JP2001144372A - Semiconductor laser device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a semiconductor laser device in which high power output operation is stabilized by suppressing wavelength splitting, due to the influence of higher order modes. SOLUTION: On a substrate 511 of n-type GaAs, an n-type clad layer 512 (AlGaAs, Al composition x=0.07, thickness t=2.86 μm), an n-type optical waveguide layer 513 (GaAs, t=0.49 μm), an n-type carrier blocking layer 514 (AlGaAs, x=0.40, t=0.03 μm), an active layer 515 (In0.18Ga0.82As quantum well layer and GaAs barrier layer), a p-type carrier block layer 516 (AlGaAs, x=0.40. t=0.03 μm), a p-type optical waveguide layer 517 (GaAs, t=0.49 μm), a ptype clad layer 518 (AlGaAs, x=0.20, thickness t=1.08 μm), and a p-type capping layer 520 (GaAs) are formed in this order, where a pair of n-type current block layer 519 (GaAs) is embedded inside the p-type capping layer 520.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an excitation light source such as a solid laser, a fiber laser, and a fiber amplifier, and a semiconductor laser device used for various laser measurements.

[0002]

2. Description of the Related Art In order to increase the output of a semiconductor laser, it is important to suppress instantaneous optical damage at the light emitting end face. For the purpose of increasing the output, the present applicant provided a carrier block layer having a larger forbidden band width than the active layer and having a small thickness on both sides of the active layer, thereby forming a conductive layer formed outside the carrier block layer. A semiconductor laser in which the degree of freedom in designing the thickness of the wave layer and the forbidden band width of the cladding layer is proposed (WO 93/16513).

In such a structure, the carriers injected into the active layer are efficiently confined by the carrier block layer, and the laser light generated in the active layer passes through the thinly formed carrier block layer and is mainly The light propagates through an optical waveguide composed of a waveguide layer and a cladding layer. By designing the optical waveguide so that the confinement of light in the waveguide layer is large, the intensity of light existing in the active layer is reduced, so that the light output that causes instantaneous optical damage at the light emitting end face is increased. As a result, a high output operation can be realized.

On the other hand, Japanese Patent Application Laid-Open No. 10-303500 discloses a waveguide layer in order to reduce the intensity of light existing in an active layer in a separated confinement structure and to increase light output at which instantaneous optical damage occurs at a light emitting end face. A structure in which the confinement of light into the light is increased is described.

[0005]

SUMMARY OF THE INVENTION Japanese Patent Application Laid-Open No. Hei 10-3035
When the confinement of light in the waveguide layer is increased as in No. 00, not only the fundamental mode but also higher-order modes can be propagated in the optical waveguide.

At this time, considering the laser oscillation conditions, the intensity of light existing in the active layer for generating the gain is highest in the fundamental mode, and free carrier absorption and substrate radiation loss are also small in the fundamental mode. Laser oscillation is more likely to occur in the fundamental mode.

However, the present inventors have found that even if laser oscillation is in the fundamental mode, the optical waveguide can also propagate higher-order modes, so that wavelength division occurs in the oscillation spectrum of laser light. When such wavelength splitting occurs, the full width at half maximum of the laser oscillation spectrum increases, and the oscillation wavelength does not continuously change even when the temperature or the injection current is continuously changed. Therefore, when such a semiconductor laser is used as an excitation light source such as a solid-state laser, a fiber laser, and a fiber amplifier, the excitation efficiency is reduced and the output is unstable, which is a problem in application.

An object of the present invention is to provide a semiconductor laser device in which wavelength splitting due to the influence of a higher-order mode in the stacking direction is suppressed and high-power operation is stabilized.

[0009]

According to the present invention, n-type and p-type optical waveguide layers having a bandgap greater than or equal to the bandgap of the active layer are provided on both sides of the active layer, respectively. And n-type and p-type cladding layers provided with n-type and p-type cladding layers having a bandgap greater than or equal to the bandgap of the optical waveguide layer so as to sandwich each optical waveguide layer. The smaller of the refractive indices of the layers is n
c1, when the real part of the effective refractive index of the first-order waveguide mode in the optical waveguide is Re (ne1), the condition of the following expression (A) is satisfied, and nc1 ≦ Re (ne1) (A) n-type and p-type A semiconductor laser device characterized in that the composition of the mold cladding layer is made asymmetric so that no higher-order waveguide mode exists in the laminating direction.

According to the present invention, the real part Re (ne1) of the effective refractive index of the first-order waveguide mode is equal to or smaller than the smaller one of the refractive indices nc1 of the n-type and p-type cladding layers. By setting a larger value, the light intensity existing in the active layer can be reduced, and the light output causing instantaneous optical damage at the end face can be increased. As a result, a high output operation can be realized.

[0011] Further, by making the compositions of the n-type and p-type cladding layers asymmetrical, higher order waveguide modes do not exist in the laminating direction. As a result, only the fundamental mode can be propagated with low loss. Wavelength splitting of the oscillation spectrum can be suppressed.

Further, according to the present invention, the laser wavelength in a vacuum is λ, the thickness between the n-type and p-type cladding layers is t, the refractive index of the n-type and p-type optical waveguide layers is nw, And the smaller one of the refractive indices of the p-type cladding layer is n
When c1, the optical waveguide including the optical waveguide layer and the cladding layer satisfies the condition of the following expression (1).

[0013]

(Equation 2)

According to the present invention, by satisfying the expression (1), the light intensity existing in the active layer can be reduced, and the light output causing instantaneous optical damage at the end face can be increased. High output operation can be realized.

Further, according to the present invention, when the larger one of the refractive indexes of the n-type and p-type cladding layers is nc2 and the effective refractive index of the fundamental waveguide mode in the optical waveguide is ne0,
It is characterized by satisfying the condition of the following expression (2). Re (ne1) <nc2 ≤ ne0 ... (2)

According to the present invention, by satisfying the expression (2), the fundamental waveguide mode can propagate in the central layer, and the primary waveguide mode leaks into the cladding layer having the refractive index nc2. . As a result, only the fundamental mode can be propagated with low loss, and wavelength splitting of the oscillation spectrum can be suppressed.

Here, the principle of the present invention will be described. Figure
4 is a sectional view showing a typical structure of a semiconductor laser device.
is there. An n-type crystal is placed on a substrate 111 made of n-type GaAs.
Rad layer 112 (AlGaAs, Al composition x = 0.2
0, thickness t = 1.2 μm), n-type optical waveguide layer 113 (Ga
As, t = 0.49 μm), n-type carrier block layer 1
14 (AlGaAs, x = 0.40, t = 0.03 μm)
m), the active layer 115 (In _0.18Ga_0.82As quantum well layer
And GaAs barrier layer), p-type carrier block layer 116
(AlGaAs, x = 0.40, t = 0.03 μm),
a p-type optical waveguide layer 117 (GaAs, t = 0.49 μm),
p-type cladding layer 118 (AlGaAs, x = 0.20,
MOVPE (metal organic chemical vapor deposition) with thickness t = 1.2 μm
Method), and a p-type cladding layer 1
A p-type cap layer 120 (GaAs) is formed on
And a pair of n-type current blocking inside the p-type cap layer 120.
The layer 119 (GaAs) is embedded and the current injection unit 101 is formed.
(Width 100 μm).

The direction of the resonator is perpendicular to the plane of the drawing, and the length of the resonator is 2.2 mm. After cleavage, the end face of the resonator is optically coated with a reflectivity of 2%, and the other end face is 96%. Are applied respectively. Substrate 1
Electrodes (not shown) for current injection are formed on the lower surface of the substrate 11 and the upper surface of the p-type cap layer 120, respectively.

FIG. 5 is a graph showing a temperature change of the oscillation spectrum of the semiconductor laser device 100 of FIG. The vertical axis is the peak wavelength (nm), and the horizontal axis is the case temperature (° C.). The operating current Iop is 2 amps. Referring to the graph, the peak wavelength changes linearly with the temperature change, and the temperature change rate of the peak wavelength shows about 0.25 nm / ° C. It changes stepwise, and it can be seen that wavelength division has occurred.

FIG. 6 is a graph showing an oscillation spectrum of the semiconductor laser device 100 of FIG. The vertical axis is the spectrum intensity (dBm), and the horizontal axis is the wavelength (nm). This graph shows wavelength splitting at a case temperature of 50 ° C.
Two peaks at 84.7 nm and a wavelength of 987.9 nm appear, and the split width becomes about 3.2 nm.

When analyzing an optical waveguide having a multi-layer slab structure such as a semiconductor laser device, the solution of the Maxwell equation can be obtained by using the step division method (refer to the document "Basics of Optical Coupling System for Optical Devices"). Application ”by Kenji Kono, 1
991). As a result of the analysis, it is found that the semiconductor laser device 100 of FIG. 4 can propagate the fundamental (0th-order) mode and the first-order mode.

FIG. 7 shows the refractive index distribution of the optical waveguide in the semiconductor laser device 100 of FIG.
4 is a graph showing a mode profile. The vertical axis is the refractive index, and the horizontal axis is the n-type cladding layer 112 and the n-type optical waveguide layer 113.
Is the position (μm) where the interface with is the origin and the upper side is positive.

Looking at the refractive index distribution, the n-type cladding layer 11
The refractive indices of the 2 and p-type cladding layers 118 are low, and the central portion sandwiched therebetween constitutes an optical waveguide having a high refractive index. As a result of the analysis, the profile of the fundamental mode shows a slightly concave monomodal curve near the carrier block layers 114 and 116, and the profile of the primary mode shows a bimodal curve. Basic mode and 1
The effective refractive indices ne0 and ne1 of the next mode are defined by eigenvalues of Maxwell's equation and are obtained by numerical calculation. In the semiconductor laser device 100 shown in FIG. 4, ne0 = 3.509, n
e1 = 3.478.

Next, the generation mechanism of wavelength splitting will be described. When the mode orders that can propagate through the optical waveguide are the fundamental mode and the primary mode, mode conversion from the fundamental mode to the primary mode and mode conversion from the primary mode to the fundamental mode slightly occur at both end faces of the semiconductor laser. . On the other hand, since the effective refractive index differs depending on the mode order, the optical resonator length of the fundamental mode is different from the optical resonator length of the first-order mode. It is believed that some type of double resonator effect occurs through such mode conversion.

Therefore, the resonance conditions of the laser resonator will be examined. The resonance condition of the fundamental mode is given by the following equation (11). Here, λm0 is the wavelength of light, L is the cavity length, ne0
Is the effective refractive index of the fundamental mode, and m0 is the number of antinodes of the standing wave. m0 · λm0 = 2 · L · ne0 (11)

The laser oscillation wavelength changes discontinuously as the number of antinodes of the standing wave increases or decreases one by one.
λ0 is given by the following equation (12) in consideration of the wavelength dependence of the effective refractive index.
Given by

[0027]

(Equation 3)

On the other hand, the resonance condition of the first mode is expressed by the following equation (1).
Given in 3). Here, λm1 is the wavelength of light, L is the cavity length, ne1 is the effective refractive index of the first-order mode, and m1 is the number of antinodes of the standing wave. m1 · λm1 = 2 · L · ne1 (13)

The wavelength interval Δλ 1 of the first-order mode is given by the following equation (14) in consideration of the wavelength dependence of the effective refractive index.

[0030]

(Equation 4)

When mode conversion from the fundamental mode to the primary mode and mode conversion from the primary mode to the fundamental mode occur on both end faces of the semiconductor laser, the resonance condition (11) of the fundamental mode and the primary mode It is considered that the loss is minimized at the wavelength that satisfies both the resonance conditions (13), and the wavelength interval Δλ01 at this time is given by the following equation (15), which corresponds to the wavelength split width.

[0032]

(Equation 5)

Here, the present invention is applied to the configuration of the semiconductor laser device 100 shown in FIG. The effective refractive indices of the fundamental mode and the first-order mode are ne0 = 3.509 and ne1 = 3.478.
Since the relationship between the refractive index and the Al composition x in the lGaAs-based semiconductor is known, the effective Al composition in the fundamental mode is 0.048, and the effective Al composition in the primary mode is 0.10. Furthermore, the wavelength dependence (differential term) of the refractive index in these effective Al compositions is -0.4 in the fundamental mode.
9 (/ μm) in the first-order mode as −0.45 (/ μm).

These values and L = 2.2 mm, λ =
By substituting 984.7 nm into the equation (15), the wavelength splitting width Δλ 01 = 3.1 nm is obtained, and it can be seen that the wavelength split width is approximately equal to the experimental value of about 3.2 nm in FIG. Therefore, it was found that the wavelength splitting as shown in FIG. 6 was caused by the double resonator effect.

In the above description, a configuration in which a carrier block layer exists as in the semiconductor laser device 100 of FIG. 4 has been described as an example. However, the above description applies to all semiconductor lasers having an optical waveguide capable of propagating higher-order modes. Wavelength splitting of the oscillation spectrum may occur.

Then, the wavelength of the laser beam in vacuum is λ,
The thickness between the two optical cladding layers is t, the refractive index of the optical waveguide layer is nw, the refractive index of the smaller of the two optical cladding layers is nc1, and the refractive index of the larger one is nc2. When the optical waveguide including the optical waveguide layer and the cladding layer satisfies the condition of the expression (1), the light intensity existing in the active layer is reduced and the optical output causing instantaneous optical damage at the end face is increased. When the effective refractive index of the fundamental guided mode is ne0 and the real part Re (ne1) of the effective refractive index of the first-order guided mode is satisfied in the semiconductor laser capable of satisfying the relationship of Expression (2), The fundamental waveguide mode can propagate in the central layer, and the primary waveguide mode leaks into the cladding layer having the refractive index nc2. As a result, only the fundamental mode can be propagated with low loss, and wavelength splitting of the oscillation spectrum can be suppressed.

[0037]

(Equation 6)

For example, in the semiconductor laser device 100 shown in FIG. 4, the effective refractive index ne1 of the first-order guided mode is 3.478, the refractive index nc2 of the cladding layer having a large refractive index is 3.42, and the effective refractive index of the fundamental mode is ne0. = 3.509,
Since the expression (2) is not satisfied, the propagation of the primary guided mode is allowed.

Therefore, by satisfying the conditions of the expressions (1) and (2), the light intensity existing in the active layer is reduced and high output operation is enabled, while the primary waveguide mode is suppressed and only the fundamental waveguide mode is set. Laser oscillation can be stably realized. Further, as shown in FIG. 2, the light intensity of the fundamental waveguide mode is widely distributed outside the active layer 515, and the intensity of light existing in the active layer 515 is further reduced. The optical output at which instantaneous optical damage occurs can be increased, and as a result, a higher output operation can be achieved.

Further, the present invention is characterized in that a carrier block layer having a forbidden bandwidth equal to or greater than the forbidden bandwidth of the active layer and the optical waveguide layer is provided between the active layer and each optical waveguide layer. And

According to the present invention, by providing a carrier block layer having a high band gap between the active layer and each optical waveguide layer, carrier confinement in the active layer and light confinement in the optical waveguide layer can be achieved. Can function independently, so that the temperature characteristics of the semiconductor laser can be improved and higher output operation can be realized.

Further, the present invention exerts its effect more effectively when applied to a semiconductor laser having a refractive index distribution structure in a stack for controlling the transverse mode of laser light.

In some applications, it is desirable that the oscillation mode shape of the semiconductor laser has a single Gaussian profile in both the vertical and horizontal directions. This is because the single mode operation can increase the optical density and facilitate coupling to the fiber.

For this reason, a SAS (self-aligned structure) structure in which layers having different refractive indexes are formed on both sides of the stripe,
An optical confinement structure is formed by forming an effective refractive index difference also in the lateral direction by a ridge structure in which both sides of the stripe are engraved, an interlayer diffusion of constituent atoms by ion implantation, and the like.

In the design of the refractive index distribution, it is generally assumed that the confinement of each mode in the vertical direction and the horizontal direction is independent of each other, but in fact, both influence each other. Thus, if the longitudinal mode confinement is designed to allow higher order modes, undesirable wavelength splitting and transverse mode disturbances may occur.

Thus, according to the present invention, by suppressing the generation of higher-order modes in the vertical direction, the mode in the horizontal direction is also stabilized, a good vertical and horizontal Gaussian profile is maintained, and good current-output characteristics can be obtained. it can.

[0047]

FIG. 1 is a sectional view showing an embodiment of the present invention. An n-type cladding layer 512 (AlGaAs, Al composition x = 0.07, thickness t = 2.86 μm) and an n-type optical waveguide layer 513 (GaAs, t = 0.49 μm) are formed on a substrate 511 made of n-type GaAs. ), N-type carrier block layer 514 (AlGaAs, x = 0.40, t =
0.03 μm), active layer 515 (In _0.18 Ga _0.82 As)
A quantum well layer and a GaAs barrier layer), a p-type carrier block layer 516 (AlGaAs, x = 0.40, t = 0.0)
3 μm), p-type optical waveguide layer 517 (GaAs, t = 0.4
9 μm), p-type cladding layer 518 (AlGaAs, x =
0.20, thickness t = 1.08 μm) is sequentially formed using MOVPE (metal organic chemical vapor deposition) or the like, and a p-type cap layer 520 (GaAs) is formed on the p-type cladding layer 518.
s), and a pair of n is formed inside the p-type cap layer 520.
The current injection portion 501 (width 100 μm) is formed by embedding the mold current blocking layer 519 (GaAs).

The direction of the resonator is perpendicular to the plane of the paper, and the length of the resonator is 2.2 mm. After cleavage, the end face of the resonator is optically coated with a reflectivity of 2%, and the other end face is 96%. Are applied respectively. Substrate 5
Electrodes (not shown) for current injection are formed on the lower surface of the substrate 11 and the upper surface of the p-type cap layer 520, respectively.

FIG. 2 shows the refractive index distribution of the optical waveguide in the semiconductor laser device 500 of FIG. 1, the effective refractive index of each mode,
4 is a graph showing a mode profile. The vertical axis is the refractive index, and the horizontal axis is the n-type cladding layer 512 and the n-type optical waveguide layer 513.
Is the position (μm) where the interface with is the origin and the upper side is positive.

Looking at the refractive index distribution, the n-type cladding layer 51
2, the refractive index of the p-type cladding layer 518 becomes about 3.52, and the refractive index of the p-type cladding layer 518 becomes particularly large as compared with FIG. Is formed.

As a result of the analysis, it is found that the profile of the fundamental mode has a slight depression near the carrier block layers 514 and 516, and shows a monomodal curve shifted toward the n-type cladding layer 512 as a whole.

The effective refractive indices ne0 and ne1 of the fundamental mode and the first-order mode are defined by the eigenvalues of the Maxwell equation and are obtained by numerical calculations. In the semiconductor laser device 500 of FIG. 1, ne0 = 3.513, Re ( ne1) = 3.
490. The smaller of the n-type cladding layer 512 and the p-type cladding layer 518 has a refractive index nc1 of about 3.
42, since the larger refractive index nc2 = about 3.50, the expression (2) is satisfied, so that propagation of higher-order modes including the first-order guided mode is suppressed.

Further, regarding the equation (1), the laser wavelength λ =
982 nm, the thickness t between the n-type cladding layer 512 and the p-type cladding layer 518 is about 1.158 μm, and the refractive index nw of the n-type optical waveguide layer 513 and the p-type optical waveguide layer 517 is 3.
By substituting 538, it can be seen that the cutoff condition of Expression (1) is satisfied.

FIG. 3 is a graph showing the temperature change of the oscillation spectrum of the semiconductor laser device 500 of FIG. The vertical axis is the peak wavelength (nm), and the horizontal axis is the temperature (° C.). From the graph, it can be seen that the peak wavelength changes linearly with the temperature change, and no wavelength splitting as shown in FIG. 5 has occurred.

The rate of temperature change of the peak wavelength is about 0.3.
4 nm / ° C., which means that the temperature change rate of the band gap of InGaAs constituting the quantum well layer of the active layer 515 is 0.38 nm / ° C. (Sadao Adachi, “Physical Properties
of III-V SemiconductorCompounds ", p100-105,1992, Jh
on Wiley & Sons, Inc.), confirming the theoretical laser operation.

FIG. 8 is a sectional view showing another embodiment of the present invention. Here, an example will be described in which a refractive index distribution structure is formed in a stack in order to control the transverse mode of laser light.

On a substrate 611 made of n-type GaAs,
n-type cladding layer 612 (AlGaAs, Al composition x =
0.09), n-type optical waveguide layer 613 (GaAs, thickness t =
0.48 μm), n-type carrier block layer 614 (Al
GaAs, x = 0.40, t = 0.03 μm), active layer 615 (In _0.18 Ga _0.82 As quantum well layer and GaAs barrier layer), p-type carrier block layer 616 (AlGaAs)
s, x = 0.40, t = 0.03 μm), p-type optical waveguide layer 617 (GaAs, t = 0.48 μm), p-type cladding layer 618 (AlGaAs, x = 0.32, t = 1.08)
μm) was sequentially formed using MOVPE (metal organic chemical vapor deposition) or the like, and a p-type cap layer 620 (GaAs) was formed on the p-type cladding layer 618. Further, in order to form a refractive index confinement structure, a pair of low refractive index n-type current blocking layers 619 (AlG
aAs, x = 0.20) and the current injection unit 601
Is formed.

The direction of the cavity is perpendicular to the plane of the paper, the cavity length is 1.8 mm, the cavity end face is cleaved, the light emitting end face is an optical coating with a reflectance of 2%, and the other end face is 96% reflectivity. Are applied respectively. Substrate 6
Electrodes (not shown) for current injection are formed on the lower surface of the substrate 11 and the upper surface of the p-type cap layer 620, respectively.

FIG. 9 is a graph showing oscillation characteristics of the semiconductor laser device 600 of FIG. 8 and a comparative example. The vertical axis is the light output (mW), and the horizontal axis is the injection current (mA). Measurement conditions are room temperature (25 ° C.) and CW (continuous) operation. In the graph, the kink indicating the mode disturbance appears at about 750 mW in the example, and it can be seen that oscillation is performed in a stable mode up to a high output.

On the other hand, the structure of the comparative example is such that an n-type cladding layer 612 (AlG
aAs, Al composition x = 0.17), n-type optical waveguide layer 613
(GaAs, thickness t = 0.48 μm), n-type carrier block layer 614 (AlGaAs, x = 0.40, t =
0.03 μm), active layer 615 (In _0.18 Ga _0.82 A)
s quantum well layer and GaAs barrier layer), p-type carrier block layer 616 (AlGaAs, x = 0.40, t = 0.
03 μm), p-type optical waveguide layer 617 (GaAs, t = 0.
48 μm), p-type cladding layer 618 (AlGaAs, x
= 0.17) was sequentially formed using MOVPE (metal organic chemical vapor deposition) or the like, and a p-type cap layer 620 (GaAs) was formed on the p-type cladding layer 618. Further, in order to form a refractive index confinement structure, a pair of low refractive index n-type current blocking layers 619 are provided inside the p-type optical waveguide layer 617.
(AlGaAs, x = 0.20) is embedded to form the current injection portion 601.

Looking at the graph, the kink is about 4 in the comparative example.
It appears at 00 mW and is inferior to the example.

In the above description, the carrier block layer 51
Although the optical waveguide structure having 4,516,614,616 has been described, the present invention can be similarly applied to an optical waveguide structure having no carrier block layer.

[0063]

As described in detail above, according to the present invention, while suppressing the wavelength splitting of the oscillation spectrum, the intensity of the light existing in the active layer is reduced, and the light that causes instantaneous optical damage at the light emitting end face is obtained. The output can be increased, and as a result, a high output operation can be realized.

Further, by providing a carrier block layer having a high band gap between the active layer and each optical waveguide layer, carrier confinement in the active layer and light confinement in the optical waveguide layer are independently performed. Since the semiconductor laser can function, the temperature characteristics of the semiconductor laser are improved and higher-power operation can be realized.

By applying the method of the present invention to a semiconductor laser having a refractive index distribution structure, the mode stability in the vertical direction contributes to the mode stability in the horizontal direction. Laser oscillation can be realized.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing one embodiment of the present invention.

FIG. 2 is a graph showing a refractive index distribution of an optical waveguide, an effective refractive index of each mode, and a mode profile in the semiconductor laser device 500 of FIG.

FIG. 3 is a graph showing a temperature change of an oscillation spectrum of the semiconductor laser device 500 of FIG.

FIG. 4 is a sectional view showing a typical structure of a semiconductor laser device.

5 is a graph showing a temperature change of an oscillation spectrum of the semiconductor laser device 100 of FIG.

FIG. 6 is a graph showing an oscillation spectrum of the semiconductor laser device 100 of FIG.

7 is a graph showing a refractive index distribution of an optical waveguide, an effective refractive index of each mode, and a mode profile in the semiconductor laser device 100 of FIG.

FIG. 8 is a sectional view showing another embodiment of the present invention.

9 is a graph showing oscillation characteristics of the semiconductor laser device 600 of FIG. 8 and a comparative example.

[Explanation of symbols]

 500, 600 Semiconductor laser device 501, 601 Current injection section 511, 611 Substrate 512, 612 N-type cladding layer 513, 613 N-type optical waveguide layer 514, 614 N-type carrier block layer 515, 615 Active layer 516, 616 P-type carrier Block layer 517,617 p-type optical waveguide layer 518,618 p-type cladding layer 519,619 n-type current blocking layer 520,620 p-type cap layer

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Koichi Igarashi 580-32, Takuji Nagaura, Sodegaura City, Chiba Prefecture Inside Mitsui Chemicals, Inc. (72) Yumi Naito Takuji Nagaura, Sodegaura City, Chiba Prefecture, Japan 580 No. 32 Mitsui Chemicals Co., Ltd. (72) Inventor Kiyofumi Muro Kiyoshi No. 580 No. 580 No. 352, Nagaura-ji Takuji, Sodegaura-shi, Chiba No. 32 Mitsui Chemicals, Inc. (72) Inventor Yoshikazu Yamada Chiba Prefecture, Sodegaura City, Chiba Prefecture, No. 580 No. 580 No. 32 Mitsui Chemicals Co., Ltd. (72) Inventor Atsushi Okubo, Chiba Prefecture, Sodegaura City, Nagaura Character Takuji 580 No. 32 Mitsui Chemicals, Inc. F-term (reference) 5F073 AA21 AA74 AA83 BA09 CA04 CB02 EA16 EA18 EA24

Claims (5)

[Claims] 1. An n-type and a p-type optical waveguide layer having a forbidden band width equal to or larger than the forbidden band width of the active layer is provided on both sides of the active layer, and the active layer and the respective optical waveguide layers are sandwiched therebetween. A semiconductor laser device provided with n-type and p-type cladding layers each having a forbidden band width greater than or equal to the forbidden band width of the optical waveguide layer, wherein the smaller one of the refractive indices of the n-type and p-type cladding layers Is the refractive index of nc1, and the real part of the effective refractive index of the first-order guided mode in the optical waveguide is Re (ne1), the condition of the following expression (A) is satisfied, and nc1 ≦ Re (ne1) (A) A semiconductor laser device characterized in that the composition of the n-type and p-type cladding layers is made asymmetric so that no higher-order waveguide mode exists in the laminating direction. 2. The laser wavelength in a vacuum is λ, the thickness between the n-type and p-type cladding layers is t, the refractive index of the n-type and p-type optical waveguide layers is nw, and the n-type and p-type When the smaller one of the refractive indices of the cladding layers is nc1,
The optical waveguide including the optical waveguide layer and the cladding layer has the following formula (1)
2. The semiconductor laser device according to claim 1, wherein the following condition is satisfied. (Equation 1) 3. When the larger one of the refractive indices of the n-type and p-type cladding layers is nc2 and the effective refractive index of the fundamental waveguide mode in the optical waveguide is ne0, the condition of the following equation (2) is satisfied. 3. The semiconductor laser device according to claim 2, wherein: Re (ne1) <nc2 ≤ ne0 ... (2) 4. A carrier block layer having a band gap greater than or equal to the band gap of the active layer and the optical waveguide layer is provided between the active layer and each optical waveguide layer. Item 4. The semiconductor laser device according to any one of Items 1 to 3. 5. The semiconductor laser device according to claim 1, wherein the lamination has a refractive index distribution structure in order to control a transverse mode of the laser beam.