JPS63293892A - Semiconductor laser - Google Patents

Abstract

PURPOSE:To obtain a semiconductor laser with narrow spectrum line width by connecting both ends of the gain region with a waveguide having lower loss and optically connecting the conducted light to a sector form diffraction lattice provided on the outside at one part of the waveguide. CONSTITUTION:After a non-reflecting film on both ends of a semiconductor laser 1, it is optically connected with a single mode fiber 2. A lens made of Si with high refractive index is used for connection. A part of the flood of the single mode fiber 2 is etched, a sector form diffraction lattice 4 is pressed on that part to optically connect the single mode fiber 2 to the diffraction lattice 4. By doing so, it is possible to vary the oscillating wavelength as the width of the spectrum line is narrowed, thereby obtaining a semiconductor laser with narrow width of the spectrum line.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a light source for optical communication, and particularly to an element structure suitable for emission wavelength operation.

[Conventional technology]

The conventional device was published in the 10th IEE International Semiconductor Laser Conference, Post-Deadline Paper Proceedings, pages 10 to 11 (10thIP, [EEIntemato
nal Sem1conductor 1aser
conference program and
abstract of post-deadl
ine papers (1986) pplo-11)
It is discussed in

[Problem that the invention seeks to solve]

In the above-mentioned conventional technology, the light emitting region in which the diffraction grating is formed is divided into two parts, and each part is independently excited to realize a single wavelength operation and also to realize a wavelength variable function. However.

The conventional technique described above has a problem in that the wavelength variable range is limited to about 20 wavelengths because it utilizes the change in refractive index caused by carrier injection. Also, the resonator length is 200μ
There is also the problem that the number of photons that can be confined within the resonator is limited due to the short length of about m, and that the spectral linewidth becomes larger than 10 MHz due to the presence of a diffraction grating in the active waveguide. occured.

The object of the present invention is first to obtain a semiconductor laser with a narrow spectral linewidth, and also to make this wavelength variable.

[Means for solving problems]

The above object is achieved by coupling both ends of the gain region with a low-loss waveguide, and by optically coupling light propagating in a part of the waveguide with a door-shaped diffraction grating provided outside.

[Effect]

By looping the resonator structure, it is possible to increase the number of photons confined within the resonator. In addition, since it is coupled to the diffraction grating in the low-loss waveguide section, changes in the refractive index due to carrier density fluctuations do not occur in the wavelength selection section, and no increase in spectral linewidth occurs, resulting in a narrower spectral linewidth. I can do it. Diffraction grating 1
If the shape is changed, the period of the diffraction grating will differ depending on the location. Wavelength tunability can be achieved by spatially changing the coupling location between the diffraction grating and the waveguide.

〔Example〕

An embodiment of the present invention will be explained below with reference to FIG. After forming antireflection films on both end faces of a semiconductor laser 1 whose gain peak has a wavelength of 1.55 μm, optical coupling was performed using a single mode fiber 2 with a length of 5 to 20 m. Si for bonding
A high refractive index lens 3 manufactured by Co., Ltd. was used. A part of the 2 flat of the single mode fiber is etched, a fan-shaped diffraction grating 4 is pressed against this part, and +B is applied using matching oil.
- The mode fiber 2 and the diffraction grating 4 are optically coupled. An optical coupler 5 was formed on the other part of the single mode fiber, and output light was taken out from the optical coupler 5 to evaluate the device.

The device oscillated at a threshold of 20 mA, and m-mode oscillation occurred at a specific oscillation wavelength determined by the period of the diffraction grating 4. The spectral linewidth is 100KHz at an optical output of 1mW, which is 1/100 to 1/1/2 when compared to a normal DFB laser.
It was found that the band was narrowed to a value of 1000. The diffraction grating 4 was fabricated on the glass surface by electron beam lithography, and was fan-shaped as shown in the figure. Therefore, the period of the diffraction grating differs depending on the location. By moving the fan-shaped diffraction grating in the direction of the arrow in FIG. 1, the oscillation wavelength could be smoothly changed. The tunable wavelength range was determined by the gain width of the semiconductor laser 1, and tuning within a range of ±50 was possible.

Note that by using a polarization-maintaining fiber instead of the m-mode fiber 2, rotation of the polarization plane due to bending, twisting, etc. of the fiber can be prevented, and a stable narrow band can be maintained even when the diffraction grating 4 is moved. The transformation was '4'.

〔Effect of the invention〕

According to the present invention, since the oscillation wavelength can be made variable while the spectral linewidth remains narrow, a semiconductor laser device suitable for use as a local light source in coherent communication can be obtained.

[Brief explanation of drawings]

FIG. 1 shows a semiconductor laser device "''"V of an embodiment of the present invention.
WtlA″Q ,′6−,,+−]゛s,.

Claims (1)

[Claims] 1. It has a structure in which a band-shaped gain region and a low-loss region connecting both ends thereof form a loop, and at least a portion of the loop has a diffraction grating that is optically coupled. Semiconductor laser device. 2. The semiconductor laser device according to item 1 above, wherein the diffraction grating has a fan shape, and the positions of the diffraction grating and a portion of the loop are relatively variable.