JPS6398176A - Optical semiconductor device - Google Patents

Abstract

PURPOSE:To obtain an optical semiconductor element in which its wavelength characteristic is linearly varied by linearly forming the lattice of diffraction grating not in parallel, and setting intervals between a line perpendicular to one lattice of reference and crossing points of the lattices equally. CONSTITUTION:When a light propagated in a semiconductor layer is coupled with a diffraction grating, a light of wavelength of lambdas = 2.m.n.d (wherein m: natural number, n: effective refractive index of medium, d: period of lattice). Accordingly, when the lattices of the diffraction grating are set not parallel and linearly varied, the period (d) of the lattice is linearly varied. Then, arbitrary one of the formed lattices is considered to be a reference lattice 3, and lines 1, 2 perpendicular thereto are separated at 1 mm. At this time, the interval between a perpendicular line 1 and the crossing points of the lattices are set to 240 nm, and the intervals between a perpendicular line 2 and the crossing points of the lattices are set to 238 nm to be linearly formed. Accordingly, elements are formed at an equal interval in parallel with the lines 1, 2, and when the interval between the elements is set to 500mum, the period of the lattices to be coupled with the elements is varied by 1 mm at an equal interval.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to an optical semiconductor device having one diffraction grating.

[Conventional technology]

A conventional optical semiconductor device having a non-parallel diffraction grating and a manufacturing method are disclosed in Japanese Patent Publication No. 57-29069-QK.

[Problem that the invention seeks to solve]

Diffraction gratings with different periods? By forming them on the same substrate, it becomes possible to form a variety of optical semiconductor elements.

For example, an integrated laser with a different oscillation wavelength can be realized by forming a distributed feedback semiconductor laser on a substrate having diffraction gratings with different periods. Possible methods for this include an interference exposure method using a cylindrical lens as shown in the above-mentioned prior art, and a method in which gratings containing partially different periods are successively formed by an interference exposure method. but.

To form a grating sequentially by interference exposure method.

Multiple interference exposures and alignment are required, making it extremely difficult to form a uniform grating. Further, although the interference exposure method using a cylindrical lens requires only 11g1l of exposure, the formed gratings are non-parallel.

For this reason, when lasers are formed at equal intervals, a problem often arises in that the emission wavelengths of the lasers are not arranged at equal intervals.

An object of the present invention is to realize an optical semiconductor element whose wavelength characteristics change linearly when optical elements are formed at regular intervals, and to show a method for manufacturing a diffraction grating for the same.

[Means for solving problems]

The above purpose can be achieved by making the grating of a single diffraction grating non-parallel and at the same time making the grating linear. It can be easily formed by forming a mask using a method and transferring the pattern onto a semiconductor substrate.

[Effect]

When light propagating in a semiconductor layer is coupled with a diffraction grating, λ
g='), -m-n-d (m: natural number, n: effective refractive index of the medium, d: period of the grating) is selected. Therefore, by making the grating of one diffraction grating nonparallel and changing it linearly, the period d of the grating changes linearly. Therefore, if elements are formed at regular intervals perpendicular to a certain reference grating, the difference in the grating period d of each element Δd
are equal. Therefore, the difference ΔλS between the wavelengths of light selected for each element becomes equal.

〔Example〕

An embodiment of the F1 invention will be described below with reference to FIGS. 1 and 2. FIG. FIG. 1 shows a part of a semiconductor substrate having a diffraction grating formed by transferring from a mask. An arbitrary one of the formed grids is considered as the reference grid 3, and grids a and b perpendicular to this are considered. Here vertical lines a and b are 1
mm apart. In this example, the distance between the vertical intersections of the grid 1 and each grid was set to 240 nm. Further, the interval between the intersection of the vertical line 2 and each grid was 238 nm. At this time, each grid is formed in a straight line. Therefore, if elements are formed parallel to the vertical line 1.2 and at equal intervals, and the spacing between elements is 500 μm, the period of the grating connected to each element will change at equal intervals of 1 mm. . Seven semiconductor lasers were formed on this substrate as shown in FIG. Here, an n-type InP substrate 5 is used as the substrate,
A diffraction grating shown in FIG. 1 is formed on this substrate, and n-type jnGaAsP (photoluminescence wavelength λPL=
1.3 μm) optical guide layer* InGaAsP active layer (λPL=1.53 μm), p-type InP layer, p-type InP layer
A GaAsP cap layer was grown. After that, oxide film stripes are formed at intervals of 500 μm in the direction parallel to the vertical M1 and M2 shown in Fig. 1, and then etched with a 5k3t-methanol-based nitrogen solution, and both sides of the MEG are filled with crystals to form a BH structure. We created a laser. Thereafter, electrodes were formed on both sides, and then the strip was opened and scribed to form a bar in which seven lasers 6 were integrated as shown in Fig. 5g2. % elements are electrically isolated and can be operated independently. FIG. 3 shows the flow-light output characteristics and spectra when each element is operated. As shown in FIG. 3, an integrated distributed feedback semiconductor laser was obtained which oscillated at a very uniform wavelength interval of 6.5±0.2 nm between each spectrum.

In this example, the oscillation wavelength is 1.5 μm? Although the RF distributed feedback laser has been described, the present invention is applicable to the 1.3 μm band and Ga laser.
It is also effective for some distributed feedback type or distributed reflection type AS systems. In addition to semiconductor lasers, the present invention is also effective for optical semiconductor devices such as optical switches with wavelength selectivity.

〔Effect of the invention〕

According to the present invention, an optical semiconductor device t having linear wavelength selection with respect to a change in one position can be easily obtained.

[Brief explanation of the drawing]

Figure 1 is an example of the present invention, which shows a partial surface of an InP substrate when a grating is formed on the InP substrate, and Figure 2 shows the integration of seven elements using the substrate shown in Figure 1. An overview diagram of a semiconductor laser integrated with distributed feedback and the third
The figure shows the current-light output characteristics and spectrum diagram of the seven elements shown in FIG. 2. Fig. 1 1 L,, P + anti-sample Fig. 2 etc. 3 Mr. E Ki,

Claims (1)

[Claims] 1. In an optical semiconductor device formed on a single substrate and having a diffraction grating inside the device, the gratings of the diffraction grating are non-parallel and linear, and one reference An optical semiconductor device comprising a diffraction grating in which the intersections of each grating and a line perpendicular to the grating are equally spaced. 2. Claim 1, characterized in that the non-parallel diffraction grating is formed by transferring light from a mask.
Optical semiconductor device as described in section.