CN112003116A

CN112003116A - Ultrashort pulse Raman fiber amplifier

Info

Publication number: CN112003116A
Application number: CN202010856801.3A
Authority: CN
Inventors: 冯衍; 祁伟骜; 周佳琦
Original assignee: Shanghai Institute of Optics and Fine Mechanics of CAS
Current assignee: Shanghai Institute of Optics and Fine Mechanics of CAS
Priority date: 2020-08-24
Filing date: 2020-08-24
Publication date: 2020-11-27

Abstract

The invention relates to an ultrashort pulse Raman fiber amplifier, which is formed by connecting a pulse laser pumping source, a continuous light signal source, a pumping/signal laser beam combining device, a Raman gain fiber and a pumping/signal beam splitting device into a whole through an optical fiber fusion splicer in sequence. The invention adopts ultrashort pulse laser as a pumping source to amplify continuous wave signal laser in a Raman fiber amplifier. Due to the rapid response process of stimulated raman scattering, continuous wave signal laser can be amplified into ultrashort pulse laser. The Raman laser has the advantages of high Raman gain, good coherence, large laser pulse energy, narrow pulse width, simple structure and the like, and has great practical value and application prospect.

Description

Ultrashort pulse Raman fiber amplifier

Technical Field

The invention relates to an ultrashort pulse Raman fiber amplifier, which has the advantages of good coherence, large laser pulse energy, narrow pulse width and simple structure, and is an all-fiber amplifier capable of generating ultrashort pulse laser with special wavelength.

Background

The ultrashort pulse laser has great application prospect in the fields of basic research, biological medical treatment, industrial processing, optical communication and the like. Meanwhile, the optical fiber laser has the advantages of compact structure, no adjustment of an optical path, high beam quality, high efficiency and the like. The ultra-fast optical fiber laser is expanded to a wave band which cannot be covered by ion transition, and is the actual requirement of a plurality of applications in the fields of medical treatment, scientific research and the like. The stimulated raman scattering effect (SRS) in optical fibers provides a potential means to obtain full-band ultrafast lasers. It is independent of the electronic energy level of the medium, has a wide gain spectrum in the optical fiber, and can occur in cascade. So, the raman fiber laser can be generated and amplified in the entire transparent band of the fiber, as long as the pump laser of the appropriate wavelength is selected. (see Y.Feng, ed., Raman Fiber Lasers, Springer Series in Optical Sciences (Springer International Publishing,2017), Vol.207.)

At present, most of researches are carried out on ultrafast mode-locked Raman fiber oscillators, and the performances of various mode-locking mechanisms are widely researched. However, in the existing report, the mode-locked raman fiber laser is not as good as the conventional rare earth ion doped mode-locked fiber laser in terms of output stability, pulse energy and other performances. And the mode-locked Raman fiber laser based on saturable absorbers such as SESAM, carbon nano tubes and graphene generally has the problem of poor stability of an output pulse sequence. This is associated with raman gain being a nonlinear process with extremely fast response speed, faster than the recovery time of a common true saturable absorber. The mode-locked Raman fiber laser based on the equivalent saturable absorber (nonlinear ring mirror and nonlinear polarization rotation) has a response speed similar to that of Raman gain due to the fact that the saturation process of the mode-locked Raman fiber laser is also based on the fiber nonlinear effect, and therefore ultrafast Raman laser output with good performance can be achieved.

Pulsed laser synchronous pumping can achieve High Raman gain per unit length and therefore may be a more optimal means to achieve High performance ultrafast Raman fiber laser output (see d.churin, j.olson, r.a.norwood, n.peyghamarian, and k.kieu, "High-power synchronized pumped femtosecond Raman fiber laser," opt.lett.40, 2529-2532 (2015)). But pulsed laser synchronous pumping techniques require long-term locking of the pulse repetition frequency to the raman cavity and any slight deviations will translate into laser output noise. Although a high-energy and high-efficiency ultrafast raman laser output can be obtained, if a low-noise output is to be obtained, the system complexity is high and the practicability is insufficient.

Disclosure of Invention

The invention provides a novel Raman fiber amplifier for obtaining ultrashort pulse fiber laser with new wavelength by using ultrashort pulse laser pumping continuous wave signal light. The amplifier not only can keep the advantage of high Raman gain of pulse pumping, but also has no technical problem of synchronization of pumping pulse and Raman light. Since continuous laser light having high coherence is used as the signal light, it is expected that the output thereof also has good coherence.

The solution of the invention is as follows:

an ultrashort pulse Raman fiber amplifier comprises a pulse laser pumping source, a continuous light signal source, a pumping/signal laser beam combining device and a Raman gain fiber, and is characterized in that: and after the pump light emitted by the pulse laser pump source and the signal light emitted by the continuous light signal source are combined by the pump/signal beam combining device, the combined signals enter the Raman gain fiber, and the pump light transfers energy and amplifies continuous light signals in the Raman gain fiber through the stimulated Raman scattering effect to obtain picosecond ultrashort pulse output with new wavelength.

The pump/signal laser beam splitting device is used for separating and outputting picosecond ultrashort pulses with new wavelengths from the residual pump light;

the pulse laser pumping source is a mode-locked laser, and the laser cavity structure for generating the ultrashort pulse can be a saturable absorber or an equivalent saturable absorber;

the pulse laser pumping source comprises lasers with multiple or more wavelengths, and the pulse width of the output laser of each pulse laser pumping source is less than 100 ps;

the continuous optical signal source comprises optical signals with multiple or more wavelengths;

the substrate material of the Raman gain fiber is quartz, phosphate, silicate, tellurate or fluoride;

at least one pulsed laser pump source and at least one continuous optical signal source₁And satisfies the relation:

where Δ v is the frequency shift corresponding to the peak of the raman gain coefficient, and c is the speed of light in vacuum.

Compared with the prior art, the invention has the technical effects that:

and ultrashort pulse laser is used as a pumping source, and continuous wave signal laser is amplified in a Raman fiber amplifier. Because stimulated raman scattering is a fast response process, continuous wave signal laser can be amplified into ultrashort pulse laser. The continuous wave substrate is filtered out by saturable absorption. The Raman gain is high, the coherence is good, the laser pulse energy is large, the pulse width is narrow, the structure is simple, and the practical value is very high.

Drawings

FIG. 1 is a schematic diagram of the structure of an ultrashort pulse Raman fiber amplifier of the present invention

FIG. 2 is a schematic block diagram of a multi-wavelength pump structure of the ultra-short pulse Raman fiber amplifier of the present invention.

Fig. 3 is a schematic block diagram of a multi-signal injection structure of the ultrashort pulse raman fiber amplifier of the present invention.

Detailed Description

The invention will be further illustrated with reference to three examples and the accompanying drawings, without limiting the scope of the invention.

It should be noted that the following detailed description is exemplary and is intended to provide further explanation of the disclosure. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs.

It is noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of example embodiments according to the present application. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, and it should be understood that when the terms "comprises" and/or "comprising" are used in this specification, they specify the presence of stated features, steps, operations, devices, components, and/or combinations thereof, unless the context clearly indicates otherwise.

Example 1, please refer to fig. 1.

Fig. 1 is a schematic block diagram of the structure of the ultrashort pulse raman fiber amplifier. The pulse laser pump source 1, the continuous optical signal source 2, the pump/signal laser beam combining device 3, the Raman gain fiber 4 and the pump/signal beam splitting device 5 are welded into a whole through an optical fiber welding machine as shown in figure 1. The central wavelength of the pulse laser pump source 1 is 1117nm, and the pulse width is less than 100 ps. The continuous optical signal source 2 has a central wavelength of 1310 nm. The pumping/signal laser beam combining device 3 is a 1117nm/1310nm wavelength division multiplexer. The Raman gain fiber 4 is a phosphor-doped silica fiber, and the Raman gain is 1.2/(W.km). The pumping/signal laser beam splitting device 5 is a 1117nm/1310nm wavelength division multiplexer.

Example 2, please refer to fig. 2.

Fig. 2 is a schematic block diagram of a multi-wavelength pump structure of the ultrashort pulse raman fiber amplifier. The central wavelengths of the pulse laser pumping source 11, the pulse laser pumping source 12 and the pulse laser pumping source 13 are 1064nm, 1067nm and 1070nm respectively, the pulse width is less than 100ps, and the laser beam combining device 14 is a wavelength division multiplexer. The central wavelength of the continuous optical signal source 2 is 1120nm, and the line width is less than 10 nm. The pumping/signal laser beam combining device 3 is a wavelength division multiplexer. The Raman gain fiber 4 is a polarization maintaining silica fiber, and the Raman gain is 1.8/(W.km). The pump/signal laser beam splitting device 5 is a 1067nm/1120nm wavelength division multiplexer.

Example 3, please refer to fig. 3.

Fig. 3 is a schematic block diagram of the multi-signal injection structure of the ultrashort pulse raman fiber amplifier. The central wavelength of the pulse laser pump source 1 is 1064nm, and the pulse width is less than 100 ps. The central wavelengths of the continuous light signal source 21, the continuous light signal source 22 and the continuous light signal source 23 are 1120nm, 1178nm and 1238nm respectively, and the line width is less than 1 nm. The laser beam combining device 24 is a wavelength division multiplexer. The pumping/signal laser beam combining device 3 is a wavelength division multiplexer. The Raman gain fiber 4 is a polarization maintaining silica fiber, and the Raman gain is 2.5/(W.km). The pump/signal laser beam splitting device 5 is a wavelength division multiplexer. Under the excitation of the pulse laser pumping source 1, the continuous light signal source 21, the continuous light signal source 22 and the continuous light signal source 23 are subjected to Raman amplification step by step, and finally, wide-spectrum ultrashort pulse output with the wavelength covering 1120nm, 1178nm and 1238nm is obtained.

It should be noted that in

embodiments

2 and 3, the laser beam combining device 14 and the laser beam combining device 24 are only used to distinguish the pulsed laser pump source from the continuous optical signal source. The pulse laser pumping sources or continuous optical signal sources in the laser pulse pumping device have no fixed sequence, and the sequence can be randomly adjusted in the laser pulse pumping device only for facilitating understanding.

Claims

1. The utility model provides an ultrashort pulse raman fiber amplifier, includes pulse laser pumping source (1), continuous light signal source (2), pumping/signal laser beam combining device (3), raman gain fiber (4), its characterized in that: after being combined by the pumping/signal combining device (3), the pumping light emitted by the pulse laser pumping source (1) and the signal light emitted by the continuous light signal source (2) enter the Raman gain fiber (4), and the pumping light transmits and amplifies the continuous light signal in the Raman gain fiber (4) through the stimulated Raman scattering effect to obtain picosecond ultrashort pulse output with new wavelength.

2. The ultrashort pulse raman fiber amplifier of claim 1, further comprising a pump/signal laser beam splitting device (5), wherein the picosecond ultrashort pulse of the new wavelength is separated from the rest of the pump light by the pump/signal laser beam splitting device (5) and outputted.

3. The ultrashort pulse raman fiber amplifier of claim 1, wherein the pulse laser pump source (1) is a mode-locked laser and the ultrashort pulse generating laser cavity structure can be a saturable absorber or an equivalent saturable absorber.

4. Ultrashort pulse raman fiber amplifier according to claim 1 or 3, wherein the pulsed laser pump source (1) comprises lasers with 1 or more wavelengths, and the pulse width of the output laser of each pulsed laser pump source (1) is <100 ps.

5. The ultrashort pulse raman fiber amplifier of claim 1, wherein the continuous optical signal source (2) comprises optical signals of 1 or more wavelengths.

6. Ultrashort pulse raman fiber amplifier according to claim 1, characterized in that the matrix material of the raman gain fiber (4) is quartz, phosphate, silicate, tellurate or fluoride.

7. Ultrashort pulse raman fiber amplifier according to any of claims 1 to 6, characterized in that the central wavelength λ of at least one pulsed laser pump source (1)₂And the central wavelength lambda of at least one continuous light signal source (2)₁And satisfies the relation: