JPH1168233A - Variable wavelength laser light source - Google Patents

Abstract

PROBLEM TO BE SOLVED: To simplify optical adjustment and constitution by eliminating the need for an optical system on one end face side of a semiconductor laser diode. SOLUTION: This light source is provided with a semiconductor laser diode 1 for which a non-reflective film 1A is applied to one end face and the other end face is turned to a cleavage surface or a high reflection film 1B, provided with reflectance higher than its reflectance is executed to it and an optical variable band-pass filter 4 for transmitting the light of a specified wavelength among the wavelength components of the emitted light. A partially reflecting film 6A for constituting an external resonator by the cleavage surface or the high reflection film 1B of the semiconductor laser diode 1 ix executed to the incident end face of an optical fiber 6 and the light which is made incident on the partially reflecting film 6A is passed through an optical fiber 6 and taken out from an output port 7.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a variable wavelength laser light source used in optical communication and the like, and more particularly to a variable wavelength laser light source using a light variable bandpass filter which is a transmission type optical element as a wavelength selecting means.

[0002]

2. Description of the Related Art In a semiconductor laser diode (Fabry-Perot), a non-reflection film is formed on one end face of the semiconductor laser diode, and the semiconductor laser diode is fed back using a wavelength-selective element, so that the other end face is formed. It is known that an external resonator is formed between the two, and laser oscillation occurs when the gain condition and the phase condition exceed the reflection loss, the scattering loss, and the like. In addition, by selecting a laser beam of an arbitrary wavelength from the emitted light emitted from the semiconductor laser diode that performs laser oscillation in this way, by feeding back the laser beam to the semiconductor laser diode, the laser beam can be used as a variable wavelength laser light source. .

FIGS. 2 and 3 are configuration diagrams showing examples of such a conventional variable wavelength laser light source, respectively. First,
2, the semiconductor laser diode 8a is provided with a low-reflection film 8b on one end surface of the semiconductor laser diode 8a, and a non-reflection film 8c on the other end surface of the semiconductor laser diode 8a. It has been subjected. Reference numeral 9b denotes a lens for converting light emitted from the semiconductor laser diode 8a into parallel light, reference numeral 12 denotes an optical variable band-pass filter disposed in front of the lens 9b, and reference numeral 13 denotes an optical variable band-pass filter disposed in front of the optical variable band pulse filter 12. Total reflection mirror 13. An external resonator is formed by the total reflection mirror 13 and the low reflection film 8b. 9a is a low reflection film 8b of the semiconductor laser diode 8a.
Is an optical fiber for transmitting laser light transmitted through the lens 9a, and the laser light is transmitted through the optical fiber 10 and output from the output port 11.

Next, the operation will be described. When laser light is emitted from the semiconductor laser diode 8a, this light is converted into parallel light by the lens 9b, and further, light of a specific wavelength is transmitted through the variable optical bandpass filter 12. When the transmitted light is reflected by the total reflection mirror 13, the light changes its direction by 180 °, travels, passes through the variable optical bandpass filter 12 and the lens 9b again, and enters the semiconductor laser diode 8a. You. The light that has entered the semiconductor laser diode 8a in this way is reflected by the surface of the low reflection film 8b having a reflectance of several percent, and is returned to the semiconductor laser diode 8a again. For this reason,
By forming an external resonator by the low reflection film 8b and the total reflection mirror 13, laser oscillation is performed.

The light generated by this laser oscillation propagates through the optical fiber 10 via the lens 9a,
1 is output. During such a light output operation, a variable wavelength laser light source can be obtained by changing the transmission wavelength of the variable optical bandpass filter 12.

On the other hand, the variable wavelength laser light source shown in FIG.
The variable bandpass filter 12 and the total reflection mirror 13 constituting the variable wavelength laser light source of FIG. 2 are omitted, and a diffraction grating 14 is used instead. The other configuration is the same as that of FIG. 2, and the same components as those of FIG. 2 are denoted by the same reference numerals, and the description thereof will not be repeated. In the conventional variable wavelength laser light source shown in FIG. 3, the light converted into parallel light by the lens 9b is incident on the diffraction grating 14, and the light whose wavelength has been selected by the diffraction grating 14 using the diffracted light is again converted into a lens. 9b, and is incident on the semiconductor laser diode 8a.
In the same manner as described above, the diffraction grating 14 and the low reflection film 8b
An external resonator is formed, and after transmitting through the lens 9a, propagates through the optical fiber 10 and is output from the output port 11.

[0007]

However, in any of the conventional variable wavelength laser light sources, the light emitted from one end face of the semiconductor laser diode 8a is fed back by the total reflection mirror 13 or the diffraction grating 14. Then, in order to take out the light emitted from the other end face as output light, optical adjustment such as optical axis alignment on both sides of the semiconductor laser diode 8a is required, and the structure becomes complicated. Alternatively, since the light is fed back by the diffraction grating 14, the light feedback amount fluctuates even with a slight change in the angle, and the arrangement of the optical components requires advanced optical axis adjustment technology and advanced technology for improving reliability. This required a great deal of fixing technology, which was a major obstacle to production.

The present invention solves the above-mentioned conventional problems. By eliminating the need for an optical system on one end surface side of a semiconductor laser diode, optical adjustment and simplification of the configuration can be realized. By using a configuration in which a part of the light condensed on the fiber is fed back, the change in the amount of feedback with respect to the incident angle can be moderated, and productivity and productivity can be improved without the need for advanced optical axis adjustment and fixing techniques. It is an object of the present invention to obtain a tunable laser light source that can improve economy.

[0009]

In order to achieve the above object, a variable wavelength laser light source according to the present invention has an antireflection film on one end surface and a cleavage surface on the other end surface or a reflection surface thereof. Semiconductor laser diode provided with a highly reflective film having a reflectance equal to or higher than a reflectance, a first lens that converts light emitted from the semiconductor laser diode into parallel light, and a wavelength component of light emitted from the first lens Among them, an optical variable bandpass filter that transmits light of a specific wavelength, and a second lens that incidently couples the transmitted light from the optical variable bandpass filter to an optical fiber are provided. A partial reflection film that forms an external resonator with the cleavage surface of the semiconductor laser diode or the high reflection film is formed on the incident end face of the optical fiber, and the incident light incident on the partial reflection film is output through the optical fiber. One in which they were taken out from the door.

In the variable wavelength laser light source according to the second aspect of the present invention, the optical variable band pulse filter is provided so that the incident angle of the laser light can be adjusted.

In the variable wavelength laser light source according to the present invention, a photodiode for monitoring an optical output is disposed on the cleavage plane side.

According to a fourth aspect of the present invention, there is provided a variable wavelength laser light source, wherein a polarization independent optical isolator is provided between an input end face of the optical fiber and an output port.

[0013]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing a variable wavelength laser light source according to the present invention. In FIG. 1, reference numeral 1 denotes a semiconductor laser diode.
Is coated with an antireflection film 1A having a reflectance of 0.1% or less. The other end face of the semiconductor laser diode 1 is a cleavage plane (reflectance is around 30%) or a high reflection film 1B having a reflectance equal to or higher than the reflectance of the cleavage plane is applied.

Reference numeral 3 denotes a lens serving as a first lens, which functions to convert the laser light 2 emitted from the semiconductor laser diode 1 into parallel light and to enter the variable optical bandpass filter 4. It should be noted that the optical variable band-pass filter 4 used has a transmission area half width of about 0.5 nm. The variable optical bandpass filter 4 functions to transmit only light having a specific wavelength λa of all the wavelength components among the incident light, and to couple the light to the optical fiber 6 by a lens 5 as a second lens. . The incident end face of the optical fiber 6 is polished perpendicular to the central axis, and the end face is provided with a partial reflection film 6A for reflecting a part of the incident light. Reference numeral 7 denotes an output port for extracting output light.

Next, the operation will be described. When the semiconductor laser diode generates laser light, the light is converted into parallel light by the lens 3 through the non-reflection film 1A, and is incident on the variable optical bandpass filter 4. The light incident on the variable optical bandpass filter 4 transmits only light of a specific wavelength λa in the entire wavelength range, and only the transmitted light is condensed by the lens 5 and is incident and coupled to the optical fiber 6. . For this reason, the condensed light is split into two at the partial reflection film 6A, which is the incident end face of the optical fiber 6, and one of them is 180
The lens 5, the variable optical bandpass filter 4,
Following the original optical path passing through the lens 3, it is returned to the semiconductor laser diode 1, and the high reflection film 1 B and the partial reflection film 6 A
Constitutes an external resonator and causes laser oscillation.

Then, the other split light passes through the partial reflection film 6A, propagates in the optical fiber 6, and is extracted from the output port 7 as output light. The partial reflection film 6A
Is formed of a dielectric multilayer film, for example, 20% reflection, 80%
% Transmission is used. At this time, the oscillation wavelength of the laser can be freely varied by changing the incident angle of the laser light on the variable optical bandpass filter 4.

Further, one end face (front end face) of the semiconductor laser diode 1 is formed as a normal cleavage plane, and light is monitored from behind by a photodiode, so that the light output can be stabilized using the monitoring result. Further, by applying a high-reflection film having a high light reflectance, the laser oscillation efficiency can be increased and a higher light output can be obtained. Similarly, with regard to the partial reflection film 6A applied to the incident end face of the optical fiber 6, it is possible to arbitrarily select whether to decrease the reflectivity to increase the light output or to increase the reflectivity to widen the variable wavelength range.

By adding a polarization independent optical isolator between the input end face of the optical fiber 6 and the output port 7,
The oscillation state of the semiconductor laser diode 1 can be further stabilized. Furthermore, by combining these components with a Peltier element, a thermistor, and the like, and adjusting the temperature of the semiconductor laser diode 1, a highly stable and highly stable variable wavelength laser light source can be obtained.

[0019]

As described above, according to the first aspect of the present invention, one end face is provided with a non-reflection film and the other end face is a cleavage plane or a high reflection film having a reflectance higher than that of the cleavage face. A semiconductor laser diode provided with a film, a first lens that converts light emitted from the semiconductor laser diode into parallel light, and transmits light of a specific wavelength among wavelength components of the light emitted from the first lens. And a second lens that couples the transmitted light from the variable optical bandpass filter to the optical fiber. The incident end face of the optical fiber perpendicular to the central axis is A cleavage surface or a high reflection film of the semiconductor laser diode is used to form a partial reflection film that forms an external resonator, and output light is extracted from an output port through the partial reflection film. The optical system on the side is unnecessary, and a part of the light condensed on the optical fiber is fed back.Thus, the change in the amount of feedback with respect to the incident angle can be moderated. The effect is that a highly stable variable wavelength laser light source having excellent stability can be obtained at low cost.

Further, according to the second aspect of the present invention, since the variable optical band pulse filter is provided so that the incident angle of the laser beam can be adjusted, there is an effect that the oscillation wavelength of the laser can be freely selected. can get.

According to the third aspect of the present invention, since a photodiode for monitoring light output is arranged on the cleavage plane side, a measure for stabilizing light output is taken according to the monitoring result. The effect that it can be obtained is obtained.

According to the fourth aspect of the present invention, since the polarization independent optical isolator is provided between the input end face of the optical fiber and the output port, the oscillation state of the semiconductor laser diode can be improved. The effect of being able to stabilize is obtained.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing a tunable laser light source according to an embodiment of the present invention.

FIG. 2 is a configuration diagram showing a conventional variable wavelength laser light source.

FIG. 3 is a configuration diagram showing another conventional variable wavelength laser light source.

[Explanation of symbols]

 Reference Signs List 1 semiconductor laser diode 1A non-reflective film 1B high-reflective film 3 lens (first lens) 4 variable optical bandpass filter 5 lens (second lens) 6 optical fiber 6A partially reflective film 7 output port

Claims (4)

[Claims] A semiconductor laser diode provided with an antireflection film on one end surface and a cleavage surface on the other end surface or a high reflection film having a reflectance equal to or higher than the reflectance of the cleavage surface; A first lens that converts light emitted from the laser diode into parallel light, a light variable bandpass filter that transmits light of a specific wavelength among wavelength components of light emitted from the first lens, and the light variable band A second lens for entering and coupling the transmitted light from the pass filter to the optical fiber; and a cleaved surface or a highly reflective film of the semiconductor laser diode, which is provided on the incident end face of the optical fiber perpendicular to the central axis. A tunable laser light source, comprising: a partial reflection film forming an external resonator; and an output port for extracting incident light incident on the partial reflection film through the optical fiber. 2. The variable wavelength laser light source according to claim 1, wherein the variable optical band pulse filter is provided so as to adjust an incident angle of the laser light. 3. The tunable laser light source according to claim 1, wherein a photodiode for monitoring an optical output is arranged on the cleavage plane side. 4. The variable wavelength laser light source according to claim 1, wherein a polarization independent optical isolator is provided between an input end face of the optical fiber and an output port.