structure and has one or more second laminated structures and a stripe portion which spatially separates the second laminated structure, and confines current and light inside the stripe portion. A semiconductor laser device including confinement means, wherein a difference between an equivalent refractive index in a layer direction inside the stripe portion and an equivalent refractive index in a layer direction outside the stripe portion is at least one of both end face portions of a laser cavity. The layer thickness from the active layer in the first laminated structure to the second laminated structure is set so that the region of the end face of the laser is larger than the region of at least the central part sandwiched between the end faces. A semiconductor laser device in which at least one end face region of both end face portions is thinner than at least a central region sandwiched between the both end face portions. 3. A first laminated structure formed on a semiconductor substrate, the first laminated structure including an active layer and a clad layer sandwiching the active layer,
A current / light which is formed on the first laminated structure and has one or more second laminated structures and a stripe portion which spatially separates the second laminated structure, and confines current and light inside the stripe portion. A semiconductor laser device including confinement means, wherein a difference between an equivalent refractive index in a layer direction inside the stripe portion and an equivalent refractive index in a layer direction outside the stripe portion is at least one of both end face portions of a laser cavity. The layer structure from the active layer in the first laminated structure to the second laminated structure is such that the end face region of the laser is larger than at least the central region sandwiched between the end face portions. A semiconductor laser device having a structure in which at least one end face portion of both end face portions is different from at least a central portion region sandwiched by the both end face portions. 4. The width of the stripe portion is configured such that a region of at least one end face portion of both end face portions of the resonator of the laser is narrower than a region of at least a central portion sandwiched by the both end face portions. 1. The semiconductor laser device described in 1 or 2 or 3.