阅读说明：本技术 一种双波长全光纤激光器 (Dual-wavelength all-fiber laser ) 是由 杨中民 孙悦怡 文晓晓 韦小明 于 2020-06-29 设计创作，主要内容包括：本发明涉及一种双波长全光纤激光器,包括泵浦激光器；第一波分复用器,第一波分复用器的输入端与泵浦激光器连接可饱和吸收镜,与第一波分复用器的公共端连接；增益光纤,增益光纤的输入端与第一波分复用器的输出端连接；全光纤非线型环,与增益光纤的输出端连接；光纤耦合器,光纤耦合器的输入端与全光纤非线型环连接；光纤耦合非线性晶体,光纤耦合非线性晶体的输入端与光纤耦合器的第一输出端相连；第二波分复用器,分别与光纤耦合器的第二输出端和光纤耦合非线性晶体的输出端相连。本发明消除了空间光学准直苛刻要求,不存在偏振敏感器件,对环境振动不敏感,从而能得到稳定的飞秒脉冲激光输出,实现特殊波长范围的双波长飞秒脉冲输出。(The invention relates to a dual-wavelength all-fiber laser, which comprises a pump laser; the input end of the first wavelength division multiplexer is connected with the pump laser and the saturable absorption mirror, and is connected with the common end of the first wavelength division multiplexer; the input end of the gain optical fiber is connected with the output end of the first wavelength division multiplexer; the all-fiber nonlinear ring is connected with the output end of the gain fiber; the input end of the optical fiber coupler is connected with the all-fiber nonlinear ring; the input end of the optical fiber coupling nonlinear crystal is connected with the first output end of the optical fiber coupler; and the second wavelength division multiplexer is respectively connected with the second output end of the optical fiber coupler and the output end of the optical fiber coupling nonlinear crystal. The invention eliminates the harsh requirement of space optical collimation, has no polarization sensitive device, and is insensitive to environmental vibration, thereby obtaining stable femtosecond pulse laser output and realizing dual-wavelength femtosecond pulse output in a special wavelength range.)

1. A dual wavelength all-fiber laser, the laser comprising:

a pump laser for generating an initial laser;

the input end of the first wavelength division multiplexer is connected with the pump laser;

the saturable absorption mirror is connected with the common end of the first wavelength division multiplexer;

the input end of the gain optical fiber is connected with the output end of the first wavelength division multiplexer;

the all-fiber nonlinear ring is connected with the output end of the gain fiber;

the input end of the optical fiber coupler is connected with the all-fiber nonlinear ring;

the input end of the optical fiber coupling nonlinear crystal is connected with the first output end of the optical fiber coupler;

and the second wavelength division multiplexer is respectively connected with the second output end of the optical fiber coupler and the output end of the optical fiber coupling nonlinear crystal.

2. The dual-wavelength all-fiber laser according to claim 1, wherein the second wavelength division multiplexer outputs a first wavelength laser having a wavelength range of 650 to 950nm and a second wavelength laser having a wavelength range of 1600 to 1870 nm.

3. The dual wavelength all-fiber laser of claim 1, wherein the all-fiber nonlinear ring comprises:

the first input end of the in-loop optical fiber coupler is connected with the output end of the gain optical fiber; the first output end of the in-loop optical fiber coupler is connected with the input end of the optical fiber coupler;

and the coated filter is also arranged between the second output end of the in-loop optical fiber coupler and the second input end of the in-loop optical fiber coupler.

4. The dual wavelength all-fiber laser of claim 1, wherein a power amplification component is further disposed between the input end of the fiber coupler and the all-fiber nonlinear ring.

5. The dual wavelength all-fiber laser of claim 3, wherein the power amplification means is a gain fiber power amplifier.

6. The dual wavelength all-fiber laser of claim 1, wherein a dispersion compensation component is further disposed between the input end of the fiber coupler and the all-fiber nonlinear ring.

7. The dual wavelength all fiber laser of claim 5 wherein the dispersion compensating element is a dispersion compensating fiber.

8. The dual wavelength all-fiber laser of claim 1, wherein the pump laser is a semiconductor laser.

9. The dual wavelength all fiber laser of claim 1 wherein the saturable absorber mirror is a semiconductor saturable absorber mirror having a surface area of 1mm x 1 mm.

10. The dual wavelength all fiber laser of claim 1, wherein the gain fiber is a thulium doped fiber with a length of 0.15m, and the initial laser has a center wavelength of 1570 nm.

Technical Field

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

Background

Lasers have since their birth played an extremely important role in various fields, such as laser processing, optical communication, biomedicine, military and the like. Various types of lasers and laser technologies are continuously developed under the drive of wide application demands, and scientists are also interested in studying higher performance lasers.

At present, in the aspect of brain imaging research, a commercial laser with a first wavelength window (650-950 nm) is a solid femtosecond laser with a spatial structure. Such femtosecond lasers are extremely expensive, large in size, poor in long-term stability, high in maintenance cost, and the comprehensive performance needs to be improved. The optical fiber laser has excellent overall performance, has the characteristics of good beam quality, high efficiency, large output power, good heat dissipation property, compact structure, high reliability and the like, can be used in severe working environment, and has relatively low manufacturing cost and maintenance cost. The femtosecond laser with a third wavelength window (1600-1870 nm) can theoretically excite a fluorescent marker through three-photon absorption, and realize high-resolution optical imaging of deep tissues. Especially in brain imaging, the laser of the third wavelength window can provide the best imaging depth and contrast. However, the laser is limited by the fact that the range of the excitation wavelength of rare earth doped ions is small, the manufacturing process of a related optical fiber type device is immature, so that the cost is high, the mode locking technology and the pulse compression technology are not complete, and the like, and no related report of an optical fiber laser with a full optical fiber structure, high stability and a femtosecond pulse laser exists in an optical fiber laser with a third wavelength window at present. Therefore, due to the lack of high-performance light sources, the research on the application of the three-photon optical imaging technology in the biomedical field, especially in the brain science, is severely limited.

The single contrast optical imaging technology has certain defects and signal blind areas, and particularly in complex biological tissues, the biological forms and characteristics of different tissue components are often shown by different contrasts. Therefore, the multi-wavelength and multi-modal nonlinear optical microscopy technology combining two-photon excitation and three-photon excitation provides more comprehensive technical support for biomedical diagnosis. However, such techniques have not been extensively studied, limited by the modern femtosecond laser technology and the incompatibility of biological microscopy imaging systems with multiple wavelength windows, particularly the first and third wavelength windows.

Disclosure of Invention

Aiming at the defects of the prior art, the invention aims to provide a dual-wavelength all-fiber laser which can break through the limitation of the prior laser technology and realize dual-wavelength femtosecond pulse output in a special wavelength range.

In order to achieve the purpose, the invention provides the following scheme:

a dual wavelength all-fiber laser, the laser comprising:

a pump laser for generating an initial laser;

the input end of the first wavelength division multiplexer is connected with the pump laser;

the saturable absorption mirror is connected with the common end of the first wavelength division multiplexer;

the input end of the gain optical fiber is connected with the output end of the first wavelength division multiplexer;

the all-fiber nonlinear ring is connected with the output end of the gain fiber;

the input end of the optical fiber coupler is connected with the all-fiber nonlinear ring;

the input end of the optical fiber coupling nonlinear crystal is connected with the first output end of the optical fiber coupler;

and the second wavelength division multiplexer is respectively connected with the second output end of the optical fiber coupler and the output end of the optical fiber coupling nonlinear crystal.

Preferably, the second wavelength division multiplexer outputs a first wavelength laser and a second wavelength laser, the wavelength range of the first wavelength laser is 650-950 nm, and the laser range of the second wavelength laser is 1600-1870 nm.

Preferably, the all-fiber nonlinear loop comprises:

the first input end of the in-loop optical fiber coupler is connected with the output end of the gain optical fiber; the first output end of the in-loop optical fiber coupler is connected with the input end of the optical fiber coupler;

and the coated filter is also arranged between the second output end of the in-loop optical fiber coupler and the second input end of the in-loop optical fiber coupler.

Preferably, a power amplification component is further disposed between the input end of the optical fiber coupler and the all-fiber nonlinear ring.

Preferably, the power amplification part is a gain fiber power amplifier.

Preferably, a dispersion compensation component is further disposed between the input end of the fiber coupler and the all-fiber nonlinear ring.

Preferably, the dispersion compensating member is a dispersion compensating fiber.

Preferably, the pump laser is a semiconductor laser.

Preferably, the saturable absorber mirror is a semiconductor saturable absorber mirror with a surface area of 1mm × 1 mm.

Preferably, the gain fiber is a thulium-doped fiber with a length of 0.15m, and the center wavelength of the initial laser is 1570 nm.

According to the specific embodiment provided by the invention, the invention discloses the following technical effects: the dual-wavelength all-fiber laser of the invention comprises: a pump laser for generating an initial laser; the input end of the first wavelength division multiplexer is connected with the pump laser; the saturable absorption mirror is connected with the common end of the first wavelength division multiplexer; the input end of the gain optical fiber is connected with the output end of the first wavelength division multiplexer; the all-fiber nonlinear ring is connected with the output end of the gain fiber; the input end of the optical fiber coupler is connected with the all-fiber nonlinear ring; the input end of the optical fiber coupling nonlinear crystal is connected with the first output end of the optical fiber coupler; and the second wavelength division multiplexer is respectively connected with the second output end of the optical fiber coupler and the output end of the optical fiber coupling nonlinear crystal. The invention uses a specially designed semiconductor saturable absorption mirror with the surface area of only 1mm multiplied by 1mm as a first reflector of a resonant cavity, and uses an all-fiber nonlinear ring as another reflector of the resonant cavity to realize the output of mode locking pulses; the design of the dual-wavelength all-fiber laser is based on an all-fiber structure, eliminates the strict requirement of spatial optical collimation, does not have a polarization sensitive device, and is insensitive to environmental vibration, so that stable femtosecond pulse laser output can be obtained, and the second wavelength division multiplexer is utilized to output femtosecond pulse lasers with two wavelengths, so that dual-wavelength femtosecond pulse output in a special wavelength range is realized.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings needed to be used in the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings without inventive exercise.

FIG. 1 is a schematic structural diagram of a dual-wavelength all-fiber laser of the present invention

Description of the symbols:

the optical fiber amplifier comprises a pump laser 1, a saturable absorption mirror 2, a first wavelength division multiplexer 3, a gain optical fiber 4, an in-loop optical fiber coupler 5, a coated filter 6, a power amplification part 7, a dispersion compensation part 8, an optical fiber coupler 9, an optical fiber coupling nonlinear crystal 10 and a second wavelength division multiplexer 11.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

The invention aims to provide a dual-wavelength all-fiber laser, which utilizes an all-fiber nonlinear ring as another reflector of a resonant cavity to realize mode-locked pulse output; the design of the dual-wavelength all-fiber laser is based on an all-fiber structure, eliminates the strict requirement of spatial optical collimation, does not have a polarization sensitive device, and is insensitive to environmental vibration, so that stable femtosecond pulse laser output can be obtained, and the second wavelength division multiplexer is utilized to output femtosecond pulse lasers with two wavelengths, so that dual-wavelength femtosecond pulse output in a special wavelength range is realized.

In order to make the aforementioned objects, features and advantages of the present invention comprehensible, embodiments accompanied with figures are described in further detail below.

As shown in fig. 1, the dual-wavelength all-fiber laser of the present invention includes: the device comprises a pump laser 1, a first wavelength division multiplexer 3, a saturable absorption mirror 2, a gain fiber 4, an in-loop fiber coupler 5, a coated filter 6, a power amplification part 7, a dispersion compensation part 8, a fiber coupler 9, a fiber coupling nonlinear crystal 10 and a second wavelength division multiplexer 11.

Wherein the pump laser 1 is used for generating an initial laser.

In an alternative embodiment, the initial laser is a laser with a center wavelength of 1570 nm.

Alternatively, the pump laser 1 may be a low power, butterfly packaged, small volume semiconductor laser.

The input end of the first wavelength division multiplexer 3 is connected with the pump laser 1, the common end of the first wavelength division multiplexer 3 is connected with the saturable absorption mirror 2, and the output end of the first wavelength division multiplexer 3 is connected with the input end of the gain optical fiber 4.

Specifically, the first wavelength division multiplexer 3 has wavelength division multiplexing with working wavelengths of 1570nm and 1840 nm.

The saturable absorption mirror 2 is connected with a common end of the first wavelength division multiplexer 3.

Specifically, the saturable absorption mirror 2 is a semiconductor saturable absorption mirror 2 with a surface area of only 1mm × 1 mm.

The input end of the gain fiber 4 is connected with the output end of the first wavelength division multiplexer 3.

Preferably, the gain fiber 4 is a thulium doped fiber with a length of 0.15 m.

A first input end of the in-loop optical fiber coupler 5 is connected with an output end of the gain optical fiber 4.

Specifically, the coupling mode of the in-loop optical fiber coupler 5 is 2 × 2 optical fiber coupling, and the first input end of the in-loop optical fiber coupler 5 is any one large splitting ratio end of the in-loop optical fiber coupler 5.

The coated filter 6 is arranged between the second output end of the in-loop optical fiber coupler 5 and the second input end of the in-loop optical fiber coupler 5.

Preferably, the coated filter 6 transmits light in a wavelength range to be realized by the laser, and reflects light of other wavelengths (including pump light).

As an optional implementation manner, two ends of the coated filter 6 are connected to the second output end of the in-loop optical fiber coupler 5 and the second input end of the in-loop optical fiber coupler 5. The second output end of the in-loop optical fiber coupler 5 and the second input end of the in-loop optical fiber coupler 5 are the same side port of the in-loop optical fiber coupler 5.

Preferably, the structure that two ends of the coated filter 6 are connected with the second output end of the in-loop optical fiber coupler 5 and the second input end of the in-loop optical fiber coupler 5 forms an all-fiber nonlinear loop.

And the remaining output end of the in-loop optical fiber coupler 5 is used as the output end of the mode-locked pulse laser.

Specifically, the pump laser 1, the first wavelength division multiplexer 3, the saturable absorber mirror 2, the gain fiber 4, the in-loop fiber coupler 5, the coated filter 6 and the mutual connection relationship form an all-fiber compact laser resonant cavity, and the femtosecond pulse output function is realized.

The specific method for realizing the functions of the all-fiber compact laser resonant cavity is to use a specially designed semiconductor saturable absorber mirror 2 with the surface area of only 1mm multiplied by 1mm as a first reflector of the resonant cavity and use an all-fiber nonlinear ring as another reflector of the resonant cavity to realize mode-locked pulse output; by utilizing the special coating band-pass filtering technology of the coated filter 6, the output laser wavelength to be realized obtains the optimal gain condition, and further obtains the optimal gain in the resonant cavity; the design of the resonant cavity is based on an all-fiber structure, eliminates the strict requirement of spatial optical collimation, does not have a polarization sensitive device, and is insensitive to environmental vibration, thereby obtaining stable femtosecond pulse laser output.

In order to provide higher stability and precision of the output laser, the invention also provides an alternative embodiment, wherein the output end of the in-loop optical fiber coupler 5 is connected with the input ends of the power amplification part 7, the dispersion compensation part 8 and the optical fiber coupler 9 in sequence.

In order to achieve the power requirements of frequency multiplication and output, the power amplification part 7 is one or more gain fiber power amplifiers. .

Preferably, the dispersion compensating member 8 is a dispersion compensating fiber.

Preferably, the coupling mode of the optical fiber coupler 9 is 1 × 2 optical fiber coupling. A first output end of the optical fiber coupler 9 is connected with an input end of the light coupling nonlinear crystal 10. A second output end of the optical fiber coupler 9 is connected with a second input end of the second wavelength division multiplexer 11.

Specifically, the first output end of the optical fiber coupler 9 is the output end of the optical fiber coupler 9 with a large splitting ratio. The second output end of the optical fiber coupler 9 is the output end of the optical fiber coupler 9 with small splitting ratio.

The light coupling nonlinear crystal 10 generates second harmonic by using a frequency doubling effect to obtain frequency doubled light with short wavelength.

And the common end of the second wavelength division multiplexer 11 is used as the output end of the dual-wavelength all-fiber laser and outputs femtosecond pulse laser with two wavelengths.

Optionally, the second wavelength division multiplexer 11 outputs a first wavelength laser and a second wavelength laser, where the wavelength range of the first wavelength laser is 650 to 950nm, and the laser range of the second wavelength laser is 1600 to 1870 nm.

Wherein 650-950 nm is the first wavelength window, and 1600-1870 nm is the second wavelength window.

Specifically, the pump laser 1 adopted by the invention is a butterfly-shaped packaged semiconductor laser with the central wavelength of 1570nm output, the first wavelength division multiplexer 3 is in wavelength division multiplexing with the working wavelengths of 1570nm and 1840nm, the saturable absorber mirror 2 is a semiconductor saturable absorber mirror 2 with the surface area of only 1mm multiplied by 1mm, the gain fiber 4 is a thulium-doped fiber with the length of 0.15m, the coupling mode is that the working wavelength of the in-loop optical fiber coupler 5 of 2 multiplied by 2 is 1840nm, the splitting ratio is 30/70, the coated filter 6 can transmit laser with the wavelength of 1840nm +/-5 nm and reflect laser with other wavelengths, the coupling mode is that the working wavelength of the optical fiber coupler 9 of 1 multiplied by 2 is 1840nm, the splitting ratio is 10/90, and the second wavelength division multiplexer 11 is in wavelength division multiplexing with the working wavelengths of 920nm and 1840 nm.

The working mode of the 920nm and 1840nm double-wavelength all-fiber laser is as follows: the pump laser 1 with the center wavelength of 1570nm pumps the gain fiber 4 through the first wavelength division multiplexer 3 to generate laser gain, the forward gain light enters the all-fiber nonlinear ring through the in-ring fiber coupler 5 with the coupling mode of 2 multiplied by 2, and the 1840nm +/-5 nm laser obtains the optimal gain condition through the coated filter 6; the reverse gain light is reflected at the semiconductor saturable absorber mirror 2 after returning to the first wavelength division multiplexer 3; the in-loop optical fiber coupler 5 returns 70% of the energy light to the resonant cavity, and 30% of the energy light is output; the output power of the pump laser 1 is adjusted, so that stable mode-locked pulse output can be obtained at the output end of the mode-locked pulse laser.

The input end of the in-loop optical fiber coupler 5 with the coupling mode of 2 x 2 outputs femtosecond pulse laser with the center wavelength of 1840nm, power amplification is carried out (> 1W) through a power amplification part 7, then the pulse width is adjusted through a dispersion compensation part 8, the optical fiber coupler 9 with the coupling mode of 1 x 2 is used for branching, one path with the splitting ratio of 90% passes through an optical fiber coupling nonlinear crystal, second harmonic is generated by utilizing the frequency doubling effect of the optical fiber coupling nonlinear crystal to obtain laser with the wavelength of 920nm, one path with the splitting ratio of 10% passes through a second wavelength division multiplexer 11 and is combined with frequency doubling light with the wavelength of 920nm, and therefore laser output with the dual wavelengths of 920nm and 1840nm is generated at the common end of the second wavelength division multiplexer 11.

The design of the laser is based on the all-fiber structure, eliminates the strict requirement of space optical collimation, does not have a polarization sensitive device, and is insensitive to environmental vibration, thereby obtaining stable and accurate femtosecond pulse laser output.

The invention uses a specially designed semiconductor saturable absorption mirror with the surface area of only 1mm multiplied by 1mm as a first reflector of a resonant cavity and uses an all-fiber nonlinear ring as another reflector of the resonant cavity. And the laser of 1840nm obtains the optimal gain condition by a special coating band-pass filtering technology, thereby obtaining the optimal gain in the resonant cavity. The accuracy of the output laser is improved.

The embodiments in the present description are described in a progressive manner, each embodiment focuses on differences from other embodiments, and the same and similar parts among the embodiments are referred to each other. For the system disclosed by the embodiment, the description is relatively simple because the system corresponds to the method disclosed by the embodiment, and the relevant points can be referred to the method part for description.

The principles and embodiments of the present invention have been described herein using specific examples, which are provided only to help understand the method and the core concept of the present invention; meanwhile, for a person skilled in the art, according to the idea of the present invention, the specific embodiments and the application range may be changed. In view of the above, the present disclosure should not be construed as limiting the invention.