Device for realizing state-controllable passive mode-locking fiber laser

Abstract

The invention provides a device for realizing a state-controllable passive mode-locked fiber laser, which belongs to the technical field of passive mode-locked fiber lasers, and aims at an annular cavity mode-locked fiber laser, optical signals in part of a cavity are converted into radio-frequency signals related to the intensity change of the optical signals through a photoelectric detector and a radio-frequency amplifier; the transmission direction of the radio frequency signal is consistent with that of the intracavity optical signal, and the input optical signal is synchronously modulated by using the electro-optical intensity modulator. The direct-current bias voltage of the polarization-maintaining variable optical attenuator and the electro-optical intensity modulator is adjusted through the control circuit, so that the state of the laser can be accurately controlled. Accurate state control is achieved based on the passive mode-locking fiber laser, and control parameters needing to be set mainly include the optical power of the pump laser, the bias direct-current voltage of the photoelectric intensity modulator and the attenuation value of the polarization-maintaining variable optical attenuator and can be accurately set through an electric control circuit; compared with an active mode-locked fiber laser, an external radio frequency signal source is omitted, and the structure of the laser is simplified.

Description

Technical Field

[0001] The invention relates to the technical field of passive mode-locked fiber lasers, and in particular to a device for realizing a state-controllable passive mode-locked fiber laser. Background Art

[0002] Actively mode-locked fiber lasers can achieve precise control of the mode-locking start time, but they require an external RF modulation signal source and regenerative mode-locking technology to achieve a stable mode-locked state. In addition, by increasing the modulation frequency by integer multiples, the mode-locked pulse width of the laser output will decrease, but the pulse width cannot be continuously adjustable.

[0003] In order to achieve self-starting mode locking of passively mode-locked fiber lasers, the following two technologies are usually used: self-starting of the mode-locked state is achieved by using a saturable absorber based on the physical properties of the material. The saturable absorber can be a semiconductor saturable absorber mirror, graphene, carbon nanotubes, etc. These saturable absorbers have the characteristic that the transmittance varies with the intensity of the incident light. Therefore, the saturable absorber can produce intensity-dependent amplitude modulation of the transmitted light in the laser resonant cavity, that is, high-peak power light waves experience lower losses than low-peak power light waves. After multiple intracavity cycles, the light waves can evolve into stable mode-locked ultrashort pulse outputs; based on nonlinear polarization rotation or the nonlinearity of the "9"-shaped cavity Amplified annular mirror mode locking technology can also achieve self-starting mode locking. Its basic working principle is to use the nonlinear phase accumulated during the optical fiber transmission of the light wave in the cavity. The nonlinear phase accumulated by the light waves with different peak powers is different. Therefore, when the light wave passes through the analyzer (nonlinear polarization rotation) or the coupler (nonlinear amplified annular mirror), the orthogonal polarization components (nonlinear polarization rotation) or the oppositely transmitted light wave components (nonlinear amplified annular mirror) have different nonlinear phases, so the transmittance related to the incident light intensity is obtained. When the laser works in the transmittance region positively correlated with the peak power, self-starting mode locking can be achieved. The shortcomings of the above two types of technical solutions are: based on the physical material characteristics, the service life of the saturable absorber is short, and the polarization state in the cavity needs to be properly adjusted before the mode locking state is obtained; the service life of the nonlinear polarization rotation or the "9"-shaped cavity nonlinear amplified annular mirror is much longer than the former, but the self-starting mode locking still needs to properly adjust the optical devices such as the polarization controller or wave plate in the cavity to obtain the best state, and the influence of environmental interference on the working stability of the laser cannot be ignored.

[0004] In summary, active mode-locking technology can reduce the mode-locking pulse width by increasing the modulation frequency, but it cannot achieve continuous adjustment of the pulse width, and active mode-locking technology requires an external modulation signal to drive the optoelectronic modulator in the cavity. Although the passive mode-locking technology has a relatively simple structure and does not require an external modulation signal source, it cannot accurately control the mode-locking start time and mode-locking state of the laser. Summary of the invention

[0005] The object of the present invention is to provide a device for a state-controllable passive mode-locked fiber laser that can achieve precise control of the mode-locking start time and continuously adjustable output laser pulse width, so as to solve at least one technical problem existing in the above-mentioned background technology.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] On the one hand, the present invention provides a device for realizing a state-controllable passive mode-locked fiber laser, wherein the passive mode-locked fiber laser is a ring cavity structure, comprising: an amplifying optical path part, a mode-locking part and a power supply electronic control part; after the optical signal passes through the amplifying optical path part, it is divided into two paths, which enter the feedforward path and the trunk path of the mode-locking part respectively; the feedforward path detects the intensity change of the optical signal and converts the optical signal into a voltage signal and sends it to the trunk path, and the trunk path modulates the optical signal of the trunk path according to the voltage signal; the power supply electronic control part is used to set the bias voltage and working point of the trunk path; the optical signal modulated by the trunk path is transmitted to the amplifying optical path part to form a cycle.

[0008] Furthermore, the amplification optical path portion is composed of a pump laser, a polarization-maintaining wavelength division multiplexer, a polarization-maintaining gain fiber, a first polarization-maintaining 1×2 coupler, and a polarization-maintaining isolator; the pump laser is connected to the polarization-maintaining wavelength division multiplexer, the polarization-maintaining wavelength division multiplexer is connected to the polarization-maintaining gain fiber, the polarization-maintaining gain fiber is connected to the first polarization-maintaining 1×2 coupler, and the first polarization-maintaining 1×2 coupler is connected to the polarization-maintaining isolator.

[0009] Furthermore, the mode-locked part is composed of a second polarization-maintaining 1×2 coupler, a polarization-maintaining adjustable optical attenuator, a photodetector, a radio frequency amplifier, a polarization-maintaining adjustable optical delay line, and an electro-optical intensity modulator; wherein the polarization-maintaining adjustable optical attenuator, the photodetector, and the radio frequency amplifier constitute the feedforward path, and the polarization-maintaining adjustable optical delay line and the electro-optical intensity modulator constitute the trunk path.

[0010] Furthermore, an input end of the second polarization-maintaining 1×2 coupler is connected to the output end of the amplifying optical path portion, and the output end of the second polarization-maintaining 1×2 coupler is respectively connected to the polarization-maintaining adjustable optical attenuator and the polarization-maintaining adjustable optical delay line, the polarization-maintaining adjustable optical attenuator is connected to the photodetector, and the output end of the polarization-maintaining adjustable optical delay line is connected to the electro-optical intensity modulator.

[0011] Furthermore, one end of the photodetector and one end of the electro-optic intensity modulator are both connected to the radio frequency amplifier, and one end of the polarization-maintaining variable optical attenuator and one end of the electro-optic intensity modulator are both connected to the power supply electronic control part.

[0012] Furthermore, the photodetector and the electro-optical intensity modulator are both connected to the radio frequency amplifier via a radio frequency coaxial line.

[0013] Furthermore, the power supply electronic control part is composed of an adjustable DC voltage source, a control circuit, and a data line; the adjustable DC voltage source is connected to the control circuit; one end of the polarization-maintaining adjustable optical attenuator is connected to the control circuit through the data line.

[0014] On the other hand, the present invention provides a method for realizing controllable state of a passive mode-locked fiber laser based on the device as described in the first aspect, wherein the control circuit is respectively connected to a polarization-maintaining adjustable optical attenuator and an adjustable DC voltage source, and the working point of the electro-optical intensity modulator is controlled by adjusting the attenuation of the optical signal and the bias DC voltage of the electro-optical intensity modulator to realize controllable state of the laser, wherein the controllable state includes: control of mode-locking start time; switching of Q-switching, mode-locking, and Q-switched mode-locking states; and adjustable mode-locking pulse width.

[0015] Furthermore, part of the intracavity optical signal is converted into an RF signal related to the intensity change of the optical signal through a photodetector and an RF amplifier. The RF signal has the same transmission direction as the intracavity optical signal and is input into an electro-optic intensity modulator to achieve synchronous modulation of the input optical signal.

[0016] Furthermore, the radio frequency signal input to the electro-optic intensity modulator is obtained by converting the intracavity optical signal through the photodetector, and no external modulation signal source is required.

[0017] The invention has the following beneficial effects: an external radio frequency signal source is omitted, and the laser structure is simplified; the DC bias voltage of the polarization-maintaining adjustable optical attenuator and the electro-optic intensity modulator is adjusted by the control circuit, so that the laser state can be precisely controlled.

[0018] Additional aspects and advantages of the present invention will be given in part in the following description, which will become obvious from the following description, or may be learned through practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without paying creative work.

[0020] Figure 1 This is a schematic structural diagram of a device for realizing a state-controllable passive mode-locked fiber laser according to an embodiment of the present invention.

[0021] Figure 2This is a schematic structural diagram of a device for realizing a state-controllable passive mode-locked fiber laser with a closed-loop feedback function according to an embodiment of the present invention.

[0022] Among them: 1-the second polarization-maintaining 1×2 coupler; 2-polarization-maintaining adjustable optical attenuator; 3-photodetector; 4-RF amplifier; 5-adjustable DC voltage source; 6-polarization-maintaining adjustable optical delay line; 7-electro-optical intensity modulator; 8-polarization-maintaining wavelength division multiplexer; 9-pump laser; 10-polarization-maintaining gain fiber; 11-the first polarization-maintaining 1×2 coupler; 12-polarization-maintaining isolator; 13-control circuit; 14-RF coaxial line; 15-data line; 16-amplification optical path part; 17-mode locking part; 18-power supply electronic control part; 19-the third polarization-maintaining 1×2 coupler; 20-photodetector. DETAILED DESCRIPTION

[0023] The embodiments of the present invention are described in detail below, and examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements with the same or similar functions. The embodiments described below by the accompanying drawings are exemplary and are only used to explain the present invention, and cannot be interpreted as limiting the present invention.

[0024] It should 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 commonly understood by those skilled in the art to which this invention belongs.

[0025] It should also be understood that terms, such as those defined in commonly used dictionaries, should be understood to have a meaning consistent with that in the context of the prior art and will not be interpreted in an idealized or overly formal sense unless as defined herein.

[0026] Those skilled in the art will appreciate that, unless otherwise stated, the singular forms "a", "an", "said" and "the" used herein may also include plural forms. 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 and / or groups thereof.

[0027] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine different embodiments or examples described in this specification and the features of different embodiments or examples, unless they are contradictory.

[0028] In the description of this specification, the terms "first" and "second" are used for descriptive purposes only and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In the description of the present invention, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0029] In the description of this specification, the terms "center", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc. indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings. They are only for the convenience of describing the present technology and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present technology.

[0030] Unless otherwise clearly specified or limited, the terms "installed", "connected", "connected", and "set" should be understood in a broad sense, for example, they can be fixedly connected or set, or detachably connected or set, or integrally connected or set. For ordinary technicians in this field, the specific meanings of the above terms in this technology can be understood according to specific circumstances.

[0031] To facilitate understanding of the present invention, the present invention is further explained below with reference to specific embodiments in conjunction with the accompanying drawings, and the specific embodiments do not constitute a limitation on the embodiments of the present invention.

[0032] Those skilled in the art should understand that the drawings are merely schematic diagrams of embodiments, and the components in the drawings are not necessarily necessary for implementing the present invention.

[0033] The present invention provides a device and method for realizing a state-controllable passive mode-locked fiber laser. For a ring cavity mode-locked fiber laser, a portion of the intracavity optical signal is converted into an RF signal related to the change in the intensity of the optical signal through a photodetector and a radio frequency amplifier. The RF signal is consistent with the transmission direction of the intracavity optical signal, and an electro-optical intensity modulator is used to synchronously modulate the input optical signal. The DC bias voltage of the polarization-maintaining adjustable optical attenuator and the electro-optical intensity modulator is adjusted by a control circuit to realize precise control of the laser state. The present invention realizes precise control of the state based on a passive mode-locked fiber laser. The control parameters that need to be set are mainly the optical power of the pump laser, the bias DC voltage of the photoelectric intensity modulator, and the attenuation value of the polarization-maintaining adjustable optical attenuator. These parameters can be accurately set through an electronic control circuit. Compared with an actively mode-locked fiber laser, the present invention has the advantages of eliminating an external RF signal source and simplifying the laser structure.

[0034] Example 1

[0035] like Figure 1 As shown, in this embodiment 1, a device for realizing a state-controllable passive mode-locked fiber laser is provided. The passive mode-locked fiber laser is a ring cavity structure, including: an amplifying optical path portion 16, a mode-locking portion 17 and a power supply electronic control portion 18; after the optical signal passes through the amplifying optical path portion 16, it is divided into two paths and enters the feedforward path and the trunk path of the mode-locking portion 17 respectively; the feedforward path detects the intensity change of the optical signal and converts the optical signal into a voltage signal and sends it to the trunk path, and the trunk path modulates the optical signal of the trunk path according to the voltage signal; the power supply electronic control portion 18 is used to set the bias voltage and working point of the trunk path; the optical signal modulated by the trunk path is transmitted to the amplifying optical path portion 16 to form a cycle.

[0036] The amplification optical path part 16 is composed of a pump laser 9, a polarization-maintaining wavelength division multiplexer 8, a polarization-maintaining gain fiber 10, a first polarization-maintaining 1×2 coupler 11, and a polarization-maintaining isolator 12; the pump laser 9 is connected to the polarization-maintaining wavelength division multiplexer 8, the polarization-maintaining wavelength division multiplexer 8 is connected to the polarization-maintaining gain fiber 10, the polarization-maintaining gain fiber 10 is connected to the first polarization-maintaining 1×2 coupler 11, and the first polarization-maintaining 1×2 coupler 11 is connected to the polarization-maintaining isolator 12.

[0037] The mode-locked part 17 is composed of a second polarization-maintaining 1×2 coupler 1, a polarization-maintaining adjustable optical attenuator 2, a photodetector 3, a radio frequency amplifier 4, a polarization-maintaining adjustable optical delay line 6, and an electro-optical intensity modulator 7; wherein the polarization-maintaining adjustable optical attenuator 2, the photodetector 3 and the radio frequency amplifier 4 constitute the feedforward path, and the polarization-maintaining adjustable optical delay line 6 and the electro-optical intensity modulator 7 constitute the trunk path.

[0038] An input end of the second polarization-maintaining 1×2 coupler 1 is connected to the output end of the amplifying optical path portion 16, and the output end of the second polarization-maintaining 1×2 coupler 1 is respectively connected to the polarization-maintaining adjustable optical attenuator 2 and the polarization-maintaining adjustable optical delay line 6, the polarization-maintaining adjustable optical attenuator 2 is connected to the photodetector 3, and the output end of the polarization-maintaining adjustable optical delay line 6 is connected to the electro-optical intensity modulator 7.

[0039] One end of the photodetector 3 and one end of the electro-optic intensity modulator 7 are connected to the radio frequency amplifier 4, and one end of the polarization-maintaining variable optical attenuator 2 and one end of the electro-optic intensity modulator 7 are connected to the power supply electronic control part 18. The photodetector 3 and the electro-optic intensity modulator 7 are connected to the radio frequency amplifier 4 through a radio frequency coaxial line 14.

[0040] The power supply electronic control part 18 is composed of an adjustable DC voltage source 5 , a control circuit 13 , and a data line 15 ; the adjustable DC voltage source 5 is connected to the control circuit 13 ; one end of the polarization-maintaining adjustable optical attenuator 2 is connected to the control circuit 13 via the data line 15 .

[0041] In this embodiment, the above-mentioned device is used to realize the controllable state of the passive mode-locked fiber laser. The control circuit 13 is connected to the polarization-maintaining adjustable optical attenuator 2 and the adjustable DC voltage source 5 respectively. By adjusting the attenuation of the optical signal and the bias DC voltage of the electro-optical intensity modulator 7, the working point of the electro-optical intensity modulator 7 is controlled to realize the controllable state of the laser. The controllable states include: mode-locking start time control; switching between Q-switching, mode-locking, and Q-switching mode-locking states; and adjustable mode-locking pulse width.

[0042] Part of the intracavity optical signal is converted into an RF signal related to the intensity change of the optical signal through the photodetector 3 and the RF amplifier 4. The RF signal has the same transmission direction as the intracavity optical signal and is input to the electro-optic intensity modulator 7 to achieve synchronous modulation of the input optical signal.

[0043] The radio frequency signal input by the electro-optic intensity modulator 7 is obtained by converting the intracavity optical signal through the photodetector 3, and no external modulation signal source is required. The control circuit 13 controls the laser state in combination with the upper computer software.

[0044] In summary, in this embodiment, the state-controllable passive mode-locked fiber laser device comprises an amplifying optical path portion consisting of a pump laser source, a polarization-maintaining wavelength division multiplexer, a polarization-maintaining gain fiber, a polarization-maintaining isolator, and a polarization-maintaining coupler; a mode-locking portion consisting of a polarization-maintaining coupler, a polarization-maintaining adjustable optical delay line, a polarization-maintaining adjustable optical attenuator, a photodetector, a radio frequency amplifier, and an electro-optical intensity modulator; and a power supply electronic control portion consisting of an adjustable DC voltage source and a control circuit. The passive mode-locked fiber laser is a ring cavity structure. After passing through the amplifying optical path portion, the optical signal is divided into two paths through a polarization-maintaining optical fiber split coupler: a feedforward path consisting of a polarization-maintaining adjustable optical attenuator, a photodetector, and a radio frequency amplifier; and a trunk path consisting of a polarization-maintaining adjustable optical delay line and an electro-optical intensity modulator. The feedforward path is used to detect the intensity change of the optical signal and convert the optical signal into a voltage signal, which is applied to the RF port of the electro-optic intensity modulator; the DC port of the electro-optic intensity modulator is connected to an adjustable DC voltage source to set the bias voltage and operating point of the electro-optic intensity modulator, and the electro-optic intensity modulator modulates the optical signal of the main optical path according to the voltage signal provided by the feedforward path; the modulated optical signal is transmitted to the amplifying optical path part, forming a cycle, and starting the next cycle.

[0045] Example 2

[0046] This embodiment 2 provides a device for realizing a state-controllable passive mode-locked fiber laser, the structure of which is as follows: Figure 1 As shown. The device is composed of an amplifying optical path part 16, a mode-locking part 17, and a power supply electronic control part 18. The amplifying optical path part 16 is composed of a pump laser 9, a polarization-maintaining wavelength division multiplexer 8, a polarization-maintaining gain optical fiber 10, a first polarization-maintaining 1×2 coupler 11, and a polarization-maintaining isolator 12; the mode-locking part 17 is composed of a second polarization-maintaining 1×2 coupler 1, a polarization-maintaining adjustable optical attenuator 2, a photodetector 3, a radio frequency amplifier 4, a polarization-maintaining adjustable optical delay line 6, an electro-optical intensity modulator 7, and a radio frequency coaxial line 14; the power supply electronic control part 18 is composed of an adjustable DC voltage source 5, a control circuit 13, and a data line 15.

[0047] The state controllable implementation method of passive mode-locked fiber laser using the device is as follows:

[0048] The passively mode-locked fiber laser adopts a fully polarization-maintaining ring cavity structure to improve the laser's ability to resist environmental interference. The pump light output by the pump laser 9 is coupled to the polarization-maintaining gain fiber 10 through the polarization-maintaining wavelength division multiplexer 8. After the optical signal is power-amplified by the polarization-maintaining gain fiber 10, a part of the optical signal is coupled to the output of the cavity through the port c of the polarization-maintaining 1×2 coupler 11, and the other part of the optical signal returns to the cavity through the port d and is coupled to the polarization-maintaining isolator 12 to ensure that the optical signal operates stably in a single direction in the laser cavity. The output optical signal of the polarization-maintaining isolator 12 is coupled to the polarization-maintaining 1×2 coupler 1, and the optical signal is divided into two paths: one path is coupled to the polarization-maintaining adjustable optical delay line 6 through the port e, and then input to the electro-optical intensity modulator 7 as the optical signal to be modulated, and the delay time of the polarization-maintaining adjustable optical delay line 6 is appropriately adjusted to ensure that the optical signal input to the electro-optical intensity modulator 7 is synchronized with the radio frequency signal; the other optical signal is coupled to the polarization-maintaining adjustable optical attenuator 2 through the port f, converted into an electrical signal by the photodetector 3, and input to the radio frequency amplifier 4 through the radio frequency coaxial line 14. The radio frequency signal is power-amplified and input to the radio frequency port a of the electro-optical intensity modulator 7.

[0049] The control circuit 13 is connected to the polarization-maintaining adjustable optical attenuator 2 through the data line 15, and is used to adjust the attenuation of the optical signal; at the same time, the control circuit 13 is connected to the adjustable DC voltage source 5, and the output port of the adjustable DC voltage source 5 is connected to the DC port b of the electro-optical intensity modulator 7, and is used to set the bias DC voltage of the electro-optical intensity modulator 7, thereby adjusting the working point of the electro-optical intensity modulator 7; the optical signal input to the electro-optical intensity modulator 7 is modulated by the intensity of the radio frequency signal, and the modulated optical signal returns to the amplifying optical path part 16, forming a cycle, and starting the next cycle. The output parameters of the control circuit are adjusted by the upper computer software to change the output voltage of the adjustable DC voltage source 5 and the optical signal attenuation value of the polarization-maintaining adjustable optical attenuator 2, so as to realize the controllable state of the laser. The amplifying optical path part 16, the locking part 17 and the power supply electronic control part 18 are three modules with relatively independent functions, which are conducive to realizing the modularization of laser production and reducing the difficulty of maintenance and troubleshooting.

[0050] The method for obtaining the switching of Q-switching, mode-locking, and Q-switching and mode-locking states is as follows: adjusting the attenuation value of the polarization-maintaining adjustable optical attenuator 2 so that the radio frequency signal output by the photodetector 3 is in the linear amplification region of the radio frequency amplifier 4, avoiding saturation distortion caused by excessive voltage of the radio frequency signal; determining the variation range of the DC voltage output by the adjustable DC voltage source 5 according to the half-wave voltage of the electro-optical intensity modulator 7, and changing the DC bias voltage of the electro-optical intensity modulator 7, so as to obtain the switching of the Q, mode-locking, and Q-switching and mode-locking states. The attenuation value of the polarization-maintaining adjustable optical attenuator 2 and the output DC voltage of the adjustable DC voltage source 5 can be directly set to obtain precise control of the mode-locking start time. After entering the mode-locking state, precise changes in the width of the mode-locking pulse can be achieved by fine-tuning the attenuation value of the polarization-maintaining adjustable optical attenuator 2 and the output DC voltage of the adjustable DC voltage source 5.

[0051] Example 3

[0052] This embodiment 3 provides a device with a closed-loop feedback function to realize a state-controllable passive mode-locked fiber laser, the structure of which is as follows: Figure 2 As shown. The device is composed of an amplifying optical path part 16, a mode-locking part 17, and a power supply electronic control part 18. The amplifying optical path part 16 is composed of a pump laser 9, a polarization-maintaining wavelength division multiplexer 8, a polarization-maintaining gain optical fiber 10, a first polarization-maintaining 1×2 coupler 11, and a polarization-maintaining isolator 12; the mode-locking part 17 is composed of a second polarization-maintaining 1×2 coupler 1, a third polarization-maintaining 1×2 coupler 19, a polarization-maintaining adjustable optical attenuator 2, a photodetector 3, a radio frequency amplifier 4, a polarization-maintaining adjustable optical delay line 6, an electro-optical intensity modulator 7, a radio frequency coaxial line 14, and a photodetector 20; the power supply electronic control part 18 is composed of an adjustable DC voltage source 5, a control circuit 13, and a data line 15. The main difference between the device for realizing state-controllable passive mode-locked fiber laser with closed-loop feedback function provided in this embodiment 3 and that in embodiment 2 lies in the mode-locking part 17: the output port f of the second polarization-maintaining 1×2 coupler 1 is connected to the input port of the third polarization-maintaining 1×2 coupler 19, the output port g of the third polarization-maintaining 1×2 coupler 19 is connected to the input port of the polarization-maintaining adjustable optical attenuator 2, the output port h of the third polarization-maintaining 1×2 coupler 19 is connected to the photodetector 20, the optical signal is converted into an electrical signal, and is fed into the control circuit 13 as a feedback signal through the RF coaxial line, thereby realizing the closed-loop feedback function of the laser.

[0053] In summary, the device for realizing state-controllable passive mode-locked fiber laser described in the embodiment of the present invention has the advantages over the active mode-locked fiber laser in that: an external modulation signal source is omitted, and the laser structure is simplified; the modulation signal in the present invention is generated by the intracavity light wave through the photodetector, so the modulation frequency is naturally consistent with the resonant cavity length, and no regenerative mode-locking technology is required to stabilize the mode-locked state, thereby further simplifying the laser structure and reducing costs. Compared with the passive mode-locked fiber laser, the advantages of the present invention are that: based on the feedforward intensity modulation, the precise control of the mode-locked start time can be achieved, and there is no need to adjust parameters such as the intracavity polarization state. It only needs to set the optical power of the pump laser, the bias DC voltage of the electro-optical intensity modulator, and the attenuation value of the adjustable attenuator. These parameters can be accurately set through the power supply electronic control part; the pulse width is adjusted by changing the DC bias voltage of the photoelectric intensity modulator, so it is easy to set.

[0054] Although the above describes the specific implementation mode of the present invention in conjunction with the accompanying drawings, it is not intended to limit the scope of protection of the present invention. Those skilled in the art should understand that various modifications or variations that can be made by those skilled in the art without creative work on the basis of the technical solution disclosed in the present invention should be included in the scope of protection of the present invention.

Claims

1. A device for realizing a state-controllable passive mode-locked fiber laser, wherein the passive mode-locked fiber laser is a ring cavity structure, characterized in that: include: an amplifying optical path portion (16), a mode-locking portion (17) and a power supply electronic control portion (18); after the optical signal passes through the amplifying optical path portion (16), it is divided into two paths and enters a feedforward path and a trunk path of the mode-locking portion (17) respectively; the feedforward path detects the intensity change of the optical signal and converts the optical signal into a voltage signal and sends it to the trunk path, and the trunk path modulates the optical signal of the trunk path according to the voltage signal; The power supply electronic control part (18) is used to set the bias voltage and working point of the trunk path; the optical signal modulated by the trunk path is transmitted to the amplifying optical path part (16), forming a cycle.

2. The device for realizing state-controllable passive mode-locked fiber laser according to claim 1, characterized in that: The amplification optical path part (16) is composed of a pump laser (9), a polarization-maintaining wavelength division multiplexer (8), a polarization-maintaining gain optical fiber (10), a first polarization-maintaining 1×2 coupler (11), and a polarization-maintaining isolator (12); the pump laser (9) is connected to the polarization-maintaining wavelength division multiplexer (8), the polarization-maintaining wavelength division multiplexer (8) is connected to the polarization-maintaining gain optical fiber (10), the polarization-maintaining gain optical fiber (10) is connected to the first polarization-maintaining 1×2 coupler (11), and the first polarization-maintaining 1×2 coupler (11) is connected to the polarization-maintaining isolator (12).

3. The device for realizing state-controllable passive mode-locked fiber laser according to claim 1, characterized in that: The mode-locking part (17) is composed of a second polarization-maintaining 1×2 coupler (1), a polarization-maintaining adjustable optical attenuator (2), a photodetector (3), a radio frequency amplifier (4), a polarization-maintaining adjustable optical delay line (6), and an electro-optical intensity modulator (7); wherein the polarization-maintaining adjustable optical attenuator (2), the photodetector (3) and the radio frequency amplifier (4) form the feedforward path, and the polarization-maintaining adjustable optical delay line (6) and the electro-optical intensity modulator (7) form the trunk path.

4. The device for realizing state-controllable passive mode-locked fiber laser according to claim 3, characterized in that: An input end of the second polarization-maintaining 1×2 coupler (1) is connected to the output end of the amplifying optical path portion (16); the output end of the second polarization-maintaining 1×2 coupler (1) is respectively connected to the polarization-maintaining adjustable optical attenuator (2) and the polarization-maintaining adjustable optical delay line (6); the polarization-maintaining adjustable optical attenuator (2) is connected to the photodetector (3); and the output end of the polarization-maintaining adjustable optical delay line (6) is connected to the electro-optical intensity modulator (7).

5. The device for realizing state-controllable passive mode-locked fiber laser according to claim 4, characterized in that: One end of the photodetector (3) and one end of the electro-optical intensity modulator (7) are both connected to the radio frequency amplifier (4), and one end of the polarization-maintaining adjustable optical attenuator (2) and one end of the electro-optical intensity modulator (7) are both connected to the power supply electronic control part (18).

6. The device for realizing state-controllable passive mode-locked fiber laser according to claim 5, characterized in that: The photoelectric detector (3) and the electro-optical intensity modulator (7) are both connected to the radio frequency amplifier (4) via a radio frequency coaxial line (14).

7. The device for realizing state-controllable passive mode-locked fiber laser according to claim 5, characterized in that: The power supply electronic control part (18) is composed of an adjustable DC voltage source (5), a control circuit (13), and a data line (15); the adjustable DC voltage source (5) is connected to the control circuit (13); one end of the polarization-maintaining adjustable optical attenuator (2) is connected to the control circuit (13) via the data line (15).

8. A method for realizing controllable state of passive mode-locked fiber laser based on the device according to any one of claims 1 to 7, characterized in that: The control circuit (13) is respectively connected to the polarization-maintaining adjustable optical attenuator (2) and the adjustable DC voltage source (5), and controls the working point of the electro-optical intensity modulator (7) by adjusting the attenuation of the optical signal and the bias DC voltage of the electro-optical intensity modulator (7), thereby realizing the controllable state of the laser. The controllable state includes: mode-locking start time control; switching between Q-switching, mode-locking, and Q-switching mode-locking states; and adjustable mode-locking pulse width.

9. The method according to claim 8, characterized in that A portion of the intracavity optical signal is converted into an RF signal related to the intensity change of the optical signal through a photodetector (3) and a RF amplifier (4). The RF signal has the same transmission direction as the intracavity optical signal and is input into an electro-optic intensity modulator (7) to achieve synchronous modulation of the input optical signal.

10. The method according to claim 9, characterized in that The radio frequency signal input by the electro-optic intensity modulator (7) is obtained by converting the intracavity optical signal through the photoelectric detector (3), and no external modulation signal source is required.

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