JP2000077773A - Semiconductor laser module with external resonator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a semiconductor laser module that is capable of making a Fabry-Perot semiconductor laser module narrow in oscillation frequency band width and easily carrying out wavelength composition. SOLUTION: When an optical fiber 13 is provided on the resonant optical path of a semiconductor laser, a band-pass filter 4 that transmits light of specific wavelength and whose half band width is 1 to 5 nm is arranged in a laser module section 100, and a reflecting point 20 where light that is transmitted through the band-pass filter 4 is reflected is provided 50 cm or more apart from a semiconductor laser element 1 at the tip of the optical fiber 13.

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement of a semiconductor laser module with an external resonator, and has a half width of about 1 nm to 5 nm which transmits a specific wavelength to the resonator. By arranging a band-pass filter (BPF) and arranging a reflection point for reflecting light transmitted through the band-pass filter at the tip of a pigtail fiber at a position about 50 cm or more away from the semiconductor laser element, a Fabry-Perot type semiconductor The present invention relates to an external resonator type semiconductor laser module capable of narrowing an oscillation wavelength range of a laser module and easily combining wavelengths. 2. Description of the Related Art Recently, with the increase in the density of a wavelength division multiplex transmission system (WDM) in optical communication, it is necessary to increase the output of a pumping light source used in an optical fiber amplifier. It has become to. However, in order to increase the output of the excitation light source, one of effective means is to use a plurality of excitation semiconductor laser modules with wavelength synthesis. On the other hand, rare-earth-doped fibers such as erbium-doped fibers (hereinafter referred to as EDFs) used in optical amplifiers can excite signal light within a wavelength range of several nm to several tens nm.
In the case of a semiconductor laser device in a pumped semiconductor laser module, since the emission wavelength changes with respect to temperature and current, a change in environmental temperature, an increase in drive current due to deterioration of the semiconductor laser device, and the like cause a problem. , The transmission wavelength of the optical fiber deviates from the effective wavelength range of the excitation of the rare-earth doped fiber, and the excitation efficiency may be reduced. [0004] For these reasons, a semiconductor laser module with an external resonator has been developed in which the reflected return light is fed back to narrow the transmission wavelength. As a structure of a semiconductor laser module with an external resonator, a structure using a fiber grating in which a diffraction grating is formed in an optical fiber by means such as irradiation of ultraviolet rays is often found. However, the reflection point for returning the reflected return light in a conventional semiconductor laser module with an external resonator is close to the semiconductor laser element (for example,
(About 50 cm or less from the semiconductor laser), there is a problem that the oscillation state of the semiconductor laser becomes unstable. Further, a semiconductor laser module with an external resonator having a structure in which a reflection point such as insertion of a half mirror is provided has been developed. However, this type of semiconductor laser module with an external resonator has a light quantity returning to the semiconductor laser element. In order to adjust the angle, it is necessary to adjust the angle with high accuracy, and there is considerable difficulty in manufacturing. The present invention solves these problems, and provides an external resonator type semiconductor laser module in which the oscillation wavelength range of a Fabry-Perot type semiconductor laser module is narrowed and wavelength synthesis and the like can be easily achieved. First, in the construction of a semiconductor laser module with an external resonator in which an optical fiber is provided on a resonance optical path of a semiconductor laser, a specific wavelength is transmitted through the laser module section. A band-pass filter having a half-value width of about 1 nm to 5 nm is arranged, and a reflection point for reflecting light transmitted through the band-pass filter is arranged at a tip of an optical fiber at a distance of about 50 cm or more from the semiconductor laser device. Second, the semiconductor laser module with an external resonator is constituted by a laser module section and a collimator module section, and the semiconductor laser element in the laser module section is constituted by a Fabry-Perot type semiconductor laser element. Third, the light having the wavelength transmitted through the band-pass filter is reflected at a reflection point provided at the tip of a pigtail fiber in the collimator module, and is returned to the semiconductor laser device. Fourth, a first lens for converting light emitted from the semiconductor laser element into collimated light and a second lens for condensing light are arranged at predetermined intervals in the laser module. Fifth, the reflection point provided on the optical fiber for coupling the light condensed by the second lens is formed of a low reflection film ion-deposited on the ferrule end face of the optical fiber. Sixth, the reflection point provided on the end face of the optical fiber utilizes the reflection (Fresnel reflection) of the ferrule end face of the optical fiber with the air layer. Seventh, the reflectance at the reflection point is 0.1 to 50%, preferably 0.5 to 50%.
10%. Eighth, the collimator module includes a first lens that converts light emitted from the fiber into collimated light, and a second lens that collects collimated light. Ninth, the low reflection film at the reflection point formed on the end face of the optical fiber is formed by bonding a glass plate or the like provided with the low reflection film. Tenth, the collimator module is configured to collimate the light emitted from the optical fiber using a spot size conversion (TEC) fiber. Eleventh, an optical component such as another wavelength band cut filter and an optical isolator is inserted into the collimator module. In a semiconductor laser module with an external resonator according to the present invention, light having a specific wavelength transmitted through a band-pass filter reflects a point at the tip of a pigtail fiber which is arranged at least 50 cm away from the semiconductor laser element. Then, the light is reflected back to the semiconductor laser device, and an external resonator is formed between the rear surface of the semiconductor laser device and the reflection point. Embodiment 1 FIG. 1 is a configuration diagram of a semiconductor laser module with an external resonator according to the present invention. Referring to FIG.
The semiconductor laser module with an external resonator is composed of a laser module section 100 and a collimator module section 101. Of the light emitted from the Fabry-Perot type semiconductor laser element 1 in the laser module section 100, the light has passed through the band-pass filter 4. By returning the light of the wavelength to the semiconductor laser device 1 at the reflection point 20 provided at the tip of the pigtail fiber 5 in the collimator module 101, the wavelength is stabilized and the band is narrowed. Reference numeral 100 denotes a laser module, and reference numeral 1 denotes, for example, a 980 nm band Fabry-Perot semiconductor laser device. Reference numeral 2 denotes a first lens that converts the light emitted from the semiconductor laser element into collimated light, and reference numeral 3 denotes a second lens that collects the collimated light. Numeral 4 transmits light in the same wavelength band as the semiconductor laser device 1, for example, a half width of 0.4.
It is a band pass filter (BPF) of about 3 nm to 10 nm, particularly 1 to 5 nm. Reference numeral 5 denotes an optical fiber for coupling the light condensed by the second lens 3;
The semiconductor laser element 1 having a length of about 0 cm or more
Has a reflection point 20 for reflecting light emitted from the light source. The reflection point 20 is made of a low reflection film ion-deposited on the ferrule end face of the optical fiber 5 and has a reflectance of 0.1 to 5
0%, especially 2-10%. Reference numeral 101 denotes a collimator module, which includes a first lens 11 for converting light emitted from the fiber 5 into collimated light, and a second lens 12 for condensing collimated light. This is an optical fiber for taking out the narrowed band light to the outside. In the semiconductor laser module with an external resonator configured as described above, for example, the light emitted from the Fabry-Perot type semiconductor laser device 1 in the 980 nm band is collimated by the first lens 2, and the light is passed through the band-pass filter (BPF) 4. Only the transmitted light of a specific wavelength is collected by the second lens 3 and coupled to the optical fiber 5. Then, a part of the light coupled to the optical fiber 5 is reflected and returned at the reflection point 20. That is, in the semiconductor laser module with an external resonator according to the present invention, the external resonator has a wavelength of 980 nm.
It is formed between the rear surface of the band Fabry-Perot type semiconductor laser device 1 and a reflection point 20 provided at the tip of the optical fiber 5.
With this external resonator, the 980 nm band Fabry-Perot type semiconductor laser device 1 having a wide oscillation wavelength
Only the specific wavelength determined by the bandpass filter 4 is
For example, it is possible to oscillate in a narrow band with a half-width of about 1 nm or less. In the above description, a low-reflection film is formed on the end face of the optical fiber 5 by ion deposition as the reflection point 20, but the reflection point 20 is formed by bonding a glass plate or the like provided with the low-reflection film. , The same effect can be obtained. Embodiment 2 In the above embodiment, the collimator module 1
Although the first lens 11 and the second lens 12 were used for 01,
Instead of the first and second lenses 11 and 12, for example, the light emitted from the optical fiber 32 is collimated using spot size conversion (TEC) fibers 31 and 32 or the like disclosed in FIG. However, the same effects as in the first embodiment can be obtained, and the present invention is not limited to the above-described embodiment. Further, as disclosed in FIG. 3, another wavelength band cut filter 4 is provided in the collimator module 101.
1. Also, by inserting an optical component such as the optical isolator 42 in the same wavelength band as the semiconductor laser element, the characteristics of the laser module can be improved. For example, by inserting a cut filter in another wavelength band (for example, a signal light of 1550 nm band), the return loss for the signal light can be secured. Further, if an optical isolator having the same wavelength band as the semiconductor laser element is inserted, return light which does not contribute to resonance to the semiconductor laser element, or the same wavelength as the semiconductor laser element when a plurality of optical elements are used facing each other. The incident light from the outside of the band can be reduced, and the operation of the semiconductor laser module can be stabilized. In these cases, the optical components may be used alone or in combination. In the above embodiment, the oscillation wavelength of the Fabry-Perot type semiconductor laser device is described as being in the 980 nm band. However, even if the Fabry-Perot type semiconductor laser device of another wavelength, for example, the 1480 nm band, transmits through the band-pass filter. The same effect can be obtained if the wavelength range is set to the 1480 nm band, so that the present invention is not limited to the above embodiment. The first effect is to narrow the oscillation wavelength of the Fabry-Perot type semiconductor laser module. The reason is that the light having the wavelength transmitted through the BPF forms an external resonator between the rear surface of the Fabry-Perot semiconductor laser device and the reflection point. The second effect is that the wavelength can be stabilized. The reason is that the wavelength temperature dependence of the bandpass filter is smaller than that of the semiconductor laser element, and even if the oscillation wavelength of the semiconductor laser element changes with temperature, the wavelength that can be extracted is almost constant regardless of the temperature. . A third effect is that the characteristics of the semiconductor laser module can be easily improved. The reason is that the provision of the collimator module makes it easy to insert other optical components, such as a wavelength band cut filter and an optical isolator, which can prevent external light from entering the semiconductor laser device, in the collimator module. This is because That is, in the semiconductor laser module with an external resonator according to the present invention, the wavelength dependence of the wavelength of the band-pass filter is smaller than that of the semiconductor laser element, so that the oscillation wavelength of the semiconductor laser element changes with temperature. Also, the wavelength that can be extracted can be set substantially constant regardless of the temperature.
In particular, it is possible to stabilize the wavelength and narrow the band of the semiconductor laser,
Wavelength multiplexing and the like are extremely easy. Further, since other optical components such as a wavelength band cut filter and an optical isolator can be easily inserted into the collimator module, external light does not enter the semiconductor laser element, and the It is easy to improve the characteristics.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an explanatory diagram showing a main structure of a semiconductor laser module with an external resonator according to the present invention. FIG. 2 is an explanatory view showing a main structure of another embodiment of a semiconductor laser module with an external resonator according to the present invention. FIG. 3 is an explanatory view showing a main structure of another embodiment of a semiconductor laser module with an external resonator according to the present invention. DESCRIPTION OF REFERENCE NUMERALS 100 laser module section 101 collimator module section 1 Fabry-Perot type semiconductor laser element 2 first lens 3 second lens 4 bandpass filter (BPF) 5 pigtail fiber 11 first lens 12 second lens 13 Optical Fiber 20 Reflection Point 31 Spot Size Conversion (TEC) Fiber 32 Optical Fiber 41 Other Wavelength Band Cut Filter 42 Optical Isolator

Claims (1)

Claims: 1. A semiconductor laser module having an external resonator having an optical fiber provided on a resonance optical path of a semiconductor laser, wherein a half value width for transmitting a specific wavelength in a laser module portion is 1 nm or more. About 5 nm, preferably 2n
A band-pass filter having a wavelength of about m to 3 nm is disposed, and a reflection point for reflecting light transmitted through the band-pass filter is disposed at a tip of an optical fiber at a distance of about 50 cm or more from the semiconductor laser device. A semiconductor laser module with an external resonator. 2. The semiconductor laser module with an external resonator according to claim 1, wherein the semiconductor laser module includes a laser module and a collimator module, and the semiconductor laser device in the laser module is a Fabry-Perot semiconductor laser. Item 2. A semiconductor laser module with an external resonator according to item 1. 3. A structure in which light having a wavelength transmitted through the band-pass filter is reflected at a reflection point provided at a tip of a pigtail fiber in the collimator module, and is returned to the semiconductor laser device. 3. The semiconductor laser module with an external resonator according to claim 1, wherein: 4. The laser module according to claim 1, wherein a first lens for converting light emitted from the semiconductor laser element into collimated light and a second lens for condensing light are arranged at predetermined intervals. 3. A semiconductor laser module with an external resonator according to claim 2. 5. A reflection point provided on an optical fiber for coupling the light condensed by the second lens, wherein the reflection point is formed by a low reflection film ion-deposited on an end face of a ferrule of the optical fiber. 4. The semiconductor laser module with an external resonator according to 3. 6. The semiconductor laser with an external resonator according to claim 3, wherein the reflection point provided on the end face of the optical fiber utilizes reflection (Fresnel reflection) of the end face of the optical fiber with the air layer. module. 7. The semiconductor with an external resonator according to claim 5, wherein the reflectance at the reflection point is 0.1 to 50%, preferably 0.5 to 10%. Laser module. 8. The collimator module includes a first lens for converting light emitted from a fiber into collimated light and a second lens for condensing collimated light therein. The semiconductor laser module with an external resonator according to claim 2. 9. The external resonator according to claim 5, wherein the low-reflection film at the reflection point formed on the end face of the optical fiber is formed by bonding a glass plate or the like provided with the low-reflection film. Attached semiconductor laser module. 10. An external resonator according to claim 7, wherein said collimator module section is configured to collimate the light emitted from the optical fiber using a spot size conversion (TEC) fiber. Attached semiconductor laser module. 11. The semiconductor laser module with an external resonator according to claim 2, wherein an optical component such as another wavelength band cut filter and an optical isolator is inserted into said collimator module.