A kind of fiber parametric oscillator based on four-wave mixing effect of ultrafast laser output

Abstract

The application discloses a kind of based on four-wave mixing effect's ultrafast laser output's fiber parametric oscillator, belong to laser technology and laser control field.It includes: pump source, wavelength division multiplexer, gain optical fiber, optical isolator, photonic crystal fiber, reflective wavelength division multiplexer, optical path delay line, 1×2 optical fiber coupler, data collector, optical fiber coupling photoelectric detector.The application utilizes passive optical fiber, gain optical fiber, photonic crystal fiber and optical fiber device not only realizes the full fiber of laser, but also improves the environmental stability of laser.Through reflective wavelength division multiplexer, 900nm signal light is filtered out and returned to ring cavity parametric oscillation, and through optical path delay line, the overlapping part of signal light and pump light is adjusted, finally through 1×2 optical fiber coupler, stable 900nm tunable ultrafast laser output is realized.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of laser technology and laser control, and relates to a kind of fiber parametric oscillator of ultrafast laser output based on four-wave mixing effect, in particular to a kind of fiber parametric oscillator of 900nm tunable ultrafast laser output based on four-wave mixing effect in photonic crystal fiber. BACKGROUND

[0002] With the development of laser technology, the demand for 900nm high-energy laser is increasingly urgent. On the one hand, 900nm laser can be used as a pump source for Yb3+-doped laser material; on the other hand, 900nm laser can be frequency-doubled to generate 450nm blue laser, which corresponds to the underwater communication window and has great application significance in deep sea communication, marine military and other fields. More importantly, this band corresponds to the atmospheric transmission window, which can be directly applied to atmospheric detection and laser radar fields. As a kind of active modern optical detection technology, laser radar fully integrates laser technology and traditional radar technology, which can quickly and accurately obtain the spatial three-dimensional information of the target, and has a wide range of applications in civil, aerospace and military fields such as automatic driving, space rendezvous and docking, target recognition, etc. It is an extremely advanced environmental perception sensor.

[0003] At present, 905nm laser radar is mainly realized by semiconductor lasers, solid (crystal and ceramic) lasers and fiber lasers. Semiconductor lasers can realize full-spectrum laser output from ultraviolet to infrared by adjusting the band gap to select the output wavelength. GaAs semiconductor lasers can realize 900nm band laser output. Xin Guofeng et al. grew InGaAs / GaAs semiconductor laser linear array by metal organic chemical vapor deposition (MOCVD) technology, and realized 900nm laser output with a peak power of 60W. However, the beam quality of semiconductor lasers is poor, which limits its application range. 905nm solid-state laser is mainly divided into titanium sapphire laser and Nd 3+ doped solid-state laser. Titanium sapphire laser can realize 650-1200nm tunable output due to its wide absorption and emission band. Zhang Lianping et al. used 532nm single-frequency green laser to end-pump titanium sapphire crystal, and realized 852-934nm band all-solid-state single-frequency tunable laser output. When the pump power is 15W, more than 2W of 922nm laser output is obtained, and the beam quality factor M 2 <1.04. However, titanium sapphire laser cannot be miniaturized and lightened due to its complex optical system, and has slow tuning speed and high maintenance cost. Nd 3+ energy level, which has 900nm( 4 F 3 / 2 → 4 I 9 / 2), 1060nm ( 4 F 3 / 2 → 4 I 11 / 2 ), 1330nm ( 4 F 3 / 2 → 4 I 13 / 2 ) and 1800nm ​​( 4 F 3 / 2 → 4 I 15 / 2 There are four transition zones. Among them, the four-level transition... 4 F 3 / 2 → 4 I 11 / 2 It is the strongest, and its emission cross-section (1060nm) is usually almost an order of magnitude higher than the other transitions. Therefore, Nd3+ doped laser materials are often used in 1060nm lasers. 4 F 3 / 2 → 4 I 9 / 2 To achieve 905nm laser output in Nd3+-doped laser materials for a three-level transition, the following problem must be solved. 4 F 3 / 2 → 4 I 11 / 2 The problem of competition for four-level transitions makes it difficult to achieve Nd 3+ Outputting 905nm lasers presents a significant challenge. Summary of the Invention

[0004] To address the various existing problems of current 900nm lasers, this invention proposes a fiber parametric oscillator (FSO) for 900nm tunable ultrafast laser output based on the four-wave mixing effect in photonic crystal fiber. The structure comprises a laser pump source and a nonlinear parametric oscillator ring cavity. The pump source consists of a seed source based on a saturable absorber mirror and a second-stage erbium-doped amplifier, resulting in a compact structure capable of long-term operation in various environments with good mode-locking stability. The nonlinear parametric ring cavity consists of a photonic crystal fiber, an optical delay line, a reflective wavelength division multiplexer, an isolator, and a fiber coupler. Wavelength tuning can be achieved by adjusting the optical delay line.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] An ultrafast laser output fiber parametric oscillator based on four-wave mixing effect consists of a mode-locked seed source based on a saturable absorber mirror, an erbium-doped MOPA secondary amplifier, and a nonlinear parametric oscillation ring cavity.

[0007] The saturable absorber mirror-based mode-locked seed source and MOPA erbium-doped two-stage amplifier system comprises a first saturable absorber mirror, a first fiber Bragg grating, a first pump source, a first wavelength division multiplexer, a first gain fiber, a first fiber isolator, a second pump source, a second wavelength division multiplexer, a second gain fiber, a second fiber isolator, a third pump source, a third gain fiber, a third fiber isolator, and a third fiber coupler. The output end of the first pump source is connected to the pump end of the first wavelength division multiplexer, the output end of the first wavelength division multiplexer is connected to the first gain fiber, the first fiber Bragg grating, the first fiber isolator, the other end of the first gain fiber is connected to the first saturable absorber mirror, the output end of the first fiber isolator is connected to the signal end of the second wavelength division multiplexer, the output end of the second wavelength division multiplexer is connected to the second gain fiber, the second fiber isolator, and the signal end of the third fiber coupler, the output end of the third fiber coupler is connected to the pump end of the third fiber coupler, and the output end of the third fiber coupler is connected to the third gain fiber, the third fiber isolator, thereby forming a complete picosecond pump source.

[0008] The nonlinear parametric oscillation ring cavity comprises a first reflective fiber wavelength division multiplexer, a photonic crystal fiber (NKT SC-5.0-1040), a reflective fiber, a fiber beam splitter, and a fourth fiber isolator, and a light path delay line. The output port of the third fiber isolator is connected to the pump end of the first reflective fiber wavelength division multiplexer, the output end of the first reflective fiber wavelength division multiplexer is connected to the input end of the photonic crystal fiber, the output end of the photonic crystal fiber is connected to the signal end of the second reflective fiber wavelength division multiplexer, the output end of the second reflective fiber wavelength division multiplexer is connected to the input end of the fiber beam splitter, the output end a of the fiber beam splitter is connected to the fourth fiber isolator, the light path delay line, the output end of the light path delay line is connected to the signal end of the first reflective fiber wavelength division multiplexer, thereby forming the oscillation ring cavity, and the output end b of the fiber beam splitter serves as the overall output end.

[0009] The center wavelengths of the Stokes and anti-Stokes sidebands of the parametric gain spectrum of the photonic crystal fiber (NKT SC-5.0-1040) are located near 1230 nm and 900 nm, respectively, under the pump of the 1030 nm ultrafast optical laser. The first reflective fiber wavelength division multiplexer and the second reflective fiber wavelength division multiplexer are both plate-type wavelength division multiplexers, which transmit 1030 nm wavelengths and reflect 900 nm wavelengths. The first reflective fiber wavelength division multiplexer is used for coupling signal light and pump light, and the second reflective fiber wavelength division multiplexer is used for filtering out 900 nm signal light to return to the oscillation ring cavity. The fourth fiber isolator is a 900 nm wavelength reflection isolator.

[0010] Compared with the prior art, the advantages of the present application are that:

[0011] This invention provides a fiber parametric oscillator (FTSO) for 900nm tunable ultrafast laser output based on a four-wave mixing effect in photonic crystal fiber. A passive mode-locked seed source is achieved using a saturable absorber mirror, and the seed source is amplified by a two-stage fiber amplifier, forming the overall pump source for the system, thus realizing stable ultrafast high-power pump laser. A reflective fiber wavelength division multiplexer provides resonant signal light to the nonlinear fiber parametric ring oscillator and filters out stray wavelengths, enabling direct output of the 900nm signal light. The spatiotemporal overlap range between the signal pulse and the chirped pump pulse is adjusted by regulating the optical path delay line in the nonlinear fiber parametric ring oscillator, achieving tunable output wavelength. The all-fiber structure provides a pulsed laser with strong environmental stability, high beam quality, and high peak power in the atmospheric transmission window band. Attached image description:

[0012] Figure 1 A schematic diagram of a fiber parametric oscillator for 900nm tunable ultrafast laser output based on the four-wave mixing effect in a photonic crystal fiber, provided for the implementation of this invention.

[0013] Figure 2 This is a logic flowchart of the present invention. Detailed Implementation

[0014] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described below with reference to several accompanying drawings and embodiments. It should be noted that, without conflict, the various embodiments or technical features described below can be arbitrarily combined to form new embodiments. The specific embodiments described herein are only for explaining the invention and do not limit the invention.

[0015] like Figure 1 As shown, this embodiment of the invention provides a fiber parametric oscillator for 900nm tunable ultrafast laser output based on four-wave mixing effect in photonic crystal fiber, comprising: a first saturable absorber mirror 1, a first pump source 2, a first wavelength division multiplexer 3, a first gain fiber 4, a first fiber Bragg grating 5, a first fiber isolator 6, a second pump source 7, a second wavelength division multiplexer 8, a second gain fiber 9, a second fiber isolator 10, a third pump source 11, a third fiber coupler 12, a third gain fiber 13, a third fiber isolator 14, a first reflective fiber wavelength division multiplexer 15, a photonic crystal fiber 16, a second reflective fiber wavelength division multiplexer 17, a third fiber coupler 18, a fourth fiber isolator 19, and an optical path delay line 20.

[0016] like Figure 2 As shown, the above-mentioned fiber parametric oscillator logic flowchart for 900nm tunable ultrafast laser output based on four-wave mixing effect in photonic crystal fiber includes the following steps:

[0017] Step 1: Adjust the connection between the saturable absorber mirror and the gain fiber, and adjust the pump power to achieve passive mode-locking.

[0018] Step 2: The mode-locked seed pulse obtained in Step 1 is amplified by a first-stage fiber core amplifier and a first-stage cladding amplifier to obtain the pump pulse of the nonlinear parametric circulator. Since the wavelength of the pump pulse is in the positive dispersion region, the pump pulse has positive chirp.

[0019] Step 3: The pump pulse enters the nonlinear parametric ring cavity through the pump section of the reflective wavelength division multiplexer, generating a parametric gain spectrum in the photonic crystal fiber, thus obtaining the signal light and idler light.

[0020] Step 4: The signal light is then filtered out by a reflective wavelength division multiplexer and returned to the ring cavity through an optical fiber beam splitter to participate in parametric oscillation. The wavelength tunability function is achieved by adjusting the spatiotemporal overlap range between the signal light and the pump pulse through an optical path delay line.

[0021] Step 5: Achieve 900nm pulse output through the other output end of the fiber optic beam splitter.

[0022] This invention provides a compact and stable fiber parametric oscillator for 900nm tunable ultrafast laser output based on four-wave mixing effects in photonic crystal fiber. The laser achieves passive mode-locked pulse output using saturable absorber mode-locking technology, with the pump pulse for the entire system obtained through a two-stage fiber amplifier. Wavelength tunability is achieved by adjusting the spatiotemporal overlap between the signal light and the pump pulse using an optical path delay line. This invention features an all-fiber design, facilitating system integration and enabling direct 900nm laser output. It can serve as a front-end light source for applications such as automotive lidar and biological multiphoton imaging, facilitating industrial application.

Claims

1. A fiber-optic parametric oscillator of ultrafast laser output based on four- wave mixing effect, characterized in that, The system comprises a mode-locked seed source based on a saturable absorber mirror, a MOPA erbium-doped two-stage amplifier and a nonlinear parametric oscillation ring cavity. The mode-locked seed source based on a saturable absorber mirror and the MOPA erbium-doped two-stage amplifier system comprises a first saturable absorber mirror, a first fiber Bragg grating, a first pump source, a first wavelength division multiplexer, a first gain fiber, a first fiber isolator, a second pump source, a second wavelength division multiplexer, a second gain fiber, a second fiber isolator, a third pump source, a third gain fiber, a third fiber isolator and a third fiber coupler; wherein the output end of the first pump source is connected to the pump end of the first wavelength division multiplexer, the output end of the first wavelength division multiplexer is connected in sequence to the first gain fiber, the first fiber Bragg grating, the first fiber isolator, the other end of the first gain fiber is connected to the first saturable absorber mirror again, and the output port of the first fiber isolator is connected to the signal end of the second wavelength division multiplexer, the output end of the second wavelength division multiplexer is connected in sequence to the second gain fiber, the second fiber isolator and the signal end of the third fiber coupler, the output end of the third fiber coupler is connected in sequence to the third gain fiber and the third fiber isolator, thereby forming a complete picosecond pump source. The nonlinear parametric oscillation ring cavity comprises a first reflective fiber wavelength division multiplexer, a photonic crystal fiber, a reflective fiber, a fiber beam splitter, a fourth fiber isolator, an optical path delay line and a second reflective fiber wavelength division multiplexer; the entire system is connected by the output port of the third fiber isolator to the pump end of the first reflective fiber wavelength division multiplexer, the output end of the first reflective fiber wavelength division multiplexer is connected to the input end of the photonic crystal fiber, the output end of the crystal fiber is connected to the signal end of the second reflective fiber wavelength division multiplexer, the output end of the second reflective fiber wavelength division multiplexer is connected to the input end of the fiber beam splitter, the output end a of the fiber beam splitter is connected in sequence to the fourth fiber isolator and the optical path delay line, the output end of the optical path delay line is connected to the signal end of the first reflective fiber wavelength division multiplexer to form an oscillation ring cavity, and the output end b of the fiber beam splitter serves as the overall output end. Under the pump of the photonic crystal fiber in the 1030 nm ultrafast optical laser, the center wavelengths of the Stokes and anti-Stokes sidebands of the parametric gain spectrum are located near 1230 nm and 900 nm, respectively; wherein the first reflective fiber wavelength division multiplexer and the second reflective fiber wavelength division multiplexer are both plate-type wavelength division multiplexers, which transmit 1030 nm wavelength and reflect 900 nm wavelength, the first reflective fiber wavelength division multiplexer is used for coupling signal light and pump light, and the second reflective fiber wavelength division multiplexer is used for filtering out 900 nm signal light to return to the oscillation ring cavity; the fourth fiber isolator is a 900 nm wavelength reflection isolator.

2. The fiber-optic parametric oscillator based on four-wave mixing effect for ultrafast laser output according to claim 1, characterized in that, The method comprises the following steps: Step 1: adjusting the butt joint of the saturable absorber mirror and the gain fiber and the pump power to achieve passive mode locking. Second step: the first step to get the mode-locked seed pulse through a core amplifier one cladding amplifier, get the pump pulse of nonlinear parametric ring, because the pump pulse wavelength is in the positive dispersion interval, both pump pulse with positive chirp; Third step: pump pulse through the reflective wavelength division multiplexer pump section into the nonlinear parametric ring cavity, generate parametric gain spectrum in photonic crystal fiber, get signal light and idler light; Fourth step: after the reflective wavelength division multiplexer filter out the signal light and return to the ring cavity through the fiber beam splitter to participate in the parametric oscillation, adjust the time and space overlap range of signal light and pump pulse through optical path delay line to realize the wavelength tunable function; Fifth step: through the other output end of the fiber beam splitter to realize 900 nm pulse output.

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