Laser and related equipment and method

Abstract

The embodiment of the invention discloses a laser and related equipment and method. The laser comprises a laser generation module, a first coupler and a reflective space structure composed of at least one reflective element, multiple paths of laser generated by the laser generation module form optical pulses in the first coupler through interference, the optical pulses are divided into two paths, one path of first optical pulse is transmitted to the reflective element, and the other path of first optical pulse is transmitted to the second coupler. And the other path of second optical pulse is output. The first light pulse is reflected back to the laser generating module by the reflecting element. The optical path of the optical pulse transmitted in the space can be changed by controlling the reflection element to move, so that the repetition frequency of the optical pulse generated by the laser generation module can be adjusted. It is understood that the back-and-forth optical path of the optical pulse in the space can be adjusted by controlling the reflection element to move, equivalently, the optical path of the optical pulse in the space is changed exponentially, and the repetition frequency of the optical pulse can be adjusted in a larger range, for example, large-range frequency modulation over 2 MHz can be achieved.

Description

Technical Field

[0001] This application relates to the field of lasers, and particularly to a laser and related devices and methods. Background Art

[0002] Femtosecond laser refers to a laser with a pulse width in the femtosecond order of magnitude in the time domain. Femtosecond laser is not monochromatic light, but is composed of a combination of light with continuously varying wavelengths near the central wavelength. By utilizing the spatial coherence of the continuously wavelength light within this range, a great compression in time is achieved, thereby realizing the output of femtosecond-order pulses. Lasers with femtosecond-order short pulses are usually realized by mode-locking technology.

[0003] The mode-locked fiber laser can output a periodic femtosecond pulse train. The pulse interval is the time period required for the laser to travel one round in the resonant cavity. Therefore, the period of the femtosecond laser pulse train is proportional to the cavity length of the laser resonant cavity. In the frequency domain, the output of the mode-locked laser is a series of equally spaced comb tooth structures, so it is also called an optical frequency comb. The spacing between two comb teeth is the repetition frequency of the laser. That is to say, the repetition frequency of the femtosecond laser pulse train is the reciprocal of the period. Therefore, in order to obtain a femtosecond laser pulse train with a locked repetition frequency, feedback control of the cavity length of the laser resonant cavity is required. However, on the basis of realizing the locking of the repetition frequency, the prior art does not provide a scheme for dynamically adjusting the repetition frequency over a large range and with high precision. Summary of the Invention

[0004] Embodiments of this application provide a laser and related devices and methods, which are beneficial to adjusting the repetition frequency of optical pulses over a larger range and improving the adjustment accuracy of the repetition frequency.

[0005] In a first aspect, embodiments of this application provide a laser. The laser includes: a laser emission device and a control device. The laser emission device includes a laser generation module, a first coupler, and a first reflection element. The laser generation module is used to generate a first laser and a second laser. The first coupler is used to interfere the first laser and the second laser to obtain an optical pulse, and the optical pulse includes a first optical pulse transmitted to the first reflection element and a second optical pulse output. The first reflection element is used to reflect the first optical pulse back to the laser generation module. The control device is used to adjust the optical path of the first optical pulse by controlling the movement of the first reflection element to adjust the repetition frequency of the optical pulse.

[0006] In this embodiment, by controlling the movement of the reflection element, the optical path of the optical pulse transmitted in space can be changed, so that the repetition frequency of the optical pulse generated by the laser generation module can be adjusted. Controlling the movement of the reflection element can adjust the optical path of the optical pulse traveling back and forth in space, which is equivalent to changing the optical path of the optical pulse in space by a multiple, facilitating a wider range of adjustment of the repetition frequency of the optical pulse. For example, a large-range change in the optical path of more than 60 mm can be achieved, and a large-range frequency modulation of more than 2 MHz can be achieved.

[0007] In some possible embodiments, the laser generation module includes a non-linear amplifying loop mirror (NALM) and a pump source. The NALM is connected to a first coupler. The pump source is used to output pump light to the NALM, and the NALM generates first laser light and second laser light according to the pump light. For example, the first laser light generated by the NALM travels clockwise in the NALM, and the second laser light generated by the NALM travels clockwise in the NALM. The first laser light and the second laser light undergo non-linear interference through the first coupler to obtain an optical pulse, and the optical pulse passing through the first coupler is divided into two paths, namely a first optical pulse transmitted to the first reflection element and a second optical pulse output. It should be understood that using the NALM reduces the mode-locking threshold and improves the mode-locking ability to resist changes in spatial length, and even when the optical path of the optical pulse is adjusted over a large range, the optical pulse can still be continuously generated.

[0008] In some possible embodiments, the NALM includes a wavelength division multiplexer (WDM) and a gain fiber. The WDM is used to couple the pump light output by the pump source to the gain fiber, and the gain fiber has an amplifying effect on light, which is beneficial for generating stable optical pulses.

[0009] In some possible embodiments, the NALM further includes a saturable absorber, which enhances the scalability of this solution.

[0010] In some possible embodiments, the laser emitting device further includes a second reflection element. The first reflection element is used to reflect the first optical pulse to the second reflection element, and then reflect the first optical pulse reflected by the second reflection element back to the laser generation module. The control device is further used to adjust the optical path of the first optical pulse by controlling the movement of the second reflection element. In this embodiment, by arranging multiple reflection elements in space, the optical path of the optical pulse in space can be adjusted over a larger range, which is more conducive to improving the adjustment range of the repetition frequency of the optical pulse.

[0011] In some possible embodiments, the laser emitting device further includes an optical fiber collimator, which is configured to collimate the first optical pulse from the first coupler. Among them, the collimated first optical pulse is transmitted in space towards the first reflecting element. It should be understood that by using the optical fiber collimator to obtain collimated spatial light, the diffusion of the light spot is small, and the reflected optical pulse is more conducive to being coupled into the optical fiber, which is beneficial to improving the mode-locking effect of the laser.

[0012] In some possible embodiments, the light beam output by the optical fiber collimator will first contract and then diverge. The collimation distance of the optical fiber collimator is the distance between the spatial position where the spot size is the same as the initial spot size and the optical fiber collimator. This distance can also be referred to as the working distance of the optical fiber collimator. The collimation distance of the optical fiber collimator is greater than the one-way distance of the first optical pulse transmitted in space. In this way, the spot size of the first optical pulse reflected back to the optical fiber collimator changes less and diffuses less compared to the initial spot size, which is more conducive to being coupled into the optical fiber and is beneficial to improving the mode-locking effect of the laser.

[0013] In some possible embodiments, the laser emitting device further includes a lens or diffractive optical elements (DOE), and the lens or DOE is located between the optical fiber collimator and the first reflecting element. The lens or DOE is configured to perform beam shaping on the first optical pulse from the optical fiber collimator and transmit the beam-shaped first optical pulse to the first reflecting element. The lens and DOE are used to perform beam shaping on the first optical pulse collimated by the optical fiber collimator to achieve an auxiliary collimation effect. The spot size of the first optical pulse transmitted to the position of the first reflecting element through the lens or DOE is the same as or close to the initial spot size output by the optical fiber collimator. In this way, the spot size of the first optical pulse reflected back to the optical fiber collimator changes less and diffuses less compared to the initial spot size, which is more conducive to being coupled into the optical fiber and is beneficial to improving the mode-locking effect of the laser.

[0014] In some possible embodiments, the second optical pulse is transmitted to the control device, and the laser emitting device further includes a piezoelectric ceramic transducer (PZT). The PZT is connected to the optical fiber collimator, and the control device is further configured to adjust the applied voltage of the PZT according to the second optical pulse to control the movement of the optical fiber collimator, so as to adjust the optical path of the first optical pulse, thereby quickly realizing the locking of the repetition frequency of the optical pulse.

[0015] In some possible embodiments, a second optical pulse is transmitted to the control device. The laser emitting device further includes a PZT, which is connected to the optical fiber in the laser generation module or the optical fiber for transmitting the first optical pulse. The control device is further configured to adjust the applied voltage of the PZT according to the second optical pulse to control the stretching of the optical fiber, so as to adjust the optical path of the optical pulse, thereby quickly realizing the locking of the repetition frequency of the optical pulse.

[0016] In some possible embodiments, the control device is specifically configured to control the movement of the first reflecting element according to the applied voltage of the PZT to adjust the optical path of the first optical pulse, thereby adjusting the repetition frequency of the optical pulse. That is to say, the control device adopts a serial control method for the PZT and the first reflecting element, that is, first adjusts the optical path of the optical pulse by controlling the PZT to achieve frequency locking. Based on the adjustment state of the PZT, if there is a risk of frequency unlocking, the movement of the first reflecting element can be further controlled to compensate for the optical path of the optical pulse, avoiding the situation of frequency unlocking during the frequency modulation process.

[0017] In some possible embodiments, the control device includes: a reference signal source, a photodetector, a mixer, a first control module, and a second control module. The reference signal source is configured to output a target reference signal. The photodetector is configured to convert the second optical pulse into an electrical signal. The mixer is configured to mix the target reference signal and the electrical signal to obtain a mixed signal. The first control module is configured to adjust the applied voltage of the PZT according to the mixed signal to control the movement of the fiber collimator, so as to adjust the optical path of the first optical pulse, so as to lock the repetition frequency of the optical pulse generated by the laser generation module to the frequency of the target reference signal. If the applied voltage of the PZT exceeds the preset voltage range, the second control module is configured to control the movement of the first reflecting element according to the applied voltage of the PZT and the preset voltage range to adjust the optical path of the first optical pulse, so as to adjust the repetition frequency of the optical pulse generated by the laser generation module. This embodiment provides a specific implementation method for adjusting the repetition frequency of the optical pulse by the control device, which can more finely adjust the repetition frequency of the optical pulse while achieving frequency locking, improving the adjustment accuracy of the repetition frequency and reducing the risk of frequency unlocking. It should be understood that in some possible scenarios, the first control module and the second control module may be two independent circuit boards respectively, or in some other possible scenarios, the first control module and the second control module may also be integrated together and implemented by a single controller.

[0018] In some possible embodiments, the control device further includes a filter. The filter is configured to filter the electrical signal. The mixer is configured to mix the target reference signal and the filtered electrical signal to obtain a mixed signal. Filtering can make the frequency error obtained after mixing more accurate.

[0019] In some possible embodiments, the frequency modulation step of the reference signal source from outputting an initial reference signal to outputting a target reference signal is less than a first preset value, where the first preset value is the frequency adjustment amount of the repetition frequency of the optical pulse corresponding to the maximum adjustment amount of the applied voltage of the PZT. That is to say, the frequency modulation step of the reference signal source cannot be too large, which can effectively avoid the occurrence of frequency unlocking.

[0020] In some possible embodiments, the frequency modulation step of the reference signal source from outputting an initial reference signal to outputting a target reference signal is greater than or equal to a second preset value, where the second preset value is the frequency adjustment amount of the repetition frequency of the optical pulse corresponding to the minimum distance of the displacement of the first reflection element. That is to say, the frequency modulation step of the reference signal source cannot be too small, which is beneficial to ensuring the speed of the frequency modulation process.

[0021] In some possible embodiments, the frequency adjustment amount of the repetition frequency of the optical pulse corresponding to the minimum distance of the displacement of the first reflection element is less than the frequency adjustment amount of the repetition frequency of the optical pulse corresponding to the maximum adjustment amount of the applied voltage of the PZT. That is to say, the adjustment amplitude for controlling the movement of the first reflection element cannot be too large, and it is necessary to ensure that frequency unlocking does not occur during the frequency modulation process.

[0022] In some possible embodiments, the laser emitting device further includes a second coupler. The second coupler is used for splitting the second optical pulse, where one of the optical pulses after splitting of the second optical pulse is transmitted to the control device, and the other optical pulse after splitting of the second optical pulse is emitted outward.

[0023] In a second aspect, an embodiment of the present application provides an electrical signal phase discrimination device, which includes a phase discriminator, a photodetector, and a laser as introduced in any one of the embodiments of the first aspect. The photodetector is used for converting the light output by the laser into a first electrical signal and transmitting the first electrical signal to the phase discriminator. The phase discriminator is used for determining the phase difference between the first electrical signal and the input second electrical signal.

[0024] In a third aspect, an embodiment of the present application provides an optical frequency comb device, which includes a laser beat frequency module, an initial frequency locking module, and a laser as introduced in any one of the embodiments of the first aspect. The laser beat frequency module is used for performing spectral broadening, frequency doubling, and beat frequency detection on the optical pulse emitted by the laser to obtain an initial frequency signal. The initial frequency locking module is used for outputting a control signal to the laser according to the initial frequency signal. The laser is used for locking the initial frequency according to the control signal and outputting an optical frequency comb signal.

[0025] In a fourth aspect, an embodiment of the present application provides an optical module. The optical module includes a laser, an electrical chip, and a modulator as introduced in any one of the embodiments of the first aspect. The electrical chip is used for driving the modulator to modulate the light emitted by the laser to obtain an optical signal.

[0026] In a fifth aspect, an embodiment of the present application provides an optical transmission device. The optical transmission device includes a wavelength division multiplexer and a plurality of optical modules as introduced in the fourth aspect. The wavelength division multiplexer is configured to multiplex the optical signals output by the plurality of optical modules and output the multiplexed optical signal.

[0027] In a sixth aspect, an embodiment of the present application provides a method for frequency modulation of an optical pulse. The method is applied to a laser, which includes a laser emission device and a control device. The laser emission device includes a laser generation module, a first coupler, and a first reflection element. The method for frequency modulation of an optical pulse includes: generating a first laser and a second laser through the laser generation module; obtaining an optical pulse by interfering the first laser and the second laser through the first coupler, where the optical pulse includes a first optical pulse transmitted to the first reflection element and a second optical pulse output; reflecting the first optical pulse back to the laser generation module through the first reflection element; and controlling the first reflection element to move through the control device to adjust the optical path of the first optical pulse.

[0028] In some possible implementation manners, the laser generation module includes a NALM and a pump source, and the NALM is connected to the first coupler. The method further includes: outputting pump light from the pump source to the NALM, and generating a first laser and a second laser through the NALM according to the pump light.

[0029] In some possible implementation manners, the NALM includes a wavelength division multiplexer WDM and a gain fiber. The method further includes: coupling the pump light output by the pump source to the gain fiber through the WDM.

[0030] In some possible implementation manners, the NALM further includes a saturable absorber.

[0031] In some possible implementation manners, the laser emission device further includes a second reflection element. The method further includes: reflecting the first optical pulse to the second reflection element through the first reflection element, and then reflecting the first optical pulse reflected by the second reflection element back to the laser generation module. The control device further controls the second reflection element to move to adjust the optical path of the first optical pulse.

[0032] In some possible implementation manners, the laser emission device further includes an optical fiber collimator. The method further includes: collimating the optical pulse from the first coupler through the optical fiber collimator, where the collimated first optical pulse is transmitted to the first reflection element in space.

[0033] In some possible embodiments, the light beam output by the fiber collimator will first contract and then diverge. The collimation distance of the fiber collimator is the distance between the spatial position where the spot size is the same as the initial spot size and the fiber collimator, and this distance can also be referred to as the working distance of the fiber collimator. The collimation distance of the fiber collimator is greater than the one-way distance that the first optical pulse travels in space. In this way, the change in the spot size of the first optical pulse reflected back to the fiber collimator is relatively small compared to the initial spot size and the diffusion is relatively small, which is more conducive to coupling into the fiber and is beneficial to improving the mode-locking effect of the laser.

[0034] In some possible embodiments, the laser emitting device further includes a lens or a DOE, and the lens or the DOE is located between the fiber collimator and the first reflecting element. The method further includes: shaping the beam of the first optical pulse from the fiber collimator through the lens or the DOE, and transmitting the beam-shaped first optical pulse to the first reflecting element. The lens and the DOE are used to shape the beam of the first optical pulse collimated by the fiber collimator to achieve an auxiliary collimation effect. The spot size of the first optical pulse transmitted to the position of the first reflecting element through the lens or the DOE is the same as or close to the initial spot size output by the fiber collimator. In this way, the change in the spot size of the first optical pulse reflected back to the fiber collimator is relatively small compared to the initial spot size and the diffusion is relatively small, which is more conducive to coupling into the fiber and is beneficial to improving the mode-locking effect of the laser.

[0035] In some possible embodiments, the second optical pulse is transmitted to the control device, and the laser emitting device further includes a PZT, and the PZT is connected to the fiber collimator. The method further includes: controlling the movement of the fiber collimator by adjusting the applied voltage of the PZT according to the second optical pulse through the control device to adjust the optical path of the first optical pulse.

[0036] In some possible embodiments, the second optical pulse is transmitted to the control device, and the laser emitting device further includes a PZT, and the PZT is connected to the fiber in the laser generation module or the fiber for transmitting the first optical pulse. The method further includes: controlling the stretching of the fiber by adjusting the applied voltage of the PZT according to the second optical pulse through the control device to adjust the optical path of the optical pulse.

[0037] In some possible embodiments, controlling the movement of the first reflecting element by the control device includes: controlling the movement of the first reflecting element according to the applied voltage of the PZT through the control device.

[0038] In some possible embodiments, the control device includes: a reference signal source, a photodetector, a mixer, a first control module, and a second control module. The method further includes: outputting a target reference signal through the reference signal source; converting a second optical pulse into an electrical signal through the photodetector; mixing the target reference signal and the electrical signal through the mixer to obtain a mixed signal; adjusting the applied voltage of the PZT according to the mixed signal through the first control module to control the movement of the fiber collimator, so as to adjust the optical path of the first optical pulse, so as to lock the repetition frequency of the optical pulse generated by the laser generation module to the frequency of the target reference signal; if the applied voltage of the PZT exceeds the preset voltage range, controlling the movement of the first reflecting element according to the applied voltage of the PZT and the preset voltage range through the second control module to adjust the optical path of the first optical pulse, so as to adjust the repetition frequency of the optical pulse generated by the laser generation module.

[0039] In some possible embodiments, the control device further includes a filter. The method further includes: filtering the electrical signal through the filter, and mixing the target reference signal and the filtered electrical signal through the mixer to obtain a mixed signal.

[0040] In some possible embodiments, the frequency modulation step of the reference signal source from outputting an initial reference signal to outputting a target reference signal is less than a first preset value, and the first preset value is the frequency adjustment amount of the repetition frequency of the optical pulse corresponding to the maximum adjustment amount of the applied voltage of the PZT.

[0041] In some possible embodiments, the frequency modulation step of the reference signal source from outputting an initial reference signal to outputting a target reference signal is greater than or equal to a second preset value, and the second preset value is the frequency adjustment amount of the repetition frequency of the optical pulse corresponding to the minimum distance of displacement of the first reflecting element.

[0042] In some possible embodiments, the frequency adjustment amount of the repetition frequency of the optical pulse corresponding to the minimum distance of displacement of the first reflecting element is less than the frequency adjustment amount of the repetition frequency of the optical pulse corresponding to the maximum adjustment amount of the applied voltage of the PZT.

[0043] In some possible embodiments, the laser emission device further includes a second coupler. The method further includes: splitting the second optical pulse through the second coupler, wherein one of the optical pulses after splitting of the second optical pulse is transmitted to the control device, and the other optical pulse after splitting of the second optical pulse is emitted outward.

[0044] In the embodiments of the present application, the laser includes a laser generation module, a first coupler, and a reflective spatial structure composed of at least one reflective element. The multiple paths of laser generated by the laser generation module interfere in the first coupler to form optical pulses, and the optical pulses are divided into two paths. One path of the first optical pulse is transmitted to the reflective element, and the other path of the second optical pulse is output. The first optical pulse is reflected back to the laser generation module by the reflective element. By controlling the movement of the reflective element, the optical path of the optical pulse transmitted in space can be changed, so that the repetition frequency of the optical pulse generated by the laser generation module can be adjusted. It should be understood that controlling the movement of the reflective element can adjust the optical path of the optical pulse traveling back and forth in space, which is equivalent to doubling the optical path of the optical pulse in space, facilitating a larger range of adjustment of the repetition frequency of the optical pulse. For example, a large-range frequency modulation of more than 2 MHz can be achieved. Moreover, by adjusting the applied voltage of the PZT to lock the repetition frequency of the optical pulse generated by the laser generation module, the direction and distance of the displacement of the reflective element can be further adjusted according to the applied voltage of the PZT. While achieving frequency locking, the repetition frequency of the optical pulse can be adjusted more precisely, improving the adjustment accuracy of the repetition frequency and reducing the risk of frequency unlocking. Description of the Drawings

[0045] Figure 1 It is the first structural schematic diagram of the laser in the embodiments of the present application;

[0046] Figure 2 It is the second structural schematic diagram of the laser in the embodiments of the present application;

[0047] Figure 3 It is the third structural schematic diagram of the laser in the embodiments of the present application;

[0048] Figure 4 It is the fourth structural schematic diagram of the laser in the embodiments of the present application;

[0049] Figure 5 It is the fifth structural schematic diagram of the laser in the embodiments of the present application;

[0050] Figure 6 It is the first schematic diagram of the optical pulse output by the fiber collimator in the embodiments of the present application during transmission in space;

[0051] Figure 7 It is the second schematic diagram of the optical pulse output by the fiber collimator in the embodiments of the present application during transmission in space;

[0052] Figure 8 It is the third schematic diagram of the optical pulse output by the fiber collimator in the embodiments of the present application during transmission in space;

[0053] Figure 9 It is the sixth structural schematic diagram of the laser in the embodiments of the present application;

[0054] Figure 10 It is a schematic flow chart for adjusting the repetition frequency of optical pulses in an embodiment of the present application;

[0055] Figure 11 It is the seventh structural schematic diagram of a laser in an embodiment of the present application;

[0056] Figure 12 It is a graph of the drift measurement results of the repetition frequency of optical pulses in an embodiment of the present application;

[0057] Figure 13 It is a comparison schematic diagram of the locking and non-locking of the repetition frequency of optical pulses in an embodiment of the present application;

[0058] Figure 14 It is a schematic diagram of a phase discrimination device for electrical signals in an embodiment of the present application;

[0059] Figure 15 It is an optical frequency comb device in an embodiment of the present application;

[0060] Figure 16 It is a schematic diagram of an embodiment of a frequency modulation method for optical pulses in an embodiment of the present application. Detailed implementation manners

[0061] The embodiment of the present application provides a laser and related devices and methods. The laser includes a laser generation module, a first coupler, and a reflective spatial structure composed of at least one reflective element. Multiple paths of laser generated by the laser generation module interfere in the first coupler to form optical pulses, and the optical pulses are divided into two paths. One path of the first optical pulse is transmitted to the reflective element, and the other path of the second optical pulse is output. The first optical pulse is reflected back to the laser generation module by the reflective element. Controlling the movement of the reflective element can adjust the optical path of the first optical pulse for round trips in space, which is equivalent to multiplying the optical path of the first optical pulse in space, and is beneficial to adjusting the repetition frequency of the optical pulse in a larger range. It should be understood that the laser provided in the embodiment of the present application can also be called a mode-locked laser or a mode-locked fiber laser, which can generate femtosecond lasers with high stability and has the ability to adjust the repetition frequency in a large range, and can be applied to the preparation of optical frequency combs, high-precision laser ranging, precision micromachining, fiber time-frequency transfer, the preparation and calibration of high-precision instruments, and other fields.

[0062] It should be noted that the terms "first", "second", etc. in the specification, claims and the above-mentioned drawings of this application are used to distinguish similar objects, rather than to limit a specific order or sequence. It should be understood that the above terms can be interchanged under appropriate circumstances, so that the embodiments described in this application can be implemented in an order other than that described in the content of this application. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusion. For example, a process, method, system, product or device that includes a series of steps or units does not necessarily have to be limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or are inherent to these processes, methods, products or devices.

[0063] Figure 1 This is the first structural schematic diagram of the laser in the embodiment of this application. As Figure 1 shown, the laser includes a laser emission device and a control device. The control device is used to adjust the laser emission device according to the optical pulse emitted by the laser emission device, so as to adjust the repetition frequency of the optical pulse and achieve the locking of the repetition frequency of the optical pulse. Among them, for the convenience of introduction, the laser emission device is divided into two parts here, namely the laser main body 10 and the spatial reflection module 20. In actual product implementation, this division may not exist. It should be understood that the laser emission device needs to be integrally packaged with sealing and vibration isolation, and active temperature control is carried out. This series of steps can reduce the parameter of the drift of the repetition frequency to a magnitude below 10 Hz.

[0064] Specifically, the laser main body 10 includes a laser generation module 101, a first coupler 102, a second coupler 103, a piezoelectric ceramic (PZT) 104, and an optical fiber collimator 105. The spatial reflection module 20 includes a first reflection element 201. The laser generation module 101 is used to generate laser. For example, the generated laser includes first laser and second laser. The first laser and the second laser undergo non-linear interference through the first coupler 102 to obtain an optical pulse, and the optical pulse passing through the first coupler 102 is divided into two paths, namely the first optical pulse transmitted to the optical fiber collimator 105 and the second optical pulse output. The second optical pulse is divided into two paths through the second coupler 103. One of the optical pulses after the second optical pulse is split is transmitted to the control device, and the other optical pulse after the second optical pulse is split is emitted outward. It should be understood that the first coupler 102 is respectively connected to the second coupler 103 and the optical fiber collimator 105 through optical fibers. The optical fiber collimator 105 collimates the input first optical pulse, and the collimated first optical pulse is transmitted to the first reflection element 201 in space, and then reflected back to the optical fiber collimator 105 by the first reflection element 201 and transmitted back to the laser generation module 101 along the original path.

[0065] Based on the above introduction, the section from the laser generation module 101 to the first reflection element 201 and back along the original path can be understood as the transmission of optical pulses in the resonator of the laser. The pulse interval is the time period required for an optical pulse to travel one round in the resonator, and the repetition frequency of the optical pulse is the reciprocal of the period. Therefore, by adjusting the optical path of the optical pulse transmitted in the resonator, the repetition frequency of the optical pulse can be adjusted. Specifically, the control device can adjust the applied voltage of the PZT 104 according to the current repetition frequency of the second optical pulse and the target frequency to which it is desired to adjust, and control the movement of the first reflection element 201 according to the applied voltage of the PZT. The specific manner of the coordinated adjustment of the PZT 104 and the first reflection element 201 will be introduced in detail below. As an example, as Figure 1 shown, the PZT 104 is connected to the fiber collimator 105. Adjusting the applied voltage of the PZT 104 can cause the PZT to drive the fiber collimator 105 to move by expansion and contraction, which can change the optical path of the first optical pulse transmitted in space, thereby adjusting the repetition frequency of the optical pulse. Controlling the movement of the first reflection element 201 can also change the optical path of the first optical pulse transmitted in space, and can also adjust the repetition frequency of the optical pulse. It should be understood that the present application does not limit the specific manner of controlling the movement of the first reflection element 201. For example, the first reflection element 201 is placed on a displacement stage, and the movement of the displacement stage is controlled to drive the movement of the first reflection element 201. It should be noted that the present application does not limit the number of reflection elements in the spatial reflection module 20 and the size of each reflection element. Several implementation manners with multiple reflection elements are introduced below, which can adjust the optical path of the optical pulse in space in a larger range, and are beneficial to improving the adjustment range of the repetition frequency of the optical pulse.

[0066] Figure 2 This is the second structural schematic diagram of the laser in the embodiment of the present application. Different from Figure 1 the embodiment shown, as Figure 2 shown, the PZT 104 can also be connected to the optical fiber for transmitting optical pulses in the laser emission device. For example, the PZT 104 can be connected to the optical fiber in the laser generation module 101. Another example is that the PZT 104 can also be connected to the optical fiber between the first coupler 102 and the fiber collimator 105. Adjusting the applied voltage of the PZT 104 by the control device can cause the PZT to deform and stretch the optical fiber, which can change the optical path of the optical pulse transmitted in the optical fiber, and can also adjust the repetition frequency of the optical pulse.

[0067] Figure 3 This is the third structural schematic diagram of the laser in the embodiment of the present application. Different from Figure 1 the embodiment shown, as Figure 3As shown, the spatial reflection module 20 further includes a second reflection element 202. The first reflection element 201 reflects the first optical pulse from the fiber collimator 105 to the second reflection element 202, and the second reflection element 202 then reflects the first optical pulse back to the first reflection element 201, and the first reflection element 201 reflects the first optical pulse back to the fiber collimator 105. It should be understood that in practical applications, on the premise that both the first reflection element 201 and the second reflection element 202 can receive the first optical pulse, the control device controls at least one of the first reflection element 201 and the second reflection element 202 to move. For example, the second reflection element 202 can be controlled to move alone. For another example, the first reflection element 201 and the second reflection element 202 can also be controlled to move together.

[0068] Figure 4 This is the fourth structural schematic diagram of the laser in the embodiment of the present application. Different from Figure 1 and Figure 3 the embodiment shown, as Figure 4 shown, the spatial reflection module 20 further includes a third reflection element 203. The first optical pulse from the fiber collimator 105 is reflected back to the fiber collimator 105 along the original path after being reflected by the first reflection element 201, the second reflection element 202, and the third reflection element 203 in sequence. It should be understood that in practical applications, on the premise that the first reflection element 201, the second reflection element 202, and the third reflection element 203 can all receive the first optical pulse, the control device controls at least one of the first reflection element 201, the second reflection element 202, and the third reflection element 203 to move. For example, the third reflection element 203 can be kept stationary, and the first reflection element 201 and the second reflection element 202 can be controlled to move together. For another example, the first reflection element 201 can be kept stationary, and the second reflection element 202 and the third reflection element 203 can be controlled to move together.

[0069] Figure 5 This is the fifth structural schematic diagram of the laser in the embodiment of the present application. As Figure 5As shown, in a possible implementation, the laser generation module 101 adopts a nonlinear amplifying loop mirror (NALM), which reduces the mode-locking threshold and improves the mode-locking's resistance to spatial length changes. Even when the optical path of the optical pulse is adjusted over a large range, the optical pulse can still be continuously generated. For example, the first laser generated by the NALM travels clockwise in the NALM, and the second laser generated by the NALM also travels clockwise in the NALM. The first laser and the second laser undergo nonlinear interference through the first coupler 102 to obtain an optical pulse. Among them, the laser generation module 101 includes a pump source 101a, a wavelength division multiplexer 101b, and a gain fiber 101c. The wavelength division multiplexer 101b is used to couple the pump light output by the pump source 101a to the gain fiber 101c in a wavelength multiplexing manner. The light passing through the gain fiber 101c has a different wavelength from the light output by the pump source 101a. It should be understood that both the wavelength division multiplexer 101b and the gain fiber 101c can be regarded as part of the devices on the NALM. The specific device composition of the NALM is not limited in this application. For example, the NALM also includes a common fiber connected to the gain fiber 101c. Another example is that the NALM may also include a saturable absorber 101d. Among them, the gain fiber 101c can be a doped fiber, and the doped fiber includes erbium-doped fiber, ytterbium-doped fiber, thulium-doped fiber, etc. In some possible implementations, the laser generation module 101 can also add a semiconductor saturable absorber mirror (SESAM) for hybrid mode-locking.

[0070] Figure 6 This is the first schematic diagram of the optical pulse output by the fiber collimator in the embodiment of the present application during spatial transmission. As Figure 6 shown, the light beam output by the fiber collimator will first contract and then diverge. The collimation distance of the fiber collimator is the distance between the spatial position where the spot size is the same as the initial spot size and the fiber collimator. This distance can also be referred to as the working distance of the fiber collimator. In a possible implementation, the collimation distance of the fiber collimator is greater than the one-way distance of the first optical pulse during spatial transmission. In this way, the spot size of the first optical pulse reflected back to the fiber collimator changes less and diffuses less compared to the initial spot size, which is more conducive to coupling into the fiber and is beneficial to improving the mode-locking effect of the laser. Taking Figure 1 the structure shown as an example, the one-way distance of the first optical pulse during spatial transmission is the distance from the fiber collimator 105 to the first reflection element 201. The collimation distance of the fiber collimator is greater than the maximum distance that the first reflection element 201 can move. That is to say, the first reflection element 201 will not move to a position beyond the collimation distance of the fiber collimator. Taking Figure 2Taking the structure shown as an example, the one-way distance that the first optical pulse travels in space is the distance that the first optical pulse travels from the fiber collimator 105 to the first reflecting element 201, and then to the second reflecting element 202. Taking Figure 3 the structure shown as an example, the one-way distance that the first optical pulse travels in space is the distance that the first optical pulse travels from the fiber collimator 105 to the first reflecting element 201, then to the second reflecting element 202, and then to the third reflecting element 203.

[0071] Figure 7 This is the second schematic diagram of the optical pulse output by the fiber collimator in the embodiment of the present application during spatial transmission. As Figure 7 shown, a lens 204 is further provided between the fiber collimator 105 and the first reflecting element 201. The lens 204 is used to perform beam shaping on the first optical pulse collimated by the fiber collimator 105, so as to achieve an auxiliary collimation effect. Taking Figure 1 the scenario shown as an example, the spot size of the first optical pulse transmitted to the position of the first reflecting element 201 after passing through the lens 204 is the same as or close to the initial spot size output by the fiber collimator 105. In this way, the spot size of the first optical pulse reflected back to the fiber collimator changes less and diffuses less compared to the initial spot size, which is more conducive to coupling into the fiber and is beneficial to improving the mode-locking effect of the laser. For Figure 2 the scenario shown, the lens 204 makes the spot size of the first optical pulse transmitted to the position of the second reflecting element 202 the same as or close to the initial spot size output by the fiber collimator 105. For Figure 3 the scenario shown, the lens 204 makes the spot size of the first optical pulse transmitted to the position of the third reflecting element 203 the same as or close to the initial spot size output by the fiber collimator 105.

[0072] Figure 8 This is the third schematic diagram of the optical pulse output by the fiber collimator in the embodiment of the present application during spatial transmission. As Figure 8 shown, a diffractive optical element (DOE) 205 is further provided between the fiber collimator 105 and the first reflecting element 201. Among them, the DOE 205 plays a role similar to that of the lens 204, which will not be elaborated here.

[0073] Figure 9 This is the sixth structural schematic diagram of the laser in the embodiment of the present application. As Figure 9As shown in the figure, the control device includes a reference signal source 301, a photodetector 302, a filter 303, a mixer 304, a first control module 305, and a second control module 306. The reference signal source 301 is used to output a target reference signal. The photodetector 302 is used to convert the second optical pulse into an electrical signal. The filter 303 is used to filter the electrical signal. The mixer 304 is used to mix the target reference signal and the filtered electrical signal to obtain a mixed signal. The first control module 305 can determine the relative error between the repetition frequency of the optical pulse generated by the laser emission device and the target frequency of the target reference signal according to the mixed signal, and adjust the loading voltage of the PZT 104 according to the relative error to control the movement of the fiber collimator 105, so as to adjust the optical path of the first optical pulse transmitted in space, so that the repetition frequency of the optical pulse can be quickly locked to the target frequency of the target reference signal. Optionally, the control device may not include the filter 303, and the mixer 304 mixes the target reference signal and the electrical signal from the photodetector 302 to obtain a mixed signal. In some possible scenarios, the first control module and the second control module may be two independent circuit boards respectively. Or, in some other possible scenarios, the first control module and the second control module may also be integrated together and implemented through a controller.

[0074] It should be noted that the repetition frequency locking of the optical pulse can be achieved within the maximum adjustable range of the loading voltage of the PZT 104. The maximum adjustable amount of the loading voltage of the PZT 104 corresponds to the maximum adjustable amount of the repetition frequency of the optical pulse that can be adjusted by the PZT 104. For example, the maximum range of the loading voltage of the PZT 104 can be 0V to 150V or -50V to 50V, etc. Taking the maximum range of the loading voltage of the PZT 104 being 0V to 150V as an example, the maximum adjustable amount of the loading voltage of the PZT 104 is 150V. The difference between the repetition frequency of the optical pulse when the loading voltage of the PZT 104 is 150V and the repetition frequency of the optical pulse when the loading voltage of the PZT 104 is 0V is the maximum adjustable amount of the repetition frequency of the optical pulse that can be adjusted by the PZT 104.

[0075] It should be understood that if the voltage applied to the PZT 104 exceeds the maximum adjustment range within which it can maintain the locking of the repetition frequency, the repetition frequency of the optical pulse will be lost during the frequency modulation process, which is simply referred to as frequency unlocking. To avoid frequency unlocking, a control range, or a preset voltage range, can be set for the voltage applied to the PZT 104. This control range is within the maximum adjustment range of its applied voltage. For example, the maximum range of the voltage applied to the PZT 104 is from 0V to 150V, and the control range can be set from 50V to 100V. If the voltage applied to the PZT 104 exceeds the control range, the second control module 306 needs to be activated. For example, if the voltage applied to the PZT 104 is less than 50V or greater than 100V, it is considered to have exceeded the control range. The second control module 306 adjusts the optical path of the first optical pulse by controlling the movement of the first reflecting element 201 to adjust the repetition frequency of the optical pulse, thereby compensating for the adjustment of the first control module 305 and bringing the voltage applied to the PZT 104 back within the control range. That is to say, the control device uses a serial control method for the PZT and the first reflecting element, that is, first, the optical path of the optical pulse is adjusted by controlling the PZT to achieve frequency locking. Based on the adjustment state of the PZT, if there is a risk of frequency unlocking, the optical path of the optical pulse can be further compensated by controlling the movement of the first reflecting element to avoid frequency unlocking during the frequency modulation process.

[0076] As an example, the voltage applied to the PZT 104 adjusted by the first control module 305 according to the mixing signal exceeds the control range, that is, the optical path of the first optical pulse transmitted in space may be too long, and there is a risk of frequency unlocking for the repetition frequency of the optical pulse. The second control module 306 controls the movement of the first reflecting element 201 to shorten the optical path of the first optical pulse transmitted in space according to the voltage applied to the PZT 104 to adjust the repetition frequency of the optical pulse, and the mixing signal also changes accordingly. The voltage applied to the PZT 104 adjusted by the first control module 305 returns to the control range.

[0077] It should be understood that although the first reflection element 201 can move within a relatively large range and a relatively large range of frequency modulation can be achieved, the adjustment amplitude of the second control module 306 for controlling the movement of the first reflection element 201 cannot be too large to ensure that frequency unlocking does not occur during the frequency modulation process. That is to say, the second control module 306 can adjust the repetition frequency of the optical pulse more precisely than the first control module 305. Therefore, the frequency adjustment amount of the repetition frequency of the optical pulse corresponding to the minimum displacement distance of the first reflection element 201 is less than the frequency adjustment amount of the repetition frequency of the optical pulse corresponding to the maximum adjustment amount of the applied voltage of the PZT 104. In other words, the accuracy of adjusting the displacement of the first reflection element 201 once is less than the maximum distance of moving the fiber collimator 105 by adjusting the applied voltage of the PZT 104. As an example, the accuracy of adjusting the displacement of the first reflection element 201 once is 20 nm, and the displacement range of the first reflection element 201 is 50 mm.

[0078] It should be noted that since the repetition frequency locking of the optical pulse can be achieved within the maximum adjustment range of the applied voltage of the PZT 104, if the relative error between the repetition frequency of the optical pulse and the target frequency of the target reference signal is large, the repetition frequency of the optical pulse cannot be locked to the target frequency at one time by adjusting the applied voltage of the PZT 104. Then, a frequency modulation step can be set for the reference signal source 301 according to the maximum adjustment range of the applied voltage of the PZT 104, and the signal output by the reference signal source 301 can be adjusted to the target reference signal with the target frequency in multiple steps by performing frequency modulation on the reference signal source 301 multiple times. A specific implementation manner is introduced below.

[0079] Figure 10 It is a schematic flow chart for adjusting the repetition frequency of the optical pulse in the embodiment of the present application. As Figure 10 shown, first, determine the initial frequency f0 and the target frequency f1 of the reference signal source 301, and then calculate the number of steps n required for the reference signal source 301 to be frequency-modulated to the target frequency f1 according to the frequency modulation step Δf of the reference signal source 301, where n = |f1 - f0| / Δf. Furthermore, each time the frequency of the reference signal output by the reference signal source 301 is adjusted, the first control module 305 adjusts the applied voltage of the PZT 104 according to the mixing signal to lock the frequency of the optical pulse to the frequency of the current reference signal. If the applied voltage of the PZT 104 exceeds the control range, the second control module 306 controls the movement of the first reflection element 201 to return the applied voltage of the PZT 104 to the control range to avoid frequency unlocking. If the applied voltage of the PZT 104 does not exceed the control range, the second control module 306 is not enabled. Then, repeating the above operation n steps is the complete process of adjusting the repetition frequency of the optical pulse.

[0080] It should be understood that the frequency modulation step Δf of the reference signal source 301 cannot be too large, otherwise frequency unlocking may occur. That is, the frequency modulation step Δf of the reference signal source 301 should be less than the first preset value, which is the frequency adjustment amount of the repetition frequency of the optical pulse corresponding to the maximum adjustment amount of the loading voltage of the PZT 104. For example, the value range of the first preset value can be 1 kHz - 50 kHz. It should also be understood that the frequency modulation step Δf of the reference signal source 301 cannot be too small, otherwise the entire frequency modulation process will be too slow. That is, the frequency modulation step Δf of the reference signal source 301 should be greater than or equal to the second preset value, which is the frequency adjustment amount of the repetition frequency of the optical pulse corresponding to the minimum distance of the displacement of the first reflection element 201. For example, the value range of the second preset value can be 1 Hz - 10 Hz.

[0081] It should be noted that in some possible scenarios, the control device may not adjust the loading voltage of the PZT 104 according to the feedback of the second optical pulse, but manually control the control device to adjust the loading voltage of the PZT 104. Correspondingly, the control device is used to manually control the movement of the first reflection element 201. In other possible scenarios, the control device can also independently control the PZT and the first reflection element respectively. For example, the control device can also directly control the movement of the first reflection element according to the mixing signal to change the optical path of the optical pulse, thereby adjusting the repetition frequency of the optical pulse.

[0082] Figure 11 This is the seventh structural schematic diagram of the laser in the embodiment of the present application. Different from Figure 1 the shown laser, as Figure 11 shown, the laser emission device further includes a third coupler 106, and the function of the third coupler 106 is similar to that of the second coupler 103. For example, the third coupler 106 can be arranged in the laser generation module 101. The third coupler 106 adopts a design of one input and two outputs. When the laser generation module 101 generates a stable optical pulse, the third coupler 106 can also split the optical pulse generated by the laser generation module 101. One of the split paths is transmitted to the first coupler 102, and the other split path is emitted outward. Thus, combined with the optical pulse emitted by the second coupler 103, multi-path optical pulse emission can be realized.

[0083] Figure 12 This is the drift measurement result graph of the repetition frequency of the optical pulse in the embodiment of the present application. As Figure 12 shown, the abscissa represents the measurement duration, and the unit is second (s); the ordinate represents the frequency drift amount, and the unit is mHz. It can be seen that the measurement result of the frequency drift is about ±1 mHz, and the frequency locking effect is good.

[0084] Figure 13This is a comparison schematic diagram of the repetition frequency of the optical pulse being locked and unlocked in the embodiments of this application. As Figure 13 shown, the abscissa represents the duration, with the unit of seconds (s); the ordinate represents the frequency stability. It can be seen that the second stability of the repetition frequency after locking is 0.3 mHz, and the effect of frequency locking is good.

[0085] As can be seen from the above introduction, the laser includes a laser generation module, a first coupler, and a reflective spatial structure composed of at least one reflective element. The multiple paths of laser generated by the laser generation module interfere in the first coupler to form optical pulses, and the optical pulses are divided into two paths. One of the first optical pulses is transmitted to the reflective element, and the other second optical pulse is output. The first optical pulse will be reflected back to the laser generation module by the reflective element. By controlling the movement of the reflective element, the optical path of the optical pulse transmitted in space can be changed, thereby the repetition frequency of the optical pulse generated by the laser generation module can be adjusted. It should be understood that controlling the movement of the reflective element can adjust the optical path of the optical pulse traveling back and forth in space, which is equivalent to doubling the optical path of the optical pulse in space, facilitating a larger range of adjustment of the repetition frequency of the optical pulse. For example, a large-range optical path change of more than 60 mm can be achieved, and a large-range frequency modulation of more than 2 MHz can be achieved. Moreover, by adjusting the applied voltage of the PZT to lock the repetition frequency of the optical pulse generated by the laser generation module, the direction and distance of the displacement of the reflective element can be further adjusted according to the applied voltage of the PZT. While achieving frequency locking, the repetition frequency of the optical pulse can be adjusted more precisely, improving the adjustment accuracy of the repetition frequency and reducing the risk of frequency unlocking.

[0086] The possible application scenarios of the above laser will be introduced below.

[0087] Figure 14 This is a schematic diagram of an electrical signal phase discrimination device in the embodiments of this application. As Figure 14 shown, the electrical signal phase discrimination device includes a laser, a photodetector, and a phase discriminator. Among them, the laser can be the laser introduced in any of the above embodiments. Specifically, the photodetector is used to convert the light output by the laser into a first electrical signal and transmit the first electrical signal to the phase discriminator. The phase discriminator also inputs a second electrical signal. For example, the second electrical signal can be a clock signal, etc. The phase discriminator is used to determine the phase difference between the first electrical signal and the second electrical signal and output an electrical phase signal of the phase discrimination error. It should be understood that the signal output by the phase discriminator can be fed back to the device that outputs the second electrical signal as a reference for adjusting the second electrical signal.

[0088] Figure 15 This is an optical frequency comb device in the embodiments of this application. As Figure 15As shown in the figure, the optical frequency comb device includes: a laser beating module, an initial frequency locking module, and a laser as introduced in any of the above embodiments. The laser beating module is used to perform spectral broadening, frequency doubling, and beat frequency detection on the optical pulses emitted by the laser to obtain an initial frequency signal. The initial frequency locking module is used to output a control signal to the laser according to the initial frequency signal. The laser is used to lock the initial frequency according to the control signal and output an optical frequency comb signal.

[0089] The following introduces the frequency modulation method of the optical pulses provided in the embodiments of the present application.

[0090] Figure 16 It is a schematic diagram of an embodiment of the frequency modulation method of the optical pulses in the embodiments of the present application. It should be noted that this method is implemented based on the laser introduced above. For the introduction of the laser, reference can be made to the relevant descriptions of the above embodiments, which will not be elaborated here. In this example, the frequency modulation method of the optical pulses includes the following steps.

[0091] 11. Generate a first laser and a second laser through a laser generation module.

[0092] Taking the NALM adopted by the laser generation module as an example, the first laser transmits clockwise in the NALM, and the second laser transmits clockwise in the NALM.

[0093] 12. Interfere the first laser and the second laser through a first coupler to obtain optical pulses.

[0094] Among them, the first laser and the second laser undergo non - linear interference through the first coupler to obtain optical pulses, and the optical pulses passing through the first coupler are divided into two paths, namely the first optical pulse transmitted to the first reflection element and the second optical pulse output.

[0095] 13. Reflect the first optical pulse back to the laser generation module through the first reflection element.

[0096] Specifically, the first optical pulse from the first coupler is collimated through an optical fiber collimator to obtain the first optical pulse transmitted in space. The first optical pulse can be reflected back to the optical fiber collimator through the first reflection element. It should be understood that the number of reflection elements in space in the present application is not limited. For example, the first optical pulse can also be reflected multiple times by multiple reflection elements in space.

[0097] 14. Adjust the applied voltage of the PZT through a control device.

[0098] Specifically, the control device converts the input second optical pulse into an electrical signal and filters it, and mixes the filtered electrical signal with a target reference signal to obtain a mixed signal. Further, the control device adjusts the applied voltage of the PZT according to the mixed signal to control the movement or stretching of the fiber optic collimator to adjust the optical path of the first optical pulse, thereby locking the repetition frequency of the optical pulse to the frequency of the target reference signal.

[0099] 15. Control the movement of the first reflecting element through the control device.

[0100] Specifically, the control device determines whether the applied voltage of the PZT exceeds the control range. If so, it indicates that there is a risk of frequency unlocking of the repetition frequency of the optical pulse. At this time, the control device controls the movement of the first reflecting element according to the applied voltage of the PZT to adjust the optical path of the first optical pulse, so as to adjust the repetition frequency of the optical pulse and make the applied voltage of the PZT return to the control range.

[0101] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than limiting them. Although the present application has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements on some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A laser, characterized in that, it comprises a laser emission device and a control device, and the laser emission device comprises a laser generation module, a first coupler and a first reflection element; the laser generation module is used for generating a first laser and a second laser; the first coupler is used for interfering the first laser and the second laser to obtain an optical pulse, and the optical pulse comprises a first optical pulse transmitted to the first reflection element and an output second optical pulse; the first reflection element is used for reflecting the first optical pulse back to the laser generation module; the control device is used for adjusting the optical path of the first optical pulse by controlling the movement of the first reflection element.

2. The laser according to claim 1, characterized in that, the laser generation module comprises a Nonlinear Amplifying Loop Mirror (NALM) and a pump source, the NALM is connected to the first coupler, the pump source is used for outputting pump light to the NALM, and the NALM is used for generating the first laser and the second laser according to the pump light.

3. The laser according to claim 2, characterized in that, the NALM comprises a Wavelength Division Multiplexer (WDM) and a gain fiber, and the WDM is used for coupling the pump light output by the pump source to the gain fiber.

4. The laser according to claim 2 or 3, characterized in that, the NALM further comprises a saturable absorber.

5. The laser according to any one of claims 1 to 4, characterized in that, the laser emission device further comprises a second reflection element; the first reflection element is used for reflecting the first optical pulse to the second reflection element, and then reflecting the first optical pulse reflected by the second reflection element back to the laser generation module; the control device is further used for adjusting the optical path of the first optical pulse by controlling the movement of the second reflection element.

6. The laser according to any one of claims 1 to 5, characterized in that, the laser emission device further comprises an optical fiber collimator, and the optical fiber collimator is used for collimating the first optical pulse from the first coupler, wherein the collimated first optical pulse is transmitted to the first reflection element in space.

7. The laser according to claim 6, characterized in that, the collimation distance of the optical fiber collimator is greater than the one-way distance of the first optical pulse transmitted in space.

8. The laser according to claim 6 or 7, characterized in that, the laser emission device further comprises a lens or a Diffractive Optical Element (DOE), and the lens or the DOE is located between the optical fiber collimator and the first reflection element; the lens or the DOE is used for beam shaping the first optical pulse from the optical fiber collimator and transmitting the beam-shaped first optical pulse to the first reflection element.

9. The laser according to any one of claims 6 to 8, characterized in that, The second optical pulse is transmitted to the control device. The laser emitting device further includes a piezoelectric ceramic PZT, the PZT is connected to the fiber collimator, and the control device is further configured to adjust the applied voltage of the PZT according to the second optical pulse to control the movement of the fiber collimator, so as to adjust the optical path of the first optical pulse.

10. The laser according to any one of claims 1 to 9, wherein, The second optical pulse is transmitted to the control device. The laser emitting device further includes a piezoelectric ceramic PZT, the PZT is connected to the optical fiber in the laser generation module or the optical fiber for transmitting the first optical pulse, and the control device is further configured to adjust the applied voltage of the PZT according to the second optical pulse to control the stretching of the optical fiber, so as to adjust the optical path of the optical pulse.

11. The laser according to claim 9 or 10, wherein, The control device is specifically configured to control the movement of the first reflecting element according to the applied voltage of the PZT.

12. The laser according to any one of claims 9 to 11, wherein, The control device includes: a reference signal source, a photodetector, a mixer, a first control module and a second control module; The reference signal source is configured to output a target reference signal; The photodetector is configured to convert the second optical pulse into an electrical signal; The mixer is configured to mix the target reference signal and the electrical signal to obtain a mixed signal; The first control module is configured to adjust the applied voltage of the PZT according to the mixed signal to adjust the optical path of the first optical pulse; If the applied voltage of the PZT exceeds a preset voltage range, the second control module is configured to control the movement of the first reflecting element according to the applied voltage of the PZT and the preset voltage range to adjust the optical path of the first optical pulse.

13. The laser according to claim 12, wherein, The control device further includes a filter; The filter is configured to filter the electrical signal from the photodetector; The mixer is configured to mix the target reference signal and the filtered electrical signal to obtain a mixed signal.

14. The laser according to claim 12 or 13, wherein, The frequency modulation step of the reference signal source from outputting an initial reference signal to outputting the target reference signal is less than a first preset value, and the first preset value is the frequency adjustment amount of the repetition frequency of the optical pulse corresponding to the maximum adjustment amount of the applied voltage of the PZT.

15. The laser according to any one of claims 12 to 14, wherein, The frequency modulation step of the reference signal source from outputting an initial reference signal to outputting the target reference signal is greater than or equal to a second preset value, and the second preset value is the frequency adjustment amount of the repetition frequency of the optical pulse corresponding to the minimum distance of the displacement of the first reflecting element.

16. The laser according to any one of claims 9 to 15, wherein, The frequency adjustment amount of the repetition frequency of the optical pulse corresponding to the minimum distance of the displacement of the first reflection element is less than the frequency adjustment amount of the repetition frequency of the optical pulse corresponding to the maximum adjustment amount of the applied voltage of the PZT.

17. The laser according to any one of claims 1 to 16, wherein, the laser emission device further includes a second coupler; the second coupler is used for splitting the second optical pulse, wherein one of the optical pulses after splitting of the second optical pulse is transmitted to the control device, and the other optical pulse after splitting of the second optical pulse is emitted outward.

18. An electrical signal phase discrimination device, wherein, comprising: a phase discriminator, a photodetector, and the laser according to any one of claims 1 to 17; the photodetector is used for converting the light output by the laser into a first electrical signal and transmitting the first electrical signal to the phase discriminator; the phase discriminator is used for determining the phase difference between the first electrical signal and the input second electrical signal.

19. An optical frequency comb device, wherein, the optical frequency comb device includes a laser beat frequency module, an initial frequency locking module, and the laser according to any one of claims 1 to 17; the laser beat frequency module is used for performing spectral expansion, frequency doubling, and beat frequency detection on the optical pulse emitted by the laser to obtain an initial frequency signal; the initial frequency locking module is used for outputting a control signal to the laser according to the initial frequency signal; the laser is used for locking the initial frequency according to the control signal and outputting an optical frequency comb signal.

20. A method for frequency modulation of an optical pulse, wherein, the method is applied to a laser, and the laser includes: a laser emission device and a control device, and the laser emission device includes a laser generation module, a first coupler, and a first reflection element; the method includes: generating a first laser and a second laser through the laser generation module; interfering the first laser and the second laser through the first coupler to obtain an optical pulse, and the optical pulse includes a first optical pulse transmitted to the first reflection element and a second optical pulse output; reflecting the first optical pulse back to the laser generation module through the first reflection element; controlling the first reflection element to move through the control device to adjust the optical path of the first optical pulse.

21. The method according to claim 20, wherein, the laser generation module includes a nonlinear gain loop mirror NALM and a pump source, and the method further includes: outputting pump light from the pump source to the NALM.

22. The method according to claim 21, wherein, the NALM includes a wavelength division multiplexer WDM and a gain fiber, and the method further includes: coupling the pump light output by the pump source to the gain fiber through the WDM.

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