CN117856015A - Pulse laser amplification system and method based on external injection signal - Google Patents

Abstract

The invention provides a pulse laser amplification system and a pulse laser amplification method based on an external injection signal, which can be applied to the technical field of low-repetition-frequency nanosecond pulse fiber laser. The system comprises: an external injection signal device and a pulse laser. The external injection signal device comprises: a first pump source configured to generate a first pump light; the resonant cavity is configured to absorb the first pump light, generate spontaneous radiation based on particle number inversion and obtain middle external injection signal light; the modulator is configured to modulate the intermediate external injection signal light to obtain target external injection signal light; and an attenuator configured to adjust the power of the out-of-target injection signal light. And a pulse laser configured to gain-amplify the initial signal light, and output the target signal light, wherein the initial signal light includes the out-of-target injection signal light and the seed signal light in the pulse laser.

Description

Pulse laser amplification system and method based on external injection signal

Technical Field

The disclosure relates to the technical field of low repetition frequency nanosecond pulse fiber lasers, and in particular relates to a pulse laser amplification system and method based on an external injection signal.

Background

The low repetition frequency nanosecond pulse fiber laser system has the characteristics of compact structure, high stability, low thermal effect, high conversion efficiency, good beam quality and the like, and has wide application in the fields of industrial processing, medical treatment and communication. The main current mode for realizing high power output is to adopt a low-power high-beam-quality nano pulse seed source, and realize the expansion of average power and energy through a main oscillation power amplification technology (MOPA-Master Oscillator Power-Amplifier).

The expansion of power and energy of a low repetition rate nanosecond pulsed fiber laser system is limited by a number of factors, of which spontaneous emission noise is an important factor. The nonlinear effects of spontaneous radiation prior to stimulated raman scattering, stimulated brillouin scattering, and the like limit the efficient extraction of system energy. In a low repetition rate nanosecond pulsed laser amplification system, there is typically a higher gain between the signal pulses due to the smaller core-to-cladding area ratio and longer service length of the gain fiber. These gains amplify the spontaneous emission noise present throughout the amplification process. Amplifying the spontaneous emission noise directly reduces the signal-to-noise ratio of the system, and the uncertain directionality of the amplified spontaneous emission noise can cause most of the spontaneous emission light to overflow the outer cladding and the coating of the gain fiber, so that the fiber is burnt out, and catastrophic damage is brought to the system.

In the related art, amplified spontaneous emission noise can be suppressed to a certain extent by methods such as reducing reflection at the inner end of the system, optimizing the length of an optical fiber, adjusting the power of a seed signal and pump light, optimizing the wavelength of the pump light, connecting and filtering an amplifying stage or using a time domain control device, adjusting the repetition frequency of the system, and the like. However, the system still has an upper amplification limit, and the further amplification spontaneous radiation suppression method still has important significance for the low-repetition-frequency nanosecond pulse optical fiber amplification system.

Disclosure of Invention

In view of the foregoing, the present disclosure provides a pulsed laser amplification system and method based on an external injection signal.

According to a first aspect of the present disclosure, there is provided a pulsed laser amplification system based on an external injection signal, comprising: an external injection signal device and a pulse laser. The external injection signal device comprises: a first pump source configured to generate a first pump light; the resonant cavity is configured to absorb the first pump light, generate spontaneous radiation based on particle number inversion and obtain middle external injection signal light; the modulator is configured to modulate the intermediate external injection signal light to obtain target external injection signal light; and an attenuator configured to adjust the power of the out-of-target injection signal light. And a pulse laser configured to gain-amplify the initial signal light including the out-of-target injection signal light and the seed signal light in the pulse laser, and output the target signal light.

According to an embodiment of the present disclosure, the external injection signal device further comprises: the first beam combiner is configured to input the first pump light to the resonant cavity.

According to embodiments of the present disclosure, the resonant cavity includes a linear resonant cavity and a ring resonant cavity.

According to an embodiment of the present disclosure, the linear resonator includes a first bragg grating, a first gain fiber, and a second bragg grating. A first Bragg grating configured to receive the first pump signal light; the first gain optical fiber is configured to enable the first pump signal light to generate particle number inversion so as to obtain spontaneous emission signal light; and the second Bragg grating is configured to screen the spontaneous emission signal light based on bandwidths of the first Bragg grating and the second Bragg grating, and continuously oscillate the spontaneous emission signal light together with the first Bragg grating to obtain middle external injection signal light.

According to an embodiment of the present disclosure, a ring resonator includes a second gain fiber, a circulator, a third Bragg grating, and a first fiber coupler. The second gain optical fiber is configured to absorb the first pumping signal light, generate particle number inversion and obtain spontaneous radiation signal light; a circulator, comprising: a first port configured to receive self-radiated signal light; a second port for receiving the spontaneous emission signal light outputted from the first port; and a third port configured to receive the spontaneous emission signal light reflected by the third bragg grating; the third Bragg grating is configured to receive the spontaneous emission signal light output by the second port, screen the spontaneous emission signal light based on the bandwidth of the third Bragg grating, and reflect the screened spontaneous emission signal light to the second port; and a first optical fiber coupler configured to receive the reflected spontaneous emission signal light to obtain intermediate external injection signal light.

According to an embodiment of the present disclosure, a pulsed laser includes a seed light source, a fiber wavelength division multiplexer, a second fiber coupler, and a fiber amplifier. A seed light source configured to generate seed signal light; an optical fiber wavelength division multiplexer configured to receive an initial signal light including a seed signal light and an off-target injection signal light; a second optical fiber coupler configured to receive the initial signal light and output; and an optical fiber amplifier configured to receive the initial signal light output by the second optical fiber coupler, amplify the initial signal light, and obtain a target signal light.

According to an embodiment of the present disclosure, a second optical fiber coupler includes: a fourth port configured to receive the initial signal light; a fifth port configured to output an initial signal light; a sixth port configured to monitor a state of the initial signal light; and a seventh port configured to monitor spontaneous emission noise generated inside the pulsed laser.

According to an embodiment of the present disclosure, an optical fiber amplifier includes: a second pump source configured to generate a second pump light; a second beam combiner configured to receive the initial signal light and the second pump light, to obtain an intermediate signal light including the initial signal light and the second pump light; the third gain optical fiber is configured to perform gain amplification on the initial signal light of the intermediate signal light to obtain target signal light; an optical fiber isolator configured to isolate return signal light and receive target signal light; and an optical fiber end cap configured to receive the target signal light output from the optical fiber isolator and output the target signal light.

A second aspect of the present disclosure provides a pulsed laser amplification method based on an external injection signal, comprising: generating first pump light; the resonant cavity absorbs the first pump light, generates spontaneous radiation based on particle number inversion, and screens out intermediate external injection signal light; modulating the middle external injection signal light to obtain target external injection signal light; and amplifying the initial signal light based on a pulse laser to output target signal light, wherein the initial signal light comprises the target external injection signal light and seed signal light in the pulse laser.

According to an embodiment of the present disclosure, gain-amplifying an initial signal light based on a pulse laser, outputting a target signal light, includes: generating a second pump light; obtaining intermediate signal light comprising the initial signal light and the second pump light; gain amplification is carried out on the intermediate signal light to obtain target signal light; the return light is isolated by the fiber isolator and the target signal light is output by the fiber end cap.

According to the embodiment of the disclosure, when the external injection device is used for obtaining the target external injection signal light, and the pulse laser is used for performing gain amplification on the initial signal light comprising the target external injection signal light and the seed signal light, the target external injection signal light is used for absorbing the reverse particle number which is not completely extracted by the seed signal light, so that spontaneous radiation generated by the reverse particle number of the part is restrained, the problem that the signal to noise ratio of a system is reduced due to spontaneous radiation noise generated by the gain optical fiber in the amplifying process is avoided, the power and the upper energy limit of the signal light in the system are improved, and meanwhile, the safety and the reliability of the system can be ensured.

Drawings

The foregoing and other objects, features and advantages of the disclosure will be more apparent from the following description of embodiments of the disclosure with reference to the accompanying drawings, in which:

fig. 1 schematically illustrates a block diagram of a pulsed laser amplification system based on an external injection signal in accordance with an embodiment of the present disclosure;

FIG. 2 schematically illustrates a block diagram of a linear resonator according to an embodiment of the disclosure;

FIG. 3 schematically illustrates a block diagram of a linear resonator based on internal modulation in accordance with an embodiment of the present disclosure;

FIG. 4 schematically illustrates a block diagram of a ring resonator according to an embodiment of the disclosure;

FIG. 5 schematically illustrates a block diagram of a ring resonator based on internal modulation in accordance with an embodiment of the present disclosure;

fig. 6 schematically shows a block diagram of a pulse laser according to an embodiment of the present disclosure;

FIG. 7 schematically illustrates a block diagram of a second fiber optic coupler according to an embodiment of the present disclosure;

fig. 8 schematically illustrates a block diagram of a fiber amplifier according to an embodiment of the present disclosure;

FIG. 9 schematically illustrates a schematic diagram of an external injection signal based pulsed laser amplification system under an external modulation based linear resonator according to an embodiment of the present disclosure;

FIG. 10 schematically illustrates a schematic diagram of an external injection signal based pulsed laser amplification system under an internal modulation based linear resonator according to an embodiment of the present disclosure;

FIG. 11 schematically illustrates a schematic diagram of an external injection signal based pulsed laser amplification system under an external modulation based ring resonator according to an embodiment of the present disclosure;

FIG. 12 schematically illustrates a schematic diagram of an external injection signal based pulsed laser amplification system under an internal modulation based ring resonator according to an embodiment of the present disclosure;

fig. 13 schematically illustrates a flow chart of a pulsed laser amplification method based on an external injection signal according to an embodiment of the present disclosure.

Detailed Description

Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings. It should be understood that the description is only exemplary and is not intended to limit the scope of the present disclosure. In the following detailed description, for purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of the embodiments of the present disclosure. It may be evident, however, that one or more embodiments may be practiced without these specific details. In addition, in the following description, descriptions of well-known structures and techniques are omitted so as not to unnecessarily obscure the concepts of the present disclosure.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the disclosure. The terms "comprises," "comprising," and/or the like, as used herein, specify the presence of stated features, steps, operations, and/or components, but do not preclude the presence or addition of one or more other features, steps, operations, or components.

All terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art unless otherwise defined. It should be noted that the terms used herein should be construed to have meanings consistent with the context of the present specification and should not be construed in an idealized or overly formal manner.

Where expressions like at least one of "A, B and C, etc. are used, the expressions should generally be interpreted in accordance with the meaning as commonly understood by those skilled in the art (e.g.," a system having at least one of A, B and C "shall include, but not be limited to, a system having a alone, B alone, C alone, a and B together, a and C together, B and C together, and/or A, B, C together, etc.).

In a low repetition frequency nanosecond pulse laser amplification system, spontaneous radiation noise existing in the whole amplification process of a gain fiber is amplified, the signal to noise ratio of the system can be directly reduced by amplified spontaneous radiation noise, most of spontaneous radiation light can overflow an outer cladding layer and a coating layer of the gain fiber due to the uncertain directionality of the amplified spontaneous radiation noise, the fiber is burnt, and catastrophic damage is brought to the system.

In view of the above problems, the inventors found that when the external injection device is used to obtain the target external injection signal light and the pulse laser is used to gain-amplify the initial signal light, the target external injection signal light can suppress the spontaneous emission noise of the system, and avoid the damage of the spontaneous emission noise to the system.

In view of this, embodiments of the present disclosure provide a pulsed laser amplification system based on an external injection signal, the system comprising: an external injection signal device and a pulse laser. The external injection signal device comprises: a first pump source configured to generate a first pump light; the resonant cavity is configured to enable the first pump light to generate particle number inversion so as to obtain middle external injection signal light; the modulator is configured to modulate the intermediate external injection signal light to obtain target external injection signal light; and an attenuator configured to adjust the power of the out-of-target injection signal light. And a pulse laser configured to gain-amplify the initial signal light, and output a target signal light, wherein the initial signal light includes the out-of-target injection signal light and seed signal light generated by the pulse laser.

The pulse laser amplification system based on the external injection signal according to the disclosed embodiment will be described in detail with reference to fig. 1 to 12.

Fig. 1 schematically illustrates a block diagram of a pulsed laser amplification system based on an external injection signal according to an embodiment of the present disclosure.

As shown in fig. 1, there is provided a pulsed laser amplification system based on an external injection signal, comprising: an external injection signaling device 100 and a pulsed laser 200.

The external injection signal device 100 includes a first pump source 110, a resonant cavity 120, a modulator 130, and an attenuator 140.

The first pump source 110 is configured to generate a first pump light.

The resonator 120 is configured to absorb the first pump light, generate spontaneous emission based on population inversion, and obtain intermediate external injection signal light.

And a modulator 130 configured to modulate the intermediate external-injection signal light to obtain the target external-injection signal light.

And an attenuator 140 configured to adjust the power of the out-of-target injection signal light.

The pulse laser 200 is configured to gain-amplify the initial signal light including the out-of-target injection signal light and the seed signal light in the pulse laser 200, and output the target signal light.

According to an embodiment of the disclosure, the first pump source 110 may be a semiconductor laser with a center wavelength of 976nm, and the generated first pump light may excite the resonant cavity 120 to pump particles in the resonant cavity 120 from a ground state to a high energy level, so as to realize population inversion, and obtain intermediate external injection signal light. Wherein the intermediate external injection signal light is continuous laser. The selection of the first pump source 110 is not limited in this disclosure, and may be selected as desired by one skilled in the art.

According to an embodiment of the present disclosure, modulator 130 may be an acousto-optic modulator or an electro-optic modulator, with an optional input-output fiber size of 10/125 μm, a rise time of 50ns at a minimum, modulating the time-domain pulse width and repetition frequency of the intermediate external injection signal. The intermediate external injection signal light passes through the modulator 130 and then outputs a target external injection signal light with adjustable pulse width from nanosecond to microsecond, which is used as the output of the target external injection signal light with adjustable repetition frequency from 1Hz to 100 KHz. The selection of modulator 130 is not limited by the present disclosure and may be selected as desired by one skilled in the art.

According to the embodiment of the disclosure, the first pump light enters the resonant cavity 120, particles in the resonant cavity 120 are pumped from a ground state to a high energy level, population inversion is realized, broadband spontaneous emission signal light is generated, corresponding bandwidth signals are generated under the selection of the first Bragg grating and the second Bragg grating, continuous oscillation is generated, and an intermediate external injection signal is formed; the modulator 130 adjusts the time domain waveform of the intermediate external-injection signal light to obtain the target external-injection signal light.

According to an embodiment of the present disclosure, the attenuator 140 may be a tunable optical power attenuator, adjustable in the range of 0-100%, and the input/output fiber may be selected to be 10/125 μm. The power of the out-of-target injection signal light is adjusted by adjusting the attenuation coefficient of the attenuator 140.

According to an embodiment of the present disclosure, the first pump source 110 generates a first pump light to be input into the resonant cavity 120, and generates a population inversion, so as to obtain a continuous laser with a central wavelength of the fiber bragg grating, i.e. an intermediate external injection signal light. The intermediate external injection signal light passes through the modulator 130 and then outputs a target external injection signal light with adjustable pulse width nanosecond to microsecond magnitude and adjustable repetition frequency of 1Hz-100KHz, and the intensity of the target external injection signal light passes through the attenuator 140 and then is adjustable. The off-target injection signal light is input to the pulse laser 200, and when the initial signal light is gain-amplified, the off-target injection signal light suppresses spontaneous emission noise generated by the system, and outputs high-quality target signal light.

According to the embodiment of the disclosure, when the external injection device is used to obtain the external injection signal light of the target, and the pulse laser 200 is used to amplify the initial signal light obtained by synthesizing the external injection signal light of the target and the seed signal light, the external injection signal light of the target is used to absorb the inverted particle number which is not completely extracted by the seed signal light, so as to inhibit the spontaneous radiation noise of the system, thereby causing the problem of reduced signal-to-noise ratio of the system, improving the power and the upper energy limit of the signal light in the system, and simultaneously ensuring the safety and reliability of the system.

According to an embodiment of the present disclosure, the external injection signal device 100 further includes: the first beam combiner is configured to input the first pump light to the resonant cavity 120.

According to an embodiment of the present disclosure, the first combiner may be an (n+1) ×1 type signal/pump combiner, and the specifications may be a signal arm 10/125 μm and a pump arm 105/125 μm. The first pump light generated by the first pump source 110 is coupled into the resonant cavity 120 through the first beam combiner. The specification of the first beam combiner is not limited in this disclosure, and one skilled in the art can select as needed.

According to an embodiment of the present disclosure, the resonant cavity 120 includes a linear resonant cavity and a ring resonant cavity.

Fig. 2 schematically illustrates a block diagram of a linear resonator according to an embodiment of the disclosure.

As shown in fig. 2, the linear resonator includes a first bragg grating 121, a first gain fiber 122, and a second bragg grating 123.

The first bragg grating 121 is configured to receive the first pump light.

The first gain fiber 122 is configured to absorb the first pump light, and generate a population inversion to obtain spontaneous emission signal light.

The second bragg grating 123 is configured to screen the spontaneous emission signal light based on bandwidths of the first bragg grating and the second bragg grating, and continuously oscillate the spontaneous emission signal light together with the first bragg grating to obtain the intermediate external-injection signal light.

According to an embodiment of the present disclosure, the first bragg grating 121 and the second bragg grating 123 are both reflective bragg gratings with a center wavelength of 1030nm. The first bragg grating 121 is a high inversion grating with a bandwidth of 0.5nm and a reflectivity R > 0.99, and the second bragg grating 123 is a partially reflective grating with a bandwidth of 0.5nm and a reflectivity r=10%.

According to embodiments of the present disclosure, the first gain fiber 122 may be a rare earth doped gain fiber, an ytterbium doped double clad fiber of 10/125 μm gauge. The doping element may be ytterbium, but the disclosure is not limited thereto, and one skilled in the art may select according to actual needs.

According to the embodiment of the present disclosure, since the center wavelength of the first bragg grating 121 is 1030nm, the reflectivity R > 0.99 is in a transmission state for an initial external injection signal of 976nm, a high reflection effect is generated for 1030nm light, and the second bragg grating 123 is a half-reflection and half-transmission grating, and a partial reflection and partial transmission effect is generated for the arriving 1030nm light, and a transmission effect is generated for other wavelength bands such as 976 nm. The first bragg grating 121, the first gain optical fiber 122 and the second bragg grating 123 form a linear resonant cavity, the first pump light is generated by the first pump source 110, enters the first bragg grating 121 through the first beam combiner, is absorbed by the first gain optical fiber 122, generates particle number inversion and generates spontaneous radiation signal light, enters the second bragg grating 123, generates continuous laser oscillation with a central wavelength of 1030nm within the bandwidth of the bragg gratings, and obtains intermediate external injection signal light.

Fig. 3 schematically illustrates a block diagram of a linear resonator based on internal modulation according to an embodiment of the present disclosure.

As shown in fig. 3, the modulator 130 may also be disposed in a linear resonant cavity to implement internal modulation to obtain the target external injection signal light, where the roles of the first bragg grating 121, the first gain fiber 122 and the second bragg grating 123 are the same as those of fig. 2, and will not be described herein. The first bragg grating 121, the first gain optical fiber 122, the modulator 130 and the second bragg grating 123 form a linear resonant cavity, the first pump light is generated by the first pump source 110, enters the first bragg grating 121 through the first beam combiner, is absorbed by the first gain optical fiber 122, generates particle number inversion and generates spontaneous emission signal light, enters the second bragg grating 123, and continuous laser light obtained through continuous oscillation is directly input into the modulator 130. In the closed state of the modulator 130, the system is in a low Q state, and the first gain fiber 122 stores energy; when modulator 130 is on, the system operates in a high Q-value state, producing an off-target injection signal light with a center wavelength of 1030nm, where Q is defined as the ratio of the total energy stored in the cavity to the energy lost per unit time in the cavity.

Fig. 4 schematically illustrates a block diagram of a ring resonator according to an embodiment of the disclosure.

As shown in fig. 4, the ring cavity includes a second gain fiber 124, a circulator 125, a third bragg grating 126, and a first fiber coupler 127.

The second gain fiber 124 is configured to absorb the first pump light, and generate a population inversion to obtain spontaneous emission signal light.

Circulator 125 includes a first port P1, a second port P2, and a third port P3.

The first port P1 is configured to receive self-radiated signal light.

The second port P2 receives the spontaneous emission signal light output from the first port P1.

The third port P3 is configured to receive the spontaneous emission signal light reflected by the third bragg grating 126.

The third bragg grating 126 is configured to receive the spontaneous emission signal light output from the first port P2, screen the spontaneous emission signal light based on a bandwidth of the third bragg grating, and reflect the screened spontaneous emission signal light to the second port P2.

The first optical fiber coupler 127 is configured to receive the reflected spontaneous emission signal light to obtain intermediate external injection signal light.

According to an embodiment of the present disclosure, the second gain fiber 124 may be a rare earth doped gain fiber, an ytterbium doped double clad fiber of 10/125 μm gauge. The doping element may be ytterbium, but the disclosure is not limited thereto, and one skilled in the art may select according to actual needs.

According to an embodiment of the present disclosure, circulator 125 is a multi-port optical element having non-reciprocal characteristics, wherein the output port fiber may be 10/125 μm. When light is input from a specific port and output from a specific port, for example, when light is input from the first port P1, light can be output from the first port P2 only, and similarly, light can be input from the first port P2 and output from the third port P3 only.

According to an embodiment of the present disclosure, the third Bragg grating 126 may be a reflective Bragg grating with a center wavelength of 1030nm, a bandwidth of 0.5nm, and a reflectivity of R > 0.99.

According to an embodiment of the present disclosure, the first fiber coupler 127 may be a fiber coupler having three output ports, a split ratio between 1-99, a split ratio of 30:70, and an output fiber size of 10/125 μm. Wherein the splitting ratio of the first fiber coupler 127 is between 1 and 99. The present disclosure is not limited to the ratio of light splitting, and one skilled in the art may select as desired.

According to an embodiment of the present disclosure, since the center wavelength of the third bragg grating 126 is 1030nm and the reflectivity R > 0.99, the initial external injection signal of 976nm is in a transmission state, and a high reflection effect is generated for 1030nm light; 1030nm light is output from the third port P3 of the circulator 125 after being reflected by the third bragg grating 126; 1030nm light output by the third port P3 enters the first optical fiber coupler 127, 30% of the light returns to the annular cavity, and 70% of the signal light is input to the first optical fiber coupler 127; the second gain optical fiber 124, the circulator 125, the third bragg grating 126 and the first optical fiber coupler 127 form a ring-shaped resonant cavity, the first pump light is generated by the first pump source 110, enters the second gain optical fiber 124 through the first beam combiner, is absorbed by the second gain optical fiber 124, generates spontaneous radiation signal light after being subjected to particle number inversion, enters the first port P1 of the circulator 125, exits from the second port P2 of the circulator 125 to the third bragg grating 126, generates continuous laser oscillation of light with the center wavelength of 1030nm in the bandwidth of the bragg grating, exits from the third port P3 to the first optical fiber coupler 127, and returns a part of light to the ring-shaped resonant cavity through the first optical fiber coupler 127 to generate continuous oscillation, so that intermediate external injection signal light is obtained.

Fig. 5 schematically illustrates a block diagram of a ring resonator based on internal modulation in accordance with an embodiment of the present disclosure.

As shown in fig. 5, the modulator 130 may also be disposed in a ring resonator, so as to implement internal modulation to obtain the target external injection signal light. The second gain fiber 124, circulator 125, third bragg grating 126, and first fiber coupler 127 function in the same manner as in fig. 4, and are not described in detail herein. The second gain fiber 124, circulator 125, third Bragg grating 126, first fiber coupler 127, and modulator 130 form a ring resonator. In the off state of modulator 130, the system is in a low Q state and second gain fiber 124 is in the energy storage stage; in the modulator 130 on state, the system is in a high Q state, producing an off-target injection signal light with a center wavelength of 1030nm, where Q is defined as the ratio of the total energy stored in the cavity to the energy lost per unit time in the cavity.

Fig. 6 schematically shows a block diagram of a pulse laser according to an embodiment of the present disclosure.

As shown in fig. 6, the pulsed laser 200 includes a seed light source 210, a fiber wavelength division multiplexer 220, a second fiber coupler 230, and a fiber amplifier 240.

The seed light source 210 is configured to generate seed signal light.

The optical fiber wavelength division multiplexer 220 is configured to receive the initial signal light including the seed signal light and the out-of-target injection signal light.

The second optical fiber coupler 230 is configured to receive the initial signal light and output.

The optical fiber amplifier 240 is configured to receive the initial signal light output from the second optical fiber coupler 230, and amplify the initial signal light to obtain the target signal light.

According to embodiments of the present disclosure, the seed light source 210 may be a semiconductor modulated seed source, or a nanosecond pulse signal light generated by a technique based on intra-cavity Q-switching, extra-cavity modulation, gain switching, or the like, as a seed light source. The seed signal light is used to extract the system gain into the fiber amplifier 240. The selection of the seed light source 210 is not limited in this disclosure, and may be selected as desired by one skilled in the art.

According to the embodiment of the present disclosure, one input end of the optical wavelength division multiplexer 220 is connected to the output end of the attenuator 140, and the other input end of the optical wavelength division multiplexer is connected to the output end of the seed light source 210, where two inputs and ports of the optical wavelength division multiplexer 220 allow different wavelength injection, and the same band injection can also be adopted. Both the input and output fibers of the fiber wavelength division multiplexer 220 may be 10/125 μm, with the input fibers allowing 1030nm and 1064nm input, respectively, and the output fibers allowing 1030nm and 1064nm common output. The optical fiber wavelength division multiplexer 220 is configured to input the adjustable off-target injection signal light and the seed signal light together into the second optical fiber coupler 230, so as to obtain a common output of the injection signal and the seed signal, i.e. the initial signal light.

According to an embodiment of the present disclosure, the input end of the second fiber coupler 230 is connected to the output end of the fiber wavelength division multiplexer 220, and the input and output port fibers may be 10/125 μm, and the splitting ratio may be selected to be 50:50. For injecting the initial signal light into the fiber amplifier 240 while monitoring the system.

According to an embodiment of the present disclosure, the seed signal light and the out-of-target injection signal light enter the optical fiber wavelength division multiplexer 220; the initial signal light including the seed signal light and the target external injection signal light is output from the optical fiber wavelength division multiplexer 220, and then enters the second optical fiber coupler 230, and is output from two output optical fiber ports of the second optical fiber coupler 230; the optical fiber amplifier 240 receives the initial signal light outputted from the second optical fiber coupler 230, and amplifies the initial signal light to obtain a target signal light.

Fig. 7 schematically illustrates a block diagram of a second fiber optic coupler according to an embodiment of the present disclosure.

As shown in fig. 7, the second fiber coupler 230 includes a fourth port P4, a fifth port P5, a sixth port P6, and a seventh port P7.

The fourth port P4 is configured to receive the initial signal light.

The fifth port P5 is configured to output the initial signal light.

The sixth port P6 is configured to monitor the state of the initial signal light.

The seventh port P7 is configured to monitor spontaneous emission noise generated inside the pulsed laser 200.

According to the embodiment of the disclosure, the second optical fiber coupler 230 is a two-way input and output, the sixth port P6 can monitor the states of the external injection signal light and the seed signal light, and the seventh port P7 can monitor the backward spontaneous emission noise generated inside the system, so that the safety and reliability of the system can be ensured.

Fig. 8 schematically illustrates a block diagram of a fiber amplifier according to an embodiment of the present disclosure.

As shown in fig. 8, the fiber amplifier 240 includes a second pump source 241, a second combiner 242, a third gain fiber 243, a fiber isolator 244, and a fiber end cap 245.

The second pump source 241 is configured to generate the second pump light.

The second beam combiner 242 is configured to receive the initial signal light and the second pump light, and obtain intermediate signal light including the initial signal light and the pump signal light.

The third gain fiber 243 is configured to gain-amplify the initial signal light of the intermediate signal light to obtain the target signal light.

The optical fiber isolator 244 is configured to isolate the return signal light and receive the target signal light.

The optical fiber end cap 245 is configured to receive the target signal light output from the optical fiber isolator 244 and output the target signal light.

According to an embodiment of the present disclosure, the second pump source 241 may be a semiconductor laser having a center wavelength of 976nm, and the generated second pump light may be excited in the third gain fiber 243 to pump particles in the third gain fiber 243 from a ground state to a high energy level to gain-amplify the initial signal light. The second pump source 241 may be a semiconductor laser, a solid state laser, or a fiber laser, and its center wavelength is located in the absorption spectrum of the gain fiber. The selection of the second pump source 241 is not limited in this disclosure, and may be selected according to actual needs by those skilled in the art.

According to embodiments of the present disclosure, the second pump source 241 may be provided as a counter pump with a non-fixed position, reducing the accumulation of nonlinearities, and improving the pulse compression performance of the pulse laser 200.

According to an embodiment of the present disclosure, the second beam combiner 242 may be an (n+1) ×1 type signal/pump beam combiner, and the specifications may be a signal arm 10/125 μm and a pump arm 105/125 μm.

According to an embodiment of the present disclosure, the third gain fiber 243 may be a rare earth doped gain fiber, an ytterbium doped double clad fiber of 10/125 μm gauge. The doping element may be ytterbium, but the disclosure is not limited thereto, and one skilled in the art may select according to actual needs.

According to embodiments of the present disclosure, the fiber optic isolator 244 may be a polarization independent isolator.

The fiber end cap 245 may be 155/250 μm in size according to embodiments of the present disclosure.

According to the embodiment of the present disclosure, the initial signal light enters the third gain optical fiber 243 through the second beam combiner 242, and simultaneously, the second pump light with the center wavelength of 976nm generated by the second pump source 241 is injected together with the initial signal light from the second beam combiner 242; the second pump light enters the third gain optical fiber 243 to generate particle number inversion, after the initial signal light enters the third gain optical fiber 243, the target external injection signal light extracts the upper energy level particle number generated by the particle number inversion, and the target external injection signal light and the seed signal light are amplified simultaneously to inhibit the spontaneous emission of the system, so that the spontaneous emission amplifying process is effectively reduced, and the seed signal light realizes larger gain.

According to the embodiment of the disclosure, when no target external injection signal light is injected into the system, only seed signal light gain and amplified spontaneous emission exist in the system, the spontaneous emission section is larger than the signal radiation section, and the spontaneous emission content generated by amplification is rapidly increased in the process of gradually increasing the pumping current until the lasing state is reached, which is the upper operation limit of the system. In the present disclosure, by injecting the off-target injection signal light between pulses, since the modulator 130 is positioned at a position where the inverted population is not sufficiently absorbed, it is possible to rob the gain divided by the spontaneous emission, that is, absorb the inverted population not sufficiently extracted by the seed signal light, delay the spontaneous emission build-up until the lasing process is generated, thereby enabling the signal light to be further amplified.

FIG. 9 schematically illustrates a schematic diagram of an external injection signal based pulsed laser amplification system under an external modulation based linear resonator according to an embodiment of the present disclosure; fig. 10 schematically illustrates a schematic diagram of an external injection signal based pulsed laser amplification system under an internal modulation based linear resonator according to an embodiment of the present disclosure.

As shown in fig. 9, the first pump light generated by the first pump source 110 enters a linear cavity through the first beam combiner 150, and the linear cavity is composed of a first bragg grating 121, a first gain fiber 122 and a second bragg grating 123. The first pump light enters the first bragg grating 121, is absorbed by the first gain fiber 122, generates particle number inversion, generates spontaneous emission signal light, and enters the second bragg grating 123; since the center wavelength of the first bragg grating 121 is 1030nm, the reflectivity R is greater than 0.99, the initial external injection signal of 976nm is in a transmission state, a high-reflection effect is generated for 1030nm light, a filtering effect is generated for the arriving spontaneous emission signal light, the second bragg grating 123 is a semi-reflection semi-transmission grating, a filtering effect is generated for the arriving spontaneous emission signal light, a partial reflection and partial transmission effect is generated for the arriving 1030nm light, a transmission effect is generated for light of other wave bands such as 976nm, and after the filtered spontaneous emission signal light returns to the gain fiber, the intermediate external injection signal light with the center wavelength within the bandwidth of the bragg grating is generated after continuous oscillation. The intermediate external injection signal light passes through the modulator 130, then outputs the target external injection signal light with adjustable repetition frequency of 1Hz-100KHz, and then adjusts the power through the attenuator 140. The attenuator 140 is used for adjusting the post injection pulse laser 200, so that the flexibility of adjusting the signal light injected outside the target is increased, and the flexibility of adjusting the whole system is further improved. The seed optical signal and the out-of-target injection signal light enter the optical fiber wavelength division multiplexer 220; the initial signal light including the seed light signal and the target external injection signal light outputted from the optical fiber wavelength division multiplexer 220 enters the fourth port P4 of the second optical fiber coupler 230, and is outputted from the fifth port P5 of the second optical fiber coupler 230 to the second beam combiner 242. The target external injection signal light and the seed signal light enter the amplifying system through the second optical fiber coupler 230, the second optical fiber coupler 230 is in two-way input and output, the sixth port P6 can detect the states of the target external injection signal light and the seed signal light, the seventh port P7 can monitor the backward spontaneous radiation noise generated in the system, and the safety and the reliability of the system can be ensured. The initial signal light and the second pump light generated by the second pump source 241 are input to the third gain optical fiber 243 together, the second pump light enters the third gain optical fiber 243 to generate particle number inversion, the target external injection signal light extracts upper energy level particle number, the target external injection signal light and the seed signal light are amplified simultaneously, the spontaneous emission of the system is restrained, the spontaneous emission amplifying process is effectively reduced, and the seed signal light achieves larger gain.

As shown in fig. 10, the modulator 130 may further form a linear resonant cavity based on internal modulation together with the first bragg grating 121, the first gain fiber 122, and the second bragg grating 123, and output the target external injection signal during the period in which the modulator 130 is turned on. After the target external injection light is input to the pulse laser 200, the spontaneous emission noise suppression flow of the target external injection signal light to the system is the same as that of the linear resonant cavity shown in fig. 9, and will not be described herein.

FIG. 11 schematically illustrates a schematic diagram of an external injection signal based pulsed laser amplification system under an external modulation based ring resonator according to an embodiment of the present disclosure; fig. 12 schematically illustrates a schematic diagram of an external injection signal based pulsed laser amplification system under an internal modulation based ring resonator according to an embodiment of the present disclosure.

As shown in fig. 11, the first pump light generated by the first pump source 110 enters the ring resonator through the first beam combiner 150, and the ring resonator is composed of the second gain fiber 124, the circulator 125, the third bragg grating 126, and the first fiber coupler 127. The first pump light enters the second gain optical fiber 124, is absorbed by the second gain optical fiber to generate particle number inversion and form spontaneous emission signal light, the spontaneous emission signal light enters the first port P1 of the circulator 125, the spontaneous emission signal light exits from the second port P2 of the circulator 125 to the third bragg grating 126, and since the center wavelength of the third bragg grating 126 is 1030nm, the reflectivity R is greater than 0.99, the initial external injection signal of 976nm is in a transmission state, a high-reflection effect is generated for 1030nm light, and 1030nm light in the spontaneous emission signal light is reflected by the third bragg grating 126 and then is output from the third port P3 of the circulator 125. The 1030nm light output from the third port P3 enters the first optical fiber coupler 127, 30% of the light returns to the ring cavity internal reference oscillation process, 70% of the signal light is output, and the intermediate external injection signal light is obtained and input to the modulator 130. The intermediate external injection signal light passes through the modulator 130, then outputs the target external injection signal light with adjustable repetition frequency of 1Hz-100KHz, and then adjusts the power through the attenuator 140. After the target external injection light is input to the pulse laser 200, the spontaneous emission noise suppression flow of the target external injection signal light to the system is the same as that of the linear resonant cavity shown in fig. 9, and will not be described herein.

As shown in fig. 12, the modulator 130 may further form an internal modulation-based ring resonator with the second gain fiber 124, the circulator 125, the third bragg grating 126, and the first fiber coupler 127, outputting an external injection signal of interest during the time the modulator 130 is on. After the target external injection light is input to the pulse laser 200, the spontaneous emission noise suppression flow of the target external injection signal light to the system is the same as that of the linear resonant cavity shown in fig. 9, and will not be described herein.

According to the embodiment of the disclosure, by using the external injection signal, the mode that the target external injection signal light and the seed signal light enter the optical fiber amplifier 240 simultaneously is realized, and the target external injection signal light absorbs the inverted particle number which cannot be completely extracted by the seed signal light, so that spontaneous radiation noise lasing in the system is established later, and the signal light output is further improved.

Fig. 13 schematically illustrates a flow chart of a pulsed laser amplification method based on an external injection signal according to an embodiment of the present disclosure.

As shown in fig. 13, the method includes operations S1310 to S1340:

in operation S1310, a first pump light is generated.

In operation S1320, the resonant cavity absorbs the first pump light, generates spontaneous emission based on the population inversion, and screens out the intermediate external injection signal light.

In operation S1330, the intermediate external-injection signal light is modulated to obtain the target external-injection signal light.

In operation S1340, the initial signal light including the out-of-target injection signal light and the seed signal light in the pulse laser is gain-amplified based on the pulse laser, and the target signal light is output.

According to an embodiment of the present disclosure, gain-amplifying an initial signal light based on a pulse laser, outputting a target signal light, includes:

generating a second pump light.

Intermediate signal light including the initial signal light and the pump signal light is obtained.

And performing gain amplification on the intermediate signal light to obtain target signal light.

The return light is isolated by the fiber isolator and the target signal light is output by the fiber end cap.

According to the embodiment of the disclosure, the resonant cavity absorbs the first pump light, spontaneous radiation occurs based on population inversion to obtain continuous oscillation, that is, intermediate external injection signal light, and the time domain of the intermediate external injection signal light is adjusted to obtain target external injection signal light at a position where the population inversion is not completely extracted. The out-of-target injection signal light and the seed signal light are input together as initial signal light into the optical fiber amplifier of the pulse laser. The second pump light and the initial signal light are subjected to gain amplification, in the amplification process, the number of inversion particles which are not completely extracted by the signal light is injected outside the target, the spontaneous radiation noise of the system is restrained, and finally the target signal light is output.

According to the embodiment of the disclosure, the external injection signal light is obtained by using an external injection mode, and when the initial signal light is amplified in gain, the external injection signal light is used for absorbing the inverted particle number of the seed signal light which cannot be completely extracted, so that the spontaneous radiation noise of the system is restrained, the problem of reduced signal-to-noise ratio of the system is further caused, the upper limit of the power and energy of the signal light in the system is improved, and meanwhile, the safety and reliability of the system can be ensured.

Those skilled in the art will appreciate that the features recited in the various embodiments of the disclosure and/or in the claims may be provided in a variety of combinations and/or combinations, even if such combinations or combinations are not explicitly recited in the disclosure. In particular, the features recited in the various embodiments of the present disclosure and/or the claims may be variously combined and/or combined without departing from the spirit and teachings of the present disclosure. All such combinations and/or combinations fall within the scope of the present disclosure.

The embodiments of the present disclosure are described above. However, these examples are for illustrative purposes only and are not intended to limit the scope of the present disclosure. Although the embodiments are described above separately, this does not mean that the measures in the embodiments cannot be used advantageously in combination. The scope of the disclosure is defined by the appended claims and equivalents thereof. Various alternatives and modifications can be made by those skilled in the art without departing from the scope of the disclosure, and such alternatives and modifications are intended to fall within the scope of the disclosure.

Claims (10)

1. A pulsed laser amplification system based on an external injection signal, comprising:

an external injection signal device comprising:

a first pump source configured to generate a first pump light;

the resonant cavity is configured to absorb the first pump light, generate spontaneous radiation based on particle number inversion and obtain middle external injection signal light;

the modulator is configured to modulate the intermediate external injection signal light to obtain target external injection signal light; and

an attenuator configured to adjust the power of the out-of-target injection signal light;

and a pulse laser configured to gain-amplify an initial signal light including the out-of-target injection signal light and seed signal light in the pulse laser, and output a target signal light.

2. The exo-implant based pulsed laser amplification system of claim 1, wherein the exo-implant signal device further comprises:

a first beam combiner configured to input the first pump light to the resonant cavity.

3. The external-injection-based pulsed laser amplification system of claim 1, wherein the resonant cavity comprises a linear resonant cavity and a ring resonant cavity.

4. The external-injection-based pulsed laser amplification system of claim 3, wherein the linear resonant cavity comprises:

a first bragg grating configured to receive the first pump light;

the first gain optical fiber is configured to absorb the first pump light, generate particle number inversion and obtain spontaneous radiation signal light;

and the second Bragg grating is configured to screen the spontaneous emission signal light based on bandwidths of the first Bragg grating and the second Bragg grating, and continuously oscillate the spontaneous emission signal light together with the first Bragg grating to obtain middle external injection signal light.

5. The external-injection-based pulsed laser amplification system of claim 3, wherein the ring resonator comprises:

the second gain optical fiber is configured to absorb the first pump light and generate particle number inversion to obtain the spontaneous emission signal light;

a circulator, comprising:

a first port configured to receive the spontaneous emission signal light;

a second port that receives the spontaneous emission signal light output by the first port; and

a third port configured to receive the spontaneous emission signal light reflected by a third bragg grating;

The third Bragg grating is configured to receive the spontaneous emission signal light output by the second port, screen the spontaneous emission signal light based on the bandwidth of the third Bragg grating, and reflect the screened spontaneous emission signal light to the second port; and

a first fiber coupler configured to receive the reflected spontaneous emission signal light to obtain the intermediate external injection signal light.

6. The exo-implant based pulsed laser amplification system of claim 1, wherein the pulsed laser comprises:

a seed light source configured to generate the seed signal light;

a fiber wavelength division multiplexer configured to receive an initial signal light including the seed signal light and the out-of-target injection signal light;

a second optical fiber coupler configured to receive the initial signal light and output; and

and the optical fiber amplifier is configured to receive the initial signal light output by the second optical fiber coupler, amplify the initial signal light and obtain the target signal light.

7. The exo-injection based pulsed laser amplification system of claim 6, wherein the second fiber coupler comprises:

A fourth port configured to receive the initial signal light;

a fifth port configured to output the initial signal light;

a sixth port configured to monitor a state of the initial signal light; and

a seventh port configured to monitor spontaneous emission noise generated inside the pulsed laser.

8. The exo-implant based pulsed laser amplification system of claim 6, wherein the fiber amplifier comprises:

a second pump source configured to generate a second pump light;

a second beam combiner configured to receive the initial signal light and the second pump light, and obtain an intermediate signal light including the initial signal light and the second pump light;

the third gain optical fiber is configured to perform gain amplification on the initial signal light of the intermediate signal light to obtain the target signal light;

an optical fiber isolator configured to isolate return signal light and receive the target signal light; and

and an optical fiber end cap configured to receive the target signal light output from the optical fiber isolator and output the target signal light.

9. A pulsed laser amplification method based on an external injection signal, applied to the pulsed laser amplification system based on an external injection signal as claimed in any one of claims 1 to 8, the method comprising:

Generating first pump light;

the resonant cavity absorbs the first pump light, spontaneous radiation is generated based on particle number inversion, and intermediate external injection signal light is screened out;

modulating the middle external injection signal light to obtain target external injection signal light;

and amplifying the initial signal light based on a pulse laser to output target signal light, wherein the initial signal light comprises the target external injection signal light and seed signal light in the pulse laser.

10. The external-injection-based pulse laser amplification method as set forth in claim 9, wherein the pulse-based laser gain-amplifies the initial signal light to output the target signal light, comprising:

generating a second pump light;

obtaining intermediate signal light comprising the initial signal light and the second pump light;

gain amplification is carried out on the intermediate signal light to obtain the target signal light;

the return light is isolated by the fiber isolator and the target signal light is output by the fiber end cap.