An all-fiber spatiotemporal mode-locked laser

Abstract

The application discloses an all-fiber time-space mode-locked laser, which comprises a pump source, a beam combiner, a multimode gain optical fiber, a coupler, a filter, an isolator and a mode-locked device, the beam combiner, the multimode gain optical fiber, the coupler, the filter, the isolator and the mode-locked device are sequentially arranged and fused to form a ring-shaped laser resonant cavity; the pump light emitted by the pump source is coupled into the multimode gain optical fiber through the beam combiner; the multimode gain optical fiber absorbs the pump light, forms population inversion and generates a laser beam; the laser beam is coupled out to the filter through the coupler, the filter transmits the laser beam to the isolator after performing spectral filtering on the laser beam; the laser beam is transmitted to the mode-locked device after passing through the isolator, and the laser beam realizes time-space mode locking through the mode-locked device. Through the multimode gain optical fiber, the mode-locked device, the filter, the isolator, the beam combiner, the coupler and other devices, high-power, high-beam-quality and stable time-space mode-locked laser output is realized.

Description

Technical Field

[0001] This application relates to the field of laser technology, and in particular to a high-beam-quality, high-power all-fiber spatiotemporal mode-locked laser. Background Technology

[0002] Laser mode-locking technology involves specially modulating a laser to force the phases of the various oscillating modes within the laser to be fixed, allowing the modes to coherently superimpose and produce ultrashort pulses. Mode-locking is the primary means of achieving ultrashort pulses and ultra-high peak power output. Mode-locked fiber lasers with ultrashort pulses and ultra-high peak power output have become extremely important tools, widely used in numerous fields such as medicine, scientific research, military, and industrial processing.

[0003] Currently, mode-locked fiber lasers based on single-mode fiber are relatively mature. However, due to the small core area and strong nonlinear effects of single-mode fiber, the power of single-mode mode-locked fiber lasers has remained at a low level. Therefore, in many applications, it is necessary to amplify the laser output power to meet application requirements. However, power amplification increases system complexity and instability, and may even alter the laser's output performance. Furthermore, due to the need for high environmental stability in application scenarios, and the fact that an all-fiber structure confines the laser transmission within the fiber, all-fiber mode-locked lasers are inevitably the mainstream development direction. Moreover, to meet energy requirements and industrial processing requirements (such as laser cutting flatness), there is an urgent need for mode-locked lasers with high beam quality. Therefore, to meet practical application needs, there is an urgent need to design a practical all-fiber mode-locked laser with a simple structure, high power, and high beam quality. Summary of the Invention

[0004] In view of this, this application proposes a high-beam-quality, high-power all-fiber spatiotemporal mode-locked laser to solve the problems of high cost, complex structure, low average output power, and poor beam quality in the prior art.

[0005] This application provides an all-fiber spatiotemporal mode-locked laser, which includes a pump source, a combiner, a multimode gain fiber, a coupler, a filter, an isolator, and a mode-locking device. The combiner, the multimode gain fiber, the coupler, the filter, the isolator, and the mode-locking device are sequentially arranged and fused together to form a ring-shaped laser resonant cavity. The pump light emitted by the pump source is coupled into the multimode gain fiber through the combiner. The multimode gain fiber absorbs the pump light, forming population inversion and generating a laser beam. The laser beam is coupled and output to the filter through the coupler. The filter performs spectral filtering on the laser beam and then transmits it to the isolator. After passing through the isolator, the laser beam is transmitted to the mode-locking device, and the laser beam achieves spatiotemporal mode-locking through the mode-locking device.

[0006] Furthermore, the laser resonant cavity is also provided with a beam combiner pigtail, one end of which is fused to the mode-locking device, and the other end is fused to the multimode gain fiber, for coupling pump light into the multimode gain fiber.

[0007] Furthermore, the combiner pigtail is made of multimode transmission fiber that matches the multimode gain fiber.

[0008] Furthermore, the multimode gain fiber is a double-clad multimode gain fiber, and the core diameter of the multimode gain fiber is greater than 20 micrometers.

[0009] Furthermore, a coupler pigtail is provided inside the laser resonant cavity. One end of the coupler pigtail is fused to the multimode gain fiber, and the other end is fused to the filter. This coupler pigtail is used to couple a portion of the laser beam to the filter and another portion of the laser beam to the outside of the laser resonant cavity.

[0010] Furthermore, a filter pigtail is also provided inside the laser resonant cavity. One end of the filter pigtail is fused to the coupler pigtail, and the other end is fused to the isolator, for transmitting the spectrally filtered laser beam to the isolator.

[0011] Furthermore, the coupler pigtail and the filter pigtail are both made of multimode graded-index optical fiber, and the core diameter of the coupler pigtail and the core diameter of the filter pigtail are both greater than 50 micrometers.

[0012] Furthermore, the laser resonant cavity is also provided with an isolator pigtail, one end of which is fused to the filter pigtail, and the other end is fused to the mode-locking device, for transmitting the spectrally filtered laser beam to the mode-locking device.

[0013] Furthermore, the isolator pigtail is a few-mode fiber, and the core diameter of the isolator pigtail is 10 micrometers.

[0014] Furthermore, the mode-locking device consists of two polarization controllers and an isolator.

[0015] The aforementioned all-fiber spatiotemporal mode-locked laser achieves high power through multimode gain fiber; stable spatiotemporal mode-locking is achieved through mode-locking devices, multimode fiber, and filtering devices; high beam quality is achieved through the nonlinear effects of multimode fiber and the filtering effect of resonant cavity; and high power, high beam quality, and stable spatiotemporal mode-locked laser output are achieved through the nonlinear effects and filtering effects of multimode gain fiber, saturable absorber, and multimode gain fiber, as well as through reasonable design and optimization of each component. This results in higher output power than mode-locked lasers based on single-mode fiber and can achieve single-mode (transverse mode) output. Attached Figure Description

[0016] For illustrative and not limiting purposes, this application will now be described with reference to preferred embodiments, and in particular with reference to the accompanying drawings, in which:

[0017] Figure 1 This is a schematic diagram of the structure of an all-fiber spatiotemporal mode-locked laser provided in an embodiment of this application.

[0018] Among them, 100 is the pump source, 200 is the laser resonator, 210 is the combiner, 220 is the multimode gain fiber, 230 is the coupler, 240 isolator, 250 is the mode-locking device, 260 is the combiner pigtail, 270 is the coupler pigtail, 280 isolator pigtail, 290 is the filter, and 291 is the filter pigtail. Detailed Implementation

[0019] To better understand the above-mentioned objectives, features, and advantages of this application, the application will be described in detail below with reference to the accompanying drawings and specific embodiments. It should be noted that, unless otherwise specified, the embodiments and features described herein can be combined with each other.

[0020] Numerous specific details are set forth in the following description to provide a thorough understanding of this application. The described embodiments are merely some, not all, of the embodiments described herein. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application.

[0021] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application.

[0022] Definitions:

[0023] Mode locking: A method for achieving ultrashort pulse output by phase locking of the longitudinal mode;

[0024] Spatiotemporal mode locking (multimode mode locking): A method to achieve phase locking of both the transverse and longitudinal modes to realize ultra-short pulse output.

[0025] To address the problem that current mode-locked fiber lasers (oscillator stages of ultrashort pulse fiber lasers) cannot achieve stable output of both high average power and high beam quality simultaneously in an all-fiber structure, this application provides a high-beam-quality, high-power all-fiber spatiotemporal mode-locked laser. The specific solution of this application embodiment is described below with reference to the accompanying drawings.

[0026] Figure 1 This is a schematic diagram of the structure of an all-fiber spatiotemporal mode-locked laser provided in an embodiment of this application. Please refer to... Figure 1 The all-fiber spatiotemporal mode-locked laser includes a pump source 100 and a laser resonant cavity 200. The laser resonant cavity 200 is equipped with a beam combiner 210, a multimode gain fiber 220, a coupler 230, a filter 290, an isolator 240, and a mode-locking device 250. The beam combiner 210, the multimode gain fiber 220, the coupler 230, the filter 290, the isolator 240, and the mode-locking device 250 are sequentially arranged and fused together to form the laser resonant cavity 200.

[0027] Pump source 100 emits pump light, and beam combiner 210 couples the pump light into multimode gain fiber 220. Multimode gain fiber 220 absorbs the pump light, forming population inversion and generating a high-power and high-beam-quality laser beam. The laser beam is coupled and output to filter 290 via coupler 230. After spectral filtering, the laser beam is transmitted to isolator 240. Isolator 240 ensures unidirectional transmission of the laser beam within the laser resonant cavity. After passing through isolator 240, the laser beam is transmitted to mode-locking device 250, which achieves spatiotemporal mode-locking.

[0028] In this embodiment, high power is achieved through multimode gain fiber; stable spatiotemporal mode locking is achieved through mode-locking devices, multimode fiber, and filtering devices; high beam quality is achieved through the nonlinear effect of multimode fiber and the filtering effect of resonant cavity; and high power, high beam quality, and stable spatiotemporal mode-locked laser output are achieved through the nonlinear effect and filtering effect of multimode gain fiber, mode-locking device, and multimode transmission fiber, and by rationally designing and optimizing each component.

[0029] This application presents a novel all-fiber resonant cavity structure. This simple and practical structure includes multimode gain fiber, mode-locking devices, filters, isolators, beam combiners, couplers, and other devices. Through the rational design of each device and the optimized layout of the resonant cavity structure, high power, high beam quality, and stable spatiotemporal mode-locking can be achieved simultaneously.

[0030] In some embodiments, a combiner pigtail 260 is further provided within the laser resonant cavity 200. One end of the combiner pigtail 260 is fused with a mode-locked device 250, and the other end is fused with a multimode gain fiber 220, for coupling pump light into the multimode gain fiber 220. Within the laser resonant cavity 200, a combiner 210 is fused with the multimode gain fiber 220 via the combiner pigtail 260. The combiner pigtail 260 uses a multimode transmission fiber matched to the multimode gain fiber, for coupling pump light into the multimode gain fiber 220.

[0031] In some embodiments, the multimode gain fiber 220 has high gain, improves population inversion when pumped to provide energy, and can simultaneously achieve high beam quality and high power output. High power is achieved through the multimode gain fiber, while high beam quality is achieved through the nonlinear effects in the multimode fiber and the filtering effects combined with those of single-mode (or few-mode) fiber.

[0032] In some embodiments, the multimode gain fiber 220 is a double-clad multimode gain fiber with a core diameter greater than 20 micrometers.

[0033] In some embodiments, a coupler pigtail 270 is also provided within the laser resonant cavity 200. One end of the coupler pigtail 270 is fused with a multimode gain fiber 220, and the other end is fused with a filter 290, used to couple the output spectral filtering, high beam quality, and high power laser beam to the filter. The coupler pigtail 270 uses a multimode graded-index transmission fiber, and the core diameter of the coupler pigtail 270 is greater than 50 micrometers. Coupler 230 simultaneously possesses the functions of spectral filtering, high beam quality output, high power output, and coupling output. The coupling ratio of coupler 230 is 20:80, with 20% used as the output port.

[0034] The embodiments of this application employ multimode gain fiber and multimode transmission fiber, which can improve the output power of the laser and utilize the nonlinear Kerr beam self-cleaning effect in the multimode fiber to achieve beam purification and output a high-quality beam. This application only requires simple fusion splicing of the pigtails of each device to achieve the various functions required for mode-locking.

[0035] The embodiments of this application effectively achieve stable spatiotemporal mode locking through the ingenious combination and optimized design of mode-locking devices, multimode optical fibers and filters.

[0036] In some embodiments, a filter pigtail 291 is also provided in the laser resonant cavity 200. One end of the filter pigtail 291 is fused to a coupler pigtail 270, and the other end is fused to an isolator 240, for transmitting the spectrally filtered laser beam to the isolator 240.

[0037] In some embodiments, the filter pigtail 291 is a multimode graded-index transmission fiber, and the core diameter of the filter pigtail 291 is greater than 50 micrometers.

[0038] In some embodiments, the isolator 240 has the functions of ensuring unidirectional transmission of signal light and spectral filtering; in combination, it may also have a mode-locking function. The laser resonant cavity 200 is also provided with an isolator pigtail 280, one end of which is fused with a filter pigtail 291, and the other end is fused with a mode-locking device 250, for transmitting the spectrally filtered laser beam to the mode-locking device.

[0039] In some embodiments, the isolator pigtail 280 is a few-mode fiber, which enables spatial filtering when the multimode fiber transmits to the few-mode fiber. The core diameter of the isolator pigtail 280 is 10 micrometers.

[0040] When the laser beam is transmitted from the filter pigtail 291 to the isolator pigtail 280, due to the different specifications of the filter pigtail 291 and the isolator pigtail 280, a spatial filtering effect is generated at the splice of the two pigtails, thereby achieving a spatial filtering effect on the laser beam.

[0041] The embodiments of this application cleverly achieve spatial filtering function through an effective combination of multimode fiber and few-mode fiber.

[0042] In some embodiments, the mode-locking device 250 has both mode-locking and spectral filtering functions. The mode-locking device 250 consists of two polarization controllers and an isolator with polarization induction function, employing a nonlinear polarization rotation (evolution) mode-locking mechanism. In other embodiments, the mode-locking device 250 may also be other saturable absorbers or mode-locking devices.

[0043] The spatially filtered laser beam is output to the mode-locking device 250, and stable spatiotemporal mode-locking is achieved through the mode-locking device, multimode fiber, and filtering device.

[0044] The embodiments of this application effectively achieve beam shaping by utilizing the nonlinear effects of multimode optical fibers (including but not limited to self-cleaning), the filtering effect of resonant cavities, the saturation absorption effect of mode-locking devices, or any combination thereof.

[0045] In some embodiments, the laser resonant cavity 200 adopts a ring cavity structure.

[0046] The aforementioned all-fiber spatiotemporal mode-locked laser achieves high power and high beam quality mode-locking, with higher output power than mode-locked lasers based on few-mode fibers, and can achieve single-mode (transverse mode) output.

[0047] The aforementioned all-fiber spatiotemporal mode-locked laser utilizes multimode gain fiber and a filtering structure based on the fiber itself to achieve spatial filtering and spectral filtering. It also combines a mode-locking device to achieve spatiotemporal mode-locking, multimode gain fiber to achieve high power, and nonlinear effects in multimode gain fiber combined with filtering effects of few-mode fiber to achieve high beam quality.

[0048] The aforementioned all-fiber spatiotemporal mode-locked laser simplifies the structure of the mode-locked laser by simply splicing the pigtails of the necessary components, reducing the complexity of the resonant cavity, improving the stability of the mode-locked laser, and lowering the manufacturing cost. The mode-locked laser of this application can achieve an average output power exceeding 3W without the need for an amplification stage, and can simultaneously achieve high beam quality output, increasing the output power by an order of magnitude compared to previous oscillators using few-mode fiber as the gain medium.

[0049] The laser provided in this application embodiment can be directly applied in some scenarios, such as the cutting of brittle materials like filters.

[0050] The specific embodiments described above do not constitute a limitation on the scope of protection of this application. Those skilled in the art should understand that various modifications, combinations, sub-combinations, and substitutions can occur depending on design requirements and other factors. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this application should be included within the scope of protection of this application.

Claims

1. An all-fiber spatiotemporal mode-locked laser, characterized in that, It includes a pump source, a combiner, a multimode gain fiber, a coupler, a filter, an isolator, and a mode-locking device. The combiner, the multimode gain fiber, the coupler, the filter, the isolator, and the mode-locking device are sequentially arranged and fused together to form a ring-shaped laser resonant cavity. The pump light emitted by the pump source is coupled into the multimode gain fiber via the combiner; the multimode gain fiber absorbs the pump light, forming population inversion and generating a laser beam; the laser beam is coupled and output to the filter via the coupler, and the filter performs spectral filtering on the laser beam before transmitting it to the isolator; after passing through the isolator, the laser beam is transmitted to the mode-locking device, and the laser beam achieves spatiotemporal mode-locking via the mode-locking device. The laser resonant cavity is also provided with a coupler pigtail. One end of the coupler pigtail is fused to the multimode gain fiber, and the other end is fused to the filter. It is used to couple a part of the laser beam to the filter and the other part of the laser beam to the outside of the laser resonant cavity. The laser resonant cavity is also equipped with a filter pigtail, one end of which is fused to the coupler pigtail and the other end is fused to the isolator, for transmitting the spectrally filtered laser beam to the isolator. Both the coupler pigtail and the filter pigtail are multimode graded-index optical fibers, and the core diameter of both the coupler pigtail and the filter pigtail is greater than 50 micrometers. The laser resonant cavity is also provided with an isolator pigtail, one end of which is fused to the filter pigtail and the other end is fused to the mode-locking device, for transmitting the spectrally filtered laser beam to the mode-locking device. The isolator pigtail is a few-mode fiber, and the core diameter of the isolator pigtail is 10 micrometers.

2. The all-fiber spatiotemporal mode-locked laser according to claim 1, characterized in that, The laser resonant cavity is also provided with a beam combiner pigtail, one end of which is fused to the mode-locking device, and the other end is fused to the multimode gain fiber, for coupling pump light into the multimode gain fiber.

3. The all-fiber spatiotemporal mode-locked laser according to claim 2, characterized in that, The combiner pigtail uses a multimode transmission fiber that is matched with the multimode gain fiber.

4. The all-fiber spatiotemporal mode-locked laser according to claim 1, characterized in that, The multimode gain fiber is a double-clad multimode gain fiber, and the core diameter of the multimode gain fiber is greater than 20 micrometers.

5. The all-fiber spatiotemporal mode-locked laser according to claim 1, characterized in that, The mode-locking device consists of two polarization controllers and an isolator.

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