JPS60180184A - Stabilizer for wavelength of semiconductor laser - Google Patents

Abstract

PURPOSE:To optimize the titled stabilizer so that the noises of output waves from a semiconductor laser are minimized by electrically changing the phase of self-injection waves to the semiconductor laser. CONSTITUTION:A semiconductor laser 2 is coupled optically with one terminal of the main line of a waveguide type directional coupler 3 constituted on a dielectric substrate 1 having an electrochemical effect, the other terminal is used as an output terminal for a wavelength stabilizer, a by-line for the directional coupler 3 is terminated by a grating reflecting filter 10 through one phase appliance 11 of the by-line, the by-line is terminated by a grating reflecting filter 9 at the other terminal of the by-line, and applied voltage to the directional coupler 3 and an electrode for the phase appliance 11 is changed. Accordingly, phase difference between output waves from a semiconductor laser and injection waves to the semiconductor laser can be adjusted electrically so that the noises from the semiconductor laser are minimized.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a stabilizing device for the purpose of stabilizing the oscillation wavelength of a semiconductor laser. It is characterized by being configured so that the noise can be adjusted to a minimum by electrically changing the noise.

Conventional configurations and their problems In order to apply semiconductor lasers to single-mode optical communications, it is necessary to cause the semiconductor laser to oscillate in a single mode.Currently, single-mode semiconductor lasers with various structures are available. being developed. In order to apply such a single mode semiconductor laser to more advanced coherent optical communications, it becomes necessary to reduce the FM noise of the semiconductor laser. In solid-state oscillators in the microwave and millimeter wave bands, such as Gunn diodes and Imbat diodes, a well-known method for reducing FM noise is to self-inject part of the oscillation output into the oscillator. In semiconductor lasers, a known method to unify the longitudinal mode is to return part of the output to the semiconductor laser using a mirror or grating, and this method is also known to improve noise. . All of these have mirrors or gratings arranged spatially, and the only adjustment parameter is the optical distance, so they have the drawback of being difficult to make delicate adjustments.

OBJECTS OF THE INVENTION An object of the present invention is to easily operate a semiconductor laser under optimal conditions where noise is minimized by changing the phase of an optical self-injected wave by electrical means.

Structure of the Invention The present invention optically couples a semiconductor laser to one terminal of the main line of a waveguide type directional coupler constructed on a dielectric substrate having an electro-optical effect, and connects the other terminal to a wavelength The output terminal of the stabilizing device is used as the output terminal of the stabilizing device, and one of the sub-lines of the directional coupler is terminated with a grating reflection filter via a phase shifter, and the other terminal of the sub-line is terminated with the grating reflection filter. By changing the voltages applied to the electrodes of the optical coupler and the phase shifter, the phase difference between the output wave of the semiconductor laser and the wave injected into the semiconductor laser can be electrically controlled such that the noise of the semiconductor laser is minimized. This is an adjustable wavelength stabilization device for semiconductor lasers.

Description of examples Examples thereof will be described below with reference to the drawings.

In the figure, 1 is a dielectric substrate having an electro-optic effect; 2 is a dielectric substrate having an electro-optic effect;
1 is a semiconductor laser, 3Ii direction generator, 4°6.7 and 8 are optical waveguides formed by metal diffusion, 6 is a voltage application electrode, 9 and 1o are grating reflection filters, 1
1 is an electrode of a phase shifter.

Next, the operation of this device will be explained. As shown in the figure, the reference plane is T1 + T2 + T5 + T4 + T5
+T6. T, choose T1, T2+T3 and T7. T5
The phase angle between T6 and T6 is θ1. θ2. Let it be θ3.

A part of the semiconductor laser output wave goes from the directional coupler 3VC to the grating reflection filter 9, and the reflected wave there is divided into a wave returning to the semiconductor laser 2 and a wave going to the sub line 7, The light then returns to the reflection filter 9, where it is reflected again and injected into the semiconductor laser 2. Now, the reference plane T1 of the output wave of the semiconductor laser 2
If the value at is a, and the value at the reference plane T1 of the input wave to the semiconductor laser 2 is b, then the core jξ b−−β77′ +le (1+α17′ 1117′
21a)a...(1) It is expressed as follows. Here, β is the coupling degree of the directional coupler, α is the number given by α−/“−7, and η and ξ are the angles given by the following equation.

η=ψ1−2θ1−2θ2. ξ=ψ1−2θ2−2θ3
1ψ, ......(2) IF11θjψ1 is the reflection coefficient of the grating reflection filter 90, 17'''21ejψ2 is the reflection coefficient of the grating reflection filter 10. The degree of coupling β of the directional coupler 3 is the reflection coefficient of the grating reflection filter 90. It can be changed depending on the value of the applied voltage V, and the phase angle θ2 is determined by the voltage V applied to the electrode 11 of the phase shifter.
′ can be changed.

Therefore, as can be seen from equation (1), the magnitude of the wave injected into the semiconductor laser and the phase difference with respect to a can be changed by changing the voltages V and V'.

It is known that the noise of a semiconductor stopper varies depending on the size of the injected wave and the phase difference between it and the outgoing wave.

Therefore, it can be seen that in the configuration of the present invention, the noise of the semiconductor laser can be electrically controlled.

Effects of the Invention As described above, the present invention has the feature that the noise of the semiconductor laser output wave can be easily optimized to minimize the noise by electrically changing the phase of the self-injected wave to the semiconductor laser. be.

[Brief explanation of the drawing]

The figure is a schematic plan view of a wavelength stabilizing device for a semiconductor laser according to an embodiment of the present invention. 1...Dielectric substrate having electro-optic effect, 2.
... Semiconductor laser, 3 ... Directional coupler, 6 ... Electrode of directional coupler, 4,6 ...
Main line optical waveguide, 7.8 Sub line optical waveguide, 9.10 Grating reflection filter, 11 Phase shifter electrode.

Claims (1)

[Claims] A semiconductor laser is optically coupled to one terminal of the main line of a waveguide type directional coupler constructed on a dielectric substrate having an electro-optical effect, and the other terminal is used as an output terminal of a wavelength stabilizing device. , further terminating one of the sub-lines of the directional coupler with a grating reflection filter via a phase shifter,
By terminating the other terminal of the sub-line with a grating reflection filter and changing the voltages applied to the electrodes of the directional coupler and the phase shifter, the output wave of the semiconductor laser and the injection wave to the semiconductor laser can be controlled. A wavelength stabilizing device for a semiconductor laser, characterized in that the phase difference of the semiconductor laser can be electrically adjusted so that the noise of the semiconductor laser is minimized.