Dynamic dispersion compensation system and compensation method for mid-infrared tunable fiber laser

Abstract

The invention belongs to the technical field of lasers, and particularly relates to a dynamic dispersion compensation system and method for an intermediate infrared tunable fiber laser, and the system comprises an intermediate infrared ultrashort pulse light source mechanism which is used for outputting negative chirped pulse laser with the wave band of 2.8-4.5 microns; the pulse compression module comprises a transmission grating I and a transmission grating II which are arranged in parallel, an aberration removal structure positioned between the transmission grating I and the transmission grating II, and a roof prism; the negative chirped pulse laser sequentially passes through the first transmission grating, the aberration removing structure and the second transmission grating and then enters the ridge prism, and the negative chirped pulse laser is reflected by the ridge prism to enable the light to sequentially pass through the second transmission grating, the aberration removing structure and the first transmission grating and then outputs near Fourier transform limit pulsed light. The distance between the plane where the first transmission grating is located and the plane where the second transmission grating is located is the grating distance. And the grating distance is adjusted through the distance adjusting part. According to the invention, dynamic dispersion compensation of the mid-infrared band can be realized.

Description

Technical Field

[0001] This invention belongs to the field of laser technology, and particularly relates to a dynamic dispersion compensation system and method for mid-infrared tunable fiber lasers. Background Technology

[0002] Currently, germanium rods are a common dispersion management solution in femtosecond pulse compression technology in the mid-infrared band. This is because germanium has a dispersion coefficient of +1685 fs at 2.8 micrometers at the edge of the absorption region. 2 Germanium exhibits a giant positive dispersion of 0.5 mm / s, which is 20 times that of fluoride fiber. This means that a germanium rod a few centimeters long can compensate for the dispersion of meter-long fluoride fibers. Therefore, semiconductor germanium is an ideal component for mid-infrared dispersion management. However, germanium rods have significant limitations in practical applications, especially their fixed length, which prevents flexible adjustment of the dispersion. This is a major drawback for mid-infrared fiber laser systems that require dynamic wavelength tuning.

[0003] Therefore, there is an urgent need for a dynamic dispersion compensation system and method for mid-infrared tunable fiber lasers. Summary of the Invention

[0004] The purpose of this invention is to provide a dynamic dispersion compensation system and method for mid-infrared tunable fiber lasers to solve the above-mentioned problems.

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

[0006] A dynamic dispersion compensation system for mid-infrared tunable fiber lasers includes:

[0007] A mid-infrared ultrashort pulse light source mechanism, wherein the mid-infrared ultrashort pulse light source mechanism is used to output negatively chirped pulse laser with a wavelength of 2.8-4.5 micrometers;

[0008] The pulse compression module includes a first transmission grating and a second transmission grating arranged in parallel, an aberration correction structure located between the first transmission grating and the second transmission grating, and a roof prism;

[0009] The negatively chirped pulsed laser passes sequentially through the first transmission grating, the aberration-reducing structure, and the second transmission grating before being incident on the roof prism. After being reflected by the roof prism, the light passes sequentially through the second transmission grating, the aberration-reducing structure, and the first transmission grating before being output as a near-Fourier transform-limited pulsed light.

[0010] The distance between the plane where the first transmission grating is located and the plane where the second transmission grating is located is the grating spacing;

[0011] The grating spacing is adjusted by the distance adjustment unit.

[0012] The dispersion of the pulse compression module is changed by adjusting the relative vertical spacing between transmission grating one and transmission grating two.

[0013] Optionally, the aberration correction structure includes a cylindrical concave mirror and a cylindrical convex mirror arranged coaxially;

[0014] The negatively chirped pulsed laser passes sequentially through the first transmission grating, the concave cylindrical mirror, the convex cylindrical mirror, and the second transmission grating before being incident on the roof prism. After being reflected by the roof prism, the light passes sequentially through the second transmission grating, the convex cylindrical mirror, the concave cylindrical mirror, and the first transmission grating before being output as the near-Fourier transform-limited pulsed light.

[0015] Optionally, the mid-infrared ultra-short pulse light source mechanism is connected to the incident optical path of the transmission grating through a reflector.

[0016] Optionally, the exit end of the first transmission grating is connected to the entrance end of the second reflector, and the exit end of the second reflector is used for light output.

[0017] Optionally, the mid-infrared ultrashort pulse light source mechanism includes a light source and a Dy 3+ ZBLAN optical fiber, wherein the light source generates a raw light beam with a wavelength of 2.8-3 micrometers, and the raw light beam enters the Dy 3+ One end of the ZBLAN optical fiber, the Dy 3 + The other end of the ZBLAN optical fiber serves as the output end of the mid-infrared ultrashort pulse light source mechanism and is connected to the pulse compression module. The original light beam is located in the Dy... 3+ Negative dispersion is generated during propagation within the ZBLAN fiber, forming the negatively chirped pulsed laser.

[0018] A method for dynamic dispersion compensation of mid-infrared tunable fiber lasers, using the aforementioned dynamic dispersion compensation system for mid-infrared tunable fiber lasers, includes:

[0019] The negatively chirped laser pulse is then fed into the pulse compression module;

[0020] This allows light to travel between the first transmission grating, the aberration-correcting structure, the second transmission grating, and the roof prism.

[0021] The grating spacing is adjusted by the distance adjustment unit to adapt to the changes in the negative chirped pulse laser band and the dispersion of the laser system;

[0022] The negatively chirped pulsed laser enters the aberration-correcting structure twice to form the near-Fourier transform-limited pulsed light.

[0023] Compared with the prior art, the present invention has the following advantages and technical effects:

[0024] Compared with traditional technologies, this invention fills the technological gap in dynamic dispersion adjustment systems for mid-infrared tunable fiber lasers. Compared with existing fixed dispersion compensation schemes, this technology can achieve adaptive dispersion management that varies with wavelength in the 2.8-4.5 micrometer band. The dispersion amount can be precisely adjusted by adjusting the grating spacing through the distance adjustment unit to adjust the dispersion characteristics of the chirped pulse amplification system, achieving active dynamic compensation for pulse chirp. It solves the key technical bottleneck of fixed germanium rod length and inflexible adjustment in traditional methods. This invention not only overcomes the technical difficulties of dynamic dispersion compensation in the mid-infrared band but also provides a completely new solution for performance optimization of tunable ultrafast lasers, possessing significant theoretical value and broad application prospects. Attached Figure Description

[0025] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly described below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0026] Figure 1 This is a front view of the structure of the present invention;

[0027] Figure 2 This is a top view of the structure of the present invention;

[0028] Among them, 1. Mid-infrared ultra-short pulse light source mechanism; 2. Reflector one; 3. Transmission grating one; 4. Cylindrical concave mirror; 5. Cylindrical convex mirror; 6. Transmission grating two; 7. Roof prism; 8. Reflector two. Detailed Implementation

[0029] 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.

[0030] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0031] Mid-infrared ultrafast lasers are widely used in biomedicine, molecular spectroscopy, materials processing, and nonlinear optics. The mid-infrared laser wavelength range is 2-20 micrometers, encompassing the vibrational energy levels of many interesting molecules. Ultrafast lasers in the 2-4 micrometer range have attracted significant attention because this band includes some molecular fingerprint regions, atmospheric optical transparency windows, and absorption peaks covering water and amino acid compounds. Therefore, 2-4 micrometer lasers have important applications in molecular spectroscopy, infrared ranging, materials processing, disease detection, and laser surgery.

[0032] Fluoride glass matrix is ​​currently the most suitable fiber matrix material for mid-infrared fiber lasers. Compared with quartz glass matrix, fluoride glass matrix can achieve longer wavelength transmission due to its low phonon energy. Simultaneously, selecting appropriate rare earth ion doping is crucial for obtaining the desired mid-infrared laser output. Currently, Er... 3+ Ho 3+ Dy 3+ These three rare earth ions are used to generate mid-infrared fiber lasers. Their emission spectra between different energy levels are mainly concentrated in the 2.5-4 micrometer band, which can be matched with the transmission spectrum of fluoride fiber (2-5 micrometers). At the same time, theoretically, they are sufficient as gain media to support the direct generation of pulse output on the fs scale, which is crucial for ultrashort pulse fiber lasers.

[0033] With the maturation of fluoride fiber drawing technology and the continuous improvement of the fabrication level of mid-infrared related devices, research on mid-infrared fiber lasers has developed rapidly. Compared with continuous-wave lasers or μs-ns pulsed lasers, mid-infrared ultrashort pulses (ps-fs) with high peak power have important application value in precision surgery, mid-infrared supercontinuum generation, precision machining of special materials, and remote sensing ranging. Moreover, in many practical applications of spectral sensing, broadband tunable mid-infrared femtosecond pulsed laser sources are required. Currently, the main methods to achieve this are wavelength-tunable mode-locked fiber lasers and pulsed lasers based on nonlinear frequency conversion. Among them, the wavelength tunability of mid-infrared mode-locked fiber lasers is limited by the gain bandwidth of rare-earth ions, which cannot achieve wide-range wavelength tuning. Soliton self-frequency shift, as an important means in nonlinear frequency conversion technology to achieve high-power broadband tunable femtosecond pulse output, has very high scientific research value.

[0034] Currently, fluoride fibers commonly used for wavelength tuning of mid-infrared fiber lasers using soliton self-frequency shifting are Dy... 3+ ZBLAN fiber optic or Dy 3+ InF3 fiber, because compared to Er 3+ and Ho 3+ Dy3+ It possesses an extremely wide radiation cross-section (2.5–3.5 micrometers) near a wavelength of 3 micrometers, meaning that as a gain medium, it can theoretically support narrower ultrashort pulses and a wider wavelength tunable range. 3+ ZBLAN fiber optic or Dy 3+ The second-order dispersion provided by InF3 fiber is negative dispersion. Unmanaged negative dispersion of fluoride fiber will significantly degrade the pulse quality, spectral stability and energy efficiency of mid-infrared laser. However, there are very few schemes for dispersion management in current research on mid-infrared fiber amplifiers.

[0035] The common approach is to use germanium rods to manage pulse dispersion. The appropriate length is selected by using the giant positive dispersion value provided by the germanium rod, thereby achieving femtosecond-level compression of the laser system. However, the adjustment of germanium rods is inflexible and introduces insertion loss. In addition, traditional grating stretchers introduce spatial chirp and astigmatism, and the optical path is complex and occupies a large space.

[0036] Currently, germanium rods are a common dispersion management solution in femtosecond pulse compression technology in the mid-infrared band. This is because germanium has a dispersion coefficient of +1685 fs at 2.8 micrometers at the edge of the absorption region. 2 Germanium exhibits a giant positive dispersion of 0.5 mm / s, which is 20 times that of fluoride fiber. This means that a germanium rod a few centimeters long can compensate for the dispersion of meter-long fluoride fibers. Therefore, semiconductor germanium is an ideal component for mid-infrared dispersion management. However, germanium rods have significant limitations in practical applications, especially their fixed length, which prevents flexible adjustment of the dispersion. This is a major drawback for mid-infrared fiber laser systems that require dynamic wavelength tuning.

[0037] Reference Figures 1 to 2 This invention discloses a dynamic dispersion compensation system for a mid-infrared tunable fiber laser, comprising:

[0038] Mid-infrared ultrashort pulse light source mechanism 1, which is used to output negatively chirped pulsed laser with a wavelength of 2.8-4.5 micrometers;

[0039] The pulse compression module includes a transmission grating 3 and a transmission grating 6 arranged in parallel, an aberration correction structure located between the transmission grating 3 and the transmission grating 6, and a roof prism 7.

[0040] The negatively chirped pulsed laser passes sequentially through transmission grating 1-3, the aberration-reducing structure, and transmission grating 2-6 before being incident on the roof prism 7. After being reflected by the roof prism 7, the light passes sequentially through transmission grating 2-6, the aberration-reducing structure, and transmission grating 1-3 before being output as a near-Fourier transform-limited pulsed light.

[0041] The distance between the plane containing transmission grating 1-3 and the plane containing transmission grating 2-6 is the grating spacing;

[0042] Adjust the grating spacing using the distance adjustment unit.

[0043] This invention provides positive dispersion by using a pulse compression module and precisely adjusts the dispersion characteristics of the chirped pulse amplification system by adjusting the grating spacing through a distance adjustment unit, thereby achieving active dynamic compensation for pulse chirp.

[0044] Near-Fourier transform-limited pulse light usually refers to the shortest pulse width that can be obtained for the pulse spectrum, meaning that the time-bandwidth product is minimized and the pulse has no chirp.

[0045] The dispersion of the pulse compression module is changed by adjusting the relative vertical spacing between transmission grating 3 and transmission grating 6, i.e., adjusting the grating spacing.

[0046] The pulse compression module is a pulse compressor that uses an Offner stretcher structure to provide positive dispersion.

[0047] This invention provides a method based on Dy 3+ ZBLAN fiber-amplified mid-infrared tunable laser dispersion management technology is suitable for pulse compression and wavelength tuning in the 2.8-4.5 micrometer band. Because fluoride fibers exhibit significant second-order negative dispersion (β2<0) during transmission, this dispersion characteristic leads to time-domain broadening and spectral distortion in ultrashort pulses, affecting pulse stability. To effectively compensate for this negative impact, a compressor with positive dispersion (β2>0) is needed for precise dispersion management. Therefore, dynamic dispersion compensation is achieved by rationally designing the pulse compression module to provide controllable positive dispersion.

[0048] The distance adjustment unit of the present invention is preferably a precision displacement stage.

[0049] The spacing between transmission grating 1 (3) and transmission grating 2 (6), i.e., the grating spacing Lg, is controlled by a precision displacement stage to match Dy3 in real time. + ZBLAN(β2=-0.148ps) 2 Negative dispersion of fiber ( / m).

[0050] Compared with traditional technologies, this invention fills the technological gap in dynamic dispersion adjustment systems for mid-infrared tunable fiber lasers. Compared with existing fixed dispersion compensation schemes, this technology can achieve adaptive dispersion management that varies with wavelength in the 2.8-4.5 micrometer band. The dispersion amount can be continuously adjusted by adjusting the spacing between the transmission grating and the aberration correction structure, solving the key technical bottleneck of fixed germanium rod length and inflexible adjustment in traditional methods. This invention not only overcomes the technical difficulties of dynamic dispersion compensation in the mid-infrared band, but also provides a brand-new solution for performance optimization of tunable ultrafast lasers, possessing significant theoretical value and broad application prospects.

[0051] As an optional implementation, the aberration correction structure includes a cylindrical concave mirror 4 and a cylindrical convex mirror 5 arranged coaxially;

[0052] The negatively chirped pulsed laser passes sequentially through transmission grating 1 3, cylindrical concave mirror 4, cylindrical convex mirror 5, and transmission grating 2 6 before being incident on roof prism 7. After being reflected by roof prism 7, the light passes sequentially through transmission grating 2 6, cylindrical convex mirror 5, cylindrical concave mirror 4, and transmission grating 1 3, and is then output as near-Fourier transform-limited pulsed light.

[0053] The concentric design of the cylindrical concave mirror 4 and cylindrical convex mirror 5 in the aberration-correcting structure ensures the system is aberration-free, improving the quality of the compressed pulse. Using this stretcher, different wavelength components diffracted by the grating are reflected between the concave and convex mirrors, maintaining wavefront flatness and reducing spatial distortion.

[0054] As an optional implementation, the mid-infrared ultra-short pulse light source mechanism 1 is connected to the incident optical path of the transmission grating 3 via a reflector 2.

[0055] As an optional implementation, the output end of the transmission grating 3 is connected to the input end of the reflector 8, and the output end of the reflector 8 is used for light output.

[0056] As an optional implementation, the mid-infrared ultrashort pulse light source mechanism 1 includes a light source and a Dy 3+ ZBLAN fiber optic cable generates a raw light beam with a wavelength of 2.8-3 micrometers from the light source. This raw light beam enters the Dy... 3+ One end of the ZBLAN fiber, Dy 3 + The other end of the ZBLAN fiber serves as the output of the mid-infrared ultra-short pulse light source mechanism 1, connected to the pulse compression module. The original light beam is in Dy 3+ Negative dispersion is generated during propagation within the ZBLAN fiber, forming the negatively chirped pulsed laser.

[0057] A method for dynamic dispersion compensation of mid-infrared tunable fiber lasers, using the aforementioned dynamic dispersion compensation system for mid-infrared tunable fiber lasers, includes:

[0058] This allows the negatively chirped laser pulse to enter the pulse compression module;

[0059] This allows light to travel between the transmission grating 1-3, the aberration-reducing structure, the transmission grating 2-6, and the roof prism 7.

[0060] The distance adjustment unit adjusts the spacing of the transmission grating to adapt to the changes in the negative chirped pulse laser band and the dispersion of the laser system;

[0061] Negatively chirped pulsed laser light enters the aberration-correcting structure twice to form near-Fourier transform-limited pulsed light.

[0062] The working principle of this invention is as follows:

[0063] The mid-infrared ultrashort pulse light source mechanism 1 emits a negatively chirped pulse laser. After being reflected by mirror 2, the negatively chirped pulse laser is incident on a transmission grating 3 at an incident angle γ. After diffraction by the grating, the beam broadens horizontally and is then projected onto a cylindrical concave mirror 4. The cylindrical concave mirror 4 reflects the light to a cylindrical convex mirror 5. The cylindrical concave mirror 4 and the cylindrical convex mirror 5 are concentric on their axes but spatially offset, not on the same horizontal plane. This concentricity eliminates aberrations. After the cylindrical concave mirror 4 reflects the incident beam to the cylindrical convex mirror 5, the cylindrical convex mirror 5 precisely controls the beam wavefront using its specific cylindrical curvature, and then reflects the beam back to the cylindrical concave mirror 4. The laser beam, after secondary reflection by the cylindrical concave mirror 4, is incident on the transmission grating 6 at an optimized angle. After diffraction by the transmission grating 6, the laser pulse frequency exhibits a linear spatial distribution, i.e., spatial chirp. The light spot forms a horizontal straight line and enters the roof prism 7, then is reflected back to the transmission grating 6, the cylindrical convex mirror 5, the cylindrical concave mirror 4, and the transmission grating 3. After exiting the transmission grating 3, the shape of the incident light spot is restored, and the spatial chirp is eliminated. The precisely controlled outgoing beam is reflected by the mirror 8 and then introduced into the light spot analysis system. The spatial intensity distribution characteristics are collected and analyzed in real time by a high-resolution CCD detector, providing key feedback data for system optimization.

[0064] This invention addresses the dispersion management problem in mid-infrared fiber amplifier systems, proposing a dispersion compensation system that fills a technological gap in dynamic dispersion adjustment systems for mid-infrared fiber lasers. This system precisely controls the negative dispersion characteristics of the positive dispersive element and the fluoride fiber, balancing the positive and negative dispersions to bring the net dispersion close to zero, preserving the pulse time-domain characteristics. By suppressing waveform distortion caused by nonlinear effects, it obtains compressed pulses close to the transform limit. Furthermore, this system reduces spectral broadening and sidelobe generation during wavelength tuning, improving spectral stability. Compared to existing fixed dispersion compensation schemes, this technology achieves adaptive dispersion management varying with wavelength in the 2.8-4.5 micrometer band, overcoming the key technical bottleneck of fixed germanium rod length and inflexible adjustment in traditional methods. This invention not only breaks through the technical challenges of dynamic dispersion compensation in the mid-infrared band but also provides a novel solution for performance optimization of tunable ultrafast lasers, possessing significant theoretical value and broad application prospects.

[0065] In the description of this invention, it should be understood that the terms "longitudinal", "lateral", "up", "down", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this invention, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this invention.

[0066] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A dynamic dispersion compensation system for a mid-infrared tunable fiber laser, characterized in that, include: Mid-infrared ultrashort pulse light source mechanism (1), wherein the mid-infrared ultrashort pulse light source mechanism (1) is used to output negative chirped pulse laser with a wavelength of 2.8-4.5 micrometers; The pulse compression module includes a first transmission grating (3) and a second transmission grating (6) arranged in parallel, an aberration correction structure located between the first transmission grating (3) and the second transmission grating (6), and a roof prism (7). The negatively chirped pulsed laser passes sequentially through the first transmission grating (3), the aberration-reducing structure, and the second transmission grating (6) before being incident on the roof prism (7). After being reflected by the roof prism (7), the light passes sequentially through the second transmission grating (6), the aberration-reducing structure, and the first transmission grating (3) before being output as a near-Fourier transform-limited pulsed light. The distance between the plane containing the first transmission grating (3) and the plane containing the second transmission grating (6) is the grating spacing; The grating spacing is adjusted by the distance adjustment unit.

2. The mid-infrared tunable fiber laser dynamic dispersion compensation system according to claim 1, characterized in that, The aberration correction structure includes a cylindrical concave mirror (4) and a cylindrical convex mirror (5) arranged coaxially; The negatively chirped pulsed laser passes sequentially through the first transmission grating (3), the cylindrical concave mirror (4), the cylindrical convex mirror (5), and the second transmission grating (6) before being incident on the roof prism (7). After being reflected by the roof prism (7), the light passes sequentially through the second transmission grating (6), the cylindrical convex mirror (5), the cylindrical concave mirror (4), and the first transmission grating (3) before being output as the near-Fourier transform-limited pulsed light.

3. The mid-infrared tunable fiber laser dynamic dispersion compensation system according to claim 1, characterized in that: The mid-infrared ultra-short pulse light source mechanism (1) is connected to the incident optical path of the transmission grating (3) through a reflector (2).

4. The mid-infrared tunable fiber laser dynamic dispersion compensation system according to claim 1, characterized in that: The output end of the transmission grating (3) is connected to the input end of the reflector (8), and the output end of the reflector (8) is used for light output.

5. The mid-infrared tunable fiber laser dynamic dispersion compensation system according to claim 1, characterized in that: The mid-infrared ultra-short pulse light source mechanism (1) includes a light source and a Dy 3+ ZBLAN fiber optic cable.

6. The mid-infrared tunable fiber laser dynamic dispersion compensation system according to claim 5, characterized in that: The light source generates a raw light beam with a wavelength of 2.8-3 micrometers.

7. The mid-infrared tunable fiber laser dynamic dispersion compensation system according to claim 6, characterized in that: The original light beam enters the Dy 3+ One end of the ZBLAN optical fiber, the Dy 3+ The other end of the ZBLAN fiber serves as the output end of the mid-infrared ultrashort pulse light source mechanism (1) and is connected to the pulse compression module. The original light beam is located in the Dy... 3 + Negative dispersion is generated during propagation within the ZBLAN fiber, forming the negatively chirped pulsed laser.

8. A method for dynamic dispersion compensation of a mid-infrared tunable fiber laser, using the dynamic dispersion compensation system for a mid-infrared tunable fiber laser as described in any one of claims 1-7, characterized in that... include: The negatively chirped laser pulse is then fed into the pulse compression module; Light is transmitted between the first transmission grating (3), the aberration-correcting structure, the second transmission grating (6), and the roof prism (7); The grating spacing is adjusted by the distance adjustment unit to adapt to the changes in the negative chirped pulse laser band and the dispersion of the laser system; The negatively chirped pulsed laser enters the aberration-correcting structure twice to form the near-Fourier transform-limited pulsed light.

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