High-power, high signal-to-noise ratio 920nm femtosecond optical parametric laser

Abstract

This invention provides a high-power, high signal-to-noise ratio (SNR) 920nm femtosecond optical parametric laser, relating to the fields of laser technology and nonlinear optics. This high-power, high SNR 920nm femtosecond optical parametric laser comprises: a 1560nm mode-locked seed source, a first 1560nm power amplifier, a first nonlinear fiber, a second 1560nm power amplifier, a second nonlinear fiber, a fiber delay, a dispersion-compensating fiber, a 1μm filter, a 1μm power amplifier, a grating pair, a mirror, a lens, a wavelength division multiplexer, and a nonlinear photonic crystal fiber. All components—the 1560nm mode-locked seed source, the first 1560nm power amplifier, the first nonlinear fiber, the second 1560nm power amplifier, the second nonlinear fiber, the fiber delay, the dispersion-compensating fiber, the 1μm filter, the 1μm power amplifier, the wavelength division multiplexer, and the nonlinear photonic crystal fiber—are connected using an all-fiber fused splicing structure. This effectively solves the limitations of Nd: fiber and solid-state laser technology in output laser power expansion, reliability, and SNR improvement.

Description

Technical Field

[0001] This invention relates to the fields of laser technology and nonlinear optics, specifically to a high-power, high signal-to-noise ratio 920nm femtosecond optical parametric laser. Background Technology

[0002] Femtosecond laser sources with specific laser parameters, serving as the core functional component of multiphoton microscopy imaging systems—fluorescent excitation sources—can open the door to the microscopic world for humankind. They provide a powerful tool for studying pathological mechanisms related to brain diseases at the subcellular, neuronal, neural circuit, and nervous system scales, and for revealing the mysteries of brain information processing, transmission, and storage. Therefore, developing effective research tools suitable for elucidating the neural activity and information processing mechanisms of animal brains during free movement—including femtosecond laser sources with specific laser parameters and corresponding two-photon microscopy imaging equipment—is of great significance.

[0003] In two-photon fluorescence microscopy, different fluorescent proteins selectively absorb femtosecond laser light at different wavelengths. Therefore, femtosecond laser sources with optimal radiation wavelengths are indispensable tools for studying specific functional areas of the nervous system in neuroscience research. Furthermore, the most commonly used light indicators in two-photon microscopy of brain tissue have peak absorption wavelengths in the 920nm band. Therefore, 920nm femtosecond lasers are the optimal wavelength for exciting fluorescent indicators in the brain and are potentially ideal light sources for exploring and revealing the pathological mechanisms of brain diseases and the mysteries of human brain function. Consequently, 920nm femtosecond laser sources have attracted widespread attention.

[0004] In the prior art, patent application CN201410164008.1 discloses a femtosecond laser based on a single-clad neodymium fiber and a ring cavity, and its fabrication method. This patent includes components such as a wavelength division multiplexer, gain fiber, isolator, and collimator. This mode-locked fiber laser achieves mode-locking through nonlinear polarization rotation. Because this mode-locked fiber laser uses an 808nm laser diode as the pump source, the output driving power of the pump laser source is limited, resulting in a maximum mode-locked output power of only tens of mW for the 920nm laser. Simultaneously, due to the radiation characteristics of neodymium-doped fiber in the 1.06μm band, the signal-to-noise ratio of the generated 920nm laser is typically low. Summary of the Invention

[0005] (a) Technical problems to be solved

[0006] To address the shortcomings of existing technologies, this invention provides a high-power, high signal-to-noise ratio 920nm femtosecond optical parametric laser. This solves the problem that, because the mode-locked fiber laser uses an 808nm laser diode as its pump source, the maximum mode-locked output power of the 920nm laser is limited to only tens of mW due to the output driving power of the pump laser source. Furthermore, the radiation characteristics of neodymium-doped fiber in the 1.06μm band typically result in a low signal-to-noise ratio for the generated 920nm laser.

[0007] (II) Technical Solution

[0008] To achieve the above objectives, the present invention provides the following technical solution: a high-power, high signal-to-noise ratio 920nm femtosecond optical parametric laser, comprising: a 1560nm mode-locked seed source, a 1560nm power amplifier, a nonlinear fiber, a 1560nm power amplifier, a nonlinear fiber, a fiber delay, a dispersion compensation fiber, a 1μm filter, a 1μm power amplifier, a grating pair, a mirror, a lens, a wavelength division multiplexer, and a nonlinear photonic crystal fiber. All components—the 1560nm mode-locked seed source, the 1560nm power amplifier, the nonlinear fiber, the 1560nm power amplifier, the nonlinear fiber, the fiber delay, the dispersion compensation fiber, the 1μm filter, the 1μm power amplifier, the wavelength division multiplexer, and the nonlinear photonic crystal fiber—are connected using an all-fiber fused splicing structure.

[0009] Preferably, the 1560nm mode-locked seed source is a dispersion-controlled ultrashort pulse laser based on erbium-doped gain fiber; the 1560nm power amplifier one and the 1560nm power amplifier two are both erbium-doped fiber amplifiers pumped by laser diodes; the nonlinear fiber one and the nonlinear fiber two are both highly nonlinear fibers; the 1μm power amplifier is a ytterbium-doped fiber gain amplifier stage pumped by laser diodes; the mode field diameter of the nonlinear photonic crystal fiber is 4.5μm, and the zero-dispersion wavelength is close to 1053nm; the adjustment accuracy of the fiber delay is 1μm; the group delay coefficient of the dispersion compensation fiber is D ~ -104ps / nm / km; and the grating pair consists of grating one and grating two.

[0010] A method for operating a high-power, high signal-to-noise ratio 920nm femtosecond optical parametric laser, characterized by the following specific steps:

[0011] The output power of S1 and the 1560nm mode-locked seed source is split into beams at a 1:1 ratio. After splitting, the beams are injected into 1560nm power amplifier one and 1560nm power amplifier two for power and energy amplification. The two amplifiers amplify the average power of the laser pulse after splitting the 1560nm mode-locked seed source into beams at a 1:1 ratio to >100mW, with a corresponding pulse width <500fs.

[0012] S2, nonlinear fiber one and nonlinear fiber two significantly broaden the incident spectrum of 1560nm femtosecond laser with an average power >100mW and pulse width <500fs amplified by 1560nm power amplifier one and 1560nm power amplifier two, respectively, and cover the 1.3μm band and 1μm band, respectively, and have the strongest spectral radiation peaks at 1.3μm and 1μm.

[0013] S3, the 1μm filter effectively filters the 1μm band spectral components generated in the nonlinear fiber 2, with a center wavelength of 1053nm and a filtering bandwidth of >4nm.

[0014] S4, the 1μm power amplifier filters the laser after it has been filtered by a 1μm filter and is prepared to be used as the parametric four-wave mixing pump laser required for the generation of 920nm laser. It amplifies the power and energy of the laser with a center wavelength of 1053nm and a bandwidth of >4nm after it has been filtered by a 1μm filter, so as to achieve an amplified laser output of >5W.

[0015] S5. The grating provides pre-chirp adjustment for the 1053nm high-power laser amplified by the 1μm power amplifier. Specifically, the chirp and pulse width of the 1053nm laser can be controlled by adjusting the spacing between grating one and grating two. The line density of both grating one and grating two is >600 lines / mm.

[0016] S6. The lens couples the 1053nm laser, which is provided with pre-chirped control by the grating pair, into the pump port of the wavelength division multiplexer and provides four-wave mixing parametric pump light for the generation of the high-power, high signal-to-noise ratio 920nm parametric laser of the present invention in the nonlinear photonic crystal fiber.

[0017] S7. The fiber delayer provides delay control for the 1.3μm band laser generated in the nonlinear fiber, wherein the 1.3μm band laser is the four-wave mixing parametric signal light required for the generation of the high-power, high signal-to-noise ratio 920nm parametric laser of this invention.

[0018] S8. The laser emitted from the fiber delayer passes through the parametric signal 1.3μm band laser of the dispersion compensation fiber and enters the nonlinear photonic crystal fiber through the signal port of the wavelength division multiplexer. It undergoes a four-wave mixing effect with the parametric pump 1053nm laser to generate a high-power 920nm femtosecond laser.

[0019] (III) Beneficial Effects

[0020] This invention provides a high-power, high signal-to-noise ratio 920nm femtosecond optical parametric laser. It possesses the following beneficial effects:

[0021] 1. This invention utilizes the nonlinear transmission characteristics of a high-average-power 1560nm linearly polarized femtosecond laser in the negative dispersion region of a highly nonlinear fiber. By employing specific spectral selection techniques, it achieves the parametric pump laser and parametric signal laser required for 920nm laser generation. Simultaneously, based on the parametric four-wave mixing nonlinear optical effect in nonlinear photonic crystal fiber, it realizes synchronously pumped high-average-power, high-signal-to-noise-ratio 920nm femtosecond fiber parametric chirped pulse amplification output, effectively solving the limitations of Nd fiber and solid-state laser technology in output laser power expansion, reliability, and signal-to-noise ratio improvement.

[0022] 2. This invention utilizes the parametric four-wave mixing gain spectrum characteristics generated by pumping at a near-zero dispersion wavelength in a nonlinear fiber. By optimizing the position of the parametric pump wavelength relative to the zero dispersion wavelength of the nonlinear fiber, a wide-band continuously tunable femtosecond laser output can be achieved, effectively overcoming the wide pulse width defects caused by the limited gain bandwidth of traditional laser media and the strong nonlinear effects during amplification. Attached Figure Description

[0023] Figure 1 This is an overall schematic diagram of the high-power, high signal-to-noise ratio 920nm femtosecond optical parametric laser proposed in this invention.

[0024] The components include: 1. 1560nm mode-locked seed source; 2. 1560nm power amplifier I; 3. Nonlinear fiber I; 4. 1560nm power amplifier II; 5. Nonlinear fiber II; 6. Fiber delayer; 7. Dispersion compensation fiber; 8. 1μm filter; 9. 1μm power amplifier; 10. Grating pair; 11. Mirror; 12. Lens; 13. Wavelength division multiplexer; 14. Nonlinear photonic crystal fiber. Detailed Implementation

[0025] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0026] Example:

[0027] like Figure 1As shown, this embodiment of the invention provides a high-power, high signal-to-noise ratio 920nm femtosecond optical parametric laser, comprising: a 1560nm mode-locked seed source 1, a 1560nm power amplifier 1, a nonlinear fiber 1 3, a 1560nm power amplifier 2 4, a nonlinear fiber 2 5, an optical fiber delay 6, a dispersion-compensating fiber 7, a 1μm filter 8, a 1μm power amplifier 9, a grating pair 10, a mirror 11, a lens 12, a wavelength division multiplexer 13, and a nonlinear photonic crystal fiber 14. All components—the 1560nm mode-locked seed source 1, the 1560nm power amplifier 1 2, the nonlinear fiber 1 3, the 1560nm power amplifier 2 4, the nonlinear fiber 2 5, the optical fiber delay 6, the dispersion-compensating fiber 7, the 1μm filter 8, the 1μm power amplifier 9, the wavelength division multiplexer 13, and the nonlinear photonic crystal fiber 14—are connected by an all-fiber fused splicing structure.

[0028] The 1560nm mode-locked seed source 1 is a dispersion-controlled ultrashort pulse laser based on erbium-doped gain fiber, with an output pulse width that can be compressed to <500 fs, a repetition frequency >1MHz, and an output power <50mW; 1560nm power amplifier 2 and 1560nm power amplifier 4 are both erbium-doped fiber amplifiers pumped by laser diodes; nonlinear fiber 3 and nonlinear fiber 5 are both highly nonlinear fibers, which can be fibers with the same parameters or fibers with different parameters, and at 1560nm, the second-order dispersion coefficient β2 <0, the third-order dispersion coefficient β3 >0, the effective mode field area is <15μm2, and the nonlinear coefficient is <15W-1·km-1. The lengths of nonlinear fiber 3 and nonlinear fiber 5 are <10cm; the 1μm power amplifier 9 is a laser... The diode-pumped ytterbium-doped fiber gain amplification stage; the nonlinear photonic crystal fiber 14 has a mode field diameter of 4.5 μm and a zero-dispersion wavelength close to 1053 nm; the fiber delayer 6 has an adjustment accuracy of 1 μm, and adjusting the fiber delayer 6 can achieve precise time synchronization between the four-wave mixing parametric pumped 1053 nm laser and the four-wave mixing parametric signal 1.3 μm band laser in the nonlinear photonic crystal fiber 14, which is a prerequisite for the generation of high parametric conversion efficiency and high signal-to-noise ratio 920 nm high-power femtosecond parametric laser; the dispersion compensation fiber 7 has a group delay coefficient of D ~ -104 ps / nm / km, and the dispersion compensation fiber 7 provides pre-chirp and pulse width control for the four-wave mixing parametric signal 1.3 μm band laser. Specifically, the chirp and pulse width of the 1.3 μm band laser can be controlled by adjusting the length of the dispersion compensation fiber 7; the grating pair 10 consists of grating one and grating two.

[0029] A method for operating a high-power, high signal-to-noise ratio 920nm femtosecond optical parametric laser, characterized by the following specific steps:

[0030] The output power of S1 and 1560nm mode-locked seed source 1 is split into beams at a 1:1 ratio. After splitting, the beams are injected into 1560nm power amplifier 1 and 1560nm power amplifier 2 and 4 respectively for power and energy amplification. The two amplifiers amplify the average power of the laser pulse after 1560nm mode-locked seed source 1 is split into beams at a 1:1 ratio to >100mW, and the corresponding pulse width is <500fs.

[0031] S2, nonlinear fiber 3, and nonlinear fiber 2 5 significantly broaden the incident spectrum of 1560nm femtosecond laser with an average power >100mW and pulse width <500fs, amplified by 1560nm power amplifier 1 2 and 1560nm power amplifier 2 4, respectively, covering the 1.3μm and 1μm bands, and exhibiting the strongest spectral radiation peaks at 1.3μm and 1μm. This allows for the subsequent spectral filtering (such as through a 1μm filter 8) to obtain a wide bandwidth and high power laser output in the 1.3μm and 1μm bands.

[0032] S3 and 1μm filter 8 effectively filter the 1μm band spectral components generated in nonlinear fiber 25, with a center wavelength of 1053nm and a filtering bandwidth of >4nm.

[0033] S4 and 1μm power amplifier 9 filter the laser from 1μm filter 8 and prepare it as the parametric four-wave mixing pump laser required for 920nm laser generation for power and energy amplification; that is, the laser with a center wavelength of 1053nm and a bandwidth >4nm after being filtered by 1μm filter 8 is amplified to achieve amplified laser output of >5W.

[0034] S5. The grating provides pre-chirp adjustment for the 1053nm high-power laser amplified by the 1μm power amplifier 9. Specifically, the chirp and pulse width of the 1053nm laser can be controlled by adjusting the spacing between grating one and grating two. The line density of both grating one and grating two is >600 lines / mm.

[0035] S6, Lens 12 couples the 1053nm laser with pre-chirped control provided by grating pair 10 into the pump port of wavelength division multiplexer 13 and provides four-wave mixing parametric pump light for the generation of the high-power, high signal-to-noise ratio 920nm parametric laser of the present invention in nonlinear photonic crystal fiber 14.

[0036] S7, the fiber delayer 6 provides delay control for the 1.3μm band laser generated in the nonlinear fiber 3, wherein the 1.3μm band laser is the four-wave mixing parametric signal light required for the generation of the high-power, high signal-to-noise ratio 920nm parametric laser of this invention;

[0037] The laser emitted from fiber delayer 6 passes through the parametric signal 1.3μm band laser of dispersion compensation fiber 7 and enters nonlinear photonic crystal fiber 14 through the signal port of wavelength division multiplexer 13. It undergoes a four-wave mixing effect with parametric pump 1053nm laser to generate high-power 920nm femtosecond laser.

[0038] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A high-power, high signal-to-noise ratio 920nm femtosecond optical parametric laser, characterized in that, include: The following components are listed: 1560nm mode-locked seed source (1), 1560nm power amplifier one (2), nonlinear fiber one (3), 1560nm power amplifier two (4), nonlinear fiber two (5), fiber delay (6), dispersion compensation fiber (7), 1μm filter (8), 1μm power amplifier (9), grating pair (10), mirror (11), lens (12), wavelength division multiplexer (13), and nonlinear photonic crystal fiber (14). The linear fiber 2 (5), fiber delayer (6), dispersion compensation fiber (7), 1μm filter (8), 1μm power amplifier (9), wavelength division multiplexer (13) and nonlinear photonic crystal fiber (14) all adopt an all-fiber fused splicing structure. Nonlinear fiber 1 3 and nonlinear fiber 2 5 are both highly nonlinear fibers, with the same parameters or different parameters. At 1560nm, the second-order dispersion coefficient β2 < 0, the third-order dispersion coefficient β3 > 0, the effective mode field area is < 15μm2, and the nonlinear coefficient is < 15W-1·km-1. The lengths of nonlinear fiber 1 3 and nonlinear fiber 2 5 are < 10cm.

2. The high-power, high signal-to-noise ratio 920nm femtosecond optical parametric laser according to claim 1, characterized in that: The 1560nm mode-locked seed source (1) is a dispersion-controlled ultrashort pulse laser based on erbium-doped ion gain fiber; the 1560nm power amplifier one (2) and the 1560nm power amplifier two (4) are both erbium-doped fiber amplifiers pumped by laser diodes; the nonlinear fiber one (3) and the nonlinear fiber two (5) are both highly nonlinear fibers; the 1μm power amplifier (9) is a ytterbium-doped fiber gain amplifier stage pumped by laser diodes; the mode field diameter of the nonlinear photonic crystal fiber (14) is 4.5μm, and the zero-dispersion wavelength position is close to 1053nm; the adjustment accuracy of the fiber delayer (6) is 1μm; the group delay coefficient of the dispersion compensation fiber (7) is D ~ -104ps / nm / km; the grating pair (10) is composed of grating one and grating two.

3. The operating method of the high-power, high signal-to-noise ratio 920nm femtosecond optical parametric laser according to claim 1 or 2, characterized in that: The specific steps include the following: The output power of S1 and 1560nm mode-locked seed source (1) is split into beams at a ratio of 1:

1. After splitting, the beams are injected into 1560nm power amplifier one (2) and 1560nm power amplifier two (4) for power and energy amplification. The two amplifiers amplify the average power of the laser pulse after 1560nm mode-locked seed source (1) is split into beams at a ratio of 1:1 to >100mW, and the corresponding pulse width is <500fs. S2, nonlinear fiber one (3) and nonlinear fiber two (5) significantly broaden the incident spectrum of 1560nm femtosecond laser with an average power >100mW and pulse width <500fs amplified by 1560nm power amplifier one (2) and 1560nm power amplifier two (4), respectively, and cover the 1.3μm band and 1μm band, respectively, and have the strongest spectral radiation peaks at 1.3μm and 1μm; S3, 1μm filter (8) effectively filters the 1μm band spectral components generated in nonlinear fiber 2 (5), with a center wavelength of 1053nm and a filtering bandwidth of >4nm. S4, 1μm power amplifier (9) filters the 1μm filter (8) and prepares it as the parametric four-wave mixing pump laser required for 920nm laser generation for power and energy amplification; that is, the laser with a center wavelength of 1053nm and a bandwidth of >4nm after filtering by the 1μm filter (8) is amplified to achieve >5W amplified laser output; S5, the grating pair (10) provides pre-chirp adjustment for the 1053nm high-power laser amplified by the 1μm power amplifier (9). Specifically, the chirp and pulse width of the 1053nm laser can be controlled by adjusting the spacing between grating one and grating two. The line density of grating one and grating two is >600 lines / mm. S6, the lens (12) couples the 1053nm laser provided by the grating pair (10) with pre-chirped control into the pump port of the wavelength division multiplexer (13) and provides four-wave mixing parametric pump light for the generation of the high-power, high signal-to-noise ratio 920nm parametric laser of the present invention in the nonlinear photonic crystal fiber (14). S7, the fiber delay unit (6) provides delay control for the 1.3μm band laser generated in the nonlinear fiber (3), wherein the 1.3μm band laser is the four-wave mixing parametric signal light required for the generation of the high-power, high signal-to-noise ratio 920nm parametric laser of the present invention; The laser emitted from the fiber delayer (6) passes through the dispersion compensation fiber (7) and the parametric signal 1.3μm band laser enters the nonlinear photonic crystal fiber (14) through the signal port of the wavelength division multiplexer (13). It undergoes a four-wave mixing effect with the parametric pumped 1053nm laser to generate a high-power 920nm femtosecond laser.

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