KR100388355B1 - A stabilized fiber grating semiconductor laser - Google Patents

Abstract

Disclosed is a stabilized optical fiber lattice semiconductor laser. The stabilized optical fiber lattice semiconductor laser of the present invention comprises: a light emitting unit which is composed of a reflecting surface and a transmitting surface to generate a beam; A light source coupling unit coupling the beam output from the light emitting unit to an optical fiber; An external resonator connected to the light source coupling part and configured to optically stabilize the wavelength of the beam output from the light emitting part and remove or mitigate the effects of birefringence or birefringence caused by bending of the optical fiber coil; And an optical fiber grating positioned at an output end of the external resonator to reflect a laser beam having a specific wavelength. According to the present invention, the packaging of the optical fiber lattice semiconductor laser can be implemented in a small size, and the optical fiber coil portion which removes or mitigates the influence of the birefringence or the birefringence due to the bending of the optical fiber coil has excellent wavelength stability, and is inexpensive and compactly packaged. This has the advantage of being possible.

Description

Stabilized fiber grating semiconductor laser

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a stabilized optical fiber lattice semiconductor laser. In particular, the external resonator of the optical fiber lattice semiconductor laser having excellent output wavelength stability is composed of an optical fiber coil portion having a long length and a small volume. A stabilized fiber grating semiconductor laser capable of removing or mitigating the effects of birefringence.

The optical fiber lattice semiconductor laser is attached to the output end of the semiconductor laser to improve the spectrum and temperature characteristics of the laser.Since the external resonator is made of silica fiber with excellent temperature characteristics, the conventional FP-LD (Fabry-Perot Compared with Laser Diode, DFB LD (Distributed Feedback Laser Diode) and DBR (Distributed Bragg Reflector), the output wavelength stability is superior to the change of driving current or external temperature. Depending on the type and design, it is possible to implement a semiconductor laser for various purposes and has the advantage of easy selection and adjustment of the precise output wavelength. In addition, since the TEC (Thermoelectric Cooler) is not required, the light source can be implemented at a lower cost than existing products. It is applied across fields.

1 is a view showing the structure of a conventional optical fiber lattice semiconductor laser. As shown in FIG. 1, the light emitting portion 10 including the reflective surface 12 and the transmissive surface 14 and the light source coupling portion 22 for coupling the beam output from the light emitting portion to the optical fiber 16, and It is composed of an external resonator including an optical fiber grating 30 at the output end. Since the optical fiber grating 30 of the output terminal serves as an external reflector, the optical fiber grating is positioned at an arbitrary distance Le from the light emitting part 10 so that the total resonance distance of the optical fiber grating semiconductor laser is determined from the length Ls of the light emitting part. Expanding to Lt (= Ls + Le) improves output wavelength stability against drive currents or external temperature changes. Wavelength change with respect to the drive current or temperature change of the conventional semiconductor laser and the optical fiber lattice semiconductor laser Can be represented by Equation 1 and Equation 2.

Equation 1

Equation 2

here, Represents the amount of change in wavelength with respect to the drive current or temperature change. Is the change in length of the light emitting portion, Is the output wavelength of the laser, Ls is the length of the light emitting portion, and Lt is the total resonance length. The output wavelength 40 of the laser occurs in a wavelength band where the oscillation mode of the laser coincides with the center wavelength of the optical fiber grating 30, and the total resonance length Lt of the optical fiber grating semiconductor laser may have a length of several mm to several m. have.

As described above, in the case of the optical fiber lattice semiconductor laser, since the external resonator is composed of an optical fiber having a long length, there is a disadvantage that small packaging is difficult.

Accordingly, an object of the present invention is to implement the packaging of the optical fiber lattice semiconductor laser to a small size by configuring the external resonator of the optical fiber lattice semiconductor laser having excellent output wavelength stability with respect to temperature or drive current changes to a long length and a small volume of optical fiber coils, At the same time, the present invention provides a stabilized optical fiber lattice semiconductor laser by presenting an optical fiber coil portion which eliminates or alleviates the effects of birefringence or birefringence caused by bending of the optical fiber coil.

1 is a view showing the structure of a conventional optical fiber lattice semiconductor laser,

2 is a view showing a structure of a stabilized optical fiber lattice semiconductor laser having an optical fiber coil portion with birefringence or birefringence removed or alleviated in order to reduce the packaging of the optical fiber lattice semiconductor laser of the present invention;

3 is a diagram illustrating a structure of a stabilized optical fiber lattice semiconductor laser capable of monitoring a beam output by installing a photodetector near a reflecting surface of a light emitting part of the optical fiber lattice semiconductor laser;

4 is a view showing the structure of a stabilized optical fiber lattice semiconductor laser in which the external resonator is inclined at an arbitrary angle to suppress the return of the beam reflected from the optical fiber end of the light source coupling portion to the light emitting portion;

5a to 5d are views illustrating various forms of the light source coupling unit;

FIG. 6 is a diagram illustrating an example of configuring an optical fiber coil part using an optical fiber coil annealed to remove or reduce birefringence of the optical fiber coil part. FIG.

7A to 7C are respectively a perspective view, a front view and a side view of an optical fiber coil unit constructed by using optical fiber coils having mutually perpendicular directions in order to remove or mitigate the effects of birefringence of the optical fiber coil unit;

8 is a view illustrating an example in which an optical fiber coil part is formed by splicing two optical fiber coils perpendicular to each other in order to remove or mitigate the influence of birefringence of the optical fiber coil part;

9 is a view illustrating an example in which an optical fiber coil part is configured by rotating two optical fiber coils having the same optical fiber bending axis to be perpendicular to each other in order to remove or mitigate the influence of the birefringence of the optical fiber coil part.

10 is a view showing an example of a configuration of an optical fiber coil portion in which the optical fiber coil is bent in a symmetrical eight-character shape around the optical fiber axis to remove or mitigate the influence of the birefringence of the optical fiber coil portion.

FIG. 11 is a view showing an example of a configuration of an optical fiber coil portion in which the optical fiber coil is bent in another eight-character shape only on one side of the optical fiber axis to remove or mitigate the influence of the birefringence of the optical fiber coil portion.

Explanation of symbols on the main parts of the drawings

10: light emitting unit

12: HR (high reflection coating)

14, 14a: transmissive surface (AR: anti-reflection coating)

16: optical fiber

18, 18a to 18k: optical fiber coil

20: optical fiber coil portion in which the effects of birefringence or birefringence are removed or alleviated

22: light source coupling portion

24: optical fiber end

30: optical fiber grating

40: output signal

50: optical fiber splice

60 lens

70: photo detector (PD)

100: output beam at the transmission surface

110: output beam at the reflective surface

The stabilized optical fiber lattice semiconductor laser for achieving the above object of the present invention, the light emitting unit for generating a beam, a light source coupling unit for coupling the beam output from the light emitting unit to the optical fiber, and the beam output from the light emitting unit In order to stabilize the wavelength of the light source, an external resonator comprising a long and bulky optical fiber coil part connected to the light source coupling part, and an optical resonator disposed at an output end of the external resonator part to reflect a laser beam of a specific wavelength. The light emitting unit may include a semiconductor laser diode or a semiconductor optical amplifier (SOA) including a reflective surface and a transmissive surface, and the optical fiber coil constituting the external resonator may be a single mode optical fiber, a multimode optical fiber, or a polarization maintaining optical fiber. In addition, it can be implemented with several kinds of optical fibers. In addition, the optical fiber grating located at the output end of the external resonator and reflecting the laser beam of a specific wavelength may be used in various types of optical fiber gratings such as a short period optical fiber grating, a chirped optical fiber grating, a sample grating, and an inclined optical fiber grating. In general, the fiber optic lattice. The operating wavelength of the optical fiber grating can be obtained by designing the center wavelength of the optical fiber grating within the gain bandwidth of the semiconductor material of the light emitting part.

Hereinafter, with reference to the accompanying drawings will be described a preferred embodiment of the present invention.

FIG. 2 is a view showing the structure of a stabilized optical fiber lattice semiconductor laser to which an optical fiber coil portion with birefringence or birefringence is removed or alleviated to reduce the packaging of the optical fiber lattice semiconductor laser of the present invention. As shown in FIG. 2, the stabilized optical fiber lattice semiconductor laser of the present invention includes a light emitting part 10 that is composed of a reflecting surface 12 and a transmitting surface 14 to generate a beam, and a beam output from the light emitting part. A light source coupling part 22 for coupling the optical fiber to the optical fiber, and an external resonating part including a long and bulky optical fiber coil part 20 connected to the light source coupling part to stabilize the wavelength of the beam output from the light emitting part; It is composed of an optical fiber grating 30 positioned at the output end of the external resonator and reflecting a laser beam of a specific wavelength, and implemented as an optical fiber coil 18 capable of small packaging of the external resonator consisting of a long optical fiber 16 in FIG. It is characterized by one. The optical fiber coil 18 may be implemented as various types of optical fibers in addition to the single mode optical fiber, multi-mode optical fiber, polarization maintaining optical fiber for general communication, the bending radius (r) of the optical fiber coil 18 is any radius that can be compact packaging And the number of bending may also have any number of at least one or more times. The optical fiber coil unit 20 composed of the optical fiber coil 18 is characterized in that the influence of the birefringence or birefringence caused by the optical fiber bending is removed or mitigated, and the implementation thereof will be described later. The output wavelength 40 of the laser can be a single wavelength or multiple wavelengths according to the type or design of the optical fiber grating 30 used as an external reflector, and can be varied by installing an additional device in the optical fiber grating 30.

FIG. 3 is a diagram illustrating a structure of a stabilized optical fiber lattice semiconductor laser capable of monitoring a beam output by installing a photodetector near a reflecting surface of a light emitting part of the optical fiber lattice semiconductor laser. As shown in FIG. 3, a beam 40 that is output by installing a photo detector PD near the reflecting surface 12 of the light emitting unit 10 of the optical fiber lattice semiconductor laser shown in FIG. 2 is output. A stabilized optical fiber lattice semiconductor laser that can monitor the The wavelength characteristics of the laser beam 40 outputted through the small amount of beam 110 transmitted through the reflective surface 12 can be observed. In this case, the beam 110 transmitted through the reflective surface 12 is transmitted. It has a much smaller value than the beam 100 transmitted through the face 14.

4 is a diagram illustrating a structure of a stabilized optical fiber lattice semiconductor laser in which the external resonator is inclined at an angle to suppress the reflection of the beam reflected at the optical fiber end of the light source coupling unit to the light emitting unit. As shown in FIG. 4, the external resonator may be formed at an arbitrary angle in order to suppress the return of the beam reflected from the optical fiber end 24 of the light source coupling part 22 shown in FIG. 2 to the light emitting part 10. A stabilized optical fiber lattice semiconductor laser is implemented. An angle between the light emitting unit 10 and an external resonator unit ( ), The beam output from the transmission surface 14 of the light emitting unit 10 is easily coupled to the optical fiber 16 and the feedback beam reflected from the optical fiber end 24 is not recombined to the light emitting unit 10. It must be designed to prevent

5A to 5D are diagrams illustrating various forms of the light source coupler 22. The light source coupling portion of the optical fiber lattice semiconductor laser is designed such that the beam coupling efficiency is high between the light emitting portion 10 and the optical fiber 16 of the external resonator portion and the beam reflected from the optical fiber end 24 and returned to the light emitting portion 10 is suppressed. 5A and 5B are examples in which the optical fiber ends 24 are formed in taped and inclined shapes to suppress the reflected beams from the optical fiber ends 24 from being fed back to the light emitting unit 10. . FIG. 5C illustrates an example in which a lens 60 is disposed between the light emitting unit 10 and the optical fiber 16 to increase light coupling efficiency. FIG. 5D illustrates an anti-reflection coating (AR) on the optical fiber end 24. This shows an example in which the beam reflected from the optical fiber end 24 is minimized.

6 to 11 illustrate various forms of the optical fiber coil unit 20 which removes or mitigates the influence of the birefringence or the birefringence due to the bending of the optical fiber. The external resonator of the optical fiber grid semiconductor laser has a small volume of the optical fiber coil 20 ) Makes the entire packaging compact. In this case, however, linear birefringence occurs in the optical fiber coil bent to an arbitrary radius r, and this birefringence causes the oscillation or the output wavelength of the laser to become unstable. Linear birefringence that occurs when the optical fiber is bent at an arbitrary radius r May be expressed as Equation 3.

----------- Equation 3

Where k represents the propagation constant in vacuum Is Poission's ratio, , Denotes a strain-optic coefficient. N represents the refractive index of the optical fiber, a represents the radius of the optical fiber, and r represents the radius due to the bending of the optical fiber.

FIG. 6 is a view showing an annealing optical fiber coil unit 20 for removing or reducing birefringence caused by optical fiber bending in the optical fiber coil 18a of the optical fiber coil 20. FIG. The radius (r) of and the number of bending may have any value, and thus the heat treatment of the optical fiber coil may also be made in various ways.

7A to 7C are perspective views, front views, and side views, respectively, of optical fiber coil parts formed by using optical fiber coils having mutually perpendicular directions in order to remove or mitigate the effects of birefringence of the optical fiber coil parts. As shown in FIGS. 7A to 7C, the amount of birefringence between the first optical fiber coil 18b and the second optical fiber coil 18c is preferably the same, and since both the bending radius and the number of bending of the coil are related to the birefringence, The bending radii r1 and r2 of two optical fiber coils 18b and 18c having the same amount may or may not be the same. The distance d between the two optical fiber coils 18b and 18c may have any value including 0, and the bending radius and the number of bending may also take any value. Two or more fiber optic coils can be configured.

8 is a view illustrating an example in which an optical fiber coil part is formed by splicing two optical fiber coils perpendicular to each other in order to remove or mitigate the effects of birefringence of the optical fiber coil part. As shown in FIG. 8, the optical fiber coils 20 having splicing optical fiber coils 18d and 18e which are perpendicular to each other in the direction of the optical fiber bending axis are removed or alleviated the effects of birefringence. The junction 50 includes both mechanical splicing or fusion splicing joints. The spliced optical fiber coils 18d and 18e have the same amount of birefringence but may be composed of different optical fibers or two or more optical fiber coils.

FIG. 9 illustrates an example in which an optical fiber coil part is formed by rotating two optical fiber coils having the same optical fiber bending axis to be perpendicular to each other in order to remove or mitigate the effects of birefringence of the optical fiber coil part. As shown in FIG. 9, the optical fiber coils 18f and 18g having the same direction as the optical fiber bending axes are rotated so that the bending axes are perpendicular to each other to remove or mitigate the effects of birefringence. . The direction of the bending shaft rotation can be left and right about the axis of the optical fiber 16.

FIG. 10 is a view illustrating an example of a configuration of an optical fiber coil unit in which an optical fiber coil is bent in a symmetrical eight-character shape around an optical fiber axis to remove or mitigate the effects of birefringence of the optical fiber coil portion. As shown in FIG. 10, two optical fiber coils 18h and 18i are arranged in eight shapes in which the optical fiber bending is symmetrical with respect to the axis of the optical fiber 16 and the bending axis is opposite to each other to eliminate or mitigate the effects of birefringence. The optical fiber coil portion 20 is shown. Here, symmetry means that optical coils having the same amount of birefringence face each other with respect to the optical fiber axis, and the radiuses r1 and r2 due to bending may or may not be the same. Fiber coils may not be located. For example, two optical fiber coils and one optical fiber coil may be facing each other about the optical fiber axis. The number of times the optical fiber bends and the distance d between the two optical fiber coils 18h and 18i may have any value.

FIG. 11 is a view showing an example of a configuration of an optical fiber coil portion in which the optical fiber coil is bent in another eight-character shape only on one side of the optical fiber axis to remove or mitigate the influence of the birefringence of the optical fiber coil portion. As shown in FIG. 11, the optical fiber coils 18j and 18k having the eight-way shape in which the bending axes are opposite to each other are formed on only one side of the optical fiber 16 axis to remove or mitigate the effects of birefringence. Some 20 are presented. The direction in which the optical fiber coils 18j and 18k are formed about the axis of the optical fiber 16 may be arbitrarily determined. The amount of birefringence of the two optical fiber coils 18j and 18k is preferably the same. When the bending radii between the two optical fiber coils 18j and 18k are the same, the number of bending should be the same so that the birefringence of the two optical fiber coils is the same. By adjusting the number of bends, the amount of birefringence can be equalized.

As described above, the stabilized optical fiber lattice semiconductor laser according to the present invention, the optical resonator of the optical fiber lattice semiconductor laser having excellent output wavelength stability with respect to temperature or drive current changes composed of a long length and a small volume of optical fiber coil portion The semiconductor laser has been compactly packaged. In addition, by presenting the optical fiber coil portion that eliminates or alleviates the effects of the birefringence and the birefringence caused by the bending of the optical fiber coil, it is expected to contribute greatly to the implementation of the optical fiber lattice semiconductor laser having excellent wavelength stability, low cost, and small package.

The present invention is not limited to the above-described embodiment, and it will be apparent that many modifications are possible by those skilled in the art within the technical spirit of the present invention.

Claims (9)

A light emitting part configured to include a reflective surface and a transmission surface to generate a beam; A light source coupling unit coupling the beam output from the light emitting unit to an optical fiber; In order to stabilize the wavelength of the beam output from the light emitting unit and to remove or mitigate the effects of birefringence or birefringence caused by the bending of the optical fiber coil, the optical fiber coil part which is connected to the light source coupling part and consists of the optical fiber coil An external resonator; And Stabilized fiber grating semiconductor laser characterized in that it comprises an optical fiber grating located at the output end of the external resonator portion reflecting a laser beam of a specific wavelength. 2. The stabilized optical fiber lattice semiconductor laser according to claim 1, wherein a photodetector is provided in the vicinity of a reflecting surface of the light emitting portion to monitor the beam output from the light emitting portion. 2. The stabilized optical fiber lattice semiconductor laser according to claim 1, wherein the external resonator is inclined at an arbitrary angle to suppress the return of the beam reflected from the optical fiber end of the light source coupling portion to the light emitting portion. 2. The stabilized optical fiber lattice semiconductor laser according to claim 1, wherein the optical fiber coil portion is made of a heat treated optical fiber coil to remove or reduce birefringence due to the optical fiber bending. The stabilized optical fiber lattice semiconductor laser according to claim 1, wherein the optical fiber coil portion is made by using optical fiber coils perpendicular to each other in order to remove or alleviate the influence of the birefringence. 2. The stabilized optical fiber lattice semiconductor laser according to claim 1, wherein the optical fiber coil parts are bonded to each other by mutually perpendicular optical fiber coils in order to remove or mitigate the effects of the birefringence. The stabilized optical fiber lattice semiconductor laser according to claim 1, wherein the optical fiber coil portion is formed by rotating the optical fiber coils having the same optical fiber bending axes to be perpendicular to each other in order to remove or alleviate the influence of the birefringence. The stabilized optical fiber of claim 1, wherein the optical fiber coil parts are formed in an eight-character shape in which the optical fiber bending is symmetrical with respect to the optical axis and the bending axes are opposite to each other so as to remove or alleviate the influence of the birefringence. Lattice Semiconductor Laser. According to claim 1, wherein the birefringence is made of the optical fiber coil is formed of an eight-fiber shape in which the optical fiber bending is formed only on any one side of the optical fiber axis, the direction of the bending axis is opposite to each other in order to remove or alleviate the influence of the birefringence Stabilized optical fiber lattice semiconductor laser.