JPH02214181A - Semiconductor laser device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a semiconductor laser device, and particularly relates to a structure that provides high output and fundamental mode oscillation.

[Prior art 1] Fig. 7 shows a semiconductor laser device, Fig. 7(a) is a perspective view showing the structure, and Fig. 7(b) shows an optical waveguide (active layer) of a conventional semiconductor laser device. The figure shown in FIG. 7(c) is a refractive index distribution diagram. In the figure, 1 is an N-type GaAs substrate, 2 is the first cladding layer, 48 Ga
n, sa As, 3 is the active layer AIo, 12 Q
100811 As, 4 is the P-shaped lip which is the second cladding layer, 41SQ80.115Ajl, 5 is the ridge area,
6 is a buried layer of 8-type GaAs; 7 is a contact layer of P-type GaAs; 8 is a Milli9 is a P-electrode; 10
is an optical waveguide having a refractive index f11, and 11 is an optical waveguide (1
0), a low refractive index region having a refractive index υz (<nx) surrounding
12 is the resonator end face, and W is the width of the optical waveguide (10).

Next, the operation will be explained. P [pole (9), N [pole (8)
), the holes and electrons injected from the buried layer (6) have a current narrowing effect, so they are efficiently concentrated in the optical waveguide (10) and recombined to have a gain and increase the current. Laser oscillation is obtained when the loss is greater than the loss.

Incidentally, the output of the obtained laser beam increases as the current increases, but the optical density increases due to optical damage (CO) on the end face (12).
D) Level A/IC is limited by the value reached.

Therefore, in order to obtain high output power, a method is generally adopted in which the width W of the optical waveguide (10) is increased in order to lower the optical density. As shown in Figure (b), since the optical waveguide has a constant width W, if W is expanded as described above in order to obtain high output, W will be r311! l
There is a problem in that when a predetermined value determined by I2 is exceeded, higher-order modes are excited.

The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to obtain a semiconductor laser device that has high output and is capable of fundamental mode oscillation.

[Means for Solving the Problems 1] A semiconductor laser device according to the present invention includes a bent optical waveguide region having an angle for emitting higher-order modes.

[Operation 1] The semiconductor laser device according to the present invention has a structure including a bent optical waveguide region having an angle for emitting a higher-order mode, so that laser light oscillating in a fundamental mode can be obtained from a wide stripe region.

(’17! Example I An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a diagram showing an optical waveguide of a semiconductor laser device according to an embodiment of the present invention. In the figure, 21a and 21b are parallel optical waveguide regions with a stripe width of W and a refractive index of 0. is allowed. 23 is the angle of Taber θp and the length of Taber.

The step is d and the refractive index is! This is the number 11 bent optical waveguide region. 24 is a low refractive index region with a refractive index of r2.

FIG. 2 is a diagram showing the concept of waveguide mode and radiation mode in a slab waveguide. Here, the critical angle θC is expressed by the following equation (1).

θc=sf low” (nz/ns) −
・(1) Maxwell's equation takes into account the boundary conditions between the optical waveguide regions 21a, 21b and the low refractive index region 24 among the light rays that enter at an angle smaller than this angle θC, while the light rays that enter at a larger angle enter the radiation mode. A mode that satisfies the following is a waveguide mode. Among these modes, the mode is classified into the zero-order mode (fundamental mode), the first-order mode, and the second-order mode from the one with the largest angle of incidence.

FIG. 3 is a conceptual diagram when the waveguide mode reaches the bent optical waveguide region. By appropriately adjusting the Taber angle θp, it is possible to propagate only the fundamental mode and radiate higher-order modes.

FIG. 4 is a conceptual diagram of nine waveguide modes that are reflected twice in the bent optical waveguide region. By reflecting twice in the bent optical waveguide region, the guided mode returns to the incident angle before entering the bent region.

An example in which the concept of FIGS. 2 to 4 is applied to a semiconductor laser device is a semiconductor laser device having a light path 411f shown in FIG. 1.

The operation will be explained below. The angle of incidence of the fundamental mode is α0
(=90-θO), and the incident angle of the first mode is αl (=90
''-θI).Since it is necessary to reflect at least once in the bending area, L < W / (tanθp+tanαl).
-2, while the fundamental mode reflected at the bend region is reflected twice.

The step d is d = W cot (2θp + αG)
- (3) must be satisfied.

In addition, if the deviation of the optical waveguide is 8, a = L tanθp ・(
4) is given by

For example - as an example, W = 6 μm, f]l = 3
．． 460, when n2=3.445, θc=84
．． 663°, αo=0.985°101=1.967°
(Iα2=2.939', therefore, the taper angle θp
is 3.370° and θp<4.352°
...You should choose (5). If θp=3.5°, L=62.8 μm, d=42.8 μm, and a=3.8 μ.

As described above, in the above embodiment, since the optical waveguide is provided with a bent region having an appropriate angle θp, a semiconductor laser device that oscillates in the fundamental mode can be obtained.

FIG. 5 is a diagram of an optical waveguide showing another embodiment of the present invention.
In the figure, 23a and 23b correspond to the eleventh and second bending regions, and conditions are set such that the higher-order mode is radiated in at least one of the bending regions. Furthermore, both θpi and θp2 are set at angles at which the fundamental mode is not emitted. FIG. 6 is a perspective view showing the structure of a semiconductor laser device having a structure in which odd-order modes are not easily excited. In the figure, 15 is a ridge region (5). The P-type impurity diffusion region 16 provided in the center is an N-type GaAa layer. In this semiconductor laser device, holes are injected through the P-type impurity diffusion region (15), so the gain becomes high at the center of the optical waveguide, and the odd-order mode is excited and becomes a fly.

Therefore, when choosing this more rigid laser structure, the higher-order mode can be considered from the second order, and since α2=2.939°, 2.398°<θp<4.352°.

Therefore, by choosing θp = 3.0°, L = 57
．． It can be set to 8μmd = 38.1μ a = 3.0μ mark.

In addition, although the case where the ridge structure was chosen as a laser structure was shown in the said Example, it is not limited to this structure.

[Effect of the invention 1 As described above, according to the present invention, the optical waveguide structure has a folded-white shape having a Taber angle that radiates higher-order modes other than the fundamental mode, so it is possible to create a semiconductor that has high output and oscillates in the fundamental mode. This has the effect of providing a laser device.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an optical waveguide of a semiconductor laser device according to an embodiment of the present invention, FIG. 2 is a diagram showing the concept of waveguide mode and radiation mode in a slab optical waveguide, and FIG. 3 is a diagram showing a bent (optical waveguide) Diagram showing the amplitude of guided modes in the region, 4th
The figure is a conceptual diagram of a waveguide mode reflected twice in a bent (optical waveguide) region, FIG. 5 is a diagram showing an optical waveguide of a semiconductor laser device according to another embodiment of the present invention, and FIG. 6 is an odd-numbered waveguide FIG. 7(a) is a perspective view showing the structure of a semiconductor laser device in which a mode is difficult to excite. FIG. 7(b) is a perspective view showing the structure of a semiconductor laser device having a conventional ridge structure.
FIG. 7(c) is a refractive index distribution diagram of the optical waveguide of FIG. 7(a). In the figure, 15 is a P-type irregularity diffusion region, 21a, 21b,
22 is a parallel optical waveguide region having a width of W, 23.23
a. 23b is a bent optical waveguide region, 24 is a low refractive index region,
θp is the angle of the taber in the bending area, L is the length of the taber in the bending area, and d is the difference in level between the left and right sides of the bending area. In addition, in the figures, the same reference numerals indicate the same or equivalent parts. Figure 1

Claims (1)

[Claims] In a semiconductor laser device having at least two end faces, at least one location has an angle that emits a higher-order mode other than the fundamental mode, and the incident angle of the fundamental mode to the end face does not change before and after input/output of this region. A semiconductor laser device characterized by having a bent optical waveguide region.