JPH0254981A - Surface-emission laser and laser array - Google Patents

Abstract

PURPOSE:To control emission of an oscillation wavelength accurately and with improved reproducibility by forming secondary or higher gratings at a part where light irradiated from an activation area hits against a light waveguide path. CONSTITUTION:A light waveguide path 2 and an activation area 3 which are parallel to the surface of a GaAs substrate 1 are provided on the GaAs substrate 1 and light is radiated in a direction which is vertical to the surface of the substrate 1 from the activation area 3. The light waveguide path 2 consists of clad layers 21 and 23 and a core layer 22 and a secondary grating is formed on the interface surface of the core layer 22 and the clad layer 23. The secondary grating joins with a guide mode in the direction of wave guide and a leak mode in a direction vertical to the direction of waveguide and can control emission of oscillation wavelength accurately and with improved reproducibility.

Description

[Detailed description of the invention] 〔overview〕 Regarding surface emitting lasers and laser arrays.

The object of the present invention is to provide a surface-emitting laser that efficiently and selectively emits only a specific wavelength, and a laser array in which such surface-emitting lasers are arranged and optically coupled.

[1] A surface emitting laser that includes a substrate, an optical waveguide parallel to the substrate surface, and an active region, and emits light from the active region in a direction perpendicular to the substrate surface, the laser emitting light from at least the active region. [2] A surface emitting laser in which a grating of secondary or higher order is formed in the portion where light hits the optical waveguide; and [2]
A laser array including a plurality of surface-emitting lasers that share a substrate and emit light in a direction perpendicular to the substrate surface, each surface-emitting laser being optically coupled by a leading waveguide parallel to the substrate surface and having a small It is constituted by a laser array in which a second-order or higher-order grating is formed in a portion where light emitted from the active region of each surface-emitting laser hits the optical waveguide.

[Industrial application field]

The present invention relates to a surface emitting laser and a laser array.

A surface-emitting laser is a laser that emits laser light in a direction perpendicular to a substrate surface, and can be formed into a two-dimensional array, so it is being researched as a device for two-dimensional optical information processing. However, it is still difficult to control the wavelength to a predetermined value, and therefore there is a desire to develop a surface emitting laser that selectively emits only a specific wavelength efficiently.

[Conventional technology]

An example of a conventional seven-surface emitting laser is one in which both sides of the substrate are made highly reflective and used as mirrors (for example, Institute of Electronics, Communication and Information Engineers Technical Report 0QE86-8 (April 1986)).

FIG. 6 shows a schematic diagram of such a conventional surface emitting laser. In FIG. 6, 1 is a substrate, 3 is an active region, 33 is a light absorption region, 4 is a cladding layer, 81 and 82 are mirrors, 1
0 and 11 are electrodes, d is the thickness of the active region, 2r is the diameter of the active region, L is the resonator length, and the arrow represents the direction of light.

The light emitted from the active region 3 passes through mirrors 81 and 82.
The resonant light that travels back and forth between the two is extracted to the outside as a laser beam. At this time, the resonant wavelength largely depends on the resonator length. However, since the resonator length is determined by the thickness of the grown crystal, it is difficult to suppress the resonator length accurately, and this structure is suitable for realizing a specific wavelength with high precision and reproducibility. It is not a structure.

Therefore, we used a dielectric multilayer film for one mirror.

Structures that selectively reflect only specific wavelengths have been devised. FIG. 7 is a schematic diagram showing a conventional example of such a surface emitting laser. In FIG. 7, 1 is a GaAs substrate, 3 is an active region, 4 is a p-type cladding layer, 24 is an n-type cladding layer, and 5 is a GaAs substrate.
6 is a cap layer, 6 is a blocking layer consisting of an n-type GaAlAs layer 61, 63 and an n-type GaAlAs layer 62, 7 is an insulating layer, 8 and 9 are mirrors and are dielectric multilayer films, 10
11 represents the n-electrode, 11 represents the n-electrode, and the arrow represents the direction of light.

Since the dielectric multilayer film selectively reflects only a specific wavelength, it has the effect of preferentially oscillating light of that wavelength.

In order to increase the selectivity, it is possible to increase the number of layers in the multilayer film, but it is difficult to increase the wavelength selectivity because it is difficult to make several tens of layers of the multilayer film with high precision.

[Problem to be solved by the invention]

Therefore, with conventional surface emitting lasers, it has been difficult to obtain light emission with an oscillation wavelength that is controlled with high precision (and good reproducibility).

The present invention uses a distributed feedback laser (DF) as a wavelength selection mechanism.
By installing an optical waveguide with a grating (diffraction grating), which is used in B lasers) and distributed reflection lasers (DBR lasers), in the light path of surface emitting lasers, it is possible to control the light with high precision and reproducibility. It is an object of the present invention to provide a surface emitting laser that emits light at an oscillation wavelength and a laser array in which such surface emitting lasers are arranged and optically coupled.

[Means to solve the problem]

FIG. 1 is a schematic diagram of a surface emitting laser of the present invention, and FIG. 2 is a schematic diagram of a laser array of the present invention. In FIGS. 1 and 2, 1 is a substrate, and 2 is a leading waveguide consisting of cladding layers 21, 23 and a core layer 22.

3.31.32 is an active region, 4, 41.42 is a p-type raft layer, 81. 82.811,812,821,
822 is a mirror, 10 is an n-electrode, 11.111,1
12 is an n-electrode.

Arrows represent the direction of light.

(1) A surface-emitting laser that includes a substrate 1, an optical waveguide 2 parallel to the substrate surface, and an active region 3, and emits light from the active region in a direction perpendicular to the substrate surface, and at least from the active region A surface emitting laser in which a second or higher order grating is formed in a portion where the emitted light hits the optical waveguide.

[2] A laser array including a plurality of surface emitting lasers that share a substrate 1 and emit light in a direction perpendicular to the substrate surface,
Each surface emitting laser is optically coupled by an optical waveguide 2 parallel to the substrate surface and at least an active region 3 of each surface emitting laser.
2 in the part where the light emitted from 1.32 hits the optical waveguide.
The above problem is solved by a laser array in which more than one grating is formed.

[Effect]

In the present invention, as a wavelength selection mechanism, an optical waveguide with a secondary or higher order grating is provided in the path of the laser light emitted from the active region of the surface emitting laser.

If the period of the grating is Δ and the propagation constant of the waveguide is β, the reflectance becomes extremely steep at a wavelength that satisfies the first-order condition, so laser oscillation occurs at this wavelength.

β= n Therefore, in order to extract one oscillation light to the outside, a grating of second or higher order is formed.

In particular, the second-order grating couples only the guided mode in the waveguide direction and the leaky mode in the direction perpendicular to the waveguide direction, so that the light traveling in the direction perpendicular to the substrate surface is coupled to the optical waveguide parallel to the substrate surface. suitable for

Furthermore, when a plurality of surface emitting lasers are optically coupled through an optical waveguide, the oscillated lights can be made to interfere with each other using guided mode light as an intermediary, and the phase relationship of the oscillated lights can be kept constant.

Note that optical loss can be reduced by forming a primary grating in a portion of the optical waveguide excluding the portion of the optical waveguide that is exposed to light from the active region.

〔Example〕

An embodiment of the present invention will be described below.

FIG. 3 shows Example (2). In Figure 3, 1 is GaA
s board, 2 is clad II! 21.23 and core layer 22
3 is a GaAs active region with a thickness of 2.5 μm, 4 is a p-GaxAl layer with a thickness of 1 μm, As (
x = 0.4) p-type cladding layer.

5 is a GaAs cap layer with a thickness of 0.2 μm, 6 is 6
1- p Ga, AI, -, tAs (x = O-4
) layer 6 2, n-Ga, Al, 8s (x=0.
4) N63, p-Ga, AI,-,
A locking layer consists of an As (x = 0.4) layer, and 7 is a monochromatic edge layer of SiO2.

8 and 9 are mirrors and represent dielectric multilayer films, 10 is an n-electrode, and 11 is an n-electrode.

The composition, thickness, and refractive index of the constituent parts of the optical waveguide 2 are shown below.

21, cladding layer 1 μm.

22. Core layer 0.4 μm.

23, cladding layer 1 μm.

81X Ga, -, As (x = 0.4)n
= 3.39 AIXGa, -, As (x = 0.2) n = 3.4
5 AlxGa, -, As (x = 0.4) n = 3.3
9. A secondary grating is formed at the interface between the core layer 22 and the cladding layer 23. Resonance wavelength λO is 0.88μm
Using the above refractive index, the propagation constant β was determined from the eigenvalue equation of this leading waveguide, and which β value was entered into the above equation to determine the circumference #A of the second-order grating. the result,
A=0.515 μm.

This example is an example in which the cladding layer in contact with the active region is formed by a leading waveguide, and the above structure can realize a surface emitting laser having an oscillation wavelength of 0.88 μm.

After hitting the optical waveguide, some of the light emitted from the active region 3 propagates through the optical waveguide in a direction parallel to the substrate surface, but 2
In a waveguide in which gratings of the following order or more are formed, the coupling with the leaky mode is large and the loss leaking to the outside of the waveguide is large. Therefore, it is possible to reduce the loss by forming a first-order grating in the optical waveguide portion other than the portion where the light emitted from the active region 3 hits the optical waveguide.
The figure shows Example 2. In FIG. 4, the symbols represent the same symbols as those in FIG. 3, and 24 indicates the thickness of 1, 5, . crm
n-GaXAt, -xAs (x = 0.4)
Represents the type craft layer.

This embodiment has a structure in which the optical waveguide is formed on the substrate surface opposite to the active region. Since the light emitted from the active region 3 is attenuated in the substrate, the substrate is made as thin as possible.

In this embodiment as well, a second-order grating is formed in the optical waveguide portion that is hit by the light emitted from the active region 3, and a first-order grating is formed in the other optical waveguide portions to improve the efficiency of light utilization. can be increased.

FIG. 5 shows Example 2, which shows a laser array including a plurality of surface emitting lasers shown in Example I of FIG.

In FIG. 5, the symbols represent the same symbols as in FIG. 3.

A plurality of surface emitting lasers share a GaAs substrate 1, and optical waveguides 2 are optically coupled to each other. A second-order grating is formed in the portion of the leading waveguide that is hit by the light emitted from the active region 3, and a first-order grating is formed in the other portion of the optical waveguide.

In such a configuration, light emitted from the active region 3 of one surface emitting laser propagates through the optical waveguide and influences an adjacent surface emitting laser or a surface emitting laser further away. By utilizing such an interference effect, the secondary surface emitting laser oscillates while maintaining a constant phase relationship with respect to the main surface emitting laser.

A function as a so-called Master-3lave laser can be realized, and a laser array whose entire array is phase-synchronized can be obtained.

〔Effect of the invention〕

As explained above, according to the present invention, the oscillation wavelength can be accurately determined by accurately suppressing the period of the grating formed in the optical waveguide of the diagonal surface-emitting laser, which has an extremely narrow oscillation wavelength range. can be realized. Furthermore, it is possible to provide a laser array that includes a plurality of surface emitting lasers and in which the plurality of surface emitting lasers oscillate while maintaining a constant phase relationship.

Such surface emitting lasers and laser arrays have high utility value as devices for two-dimensional optical information processing.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of a surface emitting laser according to the present invention. FIG. 2 is a schematic diagram of the laser array of the present invention. FIGS. 3 to 5 show examples ① to ②. FIG. 6 is a schematic diagram of a conventional surface emitting laser. FIG. 7 shows a conventional example. In fig. 1 is a substrate, which is a GaAs substrate. 2 is an optical waveguide. 21.23 is the cladding layer. 22 is the core layer. 24 is an n-type cladding layer. 3.31.32 is the active region. 33 is a light absorption region. 4.41.42 is a cladding layer, which is an n-type cladding layer. 5 is the cap layer. 6 is the blocking layer. 61.63 is p-type GaA 1^3 layer. 62 is an n-type GaAlAs layer. 7 is an insulating layer. 8 and 9 are mirrors and are dielectric multilayer films. 81, 82, 811, 812, 821.822, the mirror 10 is an n-electrode. 11, 111, and 112 are electrodes, which are n electrodes. November's Menko Marushi - Wa's Zen-style diagram, 1st figure all four swords - square array tn 4 ruled style figure 4 squares ■ figure number actual. I series pressure 1st column 1st column 6f2i 1st column 6f2i

Claims (1)

[Claims] [1] Includes a substrate (1), an optical waveguide (2) parallel to the substrate surface, and an active region (3), and emits light from the active region in a direction perpendicular to the substrate surface. 1. A surface emitting laser, characterized in that a second or higher order grating is formed at least in a portion where light emitted from the active region hits the optical waveguide. [2] A laser array including a plurality of surface emitting lasers that share a substrate (1) and emit light in a direction perpendicular to the substrate surface, each surface emitting laser having an optical waveguide (2) parallel to the substrate surface. )
1. A laser array characterized in that a grating of second or higher order is formed in a portion of the optical waveguide which is optically coupled by the surface emitting laser and is emitted from at least the active region (31, 32) of each surface emitting laser.