JPS61253881A - Distributed feedback semiconductor laser - Google Patents

Abstract

PURPOSE:To enable to regulate the projecting angle of laser projection light, by making the shape of at least one of light projecting end faces a paraboloid or circle including an ellipse. CONSTITUTION:After a mesa is formed, a P-type InP buried layer 7, N-type InP buried layer 8 and P-type InGaAsP cap layer 9 are sequentially grown by liquid phase growing. After a Cr-Au electrode 10 and AuGeNi-Cr-Au electrode 11 are deposited, the section of the end face projection laser light is made curved 12. In this way, by making the shape of the light projecting end face a paraboloid or circle including an ellipse, a lens effect for the laser projecting light at this section can be utilized to reduce the projecting angle. Moreover, by varying the form such as the curvature of the curved section of the light projecting face, the projecting angle can be regulated.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a distributed feedback semiconductor laser, and more particularly to an element with a good output beam shape.

[Background of the invention]

Since the emitted beam of a semiconductor laser is widely spread due to the small area of the active layer, it is necessary to use a lens for coupling with an optical fiber.

For this reason, it is necessary to align the optical axes of the semiconductor laser, lens, and fiber, but single mode fibers with small core diameters require precise alignment, which has been a major drawback of semiconductor lasers.

(Yonezu, "Optical Communication Device Engineering", pp. 266-280.

1982.2.15. Kogaku Tosho Co., Ltd.) [Object of the Invention] The object of the present invention is 1. The object of the present invention is to provide a distributed feedback semiconductor laser with a small beam divergence angle.

[Summary of the invention]

In a distributed feedback laser, a diffraction grating inside the device generates the optical feedback necessary for laser oscillation. Therefore, it is not necessary to make the light emitting end face mirror-like, and at least one of the light-emitting end surfaces can be made into a circular shape or a paraboloid that equalizes an ellipse. By maintaining this shape, it becomes possible to freely adjust the emission angle of the laser light. In this case, the active layer is set on the central axis of the circular output end face.

[Embodiment of the Invention] An embodiment of the present invention will be described below with reference to FIG. An n-type InGaAsP light guide layer 2 (thickness: 0, 1 pm) is formed by a primary liquid phase growth method, in which gratings with a pitch of 230 nm are formed on an n-type InP substrate 1 by an interference exposure method.
), InGaAsP active layer 3 (0,1 pm) P type I
nGaAsP anti-meltback layer 4 (0.1pm)
P-type InP gradient layer 5 (0.1 μm), P-type InGa
An AsP cap layer 6 (0.5 μm) is sequentially grown.

After this, etching is performed by chemical etching, leaving a mesa portion. After mesa formation, P-type InP buried layer 7 (1 μm) and n-type InP buried layer 8 (3 μm) were formed by liquid phase growth method.
, P type nGaAsP cap Jl19 (0,5μ
Cr-Au electrode 10,
After depositing the AuGeN1-Cr-Au electrode 11.

The light emitting end face of the laser has a curved shape 12.

As a means for this, the following method was used. First, after forming a circular shape as shown in the top view in Figure 1 by photoregistration and etching, selectively etch only the substrate near the end face and remove it.
Next, the portion of the image whose end face has not been removed is polished into a curved shape 12. In this way, by making the shape of the light emitting end face into a circular shape including an ellipse or a paraboloid, it is possible to make use of the lens effect on the emitted light of the laser in that part and to reduce the emitting angle. Furthermore, by changing the curvature and shape of the curved portion of the light-emitting end face, it is possible to adjust the output angle, and for example, the output light can be made into parallel light or converged to a certain focal point. According to this embodiment, the half-value width of the far-field pattern was about 5 degrees, which was conventionally 30''' to 40 degrees.

Incidentally, in the above explanation, the grating is provided at the boundary between 2 and 3, but it may also be provided at the boundary between 4 and 5. Moreover, not only one end surface but both end surfaces may be made into paraboloids.

〔Effect of the invention〕

According to the present invention, since the output angle of the laser beam can be freely adjusted by the laser body, sufficient splicing efficiency can be obtained without using a conventional lens when splicing an optical fiber. I can do it.

The above explanation was given using a distributed feedback semiconductor laser as an example.
The present invention is not limited to this, and the same applies to, for example, a black reflective semiconductor laser. Also, regarding the material, InGaA
In addition to sP/I n P, GaAlAs/GaAs
It's good as well.

[Brief explanation of drawings]

FIG. 1 is a rear view, a top view, and a side view of the element.

Claims (1)

[Claims] 1. In a semiconductor laser having a structure in which optical feedback for laser oscillation occurs due to periodic unevenness, a distribution characterized in that at least one of the light emitting end faces has a circular shape including an ellipse or a paraboloid. Feedback semiconductor laser.