CN116260032A

CN116260032A - Dual-wavelength Q-switched fiber laser

Info

Publication number: CN116260032A
Application number: CN202211106648.8A
Authority: CN
Inventors: 王鹏飞; 吕念; 李真睿
Original assignee: Harbin Engineering University
Current assignee: Harbin Engineering University
Priority date: 2022-09-13
Filing date: 2022-09-13
Publication date: 2023-06-13

Abstract

The invention discloses a dual-wavelength Q-switched optical fiber laser, which is characterized in that a first laser is used as a first pumping source and is sequentially connected with a first wavelength division multiplexer, a first erbium-doped gain optical fiber, a first polarization independent isolator, a first coupler, an output coupler, a carbon nano tube saturable absorber and a second coupler to form a first resonant cavity; the second laser is used as a second pumping source, is coupled into an optical path through a second wavelength division multiplexer, and is sequentially connected with a second erbium-doped gain fiber, a second polarization-independent isolator, a first coupler, an output coupler, a carbon nanotube saturable absorber and a second coupler to form a second resonant cavity; the two resonant cavities are fused through the first coupler and the second coupler and share one carbon nanotube saturable absorber, and dual-wavelength Q-switched pulse laser is output from the output coupler. According to the invention, the two resonant cavities respectively realize Q-switching at different wavelengths, and simultaneously, the two pumping sources are turned on to realize dual-wavelength Q-switching pulse laser output on a common branch, so that the dual-wavelength Q-switching pulse laser output device is simple in structure and convenient to operate.

Description

Dual-wavelength Q-switched fiber laser

Technical Field

The invention relates to the technical field of fiber lasers, in particular to a dual-wavelength Q-switched fiber laser.

Background

Since the advent of fiber lasers in the sixties of the twentieth century, fiber lasers have been a research hotspot in the international laser field, and have been widely used in the fields of optical communication and fiber sensing. The laser output may be either continuous or pulsed. The principle of Q-switched pulse laser is that in the initial stage of pumping, the number of inversion particles of energy level on the laser is accumulated in a large quantity, when the saturation value is accumulated, laser oscillation is rapidly established, the laser is output from a laser cavity in the form of single pulse, and at the moment, continuous laser output energy is compressed into extremely short pulse to be emitted. Therefore, compared with continuous laser, the pulse laser has the characteristics of high peak power, narrow pulse, good coherence and the like, is a high-quality light source, and has wide application in metal cutting, micro-manufacturing, distance measurement and medical treatment.

Currently, active techniques incorporating optical modulators such as acousto-optic modulators, electro-optic modulators, etc. in cavities are one way to achieve a Q-switched laser, but incorporating such modulators and other bulk devices in cavities can make the structure of the laser relatively complex and cumbersome. Compared with the active Q-switching scheme, the passive Q-switching technology based on the saturable absorber has the advantages of simplicity, compactness and the like, so that extensive researches are obtained. Since 1966 the first generation of saturable absorbers were used in neodymium glass lasers and successfully output pulses, various types of saturable absorbers were discovered successively and used in fiber lasers, including metal doped crystals, semiconductor saturable absorber mirrors, single-walled carbon nanotubes, gold nanotubes, etc., which can play an important role in the characteristics of Q-switched lasers.

With the further development of wavelength division multiplexing technology, the requirement of ultra-large capacity optical communication systems on multi-wavelength pulse lasers is not met by conventional single-wavelength output. The multi-wavelength fiber laser can stably output a plurality of wavelengths at the same time, and has the advantages of high beam quality, compact structure, low insertion loss and the like. There are several ways to obtain multi-wavelength operation at room temperature: direct insertion into a filter device, addition of wavelength or intensity dependent loss structures, and the use of highly nonlinear effects of materials, all of the above mentioned approaches aim to attenuate the uniform broadening effect to achieve multi-wavelength operation. However, the dual wavelength lasers described above all require precise control of the birefringence in the cavity and are therefore very sensitive to environmental disturbances.

Therefore, the person skilled in the art is dedicated to develop a dual-wavelength Q-switched optical fiber laser, which has the advantages of good output laser stability, simple operation, strong anti-interference capability and the like.

Disclosure of Invention

In view of the above-mentioned drawbacks of the prior art, the present invention is directed to providing a dual-wavelength Q-switched fiber laser.

In order to achieve the above objective, the present invention provides a dual wavelength Q-switched fiber laser, including a first laser, a first wavelength division multiplexer, a first erbium-doped gain fiber, a first polarization independent isolator, a first coupler, an output coupler, a carbon nanotube saturable absorber, a second coupler, a second laser, a second wavelength division multiplexer, a second erbium-doped gain fiber, and a second polarization independent isolator;

the first laser is used as a first pumping source and is sequentially connected with the first wavelength division multiplexer, the first erbium-doped gain fiber, the first polarization independent isolator, the first coupler, the output coupler, the carbon nanotube saturable absorber and the second coupler to form a first resonant cavity;

the second laser is used as a second pumping source, is coupled into an optical path through the second wavelength division multiplexer, and is sequentially connected with the second erbium-doped gain fiber, the second polarization-independent isolator, the first coupler, the output coupler, the carbon nanotube saturable absorber and the second coupler to form a second resonant cavity;

the first resonant cavity and the second resonant cavity are fused through the first coupler and the second coupler and share one carbon nanotube saturable absorber, and dual-wavelength Q-switched pulse laser is output from the output coupler.

Further, the first and second lasers have a center wavelength of 976 nm.

Further, the first wavelength division multiplexer and the second wavelength division multiplexer are 980/1560 nm wavelength division multiplexers.

Further, the first polarization independent isolator and the second polarization independent isolator are 1560 nm polarization independent isolators.

Further, the first erbium-doped gain fiber length is 55 cm and the second erbium-doped gain fiber length is 65 cm.

Further, the fiber laser output center wavelengths are 1532 nm and 1557 nm, respectively.

Further, the first coupler and the second coupler are 50:50 couplers.

Further, the output coupler is a 10:90 output coupler, 90% end of the 10:90 output coupler is connected into the resonant cavity to serve as a loop, and 10% end of the 10:90 output coupler serves as an output end of the fiber laser.

Further, the first and second lasers are single-mode semiconductor lasers having a maximum output power of 500 mW.

Further, the carbon nanotube saturable absorber is prepared by fully mixing 1 mg single-wall carbon nanotubes with an average diameter of 0.78 nm with 8 ml film forming agent for 24 hours by ultrasonic treatment, then dripping the mixed liquid on a glass sheet, and drying in a vacuum box to form a film.

The invention has the beneficial effects that:

(1) The invention uses the saturated absorption characteristic of the carbon nano tube as a passive Q-switching switch, and the carbon nano tube saturated absorber as a Q-switching device has the advantages of good stability, simple preparation and the like.

(2) According to the invention, the two resonant cavities respectively generate Q-switched pulse lasers with different wavelengths, and the Q-switched pulse lasers with two wavelengths are simultaneously switched, so that the output of the Q-switched pulse lasers with two wavelengths is realized.

The conception, specific structure, and technical effects of the present invention will be further described with reference to the accompanying drawings to fully understand the objects, features, and effects of the present invention.

Drawings

FIG. 1 is a schematic diagram of a preferred embodiment of the present invention;

FIG. 2 is a graph of the laser output spectrum of a preferred embodiment of the present invention;

fig. 3 is a laser output pulse train of a preferred embodiment of the present invention.

The device comprises a first 976 nm laser, a 2-first 980/1560 nm wavelength division multiplexer, a 3-first erbium-doped gain fiber, a 4-first 1560 nm polarization independent isolator, a 5-first 50:50 coupler, a 6-10:90 output coupler, a 7-carbon nanotube saturable absorber, a 8-second 50:50 coupler, a 9-second 976 nm laser, a 10-second 980/1560 nm wavelength division multiplexer, a 11-second erbium-doped gain fiber, and a 12-second 1560 nm polarization independent isolator.

Detailed Description

The following description of the preferred embodiments of the present invention refers to the accompanying drawings, which make the technical contents thereof more clear and easier to understand. The present invention may be embodied in many different forms of embodiments and the scope of the present invention is not limited to only the embodiments described herein.

In the drawings, like structural elements are referred to by like reference numerals and components having similar structure or function are referred to by like reference numerals. The dimensions and thickness of each component shown in the drawings are arbitrarily shown, and the present invention is not limited to the dimensions and thickness of each component. The thickness of the components is exaggerated in some places in the drawings for clarity of illustration.

Examples

As shown in fig. 1, the present embodiment provides a dual-wavelength Q-switched fiber laser based on dual-resonant cavities, which includes two ring-shaped resonant cavities sharing an output end and a saturable absorber, and the two ring-shaped resonant cavities serve as laser resonant cavities of 1532 nm wavelengths and 1557 nm wavelengths, respectively. The first ring resonator is used for generating 1532 and nm Q-switched pulse lasers, and the second ring resonator is used for generating 1557 and nm Q-switched pulse lasers.

Specifically, the first ring resonator comprises a first 976 nm laser 1, a first 980/1560 nm wavelength division multiplexer 2, a first erbium-doped gain fiber 3, a first 1560 nm polarization independent isolator 4, a first 50:50 coupler 5, a 10:90 output coupler 6, a carbon nanotube saturable absorber 7, and a second 50:50 coupler 8. The second ring resonator comprises a second 976 nm laser 9, a first 50:50 coupler 5, a 10:90 output coupler 6, a carbon nanotube saturable absorber 7, a second 50:50 coupler 8, a second 980/1560 nm wavelength division multiplexer 10, a second erbium doped gain fiber 11, and a second 1560 nm polarization independent isolator 12. The two ring resonators are connected by a first 50:50 coupler 5 and a second 50:50 coupler 8 and share (as output ends) a carbon nanotube saturable absorber 7 and a 10:90 output coupler 6.

More specifically, the first 976 nm laser 1 is used as a first pump source, and is sequentially connected with the first 980/1560 nm wavelength division multiplexer 2, the first erbium-doped gain fiber 3, the first 1560 nm polarization independent isolator 4, the first 50:50 coupler 5, the first 10:90 output coupler 6, the carbon nanotube saturable absorber 7 and the second 50:50 coupler 8 to form a first annular resonant cavity with 1532 nm wavelengths. The second 976 nm laser 9 is used as a second pumping source, is coupled into an optical path through a second 980/1560 nm wavelength division multiplexer 10, and is sequentially connected with a second erbium-doped gain optical fiber 11, a second 1560 nm polarization independent isolator 12, a first 50:50 coupler 5, a first 10:90 output coupler 6, a carbon nano tube saturable absorber 7 and a second 50:50 coupler 8 to form a second annular resonant cavity with 1557 nm wavelength. The two ring resonators are fused through a first 50:50 coupler 5 and a second 50:50 coupler 8, and share one carbon nanotube saturable absorber 7, and dual-wavelength Q-switched pulse laser is output from a 10:90 output coupler 6.

Preferably, both pump sources are single mode semiconductor lasers with maximum output power 500 mW, center wavelength 976 nm.

The first 976 nm laser 1 of this embodiment is connected to the first 980/1560 nm wavelength division multiplexer 2 to couple pump light into the first ring resonator, and the second 976 nm laser 9 is connected to the second 980/1560 nm wavelength division multiplexer 10 to couple pump light into the second ring resonator; first 1560 nm polarization independent isolator 4 and second 1560 nm polarization independent isolator 12 are used to ensure unidirectional transmission of light within the cavity.

The first erbium-doped gain fiber 3 has a length of 55 cm and the second erbium-doped gain fiber 11 has a length of 65 cm, and provides gains for the first ring resonator and the second ring resonator, respectively. The carbon nanotube saturable absorber 7 is used as two resonant cavity passive Q-switching switches at the same time, and is formed by cutting a single-wall carbon nanotube film into square small pieces with the width of 1 mm, directly placing the square small pieces on an optical fiber connector, and connecting the square small pieces by using a flange plate. The 10:90 output coupler 6 serves as the output device for both resonators, with 90% end connected into the resonator as a loop and 10% end as the laser output, the output spectrum being tested with a light analyzer (YOKOGAWA, AQ-6370C) and the output pulse being tested with a photodetector and oscilloscope. The laser output center wavelengths were 1532 nm and 1557 nm, respectively.

The carbon nanotube saturable absorber 7 is prepared by fully mixing 1 mg single-wall carbon nanotubes with an average diameter of 0.78 nm with 8 ml film forming agent for 24 hours by ultrasonic treatment, then dripping the mixed liquid on a glass sheet, and drying in a vacuum box to form a film.

The embodiment is based on a carbon nanotube film as a saturable absorber, and the preparation method comprises the following steps: weighing 900 mg sodium carboxymethylcellulose in a clean beaker, adding 60 ml deionized water, and stirring the prepared mixture for 24 hours by using a magnetic device to prepare a film forming agent; then 8 ml film forming agent is mixed with the 1 mg single-walled carbon nanotube, and the mixture is subjected to ultrasonic treatment for 24 hours to obtain suspension; and (3) centrifuging the suspension, dripping the supernatant onto a glass sheet, and drying in a vacuum drying oven for 6 hours to obtain the carbon nanotube film. Subsequently, the carbon nanotube film was cut into 1 mm wide pieces and placed on the fiber optic connector to realize the fabrication of the Q-switched device.

The application method of the embodiment is as follows:

the first 976 nm laser 1 is turned on, the pumping power is increased to make the first ring resonator Q-switched, 1532 nm single wavelength Q-switched laser output occurs, and the power of the second 976 nm laser 9 is increased until dual wavelength Q-switched occurs.

Fig. 2 shows the output spectrum of the laser. From the figure, it can be seen that the laser outputs at 1532 nm and 1557 nm wavelengths simultaneously, indicating that the laser produces laser light at both wavelengths simultaneously.

Fig. 3 shows the output pulse sequence at this time, and it can be seen that two pulses with different repetition frequencies are output simultaneously.

Compared with the traditional dual-wavelength Q-switched laser output, the dual-wavelength Q-switched fiber laser based on the dual resonant cavities has the advantages of being good in output laser stability, simple to operate, high in anti-interference capability and the like.

The first resonant cavity and the second resonant cavity respectively realize Q-switching at different wavelengths, and simultaneously, two pumping sources are turned on to realize dual-wavelength Q-switching pulse laser output on a common branch. By adjusting the pumping power, the laser can realize single-wavelength Q-switched pulse and double-wavelength Q-switched pulse, and the repetition frequency and pulse width of the single wavelength can be independently adjusted in the state of double-wavelength Q-switched. The device has the advantages of simple structure, convenient operation and good advantages in the fields of spectroscopy, optical communication and the like.

The foregoing describes in detail preferred embodiments of the present invention. It should be understood that numerous modifications and variations can be made in accordance with the concepts of the invention without requiring creative effort by one of ordinary skill in the art. Therefore, all technical solutions which can be obtained by logic analysis, reasoning or limited experiments based on the prior art by the person skilled in the art according to the inventive concept shall be within the scope of protection defined by the claims.

Claims

1. The dual-wavelength Q-switched fiber laser is characterized by comprising a first laser, a first wavelength division multiplexer, a first erbium-doped gain fiber, a first polarization independent isolator, a first coupler, an output coupler, a carbon nanotube saturable absorber, a second coupler, a second laser, a second wavelength division multiplexer, a second erbium-doped gain fiber and a second polarization independent isolator;

2. The dual wavelength Q fiber laser of claim 1, wherein the first and second lasers have a center wavelength of 976 nm.

3. The dual wavelength Q-switched fiber laser of claim 2, wherein said first and second wavelength division multiplexers are 980/1560 nm wavelength division multiplexers.

4. The dual wavelength Q-switched fiber laser of claim 3, wherein said first and second polarization independent isolators are 1560 nm polarization independent isolators.

5. The dual wavelength Q-switched fiber laser of claim 4, wherein said first erbium doped gain fiber has a length of 55 cm and said second erbium doped gain fiber has a length of 65 cm.

6. The dual wavelength Q-switched fiber laser of claim 5, wherein said fiber laser output center wavelengths are 1532 nm and 1557 nm, respectively.

7. The dual wavelength Q fiber laser of claim 1, wherein the first coupler and the second coupler are 50:50 couplers.

8. The dual wavelength Q-switched fiber laser of claim 1, wherein the output coupler is a 10:90 output coupler, 90% of the 10:90 output coupler being connected into a resonant cavity as a loop, 10% of the output coupler being the output of the fiber laser.

9. The dual wavelength Q-switched fiber laser of claim 2, wherein the first and second lasers are single-mode semiconductor lasers having a maximum output power of 500 mW.

10. The dual wavelength Q-switched fiber laser of claim 1, wherein the carbon nanotube saturable absorber is prepared by thoroughly mixing 1 mg single-walled carbon nanotubes with an average diameter of 0.78 nm with 8 ml film former for 24 hours, then dropping the mixed liquid onto a glass sheet, and drying in a vacuum box to form a film.