JPH0817262B2 - Single wavelength oscillation semiconductor laser device - Google Patents

Description

The present invention relates to a semiconductor laser device that oscillates at a single wavelength.

[Conventional technology]

FIG. 2 is, for example, Volume 15 No. 2, 115-121 of Technical Journal Optics.
FIG. 1 is a cross-sectional view of a conventional single-wavelength oscillation semiconductor laser device shown in page, in which (1) is an n-type InP substrate, (2) is a diffraction grating having a phase shift region in the center, and (3) is InGa
AsP guide layer, (4) InGaAsP active layer, (5) P-type In
P, (7) is an electrode metal, and (8) is a non-reflective coating film.

Next, the operation will be described. In the semiconductor laser device, both electrons in n-type InP (1) and holes in P-type InP (5) are injected into the InGaAsP active layer (4) to cause radiative recombination. In a distributed feedback (DFB) laser device having a diffraction grating (2) having a phase shift region in the active region, the light generated by radiative recombination is reflected by the diffraction grating (2) and reciprocates within the device to produce a laser beam. Leads to oscillation.

Since the diffraction grating (2) efficiently reflects light represented by the wavelength λ = 2n _eff Λ / n (n _eff is the equivalent refractive index, Λ is the pitch of the diffraction grating (2), and n is an integer), The oscillation wavelength is the wavelength having the largest gain in the active region among the wavelengths represented by λ = 2n _eff Λ / n. When the oscillation wavelength λ is represented by n = 1, the diffraction grating is called a first-order diffraction grating, and n =
The case of 2 is called a secondary diffraction grating.

In the single wavelength oscillation semiconductor laser device having the structure shown in FIG. 2, light is reflected only by the diffraction grating (2) in the active region and is confined inside the device, so that the density of light in the central part of the device becomes high. However, there is a problem that the linearity of the optical output with respect to the injection current and the stability of single wavelength oscillation are deteriorated due to the influence of hole burning and the like.

[Problems to be Solved by the Invention]

Since the conventional single-wavelength oscillation semiconductor laser device is configured as described above, the density of light in the central portion of the device is high, and the linearity of the optical output with respect to the injection current and the stability of single-wavelength oscillation are low. There was a problem.

The present invention has been made to solve the above problems, and an object thereof is to obtain a single-wavelength oscillation semiconductor laser device having excellent linearity of optical output with respect to injection current and stability of single-wavelength oscillation. And

[Means for solving the problem]

In the single-wavelength oscillation semiconductor laser device according to the present invention, the diffraction grating in the central portion of the element is of a higher order than the diffraction grating near the end face of the resonator.

[Action]

The single wavelength oscillation semiconductor laser device according to the present invention is
Since the diffraction grating at the center of the device is of a higher order than the diffraction grating near the end face of the resonator, excellent linearity of the optical output with respect to the injection current and stability of single wavelength oscillation can be obtained.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a sectional view of a single wavelength oscillation semiconductor laser device according to an embodiment of the present invention, in which (1) is n-type InP and (3)
Is an InGaAsP guide layer, (4) is an InGaAsP active layer, (5) is P-type InP, (9) is a primary diffraction grating provided near the end face of the resonator, and (10) is provided at the center of the device. It is a second-order diffraction grating having a phase shift region in the center.

Next, the operation will be described. Reflection of light by the diffraction grating is more efficiently performed by the low-order diffraction grating. Therefore,
As shown in FIG. 1, by making the diffraction grating (10) at the center of the element higher than that of the diffraction grating (9) near the end face of the resonator, the reflection intensity of light at the center of the element is increased. In the vicinity of the end face, it can be made smaller than the light reflection intensity. As a result, the light generated in the active layer (4) is not confined only in the central portion of the element by the diffraction grating (10) in the central portion of the element, but most of the light proceeds to the vicinity of the end face of the resonator, and the diffraction grating there. Is reflected by.

Therefore, the light density does not increase only in the central part of the device, and the light density becomes uniform over the entire device, hole burning is less likely to occur, the linearity with respect to the injection current of the optical output and the stabilization of single wavelength oscillation are achieved. A single-wavelength oscillation semiconductor laser device having excellent properties is obtained.

〔The invention's effect〕

As described above, according to the present invention, since the diffraction grating in the central portion of the element is of a higher order than the diffraction grating near the end face of the resonator, the linearity of the optical output with respect to the injection current and the stability of single wavelength oscillation are improved. There is an effect that an excellent single wavelength oscillation semiconductor laser device can be obtained.

[Brief description of drawings]

FIG. 1 is a sectional side view showing a single wavelength oscillation semiconductor laser device according to an embodiment of the present invention, and FIG. 2 is a sectional side view showing a conventional single wavelength oscillation semiconductor laser device. In the figure, (1) is an n-type InP substrate, (3) is an InGaAsP guide layer, (4) is an InGaAsP active layer, (5) is P-type InP,
(6) is a resonator end face, (7) is an electrode metal, (8) is a non-reflective coating film, (9) is a first-order diffraction grating provided in the vicinity of the resonator end face, and (10) is in the central part of the element. Provided 2
The next diffraction grating. In the drawings, the same reference numerals indicate the same or corresponding parts.

Claims (1)

[Claims] 1. A semiconductor laser device having a diffraction grating having a phase shift region in the center in the active region, wherein the diffraction grating at the central portion of the element is of a higher order than the diffraction grating near the end face of the resonator. Single wavelength oscillation semiconductor laser device.