CN115513764B - All-optical Q-switched switch, all-optical Q-switched laser and pulse laser output method thereof - Google Patents

Abstract

The present invention discloses an all-optical Q-switched switch, an all-optical Q-switched laser and a pulse laser output method thereof. The all-optical Q-switched switch comprises: a control light source for generating control light with adjustable repetition frequency and power waveform; a coupler for transmitting the connected intracavity laser to a combiner and a second reflector and outputting the modulated light and the intracavity laser after interference to a resonant cavity; a combiner for combining the connected intracavity laser with the control light and outputting them to a gas-filled hollow-core optical fiber; a gas-filled hollow-core optical fiber for modulating the combined light under the control of the control light to obtain modulated light and transmitting it to a first reflector; a first reflector for reflecting the modulated light after interference from the gas-filled hollow-core optical fiber and the combiner to a coupler; and a second reflector for reflecting the intracavity laser after interference to a coupler. The present invention realizes the full fiberization of the intracavity laser optical path, and has the advantages of wide working band, high tolerance power, compact structure and low insertion loss.

Description

All-optical Q-switched switch, all-optical Q-switched laser and pulse laser output method thereof

Technical Field

The invention relates to the technical field of laser devices, and in particular to an all-optical Q-switched switch, an all-optical Q-switched laser and a pulse laser output method thereof.

Background technique

Q-switched pulse lasers play an important role in material processing, lidar ranging, laser-induced breakdown spectroscopy, medical treatment and other fields. The basic principle of Q-switched pulse lasers is to modulate the loss in the laser resonant cavity. When the Q switch is closed and the loss in the cavity is high, the laser oscillation threshold cannot be reached. Under the excitation of the pump source, the number of particles in the upper energy level gradually accumulates. At this time, the Q switch is turned on, the loss in the cavity is reduced, and the number of inverted particles in the upper energy level is much higher than the laser oscillation threshold. It quickly transitions to the lower energy level through stimulated radiation, and the stored energy is released in the form of short pulses, thereby obtaining a short-pulse laser output with high peak power.

Actively Q-switched fiber lasers have been widely used in industrial marking and other scenarios due to their advantages such as adjustable repetition rate, compact structure, easy operation and maintenance, and stable output. Currently, Q-switched switches mainly use electro-optical and acousto-optic modulators with pigtail output. These electrical modulators have the following defects: their compactness and insertion loss are poor compared to all-fiber devices; the electro-optical and acousto-optic crystals have relatively low power tolerance, which limits the increase in the peak power of the laser; and their operating band is relatively narrow.

Therefore, the prior art still needs to be improved and developed.

Summary of the invention

In view of the above-mentioned deficiencies in the prior art, the object of the present invention is to provide an all-optical Q-switched switch, an all-optical Q-switched laser and a pulsed laser output method thereof, so as to solve the problems that the existing Q-switched switch using electro-optical and acousto-optic modulators with pigtail output have a gap in compactness, insertion loss, low tolerable power and narrow operating band compared with all-fiber devices.

The technical solution of the present invention is as follows:

An all-optical Q-switching switch comprises: a control light source, a combiner, a gas-filled hollow-core optical fiber, a first reflector, a second reflector and a coupler; wherein:

The control light source is connected to the combiner and is used to generate control light with adjustable repetition frequency and power waveform and transmit it to the combiner;

The coupler is connected to the combiner and the second reflector respectively, and is used to transmit the connected intra-cavity laser to the combiner and the second reflector respectively;

The combiner is connected to the gas-filled hollow-core optical fiber and the coupler respectively, and is used for combining the connected intracavity laser with the control light and then outputting the combined light to the gas-filled hollow-core optical fiber;

The gas-filled hollow-core optical fiber is connected to the combiner and the first reflector, respectively, and is used to modulate the combined light under the control of the control light to obtain modulated light and transmit the modulated light to the first reflector;

The first reflector is used to reflect the modulated light after interference from the gas-filled hollow core optical fiber and the combiner to the coupler in sequence;

The second reflector is used to reflect the intracavity laser after interference to the coupler;

The coupler is also used to output the modulated light and the intra-cavity laser after interference to the resonant cavity;

The loss of the all-optical Q-switched switch is modulated by modulating the phase of the modulated light.

According to a further configuration of the present invention, the coupler comprises: an input port, an output port, a first input/output port and a second input/output port; wherein,

The input port is connected to the resonant cavity and receives the intracavity laser output by the resonant cavity;

The first input/output port is connected to the combiner, the second input/output port is connected to the second reflector, and the intracavity laser is split into two beams via the first input/output port and the second input/output port and then output to the combiner and the second reflector respectively;

The output port is connected to the resonant cavity, and the modulated light reflected by the first reflector and the intra-cavity laser reflected by the second reflector enter the coupler through the first input/output port and the second input/output port respectively, and are output to the resonant cavity from the output port.

According to a further configuration of the present invention, the core light-guiding region of the gas-filled hollow-core optical fiber is a gas region, and the gas includes acetylene or methane; wherein the filling pressure of the gas is 0.1-5 bar.

According to a further configuration of the present invention, the length of the gas-filled hollow-core optical fiber is 1-100 cm, and the core diameter is 5-100 μm.

According to a further configuration of the present invention, the average output power of the control light source is greater than or equal to 10 milliwatts; and the wavelength difference between the operating wavelength of the control light source and the operating wavelength of the gas-filled hollow-core optical fiber is less than 1 nanometer.

According to a further configuration of the present invention, the combining mode of the combiner includes wavelength combining and energy combining; and the average withstand power of the combiner is greater than or equal to 100 milliwatts.

According to a further configuration of the present invention, the reflectivity of the first reflector and the second reflector are both greater than or equal to 50%.

Based on the same inventive concept, the present invention also provides a fully Q-switched laser, which comprises: a pump light source, a resonant cavity and the all-optical Q-switched switch as described above; wherein,

The pump light source is connected to the resonant cavity and is used to generate pump light and transmit it to the resonant cavity;

The resonant cavity is connected to the pump light source and the all-optical Q-switched switch respectively, and is used to output the intracavity laser to the all-optical Q-switched switch according to the pump light;

The all-optical Q-switched switch is used to obtain modulated light by modulating the combined light beam with the control light, and output the modulated light to the resonant cavity after interference with the laser in the cavity, so as to modulate the loss of the resonant cavity.

According to a further configuration of the present invention, the resonant cavity comprises: a first wavelength division multiplexer, a first doped optical fiber, an isolator and an output coupler; wherein

The first wavelength division multiplexer is connected to the pump light source, the first doped optical fiber and the output coupler respectively;

The first doped optical fiber is connected to the first wavelength division multiplexer and the isolator respectively;

The isolator is connected to the input end of the coupler;

The output coupler is connected to the output end of the coupler;

Alternatively, the resonant cavity comprises: a high-reflection fiber Bragg grating, a second wavelength division multiplexer, a second doped fiber and a low-reflection fiber Bragg grating; wherein,

The second wavelength division multiplexer is connected to the pump light source, the high reflection Bragg grating and the second doped optical fiber respectively;

The second doped optical fiber is connected to the input end of the coupler;

The low-reflection Bragg grating is connected to the output end of the coupler.

Based on the same inventive concept, the present invention also provides a pulse laser output method applied to the all-optical actively Q-switched laser as described above, which comprises:

The pump light generated by the pump light source outputs the intracavity laser to the coupler after passing through the resonant cavity and is transmitted in two ways through the coupler to the combiner and the second reflector respectively;

The control light source generates control light and transmits the control light to the combiner;

The combiner combines the control light with the intracavity laser and then outputs the combined light to the gas-filled hollow-core optical fiber, and then outputs the modulated light after passing through the gas-filled hollow-core optical fiber;

The modulated light and the intracavity laser after interference are reflected to the coupler by the first reflector and the second reflector, and output from the coupler to the resonant cavity, so as to modulate the loss of the resonant cavity and output pulsed laser.

The present invention provides an all-optical Q-switched switch, an all-optical Q-switched laser and a pulsed laser output method thereof. The pump light generated by the pump light source outputs the intracavity laser to the coupler after passing through the resonant cavity and is respectively transmitted to the combiner and the second reflector in two ways through the coupler. At the same time, the control light source is controlled to generate control light and transmit it to the combiner. The combiner then combines the control light with the intracavity laser and outputs the combined light to the gas-filled hollow-core fiber, and outputs the modulated light after passing through the gas-filled hollow-core fiber. The modulated light after interference is then reflected to the coupler and the intracavity laser through the first reflector and the second reflector, and then outputted from the coupler to the resonant cavity, so as to modulate the loss of the resonant cavity and output the pulsed laser. It can be seen that the all-optical Q-switched switch provided by the present invention is an all-fiber structure, which ensures the all-fiberization of the resonant cavity, so as to make the fiber laser structure more compact and the insertion loss lower. In addition, the all-optical Q-switching switch can operate at any wavelength in the light-guiding band of gas-filled hollow-core optical fiber where there is no filling gas absorption line. It is not affected by the absorption and low damage threshold of traditional electro-optical and acousto-optic crystal materials. The operating band can cover from visible light to mid-infrared. It not only has a wide operating band, but also can tolerate high optical power.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary personnel in this field, other drawings can be obtained based on the structures shown in these drawings without paying any creative work.

FIG1 is a schematic diagram of the structure of an all-optical Q-switched laser in one embodiment of the present invention.

FIG. 2 is a diagram showing changes in the power of the light source controlled by the present invention and the output power of the all-optical Q-switching switch.

FIG3 is a schematic cross-sectional view of a gas-filled hollow core optical fiber according to an embodiment of the present invention.

FIG. 4 is a diagram of output laser pulses at a repetition rate of 90 kHz in one embodiment of the present invention.

FIG. 5 is a diagram of output laser pulses at different repetition rates in one embodiment of the present invention.

FIG. 6 is a schematic diagram of the structure of an all-optical Q-switched laser in another embodiment of the present invention.

FIG. 7 is a schematic flow chart of a pulse laser output method of an all-optical Q-switched laser in the present invention.

The marks in the accompanying drawings are: 100, pump light source; 200, resonant cavity; 210, first wavelength division multiplexer; 220, first doped optical fiber; 230, isolator; 240, output coupler; 250, high-reflection FBG; 260, second wavelength division multiplexer; 270, second doped optical fiber; 280, low-reflection FBG; 300, all-optical Q-switch; 310, control light source; 320, combiner; 330, gas-filled hollow core optical fiber; 340, first reflector; 350, second reflector; 360, coupler.

Detailed ways

The present invention provides an all-optical Q-switched switch, an all-optical Q-switched laser and a pulsed laser output method thereof. In order to make the purpose, technical solution and effect of the present invention clearer and more specific, the present invention is further described in detail with reference to the accompanying drawings and examples. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

In the embodiments and the scope of the patent application, unless the text specifically defines the article, "a", "an", "the" and "the" may also include plural forms. If there are descriptions involving "first", "second", etc. in the embodiments of the present invention, the descriptions of "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" or "second" may explicitly or implicitly include at least one of the features.

It should be further understood that the term "comprising" used in the specification of the present invention refers to the presence of the features, integers, steps, operations, elements and/or components, but does not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components and/or groups thereof. It should be understood that when we refer to an element as being "connected" or "coupled" to another element, it can be directly connected or coupled to the other element, or there can be intermediate elements. In addition, the "connection" or "coupling" used herein can include wireless connection or wireless coupling. The term "and/or" used herein includes all or any unit and all combinations of one or more associated listed items.

It will be understood by those skilled in the art that, unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as those generally understood by those skilled in the art in the art to which the present invention belongs. It should also be understood that terms such as those defined in general dictionaries should be understood to have meanings consistent with the meanings in the context of the prior art, and will not be interpreted with idealized or overly formal meanings unless specifically defined as herein.

In addition, the technical solutions between the various embodiments can be combined with each other, but it must be based on the fact that ordinary technicians in the field can implement it. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

Please refer to FIG. 1 to FIG. 6 simultaneously. The present invention provides a preferred embodiment of an all-optical Q-switched laser.

As shown in FIG1 , the present invention provides an all-optical actively Q-switched laser, which includes: a pump light source 100, a resonant cavity 200, and an all-optical Q-switched switch 300. The pump light source 100 is connected to the resonant cavity 200, and is used to generate pump light and transmit it to the resonant cavity 200; the resonant cavity 200 is respectively connected to the pump light source 100 and the all-optical Q-switched switch 300, and is used to output the intracavity laser to the all-optical Q-switched switch 300 according to the pump light; the all-optical Q-switched switch 300 is used to modulate the intracavity laser to modulate the loss of the resonant cavity 200.

Specifically, the general pump light source 100 is a semiconductor laser diode or a fiber laser, and the operating wavelength is 980nm. The pump light generated by the pump light source 100 outputs the intracavity laser to the all-optical Q-switched switch 300 after passing through the resonant cavity 200, and then the all-optical Q-switched switch 300 modulates the intracavity laser to modulate the loss of the resonant cavity 200, so that the resonant cavity 200 outputs pulsed laser.

Please continue to refer to Figure 1. The all-optical Q-switched switch 300 includes: a control light source 310, a combiner 320, a gas-filled hollow-core optical fiber 330, a first reflector 340, a second reflector 350 and a coupler 360; wherein the control light source 310 is connected to the combiner 320 to generate a control light with an adjustable repetition frequency and power waveform and transmit it to the combiner 320; the coupler 360 is respectively connected to the combiner 320 and the second reflector 350 to transmit the connected intracavity laser to the combiner 320 and the second reflector 350 respectively; the combiner 320 is respectively connected to the gas-filled hollow-core optical fiber 330 and the coupler 360 to combine the connected intracavity laser with the control light and then output the combined light to the gas-filled hollow-core optical fiber. The gas-filled hollow core fiber 330; the gas-filled hollow core fiber 330 is connected to the combiner 320 and the first reflector 340 respectively, and is used to modulate the combined light under the control of the control light to obtain modulated light and transmit the modulated light to the first reflector 340; the first reflector 340 is used to reflect the modulated light after interference from the gas-filled hollow core fiber 330 and the combiner 320 to the coupler 360 in sequence; the second reflector 350 is used to reflect the intra-cavity laser after interference to the coupler 360; the coupler 360 is also used to output the modulated light after interference and the intra-cavity laser to the resonant cavity 200; wherein, the loss of the all-optical Q-switched switch 300 is modulated by modulating the phase of the modulated light.

Specifically, the control light source 310 is a power or wavelength tunable laser, and the power or wavelength of the control light source 310 can be modulated, and the modulation method includes internal modulation, external modulation, etc. In one implementation, the control light source 310 uses an externally modulated laser with an operating wavelength of 1530nm to generate a control light with adjustable repetition rate and power waveform.

The gas filled hollow core fiber 330 is filled with gas that can absorb the energy of the control light, and releases energy through a rapid relaxation process, causing the temperature and refractive index of the filling gas to change, thereby modulating the laser phase passing through the gas filled hollow core fiber 330, and after the interference of the interferometer (Michelson interferometer), the loss modulation of the all-optical Q-switched switch 300 is realized. Because the loss change of the all-optical Q-switched switch 300 is consistent with the intensity change of the control light source 310, that is, the change of the power or wavelength of the control light source 310 can cause the change of the laser phase in the gas filled hollow core fiber 330, thereby realizing the loss modulation of the all-optical Q-switched switch 300, that is, realizing the optically controlled Q-switched switch.

In a specific implementation, the pump light generated by the pump light source 100 outputs the intracavity laser to the coupler 360 after passing through the resonant cavity 200 and is respectively transmitted to the combiner 320 and the second reflector 350 in two ways through the coupler 360. At the same time, the control light source 310 generates control light and transmits it to the combiner 320. Thereafter, the combiner 320 combines the control light with the intracavity laser and outputs the combined light to the gas-filled hollow-core fiber 330, and outputs modulated light after passing through the gas-filled hollow-core fiber 330. Thereafter, the modulated light after interference and the intracavity laser are reflected to the coupler 360 through the first reflector 340 and the second reflector 350 and output from the coupler 360 to the resonant cavity 200, so as to modulate the loss of the resonant cavity 200 and output pulsed laser. The laser intensity of the two laser beams after interference is related to the phase difference between the two laser beams. The change in the intensity of the laser beam output by the coupler 360 can change the loss in the resonant cavity 200, thereby adjusting the Q value.

In addition, the loss change of the all-optical Q-switching switch 300 is consistent with the intensity change of the control light source 310. As shown in FIG2 , the control light source 310 outputs pulse light with a repetition rate of 5 kHz and a duty cycle of 50%, and the output of the all-optical Q-switching switch 300 also shows pulses with a repetition rate of 5 kHz and a duty cycle of 50%, proving that the loss of the all-optical Q-switching switch 300 can be modulated by modulating the power of the control light, thereby realizing the optically controlled Q-switching, wherein the response time constant of the all-optical Q-switching switch 300 is about 4.5 μs.

It can be seen that the all-optical Q-switched switch 300 provided by the present invention is an all-fiber structure, which realizes an optically controlled Q-switched switch, replaces the traditional electrically controlled Q-switched method with an optically controlled Q-switched method, ensures the full fiberization of the laser optical path of the resonant cavity 200, and there are no spatial optical elements in the resonant cavity 200, so that the fiber laser structure is more compact, the insertion loss is lower, it is resistant to vibration and has good beam quality. In addition, the all-optical Q-switched switch 300 can operate at any wavelength in the light-guiding band of the gas-filled hollow-core optical fiber 330 that does not have a filling gas absorption line, and is not affected by the absorption and low damage threshold of traditional electro-optical and acousto-optic crystal materials. The operating band can cover from visible light to mid-infrared bands. Not only is the operating band wide (the operating band of the electrically controlled Q-switched method is concentrated around 1064nm and 1550nm), but it also has a high tolerance to optical power. It can be used in actively Q-switched lasers to generate high-power pulsed lasers with adjustable pulse width and repetition rate. Moreover, because the all-optical Q-switched switch 300 is a light-controlled switch, the control light source 310 and the combiner 320 are connected by optical fiber, which can achieve photoelectric separation, thereby improving the anti-electromagnetic interference performance.

Please refer to Figure 1. In a further implementation of an embodiment, the coupler 360 includes: an input port, an output port, a first input/output port, and a second input/output port; wherein the input port is connected to the resonant cavity 200 and receives the intracavity laser output by the resonant cavity 200; the first input/output port is connected to the combiner 320, and the second input/output port is connected to the second reflector 350. The intracavity laser is divided into two beams by the first input/output port and the second input/output port and then output to the combiner 320 and the second reflector 350 respectively; the output port is connected to the resonant cavity 200, and the modulated light reflected by the first reflector 340 and the intracavity laser reflected by the second reflector 350 enter the coupler 360 via the first input/output port and the second input/output port respectively, and are output to the resonant cavity 200 from the output port.

Specifically, the coupler 360 is a four-port device, including an input port, an output port, a first input/output port, and a second input/output port. The intracavity laser outputted from the resonant cavity 200 enters the all-optical Q-switched switch 300 through the input port and is outputted to the combiner 320 and the second reflector 350 in two ways through the first input/output port and the second input/output port, respectively. Then, one way passes through the gas-filled hollow core fiber 330 and outputs modulated light to the first reflector 340, and the other way directly reaches the second reflector 350. Then, the lasers of the two ways are reflected from the first reflector 340 and the second reflector 350 to the first input/output port and the second input/output port after interference, and are outputted to the resonant cavity 200 through the output port. The intensity change of the laser outputted from the output port can change the loss and Q value in the resonant cavity 200.

Please refer to FIG. 1 and FIG. 3 . In a further implementation of an embodiment, the core light-guiding region of the gas-filled hollow-core optical fiber 330 is a gas region, and the gas includes acetylene or methane; wherein the filling pressure of the gas is 0.1-5 bar.

Specifically, the gas-filled hollow-core optical fiber 330 is filled with a gas that can absorb light energy, and the gas absorption line is aligned with the wavelength of the control light source 310 but away from the laser wavelength in the cavity. After the gas absorbs the energy of the control light source 310, it releases heat through the photothermal effect, causing the gas temperature and refractive index in the gas-filled hollow-core optical fiber 330 to change, thereby changing the laser phase passing through the gas-filled hollow-core optical fiber 330.

The filling gas has an absorption line with an absorption intensity of not less than 10-24 cm ^-1 /(molecule.cm ^-2 ) in the wavelength range of 1200-1700 nm, and the type of gas may be but not limited to acetylene, methane, etc. The filling pressure of the gas is 0.1-5 bar, for example, 3 bar.

Taking acetylene as an example, when the gas filled in the gas-filled hollow-core optical fiber 330 is acetylene, the filling concentration of acetylene is greater than 90%, the filling pressure is 1 atm (1.01325 bar), and the gas-filled hollow-core optical fiber 330 is mechanically fused with the single-mode optical fiber, and the acetylene gas is hermetically sealed in the gas-filled hollow-core optical fiber 330.

The length of the gas-filled hollow-core optical fiber 330 is 1-100 cm, such as 10 cm, 20 cm, or 50 cm, and the core diameter is 5-100 μm, such as 10 μm, 20 μm, or 50 μm.

The change of the power or wavelength of the control light source 310 can change the light energy absorbed by acetylene. When the laser wavelength 1530.371nm of the control light source 310 is aligned with the P(9) absorption line of acetylene, the acetylene gas absorbs the control light energy, releases energy through a rapid relaxation process, causes the temperature and refractive index of the acetylene gas to change, thereby modulating the laser phase output modulated light passing through the gas-filled hollow core fiber 330, and further realizing the loss modulation in the resonant cavity 200 after the interferometer. It can be seen that the all-optical Q-switched switch 300 is realized based on the photothermal effect of gas molecules, and thanks to the wide light-guiding band of the gas-filled hollow core fiber 330 and the narrow-band absorption characteristics of the gas, the all-optical Q-switched switch 300 can operate at any wavelength in the light-guiding band of the gas-filled hollow core fiber 330 without filling gas absorption lines, is not affected by the absorption and low damage threshold of traditional electro-optical and acousto-optic crystal materials, and the working band can cover from visible light to mid-infrared band, and has high tolerance to optical power, which is conducive to expanding the working wavelength range of the Q-switched laser and improving the peak power of the Q-switched laser.

In a further implementation of an embodiment, the output average power of the control light source 310 is greater than or equal to 10 milliwatts; the wavelength difference between the operating wavelength of the control light source 310 and the operating wavelength of the gas-filled hollow-core optical fiber 330 is less than 1 nanometer.

Specifically, the average power of the control light source 310 is greater than 10 mW to meet high-power output, and the operating wavelength of the control light source 310 is close to the absorption line of the gas-filled hollow-core optical fiber 330. For example, the wavelength difference between the operating wavelength of the control light source 310 and the operating wavelength of the gas-filled hollow-core optical fiber 330 is less than 1 nanometer, so that the gas in the gas-filled hollow-core optical fiber 330 can absorb light energy.

In a further implementation of an embodiment, the combining mode of the combiner 320 includes wavelength combining and energy combining; and the average withstand power of the combiner 320 is greater than or equal to 100 milliwatts.

Specifically, the combiner 320 is a wavelength division multiplexer or a pump combiner, and the combining modes of the combiner 320 include but are not limited to wavelength combining and energy combining, and can combine the control light output by the control light source 310 and the intracavity laser output by the resonant cavity 200 into one path for output. The average withstand power of the combiner 320 is greater than or equal to 100 milliwatts, and the withstand power is high.

In a further implementation of an embodiment, the reflectivity of the first reflector 340 and the second reflector 350 are both greater than or equal to 50%.

Specifically, the first reflector 340 and the second reflector 350 are both coated reflectors or Faraday rotators with pigtails, and the reflectivities of the first reflector 340 and the second reflector 350 are both high, above 50%, so that the energy of the modulated light and the intracavity laser reflected to the coupler 360 is sufficient. In one implementation, the reflectivities of the first reflector 340 and the second reflector 350 are both above 90%.

Please refer to Figure 1. In some embodiments, the resonant cavity 200 includes: a first wavelength division multiplexer 210, a first doped optical fiber 220, an isolator 230 and an output coupler 240; wherein the first wavelength division multiplexer 210 is respectively connected to the pump light source 100, the first doped optical fiber 220 and the output coupler 240; the first doped optical fiber 220 is respectively connected to the first wavelength division multiplexer 210 and the isolator 230; the isolator 230 is connected to the input end of the coupler 360; and the output coupler 240 is connected to the output end of the coupler 360.

Specifically, the first wavelength division multiplexer 210 , the first doped optical fiber 220 , the isolator 230 , the output coupler 240 and the all-optical Q-switched switch 300 form a ring laser resonant cavity 200 , and the quality factor can be modulated by the control light source 310 , that is, the loss of the resonant cavity 200 can be modulated.

The first doped optical fiber 220 is a gain optical fiber, which is a rare earth ion doped optical fiber, and may be, but is not limited to, ytterbium-doped optical fiber, bismuth-doped optical fiber, erbium-doped optical fiber, erbium-ytterbium co-doped optical fiber, thulium-doped optical fiber, or holmium-doped optical fiber.

Take the first doped fiber 220 as an erbium-doped fiber as an example. When the pump light output by the pump light source 100 enters the resonant cavity 200 after passing through the first wavelength division multiplexer 210 (working wavelength 980/1550nm), it is absorbed by the erbium ions in the erbium-doped fiber, and the erbium ions transition from a low energy level to a high energy level, and the number of particles is reversed. The control light source 310 makes the all-optical Q-switched switch 300 in a high-loss state, and the loss in the resonant cavity 200 is greater than the gain, and the laser oscillation condition cannot be achieved, so the upper energy level particles continue to accumulate. Thereafter, by changing the output power of the control light source 310, the all-optical Q-switched switch 300 is in a low-loss state, and the number of upper energy level particles is now much higher than the laser oscillation threshold, so a short pulse laser is quickly generated, and the laser energy leaves the resonant cavity 200 through the output coupler 240 (1:99), forming a short pulse output. As shown in FIG4 , FIG4 is a diagram of laser pulse output at a repetition rate of 90kHz. As can be seen from FIG4 , the pulse sequence is clear and stable, and the pulse width is about 1.4μs. As shown in FIG5 , FIG5 is a diagram of pulse output at different modulation frequencies. At frequencies of 10kHz-90kHz, they are all stable Q-switched pulses, and it can be seen that the pulse output is stable, wherein the repetition rate of the pulse is determined by the control light source 310 .

Please refer to Figure 6. In some embodiments, the resonant cavity 200 includes: a high-reflection FBG250 (fiber Bragg grating), a second wavelength division multiplexer 260, a second doped fiber 270 and a low-reflection FBG280; wherein the second wavelength division multiplexer 260 is connected to the pump light source 100, the high-reflection FBG250 and the second doped fiber 270 respectively; the second doped fiber 270 is connected to the input end of the coupler 360; and the low-reflection FBG280 is connected to the output end of the coupler 360.

Specifically, the high-reflection FBG250, the second wavelength division multiplexer 260, the second doped optical fiber 270, the low-reflection FBG280 and the all-optical Q-switched switch 300 constitute a linear laser resonant cavity 200 based on a fiber Bragg grating, and the quality factor can be modulated by the control light source 310, that is, the loss of the modulated resonant cavity 200. The principle of active Q-switching of the linear laser resonant cavity 200 is the same as that of the ring laser resonant cavity 200, and thus will not be described in detail.

Please refer to FIG. 7 . In some embodiments, the present invention further provides a pulse laser output method applied to the all-optical actively Q-switched laser as described above, which comprises the following steps:

S100, the pump light generated by the pump light source outputs the intracavity laser to the coupler after passing through the resonant cavity and is transmitted to the combiner and the second reflector in two paths through the coupler; the details are as described in an embodiment of an all-optical actively Q-switched laser and will not be repeated here.

S200, the control light source generates control light and transmits it to the combiner; the details are as described in an embodiment of an all-optical actively Q-switched laser, which will not be repeated here.

S300, the combiner combines the control light with the intra-cavity laser and outputs the combined light to the gas-filled hollow-core optical fiber, and outputs the modulated light after passing through the gas-filled hollow-core optical fiber; the details are as described in an embodiment of an all-optical actively Q-switched laser, which will not be repeated here.

S400, the first reflector and the second reflector reflect the modulated light and the intracavity laser after interference to the coupler, and output from the coupler to the resonant cavity to modulate the loss of the resonant cavity and output pulsed laser. The details are as described in an embodiment of an all-optical actively Q-switched laser, which will not be repeated here.

In summary, the all-optical Q-switched switch, all-optical Q-switched laser and pulse laser output method provided by the present invention have the following beneficial effects:

The all-optical Q-switch is an all-fiber structure, which ensures the all-fiberization of the resonant cavity, making the fiber laser structure more compact and the insertion loss lower;

The all-optical Q-switching switch can work at any wavelength in the light-guiding band of gas-filled hollow-core optical fibers without filling gas absorption lines. It is not affected by the absorption and low damage threshold of traditional electro-optical and acousto-optic crystal materials. The working band can cover the range from visible light to mid-infrared. It not only has a wide working band but also tolerates high optical power. It can be used in actively Q-switched lasers to generate high-power pulsed lasers with adjustable pulse width and repetition rate.

The all-optical Q-switched switch is a light-controlled switch, and the light-controlled light source and the combiner are connected by optical fiber, which can realize photoelectric separation, thereby improving the anti-electromagnetic interference performance.

It should be understood that the application of the present invention is not limited to the above examples. For ordinary technicians in this field, improvements or changes can be made based on the above description. All these improvements and changes should fall within the scope of protection of the claims attached to the present invention.

Claims (10)

1. An all-optical Q-switch, comprising: controlling a light source, a combiner, a gas filled hollow fiber, a first reflector, a second reflector and a coupler; wherein,

The control light source is connected with the wave combiner and is used for generating control light with heavy frequency and adjustable power waveform and transmitting the control light to the wave combiner;

the coupler is respectively connected with the wave combiner and the second reflecting mirror and is used for respectively transmitting the accessed laser in the cavity to the wave combiner and the second reflecting mirror;

The combiner is respectively connected with the gas-filled hollow optical fiber and the coupler and is used for combining the accessed laser in the cavity with the control light and then outputting combined light to the gas-filled hollow optical fiber;

The gas filling hollow optical fiber is respectively connected with the wave combiner and the first reflecting mirror and is used for modulating the combined beam light under the regulation and control of the control light to obtain modulated light and transmitting the modulated light to the first reflecting mirror;

The first reflecting mirror is used for reflecting the interfered modulated light to the coupler from the gas-filled hollow fiber and the combiner in sequence;

The second reflecting mirror is used for reflecting the interfered laser in the cavity to the coupler;

The coupler is also used for outputting the interfered modulated light and the laser in the cavity to a resonant cavity;

Wherein the loss of the all-optical Q-switched is modulated by modulating the phase of the modulated light.

2. The all-optical Q-switch of claim 1, wherein the coupler comprises: the device comprises an input port, an output port, a first input/output port and a second input/output port; wherein,

The input port is connected with the resonant cavity and is connected with the laser in the cavity output by the resonant cavity;

The first input/output port is connected with the wave combiner, the second input/output port is connected with the second reflecting mirror, and the laser in the cavity is divided into two beams by the first input/output port and the second input/output port and then is output to the wave combiner and the second reflecting mirror respectively;

The output port is connected with the resonant cavity, and the modulated light reflected by the first reflecting mirror and the laser in the cavity reflected by the second reflecting mirror enter the coupler through the first input/output port and the second input/output port respectively and are output to the resonant cavity from the output port.

3. The all-optical Q-switch of claim 1, wherein the core light guiding region of the gas-filled hollow-core optical fiber is a gas region, the gas comprising acetylene or methane; wherein the filling pressure of the gas is 0.1-5 bar.

4. The all-optical Q-switch of claim 3, wherein the gas-filled hollow-core fiber has a length of 1-100 cm and a core diameter of 5-100 microns.

5. The all-optical Q-switch of claim 4, wherein the control light source has an output average power of 10 milliwatts or greater; the wavelength difference between the working wavelength of the control light source and the working wavelength of the gas-filled hollow fiber is less than 1 nanometer.

6. The all-optical Q-switch according to claim 1, wherein the wave combining means of the wave combiner includes wavelength combining and energy combining; the average withstand power of the combiner is greater than or equal to 100 milliwatts.

7. The all-optical Q-switch of claim 1, wherein the first and second mirrors each have a reflectivity of 50% or greater.

8. An all-optical Q-switched laser, comprising: a pump light source, a resonant cavity and an all-optical Q-switch as claimed in any one of claims 1 to 7; wherein,

The pump light source is connected with the resonant cavity and is used for generating pump light and transmitting the pump light to the resonant cavity;

the resonant cavity is respectively connected with the pumping light source and the all-optical Q-switch and is used for outputting laser in the cavity to the all-optical Q-switch according to the pumping light;

the all-optical Q-switch is used for modulating the beam combining light through the control light to obtain modulated light, and outputting the modulated light and the laser in the cavity to the resonant cavity after interference so as to modulate the loss of the resonant cavity.

9. The all-optical Q-switched laser of claim 8, wherein the resonant cavity comprises: the device comprises a first wavelength division multiplexer, a first doped optical fiber, an isolator and an output coupler; wherein,

The first wavelength division multiplexer is respectively connected with the pumping light source, the first doped optical fiber and the output coupler;

the first doped optical fiber is connected with the first wavelength division multiplexer and the isolator respectively;

the isolator is connected with the input end of the coupler;

The output coupler is connected with the output end of the coupler;

or the resonant cavity comprises: a high anti-FBG, a second wavelength division multiplexer, a second doped fiber and a low anti-FBG; wherein,

The second wavelength division multiplexer is respectively connected with the pumping light source, the high-reflection FBG and the second doped optical fiber;

the second doped optical fiber is connected with the input end of the coupler;

the low anti-FBG is connected with the output end of the coupler.

10. A pulsed laser output method for use with an all-optical Q-switched laser as claimed in claim 8, comprising:

the pumping light generated by the pumping light source outputs laser in the cavity to the coupler after passing through the resonant cavity and is respectively transmitted to the combiner and the second reflector in two paths through the coupler;

The control light source generates control light and transmits the control light to the combiner;

The wave combiner combines the control light with the laser in the cavity and then outputs combined light to the gas-filled hollow fiber, and outputs modulated light after passing through the gas-filled hollow fiber;

The first reflecting mirror and the second reflecting mirror reflect the interfered modulated light and the laser in the cavity to the coupler and output the reflected light and the laser in the cavity from the coupler to the resonant cavity so as to modulate the loss of the resonant cavity and output pulse laser.