JPH07106686A - Semiconductor laser - Google Patents

Abstract

PURPOSE:To obtain an excellent beam spot profile easily by forming a first electrode on a cap layer formed on one main surface of a semiconductor substrate' and a second electrode on the other main surface and specifying the stripe width thereby facilitating the design of optical leans and the like. CONSTITUTION:The semiconductor.laser of planar stripe structure has the stripe width varying gradually between S1 at a part remote from the optical edge 12 and S2 at the optical edge. Assuming the distance of an imaginary light source emitting light in parallel with the junction plane from the optical edge is D, the radius of curvature of the isophase plane of light emitted from the optical edge is R, and the half width of near field pattern on the optical edge is W, the distance D is maximized at some value of R with W as a parameter. The distance D increases as the half width W increases whereas the radius of curvature R increases as S1 increases and the half width W increases as S2 increases and thereby the stripe width S. is set at 5-10mum and S2 is set at 0.5-4mum.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is a semiconductor laser suitable for use as a light source for recording and / or reproducing in a recording or reproducing apparatus such as an optical video disk, a digital audio disk or the like, and in particular, a planar stripe. It relates to a semiconductor laser having a structure.

[0002]

2. Description of the Related Art Conventional general semiconductor lasers are roughly classified into a refractive index guide (index guide) type and a gain guide (gain guide) type by a vertical mode confinement mechanism, that is, a waveguide mechanism.

As an example of a refractive index guide type semiconductor laser, for example, FIG. 8 shows a schematic enlarged plan view thereof, and FIG.
A semiconductor laser 10 having a structure shown in the sectional view of FIG.

The semiconductor laser 10 is an N-type GaA.
On the s substrate 1, a first N-type Al _y Ga _{1- y} As is formed.
A cladding layer 2, an active layer 3 made of N-type Al _x Ga _1-x As, the second cladding layer 4 and the N-type GaAs cap layer similar N-type made of Al _y Ga _1-y AS 5 Are sequentially epitaxially grown, and a high-refractive-index layer 6 is formed in the center thereof, for example, in the form of a stripe extending in one direction and introducing P-type impurity Zn by selective diffusion or the like.

The depth of the high-refractive index layer 6 is selected such that it penetrates into the active layer 3 or a depth of several thousand Å into the first cladding layer 2.

An insulating layer 7 made of SiO ₂ or the like is formed on the surface of the semiconductor layer 5, and one electrode 8 is ohmically deposited on the high refractive index layer 6 through an electrode window formed in the insulating layer 7 to form a substrate 1. The other electrode 9 is also ohmicly deposited on the back surface of the.

In this way, a refractive index difference is formed between the portion where the layer 6 is present and the portion where the layer 6 is not present in the active layer 3, whereby the light oscillation region is regulated in a stripe shape.

As an example of the planar stripe type of the gain guide type semiconductor laser, there is the one shown in FIG. 10, for example. Even in this case, for example, N-type G
A first substrate made of N-type Al _y Ga _1-y As on aAs substrate 1.
Clad layer 2 is formed on the n-type or p-type
_-Type Al _x Ga _1-x As active layer 3, further on it P-type Al _y Ga _1-y As second cladding layer 4, and on top of this P-type GaAs cap layer 5 are sequentially formed by epitaxial growth. For example, a striped electrode 8 extending in the direction orthogonal to the paper surface in FIG. 9 is also formed in the center of the insulating layer 7 formed on the semiconductor layer 5. It is formed by ohmic contact through the electrode window on the stripe, and the other electrode 9 is also formed by ohmic contact on the back surface of the substrate 1.

In the semiconductor laser having such a structure, the stripe-shaped electrode 8 concentrates the operating current, and the operating current injected immediately under the stripe forms a stripe-shaped oscillation region in the active layer. To be done. That is, the gain distribution resulting from the lateral concentration distribution of the injected carriers in the active layer determines the lateral mode.

Incidentally, the width of the stripe-shaped oscillation region in the conventional semiconductor laser of this kind of stripe structure is set to a uniform width S in each part as shown in FIG.

The above-mentioned refractive index guide type semiconductor laser and gain guide type semiconductor laser have their respective advantages, but have their respective drawbacks. That is, in the refractive index guide type, since the longitudinal mode is a single mode, for example, when it is used as a writing (recording) or reading (reproducing) light source in an optical video disc or the like, noise due to return light is generated. Despite its weakness, it is easy to set the focal position for actual use because the so-called beam waist position, that is, the virtual light source position is near the light end face (light reflecting surface from the semiconductor laser). Has the advantage.

Furthermore, a far-field image in a cross section in the direction parallel to the junction, a so-called far field pattern (fa
(r field pattern) is bilaterally symmetric, and similarly, when a minute spot is obtained by condensing with an optical system such as an objective lens as reading or writing light in actual use, it is easy to obtain a spot shape with small distortion. There are advantages.

On the other hand, the virtual light source position in the above-described gain guide type semiconductor laser exists on the light end face of the light emitting region for the light perpendicular to the junction, but for the light in the direction parallel to the junction. 20 μm inside the optical edge
However, the far field pattern is asymmetrical and the astigmatism is large, which is disadvantageous in obtaining a minute spot with small distortion. However, this gain guide type semiconductor laser has an advantage that the longitudinal mode is a multimode and the influence of the above-mentioned return light noise and mode hopping noise is small.

[0014]

SUMMARY OF THE INVENTION The present invention has the advantages of a gain-guided semiconductor laser, and is designed to improve astigmatism, for example, a write or read light source for optical video discs or digital audio discs. The present invention provides a semiconductor laser in which the design of the optical lens and the like is facilitated and an excellent beam spot shape can be easily obtained.

[0015]

According to a first aspect of the present invention, at least a first clad layer, an active layer, a second clad layer and a cap layer are sequentially laminated on one main surface of a semiconductor substrate, and the cap is formed. A first electrode is formed on the layer, a second electrode is formed on the other main surface of the semiconductor substrate, and the stripe width is S ₁ at a position distant from the light end face and S ₂ at the light end face, and in between In the semiconductor laser having a planar stripe structure in which the stripe width is continuously changed, the distance of the virtual light source of light parallel to the junction surface from the light end face is D, the light emitted from the light end face, etc. Assuming that the radius of curvature of the phase surface is R and the half-value width of the near-field image of light at the light end face is W, D becomes maximum at a certain value of R with W as a parameter, and the larger W is, the larger D is. , also ho large S ₁ to nearly independent R is large, with the higher the S ₂ greater W is large, 5 to 10 [mu] m and S _1, S ₂
Is set to 0.5 to 4 μm.

According to a second aspect of the present invention, at least a first clad layer, an active layer, a second clad layer and a cap layer are sequentially laminated on one main surface of a semiconductor substrate, and the first clad layer is formed on the cap layer. An electrode is formed, a second electrode is formed on the other main surface of the semiconductor substrate, and the stripe width is S ₁ at a distance from the light end surface and S ₂ at the light end surface, and the stripe width is continuous between them. In a semiconductor laser having a planar stripe structure that changes dynamically, the distance of a virtual light source of light parallel to the junction surface from the light end face is D, and the radius of curvature of the equiphase surface of light emitted from the light end face is R, where W is the half-value width of the near-field image of the light on the light end face, D becomes maximum at a certain value of R with W as a parameter, and the larger W is, the larger D is. _The larger ₁ is, the larger R is and S Using the fact that W is larger as ₂ is larger, S ₁ is set to 20 μm or more, and S ₂ is 0.5 to
Set to 4 μm.

[0017]

According to the above-described structure of the present invention, the astigmatism can be improved even though it is a gain guide type.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention adopts a gain guide type structure having a stripe structure.

In the present invention, for example, the first cladding layer 2, the active layer 3,
The second clad layer 4, the cap layer 5 and the like are sequentially epitaxially grown, and the pattern of the ohmic contact portion of the electrode 8 with respect to the cap layer 5 is shown by reference numeral 11 in FIG. Striped,
In particular, a planar taper stripe structure is adopted in which the stripe width is S ₁ at a distance from the light end face 12 and S ₂ at the light end face, and a taper 13 that smoothly changes between them is formed. , D is the distance from the light end face 12 of the virtual light source of light parallel to the cemented surface, R is the radius of curvature of the equiphase surface of the light emitted from this light end face 12, and the near-field image of the light at the light end face 12 is Assuming that the half-width of W is W, D becomes maximum at a certain value of R with W as a parameter, and the larger W is, the larger D is. Also, almost independently, the larger S ₁ is, the larger R is and the larger S ₂ is. The larger W is, the smaller S ₁
Is set to be large or small with the maximum value as a boundary, and S ₂ is made small to make R large and W small. That is, in the present invention, S ₁ is 5 to 10 μm and S ₂ is 0.
Set to 5-4 μm. Alternatively, S ₁ should be 20 μm or more,
Set S ₂ to 0.5-4 μm.

The present invention is an electrode stripe type in which current is concentrated by forming a substantially electrode-deposited pattern in a stripe shape, or a stripe-shaped junction is formed by selective ion implantation or selective diffusion of impurities. Various configurations such as a cushion stripe type or a proton irradiation type in which a high resistance region is formed by proton irradiation to form a stripe-shaped current path can be adopted.

The characteristics of the semiconductor laser according to the present invention will be understood from the description given below. That is, the emitted beam in the gain guide type laser as described in FIG. 10 generally has astigmatism. That is, in this laser, the light in the direction perpendicular to the junction exists in its beam waist, that is, the virtual light source exists at the light emitting end surface (light end surface) of the laser, but the virtual light source for light parallel to the junction is inside the optical end surface. And the distance from the light end face of this virtual light source is D, this distance D is an amount corresponding to the amount of astigmatism, and this D is given by Equation 1.

[Equation 1]

Here, W is the half-value width (1 / e ^{2 of the} width) of the near-field image on the light end face, R is the radius of curvature of the equiphase surface of the light emitted into the air in the vicinity of the light end face, λ Is the wavelength of the light.

When the distance D is plotted as a function of the radius of curvature R with the half-width W as a parameter based on the equation 1,
It can be seen that the distance D takes a maximum value at a certain radius of curvature R, as shown by the curves a and b in FIG. Here, the curve b is larger than the curve a in the case where W is large, and as is clear from this, in order to reduce the astigmatism and therefore the distance D, (I) the half width W is reduced, and It can be seen that there are two methods of making the radius of curvature R sufficiently large (II) making the half-width W small and making the radius of curvature R sufficiently small.

However, in the case of a stripe type gain guide type laser, the full width at half maximum W and the radius of curvature R are dependent on the stripe width S of W∝S ^1/2 and R∝S, respectively. The method (I) cannot be immediately adopted. That is, if the stripe width S is increased in order to increase R,
Along with that, W becomes large. In comparison, (I
In the method of I), if the stripe width S is designed to be narrow, W
Since both R and R can be reduced, astigmatism can be reduced. However, narrowing the stripe width in this way causes an increase in the threshold current density and a decrease in the differential efficiency in the photo-current characteristics. Therefore, it is practically difficult to obtain a highly reliable one having small astigmatism and excellent light-current characteristics.

In comparison with this, as shown in FIG.
Different stripe width S₁And S ₂With two
Gain-guided laser with resonators arranged in series
(A) The size of the near-field image is
Ip width S₂Is determined by. (B) The radius of curvature R of the equiphase surface is the stripe on the center side.
Width S₁Is determined by. I knew that. From these matters (a) and (b), (a) the central stripe width S₁Of the end face
Stripe width S₂Is small, the above-mentioned astigmatism is small.
It conforms to the method (I) for drilling. (B) Width S₁The S₁= 5 to 10 μm is practically no problem
Width is small enough and width S₂Of a small enough width
If it is 0.5 to 4 μm, the astigmatism mentioned above is reduced.
Consistent with method (II) for. I got the result.

That is, in the case of the general gain guide type configuration, the size of the near-field image is determined by the gain guide width generated by the so-called lateral flow of the current in the direction parallel to the junction. The size of the visual field image tends to be larger than the stripe width. On the other hand, in the case of the configuration of (a) above, a refractive index guide type laser is obtained in that the near field image is small and the radius of curvature R of the equiphase surface is large due to the above (a) and (b). Similar results are obtained, and the astigmatism is small and can be made 10 μm or less. Further, in the case of the above configuration (b), although the gain guide type configuration is adopted, the astigmatism D is 10 to 15 μm because the radius of curvature R of the equiphase surface of the light emitted from the optical end face becomes small. Is in the range of
Moreover, there is little characteristic deterioration which is a problem in the narrow stripe type laser as described above, and the characteristic is excellent as a gain guide type laser.

The present invention was made based on the consideration of the above (a) and (b). Next, these (a) and (b)
Will be described. As shown in FIG. 1, the stripe width of the oscillation region has widths S ₂ and S ₁ which are different from each other in the optical end face 12 and in the part farther from the optical end face 12, respectively, and the width between the two is smooth. In a so-called tapered stripe type semiconductor laser that changes, in the plane parallel to the junction surface, the stripe extension direction is z, the direction orthogonal to this is x, and these x and the direction orthogonal to z are y. It is assumed here that the spatial gain distribution depends on x and z. The source of the electromagnetic wave is in the center of the stripe region 11, and the stripe width is sufficiently wide.
As a result, the TE wave generated here propagates as a substantially plane wave to the tapered portion. The wave equation to be solved here is Equation 2.

[Equation 2] ▽ ² E + k ² (x) E = 0 (2)

Now, in order to analytically obtain the solution thereof, only the case where the x dependence of the wave vector k is treated as Equation 3 will be considered.

## EQU3 ## k ² (x) = k ² −kk ₂ x ² (k ₂ is a complex number) (3)

When the wave equation of the equation (2) is solved based on these assumptions, the equation 5 is obtained.

[ ^Equation 4] E = Ψ (x, y, z) e ^−ikz (4)

[Equation 5] Is obtained. By substituting equation (5) into equation (4) assuming that Ψ can be written as equation (6), equation (7) is obtained.

[Equation 6]

[Equation 7] ^{-Q 2 x 2 -2iQ-kx 2} Q'-2kP'-kk 2 x 2 = 0 ‥‥ (7)

Now, in order for Equation (7) to hold true,

[Equation 8]

To solve this equation (8), Q = kS '/ S
Substituting into the differential equation for Q,

## EQU9 ## S ″ + S (k ₂ / k) = 0 (9) is obtained. The solution of this equation (9) is

[Equation 10] Becomes

Therefore, also

[Equation 11] Becomes

Therefore, Q (z) is

[Equation 12] Becomes

Now, if a new function q (z) ≡k / Q (z) is introduced and q ^-1 (z) can be divided into a real number part and an imaginary number part,

[Equation 13] Becomes

Here, R (z) is the radius of curvature of the equiphase surface at the tip of the light in the z direction, and W (z) is the light beam spot width (half-value width) in the z-axis direction. Now, the concrete form of q (z) is obtained, and the behavior of R (z) and W (z) is analyzed. Now suppose the wave vector k depends on x ^2.

[Equation 14] Suppose we can write (where g _P and α are real numbers).

According to the expressions (3) and (12),

[Equation 15] Then, by comparing these equations (12) and (13),

## EQU16 ## k ₂ = iα ₂ (14) is obtained. Here, the specific form of α ₂ is, for example,

[Equation 17] May be assumed (S is the stripe width).

Substituting equation (14) into equation (10), and
When (z) is calculated,

[Equation 18] Becomes

Now When the denominator of the equation (16) q (z) is A and the numerator is B,

A = − (q ₀ / z) (1 + i) Qsin {(1 + i) θ} + cos (1 + i) θ = − (q ₀ / z) (1 + i) θ (sinθcoshθ + icosθsinhθ) + (cosθcoshθ−isinθsinhθ)

[Equation 20]

As can be seen from the subsequent numerical calculation, θ <
Since it can be regarded as 1, the above A and B can be simplified as follows.

[Equation 21]

[Equation 22] And therefore

[Equation 23] Becomes

And

## EQU24 ## If Z ₀ is defined as q ₀ ≡iπW ₀ ² / λ≡iZ ₀ ,

[Equation 25] And hence

[Equation 26] Therefore

[Equation 27]

[Equation 28]

[Equation 29]

[Equation 30]

Next, the effective distance D from the light end face at the beam waist position, that is, the virtual light source position will be examined.

First, regarding the consideration of the distance D, the astigmatism amount of the semiconductor laser will be examined in terms of the correspondence between the position giving the minimum value of the beam spot size inside the actual cavity resonator and the position given by the measurement. Can be uniquely determined by a model in which the Gaussian beam propagates in free space, given the half-width W of the near-field image at the light end face and its emission angle θ. Does not depend on the waveguiding mechanism.

Therefore, for example, a weak refractive index guide type laser, that is, the radius of curvature R of the equiphase surface of the emitted light
It is naturally expected that the virtual light source distance D will be measured by the half-width W of the near-field image and the emission angle θ even in the case of a finite laser, and in fact, the virtual light guide distance in the currently available refractive index guided laser Light source distance D is 4 to 8 μm
It has been empirically revealed to have the astigmatism of.

That is, the fact that the astigmatism is smaller in the refractive index guide type laser than in the gain guide type laser is that the spot width (half-value width) of the near-field image in the refractive index guide laser is the gain guide. It is considered to be determined by being smaller than that of the type laser.

The beam waist position in the direction orthogonal to the joining, that is, in the vertical direction is almost at the optical end face position, and the half width in this direction is about 0.3 μm, which is parallel to the joining, that is, in the lateral direction, Much smaller,
Further, it is easily understood from the fact that there is a sufficiently large difference in refractive index in the vertical direction as compared with the difference in refractive index in the horizontal direction.

How the waveguide mechanism of each laser participates in the beam waist is concretely solved by solving the wave equation corresponding to each waveguide mechanism to determine the half width W of the beam spot at the optical end face. And the radius of curvature R of the equiphase surface of the light are independently determined. Then, if the width W of the beam spot size at the light end face and the radius of curvature R of the equiphase surface at the front end of the light are determined in this way, first

[Equation 31] The output angle θ of light is determined by.

Then, the light source distance D is finally determined from W and θ.

[Equation 32] Is determined.

It will be appreciated from the above considerations that once the waveguiding feature and the electrode stripe geometry are provided, the distance D is uniquely determined.

Further, the above-mentioned analysis reveals, for the first time, the correspondence between the actual distribution of light (or TE wave) in the resonant cavity and the effective astigmatism measured.

Now, a taper stripe type laser determined based on the above analysis, that is, as shown in FIG. 4, the stripe width is S ₁ at the central portion and S at the optical end face 12
The relationship between S ₁ and the light source distance D when S ₂ = 3 μm in the case where the width is gradually changed from the part having ₂ and the width S ₁ to the width S ₂ by the taper 13 The calculation result of is shown by a dot + in FIG. In the figure, the mark x shows the case of a conventional general structure in which the stripe width is a uniform width S ₁ .

In this case, The values of D have quite different values depending on how these parameters are taken, but these calculation results almost reproduce the measured data by the present inventors. As described above, in the case of the tapered stripe structure, the virtual light source, that is, the distance D from the light end face at the beam waist position, is controlled by controlling the stripe width S ₂ at this light end face, that is, the light emission portion, and It can be seen that it can be reduced to about 10 μm without much dependence on S ₁ (the matter of (a) above).

The physical basis of this calculation result is that (i) the half-width W of the near-field image is small. (Ii) The radius of curvature R of the isophase surface of light near the light end face is small. Due to

Looking at (ii), the distance D of the light source is
Physically, the half width W at the light end face and the radius of curvature R

It is easily confirmed that D = (R / n) [1+ (λR / nπW ² ) ² ] ^-1 (1) 'is described. (R / n is
Radius of curvature of the isophase surface of light propagating in the air near the light end face).

The relationship between R / n and D according to the equation (1) ′ is the curve shown in FIG. 2. From this, D is (I ′) R / n <λ / πW ² It is understood that it decreases and (II ′) decreases with R as R / n> λ / πW ² . This corresponds to (I) and (II) above. According to the above analysis, by appropriately designing the taper length L in the taper stripe structure, It can be seen that the gain guide type semiconductor laser having the astigmatism is obtained.

Further specific examples will be given.

Example 1 As shown in FIG. 4, GaAs was prepared in the same manner as described with reference to FIG.
Each semiconductor layer is successively epitaxially grown on the substrate 1 sequentially by an epitaxial method, for example, a vapor phase growth method by thermal decomposition. In FIG. 4, the portions corresponding to those in FIG. 10 are denoted by the same reference numerals and duplicate description is omitted, but in this case, the ohmic adhered portion of the electrode 8 to the cap layer 5, that is, the pattern of the electrode window 7a of the insulating layer 7. As shown in FIG. 5, the width is S ₁ at the central portion and the width is S ₂ at the end face 12, and both are linearly connected by the tapered portion 13.
Then, assuming that the length of the tapered portion 13 is L, S ₁ =
8 μm, S ₂ = 3 μm, the total length of the stripe is 250 μm
m, the length of the portion having the width S ₂ is selected to be 10 μm, and L is 10 μm, 20 μm, and 40 μ, respectively.
Planar-stripe type lasers selected for m, 80 μm, and 125 μm were prepared.

Example 2 With the same configuration as in Example 1, S ₁ = 6 μm, S ₂ =
3 μm, the total length of the stripe is 250 μm, and L is 10 μm, 20 μm, and 40 μ respectively.
m and 80 μm.

Example 3 With the same configuration as in Example 1, S ₁ = 20 μm, S ₂
= 3 μm, the total stripe length is 250 μm, and L
= 80 μm.

In any of the embodiments, the threshold current,
The semiconductor laser was excellent in astigmatism, far-field pattern, and life.

When the relation between the astigmatism amount D and the length L was measured, the result shown in FIG. 6 was obtained. According to this
It can be seen that it is desirable to set L to 100 μm or more in order to reduce astigmatism.

Further, the above-mentioned semiconductor laser according to the present invention has a reduced threshold current density (threshold current / electrode area), and as a result, the semiconductor laser is deteriorated even in the life test as compared with the usual semiconductor laser having a uniform stripe width of 5 μm. It was confirmed that the rate decreased.

The tapered portion 13 may have a shape such as a straight line, a parabola, or a hyperbola, and the stripe portion 11 and the tapered portion 13 may be connected smoothly. Further, the end portion of the tapered portion 13 may have a portion having a constant width of S ₂ .

In the above example, the uniform width S is obtained.
_There is a case where the portion having ₁ and the portion having a different width but a uniform width S ₂ are connected by the tapered portion 13, but as shown in FIG. The pattern may be, for example, a zigzag pattern so that the envelopes of the protrusions on both sides thereof form a taper.

[0064]

As described above, according to the present invention, since a gain guide type semiconductor laser having a small astigmatism can be constructed, noise due to returning light as a light source for various optical recording / reproducing is small and a beam spot shape is excellent. The light source can be configured.

[Brief description of drawings]

FIG. 1 is a diagram showing a pattern of a stripe structure of a semiconductor laser of the present invention.

FIG. 2 is a diagram showing a relationship between a radius of curvature of an equiphase surface in front of a virtual light source and a distance from a light end surface of the light source.

FIG. 3 is a calculation result diagram for explaining the present invention.

FIG. 4 is an enlarged sectional view of an example of a semiconductor laser according to the present invention.

FIG. 5 is a diagram showing a pattern of a stripe structure.

FIG. 6 is a diagram showing a measurement result of a relationship between a taper length and an aberration amount.

FIG. 7 is a partial pattern diagram of a stripe according to another example of the present invention.

FIG. 8 is an enlarged plan view of a conventional general semiconductor laser.

FIG. 9 is an enlarged cross-sectional view thereof.

FIG. 10 is an enlarged cross-sectional view of another example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Substrate 2,4 Clad layer 3 Active layer 5 Cap layer 7 Insulating layer 7a Electrode window 8,9 Electrode 12 Optical end face 13 Tapered part

Claims (2)

[Claims] 1. At least a first cladding layer, an active layer, a second cladding layer, and a cap layer are sequentially laminated on one main surface of a semiconductor substrate, and a first electrode is formed on the cap layer, A second electrode is formed on the other main surface of the semiconductor substrate, and S is formed when the stripe width is separated from the optical end surface.
₁ and S ₂ at the light end face, and in the semiconductor laser with a planar stripe structure in which the stripe width continuously changes between them, the distance from the light end face of a virtual light source of light parallel to the junction surface Let D be R, the radius of curvature of the isotropic layer surface of the light emitted from the light end face be R, and the half-width of the near-field image of the light at the light end face be W, then D is a parameter at W and R is at a certain value. becomes maximum, by W is D larger the larger and the more R is larger S ₁ is greater almost independently, using the higher S ₂ is greater W is large, the S ₁ 5 to 10 [mu] m, the S ₂ 0 A semiconductor laser having a thickness of 0.5 to 4 μm. 2. A semiconductor substrate having at least a first surface on one main surface.
First cladding layer, active layer, second cladding layer, cap
The layers are sequentially stacked, and the first electrode is formed on the cap layer.
And a second electrode is formed on the other main surface of the semiconductor substrate.
And when the stripe width is far from the optical end face, S
₁Then, at the light end face, S₂And the stripe width above between
Semi-conducting planar stripe structure with continuous variation of
In the body laser, the distance from the optical end face of the virtual light source of the light parallel to the cemented surface
The separation is D, and the radius of curvature of the equiphase surface of the light emitted from the light end face
Is R, and the half-width of the near field of light at the light end face is W.
And with W as a parameter, D is maximum at a certain value of R.
And the larger W is, the larger D is.
Independently S₁Is larger, R is larger, and S ₂Is big
Using the fact that W is large, S₁Is set to 20 μm or more, and S₂To 0.5-4 μm
A semiconductor laser characterized by being set.