JPS60186083A - Distributed feedback type semiconductor laser element - Google Patents

Abstract

PURPOSE:To radiate a laser beam of isotropic high output having a small expensing angle in a single mode by providing a waveguide which has an active layer in a semiconductor, and forming the surface of the waveguide in irregular periodical surface in two dimensions therein, and uniformly exciting the active layer. CONSTITUTION:A waveguide 2 which contains an active layer is formed on a semiconductor substrate 1, and a semiconductor layer 3 is formed thereon, and an irregular periodical surface is formed on the surface of the waveguide 2 in the directions (x) and (y). When a current is flowed to the element or a light is excited, a distributed feedback occurs due to the diffraction grating in both the directions (x) and (y) to generate lasers in the directions (xsi) and (eta), and the sole distributed feedbacks of the grating in the directions (x) and (y) are generated. Accordingly, the laser lights of the directions (xsi) and (eta) are coupled, and the entire surface of the grating is oscillated in the same phase. In this case, the grating having high order grating of even number is provided and the period of the irregular surface is formed near the even times of the laser oscillation half wavelength of the laser in the active layer. Then, the laser light in the waveguide is radiated from the entire surface in the upward perpendicular direction from x-y plane. Thus, the two-dimensional expanding angle can be reduced and the large light output can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a semiconductor laser device provided with a two-dimensional diffraction grating.

[Background of the invention]

Conventionally, a distributed feedback laser equipped with a -dimensional diffraction grating is
It has advantages such as being able to obtain a single-longitudinal mode and being easy to incorporate into optical integrated circuits, and continuous operation at room temperature has been confirmed in semiconductors (Journal of the Japanese Society of Crystallography,
V, 18.397-399 (1976)).

By the way, when a high-order diffraction grating is provided, the laser light within the waveguide is scattered to the outside, but since this light is coherently scattered over a long section, a beam with a small divergence angle can be obtained. However, in the case of a -dimensional diffraction grating, the divergence angle is narrowed only in one direction, but the other directions remain the same as before.

[Purpose and outline of the invention]

The present invention eliminates this drawback by providing a waveguide including an active layer in a semiconductor, and
A periodic unevenness is created two-dimensionally inside the guide so that the laser light is scattered outside the guide, and the scattered light can be extracted to the outside of the element, and the guide with the two-dimensional periodic structure The present invention provides a shear distributed feedback semiconductor laser device characterized by uniformly exciting an active layer within a wave path.

[Embodiments of the invention]

The present invention will be explained in detail below using examples.

FIG. 1 is a schematic explanatory diagram showing an example of implementation of the present invention,
The present invention will be described in detail using the same figure.

As shown in FIG. 1(a), a waveguide 2 including an active layer is provided on a semiconductor substrate 1, and a semiconductor layer 3 is provided thereon, and periodic irregularities are formed on the surface of the waveguide 20 as shown in FIG. ), they are constructed in the X direction and in the X direction. The period of this unevenness is set to be around an integral multiple of a half wavelength of laser oscillation in the active layer. 4 and 5 are electrodes. When a current is passed through this element or it is excited by light, distributed feedback occurs due to the diffraction gratings in both the X and X directions, and the laser oscillations in the ξ and η directions are distorted by 4 times. However, since distributed feedback of the diffraction gratings in the X direction and the X direction alone also occurs, the laser beams in the ξ direction and the η direction are combined, and the entire surface of the diffraction grating oscillates with the same phase. In this case, if an even-order high-order diffraction grating is provided,
In other words, when the period of the unevenness is set close to an even number multiple of the laser oscillation half wavelength in the active layer, the laser light in the waveguide becomes x −
It is radiated vertically upward from the y-plane. Since this radiation light is emitted from the entire surface, laser light with a small two-dimensional spread angle can be obtained. The divergence angle is generally within 1° and within 10 milliradians. Furthermore, since the laser beam is emitted from a wide area, a large optical output can be obtained.

- As an example, the size of the area with the diffraction grating is 200 μm
If X is 200 μm, a pulse output of 20 W can be obtained. Furthermore, since it is a distributed feedback type, the longitudinal mode is naturally a single mode. When we solved the two-dimensional coupled wave equation for the laser oscillation conditions for such a device, it became clear that the device oscillates at a lower threshold current density than conventional distributed feedback lasers. In the above element example, approximately 1,2
The threshold current value is about that of a human.

As the semiconductor material used in the present invention, 0.7 to 0.9μ
For the oscillation wavelength of m, a GaAlAs system is used. n-type Ga
As a substrate, n-Al□ on it, 3. GaO,
7AS'+P"0.05GaO, 9!5As (active layer)
. On top of that Alo3Gao7A
Grow the s-layer. In order to extract light from the center of the element, the central part (in the above example, 200 μm x 200
ttm), the Or-A and u electrodes are formed by vapor deposition. On the substrate side, an AuGeNi-All electrode is formed by vapor deposition. For continuous operation, the P side is bonded to Sl or diamond using In or Au-Sn solder. In this case, a hole of 200 μm x 200 μm is made in the metal electrode film on the substrate side, and a Ga
There are also n A lo, 3 Ga o, 7 in the As substrate.
A hole is made by chemical etching up to the As layer. This is from K.
It is possible to prevent laser light from being absorbed by the substrate. At an oscillation wavelength of 1.1-1.5 μm, Oa I n
The A s P system is used. In this case, if Ir1l) is used for the substrate, there is no need to make holes in the substrate because the substrate is transparent to laser light even in the case of continuous operation.

〔Effect of the invention〕

As described above, according to the present invention, it is possible to obtain a semiconductor laser device that emits an equidirectional, high-output laser beam in single longitudinal and transverse modes with a small divergence angle. Further, according to the present invention, since laser light is obtained from the element surface,
Integration with other elements, such as FB'l', is also easy.

[Brief explanation of the drawing]

FIG. 1 is a schematic explanatory diagram of the laser device of the present invention. In the figure, 1: Semiconductor substrate 2: Waveguide including active layer 3: Semiconductor layer 4.5゛ electrode Representative Patent Attorney Junnosuke Nakamura

Claims (1)

[Claims] ], in a semiconductor laser device in which a waveguide including an active layer is provided in a semiconductor, a laser is oscillated within the waveguide by two-dimensionally providing unevenness on the surface or inside of the waveguide including the active layer. The light is scattered to the outside of the waveguide, the active layer in the waveguide having the two-dimensional periodic structure is uniformly excited, and the scattered light is taken out to the outside of the device. Distributed feedback semiconductor laser device.