JP2000194023A - Semiconductor laser module - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a semiconductor laser module having improved stabilizing operation characteristic. SOLUTION: Exit light from a semiconductor laser element 1 is converted into collimated light and is converged by lenses 2, 3 and the converged light is taken out to outside by an optical fiber 4. In the optical fiber 4, fiber gratings 5a, 5b having two peak wavelengths are provided. The two peak wavelengths are set at a longer wavelength side and a shorter wavelength side from a central value of effective excitation wavelength band of an optical fiber amplifier. By this constitution, even when wavelength of the semiconductor laser element 1 is changed by temp. characteristic or the like and is out of a lock range of a reflector of one hand, the wavelength is locked in the excitation effective wavelength zone of rare earth-added fiber by the reflector of another hand, module operation in a wide temp. range is realized, tolerance of element wavelength is widened and yield of the semiconductor laser element is improved. Further, wavelength components which do not contribute to amplification at EDF can be reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a pumped semiconductor laser module for a fiber grating applied to optical communication.

[0002]

2. Description of the Related Art Conventionally, semiconductor laser modules are generally used for optical communication. In particular, with the recent long-distance optical communication, optical fiber amplifiers that can amplify light without converting it into electricity have been used. For example, for an optical fiber amplifier in the 1550 nm band, a rare earth element or a transition metal is added as a laser active material, and in particular, erbium is generally used. As the excitation wavelength band of the erbium-doped optical fiber amplifier,
There are a 980 nm band and a 1480 nm band, and an excitation light source in this wavelength band has been developed.

Referring to FIG. 12, the effective excitation wavelength band of a general EDF (erbium-doped fiber as a rare earth-doped fiber) is 975 to 985 nm.

[0004]

However, in the above-mentioned prior art, the wavelength range that can be used for excitation is determined.
Particularly in the 980 nm band, the effective excitation wavelength range is as narrow as about 10 nm, which affects the yield of the semiconductor laser device. The temperature dependence of the wavelength change of the semiconductor laser device is generally about 3 nm / 10 ° C. Therefore, when the semiconductor laser element temperature changes by about 40 ° C. or more, the wavelength of the semiconductor laser element deviates from the effective excitation range.

A fiber grating (hereinafter referred to as F
There is a method of stabilizing the wavelength by locking the wavelength using an external reflector such as G), but this has the following problems.

FIG. 9 shows a case where the temperature of the semiconductor laser element is intermediate, and FIG. 10 shows a case where the temperature of the semiconductor laser element is low.
Is the case of high temperature. In these figures, the characteristic curve 42 is the spectrum of the semiconductor laser device at a low temperature, the characteristic curve 43 is the spectrum of the semiconductor laser device at a high temperature, and the characteristic curve 41 is the spectrum at an intermediate temperature (about room temperature).

If the lock wavelength of the FG (fiber grating) is 980 nm, the wavelength of the semiconductor laser
When the lock wavelength of G is close, only the lock wavelength of FG is extracted as shown by the characteristic curve 31. However, when the wavelength of the semiconductor laser device shifts due to a low or high temperature, the FG lock wavelength cannot be completely drawn, and a part of the semiconductor laser device spectrum such as the characteristic curves 32 and 33 appears. This is a wavelength outside the effective pumping range of the EDF, and the gain of the EDF amplifier is reduced accordingly. The wavelength range of the semiconductor laser element that can be completely drawn into the FG is about ± 7 nm of the peak wavelength of the FG.

On the other hand, generally, the wavelength distribution at the time of manufacturing a semiconductor laser device is not uniform as shown in FIG. 12, but varies within a wafer and shows a distribution as shown in FIG. The shaded area is the wavelength range of the semiconductor laser element that can be drawn in by FG, but even if the semiconductor laser element wavelength distribution peak is at 980 nm as shown by the solid line, about 20% of the wavelength is defective.
If the peak shifts to one of the long and short wavelengths depending on the lot, the number of defectives further increases, and the yield deteriorates.

The present invention solves these problems and keeps the wavelength of the semiconductor laser module within the effective excitation range even when the temperature of the semiconductor laser element changes and the wavelength shifts, and further improves the yield of the semiconductor laser element. The purpose is to provide a module.

[0010]

In order to achieve the above object, a semiconductor laser module according to the first aspect of the present invention is provided.
A semiconductor laser device that emits laser light in a desired wavelength band, and a semiconductor laser module having a fiber grating that reflects a specific wavelength component in the wavelength band to the semiconductor laser device, wherein the fiber grating has two peak wavelengths, The peak wavelength is set to a wavelength before and after a predetermined wavelength of light emitted from the semiconductor laser element.

Further, the above fiber grating has
It has a reflectivity of 0.1 to 5%, especially 1 to 4%, and a peak wavelength bandwidth of about 0.3 to 3 nm, especially 1 to 2 nm.
It is good to have.

According to a third aspect of the present invention, there is provided a semiconductor laser module which emits a laser beam having a predetermined wavelength, a condensing means for converting light emitted from the semiconductor laser element into collimated light and condensing the same, An optical fiber for forming a grating having two peak wavelengths at the band interval and extracting light condensed by the light condensing means to the outside.

The above-mentioned condensing means may be constituted by one condensing means for performing conversion and condensing, or a first condensing means for converting the light emitted from the semiconductor laser element into collimated light. And a second light collector for collecting light.

Further, it is preferable that the two peak wavelengths of the irradiation means are set to wavelengths before and after a predetermined wavelength of light emitted from the semiconductor laser element is included.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, an embodiment of a semiconductor laser module according to the present invention will be described in detail with reference to the accompanying drawings. 1 to 8 show an embodiment of the semiconductor laser module of the present invention. These figures 1
4 to 4 are diagrams for explaining the operation of the first embodiment, and FIGS. 6 to 8 are diagrams for explaining the operation of the second embodiment. FIG. 5 shows an embodiment using another optical system.

This configuration will be described as an erbium-doped fiber (hereinafter, EDF) as a rare earth-doped fiber. FIG. 12 shows an example of the wavelength characteristic of the EDF gain in the 980 nm band.

FIG. 1 is a configuration diagram of the present semiconductor laser module. In FIG. 1, a semiconductor laser device 1 in the 980 nm band is a first lens 2 for converting the emitted light of the semiconductor laser device into collimated light, and a second lens 3 for condensing the collimated light. Also, the second lens 3
Optical fiber 4 to extract the light collected by the
Is provided. Reference numerals 5a and 5b denote fiber gratings formed in the optical fiber 4.

One of the fiber gratings 5a is 9
It has a peak wavelength of 75 nm. The other fiber grating 5b has a peak wavelength of 985 nm. Each of the two fiber gratings 5a, 5b has a reflectivity of 0.1-5%, especially 1-4%. Further, as a peak wavelength bandwidth, 0.3 to 3 n
m, especially 1-2 nm.

The effective excitation wavelength band of a general EDF (erbium-doped fiber as a rare earth-doped fiber) is:
As shown in FIG. 12, the thickness is 975 to 985 nm. Here, the wavelength of the grating was set to 975 nm and 985 nm in order to secure a wavelength band as wide as possible and to increase the excitation efficiency as much as possible. However, the numerical value may be set arbitrarily according to the characteristics of each EDF.

(Explanation of Operation) Light emitted from the 980 nm band semiconductor laser element 1 is collimated by the first lens 1, condensed on the optical fiber 4 by the second lens 3, and An external resonator is formed by one of the fiber gratings 5a and 5b formed by means such as irradiation,
m light is extracted outside. If the oscillation wavelength of the semiconductor laser element is 975 nm or less, light of 975 nm is extracted by the fiber grating 5a, and if it is 985 nm or more, light of 985 nm is extracted by the fiber grating 5b. In the case where the wavelength is 975 nm or more and 985 nm or less, the light is drawn to the closer one of the grating wavelengths, and either wavelength is extracted to the outside. This operation will be described with reference to the drawings.

FIG. 2 shows that when the temperature of the semiconductor laser device is low,
3 shows the case where the temperature of the semiconductor laser element is high, and FIG. 4 shows the case where the temperature is intermediate. Each shows the spectrum characteristics 21 to 23 of the semiconductor laser device at each temperature. When the temperature is low, the wavelength of the element is drawn to 975 nm, and the oscillation characteristic 11 is obtained. 985 if the temperature is high
The wavelength of the element is drawn to nm, and the oscillation characteristic 12 is obtained.
At an intermediate temperature, oscillation may occur at both peaks.
In any of these cases, the wavelength of the semiconductor laser can be locked in the effective excitation wavelength band of the EDF.

In the semiconductor laser module according to the first embodiment, the effective pumping wavelength band of the optical fiber amplifier is set at two wavelengths longer and shorter than the center value of the effective pumping wavelength range.
Reflectors having different peak wavelengths. In FIG. 1, two types of reflectors provided in an optical fiber, for example, have peak wavelengths at positions shifted by several nm from the center value of the effective excitation wavelength band of the rare-earth-doped fiber to the long wavelength side and the short wavelength side, respectively. Reflector. As a result, even if the wavelength of the semiconductor laser element changes due to temperature characteristics or the like and goes out of the lock range of one of the reflectors, the other reflector locks the wavelength to the excitation effective wavelength band of the rare-earth-doped fiber, Module operation in a wide temperature range can be realized.

According to the above embodiment, by providing two types of reflection peaks of the reflector at intervals of several nm, the allowable range of the device wavelength is expanded. Therefore, the yield of the semiconductor laser device is improved.

Further, two kinds of reflection peaks of the reflector are provided at intervals of several nm to extend the range in which the device wavelength can be drawn. Therefore, the operating temperature range of the semiconductor laser device is expanded.

Further, wavelength components that do not contribute to amplification in the EDF can be reduced. For example, it is a wavelength component like the peak 33 in FIG. According to the present embodiment, such a wavelength component 33 can be reduced. Thereby, the efficiency of the EDF can be improved.

(Other Embodiments) In the above embodiment, the ED
Although the description has been given of the 980 nm band having a narrow effective wavelength band of F, the wavelength of the reflector may be set to the upper and lower limits of the effective wavelength band in another wavelength band, for example, the 1480 nm band.

In FIG. 1, it is assumed that the semiconductor laser device 1 has a band of 1480 nm.

FIGS. 6, 7 and 8 show operating characteristic diagrams. 9
As in the case of the 80 nm band, the wavelength of the semiconductor laser device deviates from the effective excitation band at low and high temperatures, but is pulled into the band by the reflector. Also, since the effective excitation range is wide in the 1480 nm band, when the wavelength of the semiconductor laser element is between the peak wavelengths of the two types of reflectors, the wavelength cannot be completely drawn to the wavelengths of both reflectors as shown in FIG. There is. However, there is no problem because it is within the effective excitation wavelength band.

Although EDF is assumed in the first embodiment, similar effects can be obtained with other rare-earth doped fibers when a semiconductor laser pumping light source in the effective pumping wavelength band is used.

In the above embodiment, the optical system is a two-lens system, but a single-lens system may be used as shown in FIG. Means that can condense the emitted light of the laser element with a spherical fiber or the like may be used. Any optical system may be used as long as the light of the wavelength reflected by the reflector returns to the semiconductor laser device.

The above embodiment is an example of a preferred embodiment of the present invention. However, it is not limited to this.
Various modifications can be made without departing from the spirit of the present invention. For example, the above two embodiments and the optical wavelength bands used in the description are merely examples, and do not limit the configuration of the present invention.

[0032]

As is apparent from the above description, according to the semiconductor laser module of the present invention, the laser light of a predetermined wavelength is converted into collimated light by the light condensing means, and the light condensed is converted into light by the optical fiber. The optical fiber has a fiber grating formed by an irradiating means such as ultraviolet irradiation in the optical fiber.

According to the above configuration, the effective excitation wavelength band of the optical fiber amplifier is a reflector having two types of peak wavelengths on the long wavelength side and the short wavelength side from the center value of the effective excitation wavelength range. Even if the wavelength of the semiconductor laser element changes due to temperature characteristics or the like and goes out of the lock range of one of the reflectors, the other reflector locks the wavelength to the effective wavelength band of excitation of the rare-earth-doped fiber. It is possible to realize a module operation in a range. Thereby, the allowable range of the device wavelength is widened, and the yield of the semiconductor laser device is improved. Furthermore, wavelength components that do not contribute to amplification in the EDF can be reduced.

[Brief description of the drawings]

FIG. 1 is a first embodiment of a semiconductor laser module of the present invention.
FIG.

FIG. 2 is a diagram showing operating characteristics of a semiconductor laser module with an FG when a semiconductor laser element temperature is low.

FIG. 3 is a diagram showing operating characteristics of a semiconductor laser module with an FG when a semiconductor laser element temperature is high.

FIG. 4 is a diagram showing operating characteristics of the semiconductor laser module with an FG when the semiconductor laser element temperature is intermediate.

FIG. 5 is a diagram showing a configuration according to another embodiment 2.

FIG. 6 is a diagram showing an operation characteristic 1 corresponding to the second embodiment.

FIG. 7 is a diagram showing an operation characteristic 2 corresponding to the second embodiment.

FIG. 8 is a diagram illustrating an operation characteristic 3 corresponding to the second embodiment.

FIG. 9 is a diagram showing a case where the temperature of a conventional semiconductor laser element is intermediate.

FIG. 10 is a diagram showing a problem that occurs when the temperature of a conventional semiconductor laser device is low.

FIG. 11 is a diagram showing a problem that occurs when the temperature of a conventional semiconductor laser device is high.

FIG. 12 is a diagram showing gain characteristics of a general EDF.

FIG. 13 is a diagram showing a wavelength distribution in a wafer of a conventional semiconductor laser device.

[Explanation of symbols]

Reference Signs List 1 semiconductor laser element 2, 3, 6 lens (condenser) 4 optical fiber 5 fiber grating 11, 12, oscillation characteristic 21, 22, 23 spectrum characteristic 41, 42, 43 (spectrum of semiconductor laser element) characteristic curve

Claims (6)

[Claims] 1. A semiconductor laser module having a semiconductor laser device that emits laser light in a desired wavelength band and a fiber grating that reflects a specific wavelength component in the wavelength band to the semiconductor laser device, wherein the fiber grating has a peak. Has two wavelengths,
A semiconductor laser module, wherein the peak wavelength is set to a wavelength before and after a predetermined wavelength of light emitted from the semiconductor laser element. 2. The fiber grating has a reflectivity of 0.1 to 5%, especially 1 to 4%, and a peak wavelength bandwidth of about 0.3 to 3 nm, particularly 1 to 2 nm. The semiconductor laser module according to claim 1, wherein the semiconductor laser module is configured. 3. A semiconductor laser device that emits laser light of a predetermined wavelength, a light condensing unit that converts light emitted from the semiconductor laser device into collimated light and condenses the light, and has two peak wavelengths at a predetermined band interval. An optical fiber for forming a grating and for taking out light condensed by the light condensing means to the outside. A semiconductor laser module comprising: 4. The semiconductor laser module according to claim 3, wherein said condensing means is constituted by one condensing device for performing conversion and condensing. 5. The light-collecting means includes a first light-collecting device that converts light emitted from the semiconductor laser device into collimated light and a second light-collecting device that collects the collimated light. The semiconductor laser module according to claim 3, wherein: 6. The semiconductor laser device according to claim 3, wherein the two peak wavelengths of the irradiating means are set to wavelengths before and after a predetermined wavelength of light emitted from the semiconductor laser device. 13. A semiconductor laser module according to