Thulium-doped fiber laser

Abstract

The utility model discloses a thulium-doped fiber laser. The thulium-doped fiber laser comprises a pumping source, a thulium-doped gain medium, a resonant cavity structure, a mode locking device, a compensation controller and a wavelength regulator. According to the thulium-doped fiber laser provided by the embodiment of the invention, the overall functions of the laser are more comprehensive and wide.

Description

Technical Field

[0001] The present application relates to the field of lasers, and in particular to a thulium-doped fiber laser. Background Art

[0002] In recent years, fiber lasers based on different mode-locking methods have been realized one after another, so that the operating wavelength is usually within 1200nm-1600nm. These lasers can achieve different types of soliton mode-locked pulse outputs in different structural states, including traditional self-similar solitons, dissipative solitons, dispersion-managed solitons, etc. The main application fields include ultrafast optics, fiber optic sensing, optical communications, etc., which are relatively mature, but thulium-doped fiber lasers working near 2000nm are still in the development stage.

[0003] Thulium-doped fiber lasers are in the 2um band, where there is a high water absorption peak, especially near the 1940nm wavelength, where the water absorption coefficient is as high as 14cm-1, and have a high penetration depth into biological tissues. When 1940nm laser irradiation occurs, a strong thermal effect is produced, which can be widely used in tissue cutting, urethral calculi and kidney stone lithotripsy, hemostasis and other applications.

[0004] In the related art, most thulium-doped fiber lasers have only tuning but no dispersion compensation mechanism, or have dispersion compensation but no tuning, which limits the application of lasers. Therefore, the present application proposes a wavelength-tunable and dispersion-controllable laser to make the overall function of the laser more comprehensive and extensive. Utility Model Content

[0005] The embodiment of the present application provides a thulium-doped fiber laser, which can make the overall function of the laser more comprehensive and extensive.

[0006] The thulium-doped fiber laser provided in this application comprises:

[0007] A pump source, used for providing pump light;

[0008] A thulium-doped gain medium, connected to the pump source, for exciting and amplifying the pump light to form a laser of a corresponding wavelength;

[0009] A resonant cavity structure, wherein the resonant cavity structure is formed by connecting the pump source and the thulium-doped gain medium, and the resonant cavity structure serves as a positive feedback loop for forming laser oscillation and outputting laser light;

[0010] A mode locking device, connected to the pump source, for modulating the laser and forming a pulse;

[0011] A compensation controller, connected between the pump source and the mode locking device, for controlling the dispersion coefficient of the resonant cavity structure to obtain a pulse of a determined target frequency;

[0012] The wavelength adjuster is connected between the pump source and the mode-locking device and is used to adjust the wavelength of the pulse to obtain a pulse of a determined target wavelength.

[0013] In some embodiments of the present application, the laser further includes a wavelength division multiplexer, which is connected to both the pump source and the thulium-doped gain medium. The pump source is used to generate pump light, and when the pump light passes through the wavelength division multiplexer and is injected into the thulium-doped gain medium, stimulated amplification is achieved to generate 2um laser.

[0014] In some embodiments of the present application, the pump source is a 793nm double-ended pump tube.

[0015] In some embodiments of the present application, two wavelength division multiplexers are provided;

[0016] The thulium-doped gain medium is a thulium-doped gain optical fiber, and the thulium-doped gain optical fiber is connected between the two wavelength division multiplexers.

[0017] In some embodiments of the present application, the mode locking device includes a polarization-dependent isolator for converting an incident pulse into linearly polarized light, and a polarization controller for converting the linearly polarized light into elliptically polarized light;

[0018] The polarization controller is connected to the wavelength adjuster, two polarization controllers are provided, and the polarization-dependent isolator is connected between the two polarization controllers;

[0019] The laser also includes a polarization analyzer, and the polarization controller PC is also used to cooperate with the polarization analyzer to control the pulse to form an equivalent saturable absorber in the resonant cavity structure.

[0020] In some embodiments of the present application, the laser further includes a polarization-maintaining isolator for limiting unidirectional transmission of the laser in the resonant cavity structure.

[0021] In some embodiments of the present application, the compensation controller is a compensation optical fiber that adjusts and controls the dispersion amount in the resonant cavity structure.

[0022] In some embodiments of the present application, the wavelength adjuster is a Fabry-Perot etalon, and the Fabry-Perot etalon is connected between the wavelength adjuster and the mode locking device;

[0023] The Fabry-Perot etalon includes two optical surfaces and an actuator for adjusting the distance between the two optical surfaces.

[0024] In some embodiments of the present application, the laser further includes a coupler output device for monitoring the output power and spectral shape of the 2um laser, and the coupler output device is connected between the pump source and the mode locking device.

[0025] In some embodiments of the present application, the resonant cavity structure is a ring cavity structure.

[0026] In the thulium-doped fiber laser of the embodiment of the present application, a pump source provides pump light which passes through a thulium-doped gain medium, and emits the pump light to form a laser of a corresponding wavelength, thereby obtaining a 2um laser; a resonant cavity structure forms laser oscillation and modulates the laser light through a mode-locking device to form a pulse, and then a compensation controller adjusts the dispersion, thereby obtaining a pulse of a determined target frequency, thereby achieving controllable dispersion; at the same time, a wavelength adjuster adjusts the wavelength of the pulse, thereby obtaining a pulse of a determined target wavelength, thereby achieving precise wavelength tuning; thereby achieving a more comprehensive and extensive overall function of the laser. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For those skilled in the art, other drawings can be obtained based on these drawings without creative work.

[0028] Figure 1 It is a structural schematic diagram provided in an embodiment of the present application.

[0029] LD, pump source; WDM, wavelength division multiplexer; Tm, thulium-doped gain medium; DCF, compensation fiber; FP, Fabry-Perot etalon; PC, polarization controller; PD-ISO, polarization-dependent isolator; OC, output coupler. DETAILED DESCRIPTION

[0030] The technical solutions in the embodiments of the present application will be described clearly and completely below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present application.

[0031] In the description of the present application, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present application. In addition, the terms "first" and "second" are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present application, the meaning of "multiple" is two or more, unless otherwise clearly and specifically defined.

[0032] In the description of this application, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection, an electrical connection, or mutual communication; it can be a direct connection, or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0033] In the present application, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may include that the first and second features are in direct contact, or may include that the first and second features are not in direct contact but are in contact through another feature between them. Moreover, a first feature being "above", "above" and "above" a second feature includes that the first feature is directly above and obliquely above the second feature, or simply indicates that the first feature is higher in level than the second feature. A first feature being "below", "below" and "below" a second feature includes that the first feature is directly below and obliquely below the second feature, or simply indicates that the first feature is lower in level than the second feature.

[0034] The disclosure below provides many different embodiments or examples to realize the different structures of the present application. In order to simplify the disclosure of the present application, the parts and settings of specific examples are described below. Of course, they are only examples, and the purpose is not to limit the present application. In addition, the present application can repeat reference numbers and / or reference letters in different examples, and this repetition is for the purpose of simplification and clarity, which itself does not indicate the relationship between the various embodiments and / or settings discussed. In addition, the various specific processes and material examples provided by the present application, but those of ordinary skill in the art can appreciate the application of other processes and / or the use of other materials.

[0035] For details, please refer to Figure 1 The embodiment of the present application provides a thulium-doped fiber laser, which includes a pump source LD, a thulium-doped gain medium Tm connected to the pump source LD, a resonant cavity structure, a mode locking device, a compensation controller, and a wavelength adjuster.

[0036] The pump source LD is used to provide pump light; the thulium-doped gain medium Tm is connected to the pump source LD, and is used to excite and amplify the pump light to form a laser of a corresponding wavelength; the resonant cavity structure is formed by connecting the pump source LD and the thulium-doped gain medium Tm, and the resonant cavity structure serves as a positive feedback loop to form laser oscillation and output laser; the mode locking device is connected to the pump source LD, and is used to modulate the laser and form pulses; the compensation controller is connected between the pump source LD and the mode locking device, and is used to control the dispersion coefficient of the resonant cavity structure to obtain pulses of a determined target frequency; the wavelength adjuster is connected between the pump source LD and the mode locking device, and is used to adjust the wavelength of the pulse to obtain pulses of a determined target wavelength.

[0037] In the thulium-doped fiber laser of the embodiment of the present application, the pump source LD provides pump light which passes through the thulium-doped gain medium Tm, emits a large pump light to form a laser of the corresponding wavelength, and a 2um laser can be obtained; the resonant cavity structure forms laser oscillation and modulates it through a mode-locking device to form a pulse, and then the dispersion is adjusted by a compensation controller, so that a pulse of a determined target frequency can be obtained, and dispersion control is achieved; at the same time, the wavelength adjuster adjusts the wavelength of the pulse, so that a pulse of a determined target wavelength can be obtained, and precise wavelength tuning is achieved; finally, the overall function of the laser is made more comprehensive and extensive.

[0038] In some embodiments, the resonant cavity structure is a ring cavity structure, forming an optical channel.

[0039] In some embodiments, the laser also includes a wavelength division multiplexer WDM, which is connected to both a pump source and a thulium-doped gain medium Tm. The pump source is used to generate pump light, and when the pump light passes through the wavelength division multiplexer WDM and is injected into the thulium-doped gain medium Tm, it is stimulated to be amplified to generate 2um laser.

[0040] In some embodiments, the pump source LD is a 793nm double-ended pump tube; the use of double-ended pumping can improve the pumping efficiency and the output laser power; the 793nm pump tube is injected into the thulium-doped gain fiber through a wavelength division multiplexer WDM by double-ended pumping to generate 2um laser by stimulated amplification, and a pump source LD with a wavelength of 793nm is used, which is at the absorption peak of thulium ions and has high energy absorption efficiency, thereby providing excitation energy for the thulium-doped gain fiber.

[0041] In some embodiments, the thulium-doped gain medium Tm is a thulium-doped gain optical fiber, two wavelength division multiplexers WDM are provided, and the thulium-doped gain optical fiber is connected between the two wavelength division multiplexers WDM to form an optical channel.

[0042] In some embodiments, the mode locking device includes a polarization-dependent isolator PD-ISO for converting an incident pulse into linearly polarized light, and a polarization controller PC for converting linearly polarized light into elliptically polarized light; the polarization controller PC is connected to a wavelength adjuster, two polarization controllers PC are provided, and the polarization-dependent isolator PD-ISO is connected between the two polarization controllers PC; the laser also includes an analyzer, and the polarization controller PCPC is also used to cooperate with the analyzer to control the pulse to form an equivalent saturable absorber in the resonant cavity structure.

[0043] Among them, the incident light pulse will become linearly polarized light after passing through the polarization-dependent isolator PD-ISO, and the linearly polarized light will be converted into elliptically polarized light through the polarization controller PC. The polarization states of the pulses of the elliptically polarized light will also produce different phases due to self-phase modulation and cross-phase modulation when the two orthogonal components are transmitted in the optical fiber. The accumulated nonlinear phase shifts at positions with different pulse intensities are also different; therefore, the polarization controller PC controls the polarization state of the light pulse so that the light that meets the polarization can pass smoothly, thereby improving the quality of the mode-locked pulse output by the laser.

[0044] Specifically, by adjusting the two polarization controllers PC, the polarization state of the central part of the pulse is the same as the direction of the analyzer. By adjusting the angles of the two polarization controllers PC, most of the pulse peak part is transmitted, while the pulse edge part is mostly lost due to its low transmittance. In this way, an equivalent saturable absorber can be formed in the resonant cavity structure, thereby realizing the adjustment of the pulse width and increasing the pulse peak power.

[0045] In some embodiments, the laser further includes a polarization-maintaining isolator for limiting unidirectional transmission of the laser in the resonant cavity structure. The polarization-maintaining isolator in the resonant cavity structure can ensure or limit unidirectional transmission of the laser in the cavity.

[0046] Due to the principle of dispersion, ordinary optical fibers exhibit large negative dispersion at 2um, which is usually detrimental to the quality of the generated mode-locked soliton pulses. The compensation controller can be used to control the dispersion coefficient of the resonant cavity structure and compensate for the dispersion in the resonant cavity structure to a certain extent, so as to obtain high-quality laser mode-locked pulses and obtain pulses of a certain target frequency. In some embodiments, the compensation controller is a compensation optical fiber DCF that adjusts and controls the dispersion amount in the resonant cavity structure. By determining the target pulse shape, the dispersion coefficient and length of the optical fiber in the resonant cavity structure are accurately controlled, and a section of dispersion-compensating optical fiber DCF is added to the cavity to control the dispersion coefficient in the cavity to obtain the required laser pulse.

[0047] In some embodiments, the wavelength adjuster is a Fabry-Perot etalon FP (FP etalon), and the Fabry-Perot etalon FP is connected between the wavelength adjuster and the mode locking device. The Fabry-Perot etalon FP includes two optical surfaces and an actuator for adjusting the distance between the two optical surfaces.

[0048] Specifically, the optical surface of the Fabry-Perot etalon FP adopts an optical structure of an optical flat plate group with two parallel high-reflectivity films for reflecting light; the actuator includes a stepper motor, and the Fabry-Perot etalon FP also includes a circuit board and a circuit program. The stepper motor is started by controlling the circuit board program, and the actuator end of the stepper motor moves, and the actuator end then drives the optical surface of the FP etalon to move at a certain ratio, thereby accurately controlling the distance between the two optical planes, and then accurately adjusting the wavelength of the thulium-doped laser; wherein the actuator end of the stepper motor drives the optical surface of the FP etalon to move at a certain ratio, and the certain ratio can be 100:1, so that the wavelength adjustment is more stable.

[0049] Of course, in some embodiments, the wavelength adjuster may also be a tunable filter, which is connected to the pump source LD, and the selection of different laser wavelengths may be achieved through the tunable filter.

[0050] In some embodiments, the laser further includes a coupling output OC for monitoring the output power and spectral shape of the 2um laser, and the coupling output OC is connected between the pump source LD and the mode locking device to maximize the output laser conforming to the expected shape.

[0051] The thulium-doped fiber laser of this embodiment adopts a ring cavity structure. By compensating the fiber DCF and FP standard tool, it can not only accurately control the dispersion coefficient and length of the fiber in the cavity, but also accurately adjust the wavelength of the thulium-doped laser. The mode-locking device and the equivalent saturable absorber further ensure the quality of the mode-locked pulse, realizing the integration of precise wavelength tuning and dispersion control, and the overall laser function is more comprehensive and extensive.

[0052] In the above embodiments, the description of each embodiment has its own emphasis. For parts that are not described in detail in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.

[0053] The above is a detailed introduction to a thulium-doped fiber laser provided in an embodiment of the present application. Specific examples are used in this article to illustrate the principles and implementation methods of the present application. The description of the above embodiments is only used to help understand the technical solution and its core idea of ​​the present application. Ordinary technicians in this field should understand that they can still modify the technical solutions recorded in the aforementioned embodiments, or replace some of the technical features therein with equivalents; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A thulium-doped fiber laser, characterized in that: include: A pump source, used for providing pump light; A thulium-doped gain medium, connected to the pump source, for exciting and amplifying the pump light to form a laser of a corresponding wavelength; A resonant cavity structure, wherein the resonant cavity structure is formed by connecting the pump source and the thulium-doped gain medium, and the resonant cavity structure serves as a positive feedback loop for forming laser oscillation and outputting laser light; A mode locking device, connected to the pump source, for modulating the laser and forming a pulse; A compensation controller, connected between the pump source and the mode locking device, for controlling the dispersion coefficient of the resonant cavity structure to obtain a pulse of a determined target frequency; The wavelength adjuster is connected between the pump source and the mode-locking device and is used to adjust the wavelength of the pulse to obtain a pulse of a determined target wavelength.

2. The thulium-doped fiber laser according to claim 1, characterized in that: The laser also includes a wavelength division multiplexer, which is connected to both the pump source and the thulium-doped gain medium. The pump source is used to generate pump light, and when the pump light passes through the wavelength division multiplexer and is injected into the thulium-doped gain medium, stimulated amplification is generated to generate 2um laser.

3. The thulium-doped fiber laser according to claim 2, characterized in that: The pump source is a 793nm double-ended pump tube.

4. The thulium-doped fiber laser according to claim 2, characterized in that: The wavelength division multiplexer is provided with two; The thulium-doped gain medium is a thulium-doped gain optical fiber, and the thulium-doped gain optical fiber is connected between the two wavelength division multiplexers.

5. The thulium-doped fiber laser according to claim 1, characterized in that: The mode locking device comprises a polarization-dependent isolator for converting an incident pulse into linearly polarized light, and a polarization controller for converting the linearly polarized light into elliptically polarized light; The polarization controller is connected to the wavelength adjuster, two polarization controllers are provided, and the polarization-dependent isolator is connected between the two polarization controllers; The laser also includes a polarization analyzer, and the polarization controller PC is also used to cooperate with the polarization analyzer to control the pulse to form an equivalent saturable absorber in the resonant cavity structure.

6. The thulium-doped fiber laser according to any one of claims 1 to 5, characterized in that: The laser also includes a polarization-maintaining isolator for limiting the unidirectional transmission of the laser in the resonant cavity structure.

7. The thulium-doped fiber laser according to any one of claims 1 to 5, characterized in that: The compensation controller is a compensation optical fiber for adjusting and controlling the dispersion amount in the resonant cavity structure.

8. The thulium-doped fiber laser according to any one of claims 1 to 5, characterized in that: The wavelength adjuster is a Fabry-Perot etalon, and the Fabry-Perot etalon is connected between the wavelength adjuster and the mode locking device; The Fabry-Perot etalon includes two optical surfaces and an actuator for adjusting the distance between the two optical surfaces.

9. The thulium-doped fiber laser according to any one of claims 1 to 5, characterized in that: The laser also includes a coupler output device for monitoring the output power and spectrum shape of the 2um laser, and the coupler output device is connected between the pump source and the mode locking device.

10. The thulium-doped fiber laser according to any one of claims 1 to 5, characterized in that: The resonant cavity structure is a ring cavity structure.

Images