JPS61263185A - Semiconductor laser array device - Google Patents

Abstract

PURPOSE:To obtain the high-output laser beams of one far-field pattern up to a high injection region by mounting an external resonance surface, which selectively reflects outgoing beams at a 0 deg. phase mode to a position facing a cleavage end surface, on which a thin film reducing optical reflectivity is formed, and projects outgiong beams to an active waveguide again. CONSTITUTION:A laser array element 30 is brazed to a radiator 33 and fitted to a susceptor 34, and a concave mirror 35 is set up in an oppositely facing manner on the end surface side, which is coated with an Al2O3 film 31 and reflectivity thereof extends over several %. Positional relationship between the semiconductor laser array element 30 and the concave mirror 35 is set so that laser beams emitted from an active region in the element 30 are reflected by the concave mirror 35 and projected to the active region in the semiconductor laser array element 30 again at that time. Outgoing beams at a 0 deg. phase mode are returned to the active layer region approximately completely and selectively. Accordingly, the loss of a resonator surface at the 0 deg. phase mode is reduced, and oscillation threshold gains are also minimized.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to the structure of a phase-locked semiconductor laser array device.

<Prior art and its problems> When operating a semiconductor laser at high output, the maximum output of a single semiconductor laser element is currently limited to about 50 mW, considering all practical aspects. Therefore, research into semiconductor laser arrays, which aims to increase output by arranging multiple semiconductor lasers on the same substrate, has been attracting attention. FIG. 3 shows the basic structure, refractive index, and electric field intensity distribution of a refractive index waveguide type semiconductor laser array. n-GaA
A plurality of KV-shaped stripe grooves 12 are arranged in parallel on the s-substrate 11, on which an n-GaAtAs cladding layer 13 and a p-GaAs active layer I L I)-GaAt for laser oscillation are formed.
An As clad layer 15 and a p-GaAs cap layer 16 are sequentially deposited to form a current confinement insulating film 17 and an n-side electrode! 8 and a p-side electrode 19 are formed, and a driving current is injected.

However, in a normal refractive index waveguide type semiconductor laser array, as shown in FIG. 3(3), the phosphorescence that oozes out to both sides of the groove 12 is absorbed by the n-GaAs substrate 11, as shown in FIG. 3(3). Transverse effective refractive index (neff)
A distribution is formed. The light intensity distributions of the oscillation region and the intermediate region are shown in Figure 3 (A).

It is shown by B. Here, the oscillation region corresponds to the active layer 14 directly above the groove 12, and the intermediate region is a non-oscillation region located in between. Diagram! As is clear, the intermediate region becomes a loss region. At this time, the oscillation threshold gain of the mode in which the proportion of light intensity decreases in the intermediate region is the smallest. Therefore, the oscillation threshold gain of the 180° phase mode in which the phase of the electric field in adjacent laser oscillation regions is inverted by 180° and becomes zero in the intermediate region as shown in FIG.
The electric field phase of adjacent semiconductor lasers becomes 0 as shown in D), which is smaller than the 0 phase mode in which the electric field exists even in the intermediate region. As a result, when the total injection current gradually increases through both the p-side electrode 19 and the n-side electrode 18, this 1
The 80° phase mode oscillates, and if the injection current is further increased, the 0 phase mode oscillates.

The far-field image of the emitted beam in the above semiconductor laser array device is as shown in Figure 4 (A) 03).
indicates the 180° phase mode, and Fig. 4 G3) indicates the 0° phase mode. In other words, the far-field image of the laser array in the low injection region is similar to that shown in Fig. 4 (3), and in the high injection region both modes shown in Fig. 4 (3) and Fig. 4 [F]) are present. They are mixed and form a box shape. In the 180 phase mode, when the light is focused all around the lens, the two beam phases are out of 1800, so the light cannot be focused on one minute laser spot, and it is difficult to focus on a minute laser spot T in optical disk systems, etc.
It cannot be used as a light source for an optical information processing system that requires 0. <Objective of the Invention> The present invention provides an object in which a plurality of laser oscillation regions formed on the same substrate all oscillate simultaneously with the same phase and a single laser oscillation region. An object of the present invention is to provide a semiconductor laser array device that emits a high-output laser beam with a one-peak radiation pattern.

<Structure of the Invention> In a semiconductor array device having a plurality of active waveguides, the present invention reduces the reflectance of at least one resonant cleavage plane compared to the value when the arms are fully open and is limited to a position facing the cleavage plane. A semiconductor laser array device is constructed by installing a reflecting mirror with an aperture in the 0-phase mode and configuring the laser beam emitted in 0-phase mode to be mainly reflected by this reflecting mirror and re-entering the laser array element. It is characterized by being set to oscillate synchronously with a 0° phase.

<Embodiment> Hereinafter, one embodiment of the present invention will be described using a GaAs-GaAtAs semiconductor laser array having a flat active layer as shown in FIG. 3 as an example. The semiconductor laser array device shown in FIG. 3(A) is manufactured as follows. n-GaAs substrate! 1, a total of five V-shaped stripe grooves of width W +2 are formed by etching at a pitch of D in parallel to each other. On the 11th surface of the substrate having 12 grooves, n-GaA
Epitaxial growth is performed on a multilayer crystal layer for laser operation with a double heterojunction structure consisting of a tAs cladding layer 13, a p (or n)-GaAs (or GaAtAs) active layer 14, a p-GaAtAs cladding layer 15, and a p-GaAs cap layer 16. After that, an insulating film 17 made of 5t3N4 for current confinement is patterned on the p-GaAs cap layer 16 for making ohmic contact, and then an n-side electrode made of metal such as A u + G e + N 1 is formed. 18 and a p-side electrode 19 are formed on the GaAs substrate 11 and the cap layer 16, respectively.

The semiconductor laser array wafer obtained above is cleaved so that the total resonator length is 250 pm, and a Fabry-Bello resonator is formed at the interosseous end surface. Next, at one cleavage plane, At
203 film is coated by all-electron beam evaporation method. The reflectance of this cleavage plane is about several percent.

Next, an At203 film having a thickness of λ/2 is deposited on the cleavage plane on the opposite side, and the total reflectance of this cleavage plane is set to 30%.

Note that any oxide film other than At203 or an amorphous silicon film may be used as the thin film covering the cleavage plane. Furthermore, it is divided into individual semiconductor laser array elements. Through the above steps, the basic elements of the semiconductor rape array device used in this example are manufactured.

FIG. 1 is a basic configuration diagram of a semiconductor laser array device showing one embodiment of the present invention, which is fabricated through the above process and then incorporates a semiconductor and an array element. Laser array element 3
The cleavage plane in the resonance direction of 0 is coated with an At203 film 31 having a thickness of λ/4 and an At203 film 32 having a thickness of λ/2. This laser array element 30 is attached to a support 34 by brazing with indium to a heat sink 33 having good thermal conductivity such as copper or diamond. Next, a concave mirror 35 is installed to face the cleaved surface having a reflectance of several percent, that is, the end surface covered with the At203 film 31 having a thickness of λ/4. In this case, the semiconductor laser array element 30 and the concave mirror 35 are accurately aligned so that the companion laser light emitted from the active region of the semiconductor laser array element 30 is reflected by the concave mirror 35 and re-enters the active region of the semiconductor laser array element 30. The size of the 0 concave mirror 35 that sets the positional relationship is such that the aperture angle seen from the active region is approximately 4 degrees in the direction parallel to the P-N junction surface of the semiconductor laser array element 30 and approximately 50 degrees in the perpendicular direction. Almost all of the emitted light can be selectively returned to the active layer region. Therefore, the loss in the resonator surface in the 0 phase mode is much smaller than the loss in the resonator surface in the 180 phase mode. As a result, the loss due to substrate absorption inside the laser array element 30 in the 0 phase mode is larger than that in the 180 film phase mode, but the overall loss constituted by the external resonator is smaller than in the 180 phase mode. -The oscillation threshold gain also becomes smaller.

FIG. 2(3)(B) is a configuration diagram of a semiconductor laser array device showing another embodiment of the present invention, and FIG. 2(3) is a side view;
) in FIG. 2 is a plan view. In this embodiment, instead of the concave mirror used in the previous embodiment, a convex lens 36 and a plane mirror 37?
Similar effects have been obtained using the same method.

FIG. 2(A) shows the optical path of the emitted light in a direction perpendicular to the P-N junction of the semiconductor laser array element, and FIG. 2(B) shows the entire optical path of the emitted light in the direction parallel to the P-N junction. The laser light emitted from the semiconductor laser array element 30 passes through a convex lens 36 to become a parallel beam of light, is reflected by a plane mirror 37, travels the original optical path in the opposite direction, and is returned to the laser array element 30. Is it possible to use the semiconductor laser array device of the present invention even if the convex lens 36 and plane mirror 37 are used in this way? There are 5 Q active layers that can be configured, and the active waveguide width W is 4 μm1 Medium M: region width W8
1μm1 A semiconductor laser array device with one cleavage plane having a reflectance of approximately 30%, the other having a reflectance of approximately 3%, and a concave mirror having a reflectance of approximately 95% was exploded, and its characteristics were examined to find the oscillation threshold current. oscillates in 0 phase mode at approximately 150 mA and up to 150 mW optical output, and! The 80° phase mode oscillation can be completely suppressed.ft.

Incidentally, the semiconductor array of the present invention is made of the above-mentioned GaAs-GaA
Not limited to tAs-based materials, but also InP-InGaAsP-based and other materials? It can be applied to nine semiconductor laser array devices.

<Effects of the Invention> As explained in detail above, the present invention provides a semiconductor laser array element in which the reflectance of one cleavage plane is completely reduced and the emitted light in the 0-phase mode is selectively reflected by facing opposite to this cleavage plane. It forms an external resonant surface that allows the light to re-enter the active region, and θ.

Phase mode resonator mirror loss Gold 180 can be significantly reduced compared to phase mode resonator mirror loss,
Loss in 0 phase mode is 80% compared to phase mode, so the oscillation threshold current in 0 phase mode is 180%
As a result, it is possible to realize a semiconductor laser array device that emits the laser source synchronized with the 0° phase, and it is possible to realize a semiconductor laser array device that emits the laser source synchronized with the 0° phase. It becomes possible to obtain a high-power laser beam with a visual field image.

[Brief explanation of drawings]

FIG. 1 is a basic configuration diagram of a semiconductor laser array device showing one embodiment of the present invention. FIG. 2(A) 03) is a side view and a plan view of a semiconductor laser array device showing another embodiment of the present invention. FIG. 3(A)[F]>(C)■) is an explanatory diagram showing the basic structure, refractive index, and electric field intensity distribution of a refractive index waveguide type semiconductor laser array element. Figure 4 (a) [F
]) is an explanatory diagram showing a far-field image in a direction parallel to the active layer. 11...GaAs substrate 12...groove 13...n
- Cladding layer 14... Active layer 15... P-cladding layer 16... Cap layer 30... Semiconductor laser array element 31.32... At203 film 35...
・Concave mirror 36...Convex lens 37...Plane mirror Agent Patent attorney Aihiko Fukushi (and 2 others) Figure 1 (C) Pilgrimage

Claims (1)

[Claims] 1. A plurality of parallel active waveguides are arranged in parallel between a pair of cleaved end faces constituting a laser oscillation resonator, a thin film that reduces light reflectance is formed on one of the cleaved end faces, and a thin film is formed on the cleaved end face. A semiconductor laser array device characterized in that an external resonant surface is provided at a facing position to selectively reflect the emitted light in the 0° phase mode and cause it to re-enter the active waveguide.