Dual-band tuning optical fiber nonlinear micro-spectrum mixed excitation source device and method

Abstract

The invention discloses a dual-band tuning optical fiber nonlinear micro-spectrum excitation source device and a dual-band tuning optical fiber nonlinear micro-spectrum excitation method. Comprising a seed resonant cavity, a first optical fiber isolator, a pre-amplification stage, a first optical fiber beam splitter, a main amplification stage, a second optical fiber isolator, a first optical fiber connector, an optical fiber parametric oscillation resonant cavity, a fourth pump laser, a fourth pump laser, a second optical fiber beam splitter, a second optical fiber connector, a second photonic crystal fiber and a second chirped fiber grating. And a third adjustable optical delayer and a third optical fiber connector. According to the invention, the construction of the nonlinear multi-mode micro-spectrum imaging system is greatly simplified, the system has the characteristics of high stability, high reliability, high flexibility, low maintenance cost and the like, and the popularization and application of the portable nonlinear multi-mode micro-spectrum imager are promoted.

Description

Technical Field

[0001] The present invention relates to the field of laser technology and nonlinear microscopic imaging technology, in particular to an optical fiber nonlinear microscopic ultrafast pulse mixing excitation source and method. Background Art

[0002] Nonlinear microspectral imaging has become a highly effective biomedical imaging technique. For example, multiphoton imaging utilizes near-infrared ultrafast laser pulses to stimulate nonlinear light-matter interactions, providing inherent three-dimensional slicing capabilities. Coherent Raman scattering, a third-order nonlinear optical process based on the coherent excitation of molecular vibrations, facilitates label-free, molecule-specific contrast at subcellular resolution. Multimodal microscopic imaging techniques, including coherent Raman, two-photon fluorescence, and second harmonic generation imaging, have promising clinical application potential, for example, in the detection of cardiovascular disease, breast cancer lesions, and brain tumors.

[0003] The development of nonlinear microscopic spectroscopy is highly dependent on ultrashort pulse excitation sources. The generation of coherent Raman signals requires two time-synchronized, spatially overlapping, tunable picosecond or femtosecond pulses to ensure that their frequency difference matches the vibration frequency of the molecule to be measured. Currently, such ultrashort pulse sequences are usually generated using a spatial excitation source system that combines a titanium sapphire laser or a frequency-doubled Nd:YVO4 laser with an optical parametric oscillator. However, such spatial systems are not only expensive and complex, but also difficult to maintain and calibrate, requiring professional optical experts, which seriously hinders their application development. Fiber lasers have the advantages of small size, light weight, and stability. By utilizing the high nonlinear effect of photonic crystal fibers, they can effectively convert optical parametric frequencies within the fiber and achieve synchronization of pulses in time and space. They are the only choice for building highly portable and highly stable excitation sources for nonlinear microscopic spectroscopy.

[0004] In current multimodal nonlinear imaging technologies, such as coherent Raman scattering, two-photon excited fluorescence and second harmonic generation integrated multimodal nonlinear imaging systems rely on femtosecond pulse fiber excitation sources. Since only femtosecond pulses are output, the spectral resolution capability is lost. Summary of the Invention

[0005] In response to the problems existing in traditional nonlinear microscopic spectroscopy excitation source devices, the present invention proposes a dual-band tuned fiber nonlinear microscopic spectroscopy hybrid excitation source device and method. By combining passive mode locking technology, laser amplification technology and nonlinear frequency conversion technology, it realizes the synchronous tuning of two dual-band picosecond and femtosecond pulses.

[0006] The present invention is achieved by utilizing the following technical solutions:

[0007] In a first aspect, the present invention provides a dual-band tuned fiber nonlinear micro-spectroscopy excitation source device, which includes a seed resonant cavity, a first fiber isolator 10, a pre-amplifier stage, a first fiber beam splitter 14, a main amplifier stage, a second fiber isolator 18, a first fiber connector 19, a fiber parametric oscillator resonant cavity, a fourth pump laser 22, a fourth pump laser 22, a second fiber beam splitter 28, a second fiber connector 29, a second photonic crystal fiber 30, a second chirped fiber grating 31, a third tunable optical delay 32, and a third fiber connector 33, which are connected in sequence;

[0008] The seed resonant cavity includes a saturable absorber 2, a first tunable optical delay 3, a diffraction grating 4, an aspheric lens 5, a first ytterbium-doped fiber 6, a first wavelength division multiplexer 7, a first pump laser 8 and a first chirped fiber grating 9 connected in sequence; the pre-amplification stage includes a second wavelength division multiplexer 11, a second pump laser 12 and a second ytterbium-doped fiber 13 connected in sequence; the main amplification stage includes a first signal pump combiner 15, a third pump laser 16 and a third ytterbium-doped fiber 17 connected in sequence; the fiber parametric oscillation resonant cavity includes a third wavelength division multiplexer 20, a second signal pump combiner 21, a fourth ytterbium-doped fiber 23, a first photonic crystal fiber 24, a fiber coupler 25, a second tunable optical delay 26 and a delay fiber 27 connected in sequence.

[0009] In a second aspect, the present invention provides a method for realizing dual-band tunable fiber nonlinear microscopic spectroscopy excitation, comprising the following steps:

[0010] Through the seed resonant cavity, the saturable absorber 2 achieves passive mode locking to generate picosecond pulses as seed light; the first adjustable optical delay device 3 controls the repetition frequency of the seed light, the diffraction grating 4 generates diffracted light from the collimated broadband spontaneous radiation light, the aspheric lens 5 collimates the broadband spontaneous radiation light onto the diffraction grating 4, the first pump laser 8 outputs the first pump light, the first ytterbium-doped fiber 6 serves as the gain medium in the seed resonant cavity, and broadband spontaneous radiation light is generated by the first pump light. The first wavelength division multiplexer 7 combines the first pump light and the pulse light into the same optical fiber, namely the first ytterbium-doped fiber 6, and the first chirped fiber grating 9 partially reflects and transmits the pulse light in the range of 1010 to 1075 nm.

[0011] The first optical fiber isolator 10 realizes unidirectional transmission of seed light;

[0012] Through the pre-amplification stage, the second pump laser 12 generates a second pump light, and the second wavelength division multiplexer 11 combines the second pump light and the seed light into the same optical fiber, namely the second ytterbium-doped optical fiber 13. The second ytterbium-doped optical fiber 13 generates broadband spontaneous emission light through the second pump light to pre-amplify the incoming seed light;

[0013] The pre-amplified seed light is evenly divided into two beams of pulsed light by the first optical fiber beam splitter 14;

[0014] Through the main amplifier stage, the third pump laser 16 generates a third pump light, and the first signal pump combiner 15 combines the third pump light with the pulse light split after pre-amplification into the same optical fiber, namely the third ytterbium-doped optical fiber 17. The third ytterbium-doped optical fiber 17 generates broadband spontaneous emission light through the third pump light, and performs main amplification on the pulse light split after pre-amplification;

[0015] The second optical fiber isolator 18 realizes unidirectional transmission of the main amplified pulse light, the first optical fiber connector 19 outputs Stokes light, and the fourth pump laser 22 generates the fourth pump light;

[0016] Through the fiber parametric oscillation resonant cavity, the third wavelength division multiplexer 20 combines the pulse light after pre-amplification and the pulse light after fiber parametric frequency conversion into the same optical fiber, namely the input optical fiber of the second signal pump combiner 20. The second signal pump combiner 20 combines the fourth pump light, the pulse light after pre-amplification and the pulse light after fiber parametric frequency conversion into the same optical fiber, namely the fourth ytterbium-doped optical fiber 23. Broadband spontaneous radiation light is generated by the fourth pump light to perform main amplification on the pulse light after pre-amplification. The first photonic crystal fiber 24 forms a four-wave mixing gain. The optical fiber coupler 25 partially outputs the pulse light after four-wave mixing frequency conversion. The second adjustable optical delay 26 adjusts the intrinsic repetition frequency of the fiber parametric oscillation resonant cavity to be an integer multiple of the repetition frequency of the seed light. The delay optical fiber 27 increases the cavity length of the fiber parametric oscillation resonant cavity.

[0017] The pulse light outputted from the fiber parametric oscillation resonant cavity is evenly divided into two beams of pulse light again by the second fiber beam splitter 28, wherein one beam of picosecond pulse light serves as the fifth pump light, the second fiber connector 29 outputs the fifth pump light, the second photonic crystal fiber 30 generates self-phase modulation, broadens the spectrum of the other beam of pulse light splitted by the second fiber beam splitter (28), the other beam of pulse light is compressed into a femtosecond pulse after passing through the second photonic crystal fiber 30 and the second chirped fiber grating 31 in sequence, the third adjustable optical delay 32 adjusts the delay between the femtosecond pulse and the fifth pump light, and the third fiber connector 33 outputs the final femtosecond pulse light.

[0018] In some embodiments, the method further comprises the following steps:

[0019] The output power of the first pump laser is controlled to achieve passive mode locking of the seed source. At the same time, the electrically controlled rotary stage and the first adjustable optical delay device 3 are adjusted so that the output wavelength and repetition frequency of the seed light are tuned within the ranges of 1010-1075 nm and 45-55 MHz, respectively. The output pulse width of the seed light is 1-20 ps, and the average power is 1-10 mW.

[0020] In some embodiments, the output power of the second pump laser is controlled so that the average power of the pre-amplified seed light is 30-100 mW.

[0021] In some embodiments, the power of the third pump laser 16 is adjusted to obtain Stokes light with an average power of 700mW to 900mW at the first optical fiber connector 19, with a wavelength and repetition frequency synchronized with the seed light and an output pulse width of 1 to 20ps.

[0022] In some embodiments, a second optical fiber splitter 28 is included to divide the light output from the optical fiber coupler 25 into two beams, one of which is output as the fifth pump light at the second optical fiber connector 29 in a time-coordinated manner. The wavelength of the fifth pump light is synchronously tuned with the wavelength of the seed light in the range of 730 to 1015 nm. The power of the fourth pump laser 22 is adjusted so that the average power of the fifth pump light at the second optical fiber connector 29 is 100 mW to 150 mW, and the pulse width is 1 to 20 ps.

[0023] In some embodiments, the wavelength of the final femtosecond pulse is synchronously tuned with the seed light in the range of 730 to 1015 nm, with an average power of 100 to 700 mW and a pulse width of 80 to 120 fs.

[0024] Compared with the existing devices, the beneficial technical effects achieved by the present invention are as follows:

[0025] 1) The dual-band tuned fiber nonlinear microscopic spectroscopy hybrid excitation source developed by the present invention outputs a total of three synchronized ultrashort pulses, two of which are strictly time-aligned, while the femtosecond pulse lags behind the picosecond pulse for a period of time. Coherent Raman scattering using tuned picosecond pulses can achieve high spectral resolution;

[0026] 2) The present invention adopts an optical fiber structure to design a dual-band tuned optical fiber nonlinear microscopic spectroscopy hybrid excitation source. The excitation source device generates three ultrashort pulses based on the same seed pulse and has natural synchronization. The passive mode locking technology and the four-wave mixing nonlinear effect frequency conversion technology are used to generate two picosecond pulses that can achieve synchronous tuning of wavelength and repetition frequency, and the two pulses are always consistent in timing, while the other femtosecond pulse is obtained after picosecond pulse compression and is output in a staggered synchronization manner that lags behind the picosecond pulse for a period of time. The application of co-synchronization and staggered synchronization of picosecond and femtosecond pulses can meet the excitation light requirements of different nonlinear imaging. The two time-co-synchronized picosecond pulses can be used for coherent Raman scattering microscopic spectroscopy imaging, while the time-staggered synchronized tunable femtosecond pulses can perform two-photon excitation fluorescence and second harmonic imaging of multiple components. Therefore, the femtosecond pulse can achieve efficient excitation, for example, two-photon excitation fluorescence and second harmonic imaging, and can achieve the purpose of simultaneously acquiring multi-dimensional information, providing sufficient information for stably acquiring the characteristics of the sample to be tested.

[0027] 3) This invention will greatly simplify the construction of nonlinear multimodal microspectral imaging systems, and has the characteristics of high stability, high reliability, high flexibility, and low maintenance cost, which will promote the popularization and application of portable nonlinear multimodal microspectral imagers. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 This is a schematic diagram of the device structure of the dual-band tuned fiber nonlinear micro-spectroscopy hybrid excitation source proposed in the present invention;

[0029] Figure 2 is the relative change curve of Stokes light and the fifth pump light;

[0030] Figure 3 This is the four-wave mixing spectrum formed after the amplified seed light enters the first photonic crystal fiber;

[0031] Figure 4 Schematic diagram of the relative positions of picosecond pulses and femtosecond pulses in the timing sequence;

[0032] Reference numerals:

[0033] 1. Electric control rotating stage, 2. Saturable absorber, 3. First tunable optical delay, 4. Diffraction grating, 5. Aspheric lens, 6. First ytterbium-doped fiber, 7. First wavelength division multiplexer, 8. First pump laser, 9. First chirped fiber grating, 10. First fiber isolator, 11. Second wavelength division multiplexer, 12. Second pump laser, 13. Second ytterbium-doped fiber, 14. First fiber beam splitter, 15. First signal pump combiner, 16. Third pump laser, 17. Third ytterbium-doped fiber, 1 8. Second optical fiber isolator, 19. First optical fiber connector, 20. Third wavelength division multiplexer, 21. Second signal pump combiner, 22. Fourth pump laser, 23. Fourth ytterbium-doped optical fiber, 24. First photonic crystal fiber, 25. Optical fiber coupler, 26. Second adjustable optical delay, 27. Delay optical fiber, 28. Second optical fiber beam splitter, 29. Second optical fiber connector, 30. Second photonic crystal fiber, 31. Second chirped fiber Bragg grating, 32. Third adjustable optical delay, 33. Third optical fiber connector. DETAILED DESCRIPTION

[0034] The technical solution of the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments. The described specific embodiments are only used to explain the present invention and are not intended to limit the present invention.

[0035] like Figure 1 The structure of the dual-band tunable fiber nonlinear micro-spectroscopy excitation source device of the present invention is shown, and the device includes an electrically controlled rotating stage 1, a saturable absorber 2, a first tunable optical delay 3, a diffraction grating 4, an aspheric lens 5, a first ytterbium-doped fiber 6, a first wavelength division multiplexer 7, a first pump laser 8, a first chirped fiber grating 9, a first fiber isolator 10, a second wavelength division multiplexer 11, a second pump laser 12, a second ytterbium-doped fiber 13, a first fiber beam splitter 14, a first signal pump combiner 15, and a third pump The optical fiber includes a first optical fiber connector 19, a third wavelength division multiplexer 20, a second signal pump combiner 21, a fourth pump laser 22, a fourth ytterbium-doped optical fiber 23, a first photonic crystal fiber 24, a fiber coupler 25, a second adjustable optical delay 26, a delay optical fiber 27, a second optical fiber splitter 28, a second optical fiber connector 29, a second photonic crystal fiber 30, a second chirped fiber grating 31, a third adjustable optical delay 32, and a third optical fiber connector 33.

[0036] The saturable absorber 2, the first tunable optical delay 3, the diffraction grating 4, the aspheric lens 5, the first ytterbium-doped optical fiber 6, the first wavelength division multiplexer 7, and the first chirped fiber grating 9 constitute a seed light resonant cavity. The first pump laser 8 generates a first pump light, which passes through the first wavelength division multiplexer 7 and enters the first ytterbium-doped optical fiber 6 to stimulate broadband spontaneous emission light. The first pump light is then collimated by the aspheric lens 5 onto the diffraction grating 4 to generate diffracted light. The diffracted light passes through the first tunable optical delay 3, forms a pulse, and is reflected by the saturable absorber 2 fixed on the electrically controlled rotating stage 1. The diffracted light then passes through the first tunable optical delay 3 and the diffraction grating 4 again and is refocused by the aspheric lens 5 back to the first ytterbium-doped optical fiber 6. Then, 20% of the light is output from the first chirped fiber grating 9, and 80% of the light is reflected back to the seed light resonant cavity. The loss of incident light by the saturable absorber 2 decreases as the light intensity increases. The pulse formed by the saturable absorber 2 oscillates back and forth within the seed light resonator and is gradually amplified by the feedback provided by the resonator. When the intracavity gain exceeds the loss, the saturable absorber 2 compresses the intracavity oscillating pulse into a picosecond pulse, achieving passive mode locking and outputting the seed light from the first chirped fiber grating 9. The seed light passes through the first fiber isolator 10, then through the second wavelength division multiplexer 11 into the second ytterbium-doped fiber 13. The second pump laser 12 generates a second pump light, which passes through the second wavelength division multiplexer 11 and enters the second ytterbium-doped fiber 13, pre-amplifying the incoming seed light. The pre-amplified seed light is evenly split into two pulses by the first fiber beam splitter 14. One of the pulses passes through the first signal pump combiner 15 and enters the third ytterbium-doped fiber 17. The third pump laser 16 generates a third pump light beam, which passes through the first signal pump combiner 15 and enters the third ytterbium-doped fiber 17, where it performs primary amplification on the pre-amplified split pulse light. The pulses undergoing primary amplification pass through the second fiber isolator 18 and are output as Stokes light at the first fiber connector 19. Another pulse light beam passes through the third wavelength division multiplexer 20, the second signal pump combiner 21, and enters the fourth ytterbium-doped fiber 23. The fourth pump laser 22 generates a fourth pump light beam, which passes through the second signal pump combiner 21 and enters the fourth ytterbium-doped fiber 23, where it performs primary amplification on the pre-amplified split pulse light. The third wavelength division multiplexer 20, the second signal pump combiner 21, the fourth ytterbium-doped fiber 23, the first photonic crystal fiber 24, the fiber coupler 25, the second tunable optical delay 26, and the delay fiber 27 form a fiber parametric oscillator resonator. The fiber parametric oscillator resonator performs frequency conversion and amplification on the incident pulse light. The pulsed light after the main amplification enters the first photonic crystal fiber 24 to generate four-wave mixing gain, and then passes through the fiber coupler 25, the second adjustable optical delay 26, the delay fiber 27, the third wavelength division multiplexer 20, the second signal pump combiner 21 and the fourth ytterbium-doped fiber 23 in sequence to return to the first photonic crystal fiber 24 to form fiber parametric oscillation, and finally the pulsed light after four-wave mixing frequency conversion is output from the fiber coupler 25.The second fiber beam splitter 28 divides the pulse light output by the fiber parametric oscillation into two beams of pulse light again. One beam of picosecond pulse light is output at the second fiber connector 29 as the fifth pump light, and the other beam of pulse light is compressed into femtosecond pulse light after passing through the second photonic crystal fiber 30 and the second chirped fiber grating 31 in sequence, and then passes through the third adjustable optical delay 32 to output the femtosecond pulse light at the third fiber connector 33.

[0037] The electrically controlled rotating stage 1 adjusts the reflection angle by rotating the saturable absorber 2 to obtain a set of reflected lights, so that the seed light is tuned within the wavelength range of 1010 to 1075 nm.

[0038] The saturable absorber 2 is used to achieve passive mode locking and generate picosecond pulses.

[0039] The first adjustable optical delay device 3 is used to control the repetition frequency of the seed light to be tuned within the range of 45 to 55 MHz.

[0040] The diffraction grating 4 generates diffracted light from the collimated broadband spontaneous radiation light.

[0041] The aspheric lens 5 collimates the broadband spontaneous radiation light onto the diffraction grating 4 .

[0042] The first ytterbium-doped optical fiber 6 serves as a gain medium in the seed resonant cavity and generates broadband spontaneous emission light through the first pump light.

[0043] The first wavelength division multiplexer 7 is used to combine the first pump light generated by the first pump laser 8 and the pulse light into the same optical fiber.

[0044] The first pump laser 8 is used to generate a first pump light.

[0045] The first chirped fiber grating 9 is used for partially reflecting and transmitting light within the range of 1010-1075 nm.

[0046] The first optical fiber isolator 10 is used to realize unidirectional transmission of light and block reverse light.

[0047] The second wavelength division multiplexer 11 is used to combine the second pump light generated by the second pump laser 12 and the seed light into the same optical fiber.

[0048] The second pump laser 12 is used to generate a second pump light.

[0049] The second ytterbium-doped optical fiber 13 generates broadband spontaneous emission light through the second pump light to pre-amplify the incoming seed light.

[0050] The first optical fiber beam splitter 14 is used to evenly split the pre-amplified seed light into two beams of pulsed light.

[0051] The first signal pump combiner 15 is used to combine the third pump light generated by the third pump laser 16 and the pulse light split after pre-amplification into the same optical fiber.

[0052] The third pump laser 16 is used to generate a third pump light.

[0053] The third ytterbium-doped optical fiber 17 generates broadband spontaneous emission light through the third pump light, and performs main amplification on the pulse light split after pre-amplification.

[0054] The second optical fiber isolator 18 is used to realize unidirectional transmission of light and block reverse light.

[0055] The first optical fiber connector 19 outputs Stokes light.

[0056] The third wavelength division multiplexer 20 is used to combine the pulse light after pre-amplification and the pulse light after fiber parametric frequency conversion into the same optical fiber.

[0057] The second signal pump combiner 21 is used to combine the fourth pump light generated by the third pump laser 22, the pulse light split after pre-amplification, and the pulse light obtained by fiber parametric frequency conversion into the same optical fiber.

[0058] The fourth pump laser 22 generates fourth pump light.

[0059] The fourth ytterbium-doped optical fiber 23 generates broadband spontaneous emission light through the fourth pump light, and performs main amplification on the pulse light split after pre-amplification.

[0060] The first photonic crystal fiber 24 is used to generate four-wave mixing gain.

[0061] The optical fiber coupler 25 partially outputs the pulse light that has undergone four-wave mixing frequency conversion.

[0062] The second adjustable optical delay 26 is used to adjust the intrinsic repetition frequency of the fiber parametric oscillation resonant cavity to be an integer multiple of the repetition frequency of the seed light.

[0063] The delay fiber 27 is used to increase the cavity length of the fiber parametric oscillation resonant cavity.

[0064] The second fiber beam splitter 28 is used to evenly split the pulse light output by the fiber parametric oscillator into two beams of pulse light, one of which is a picosecond pulse light serving as the fifth pump light.

[0065] The second optical fiber connector 29 is used to output the fifth pump light.

[0066] The second photonic crystal fiber 30 is used to generate self-phase modulation and broaden the spectrum of the fifth pump light.

[0067] The second chirped fiber grating 31 is used to compress another beam of pulsed light into a femtosecond pulse after it passes through the second photonic crystal fiber and the second chirped fiber grating in sequence.

[0068] The third adjustable optical delay line 32 is used to adjust the delay between the femtosecond pulse and the fifth pump light.

[0069] The third optical fiber connector 33 outputs femtosecond pulse light.

[0070] Specifically, the spectral bandwidth of the diffraction grating 4 is 1 to 5 nm, so that the output pulse width of the seed light is 1 to 20 ps.

[0071] The first ytterbium-doped optical fiber 6 and the second ytterbium-doped optical fiber 13 are single-mode polarization-maintaining ytterbium-doped optical fibers.

[0072] The first wavelength division multiplexer 7 , the second wavelength division multiplexer 11 and the third wavelength division multiplexer 20 are all wavelength division multiplexers whose pigtails are polarization-maintaining optical fibers.

[0073] The operating wavelength range of the first chirped fiber grating 9 is 1010-1075 nm, and the reflectivity and transmittance are 80% and 20% respectively.

[0074] The splitting ratio of the first optical fiber beam splitter 14 and the first optical fiber beam splitter 28 is 50:50, and the pigtail is a polarization-maintaining optical fiber.

[0075] The first signal pump combiner 15 and the first signal pump combiner 21 are used to combine multimode pump light and signal light, and the pigtail is a polarization-maintaining fiber.

[0076] The third ytterbium-doped optical fiber 17 and the fourth ytterbium-doped optical fiber 23 are double-clad polarization-maintaining ytterbium-doped optical fibers.

[0077] The present invention also proposes a method for realizing a dual-band tuned fiber nonlinear microspectroscopy hybrid excitation source, which comprises the following steps:

[0078] Step 1: Control the output power of the first pump laser 8 to achieve passive mode locking of the seed source. At the same time, adjust the electrically controlled rotary stage 1 and the first adjustable optical delay 3 so that the output wavelength and repetition frequency of the seed light are tuned in the range of 1010-1075 nm and 45 MHz-55 MHz, respectively. The output pulse width of the seed light is 1-20 ps and the average power is 1-10 mW.

[0079] Step 2: The seed light enters the pre-amplification stage consisting of the second pump laser 12, the second wavelength division multiplexer 11, and the second ytterbium-doped fiber 13. The output power of the second pump laser 12 is controlled so that the average power of the pre-amplified seed light is 30-100 mW. The amplified seed light is then evenly divided into two pulsed lights using the first fiber beam splitter 14. One of the pulsed lights is amplified by the main amplifier stage consisting of the first signal pump combiner 15, the third pump laser 16, and the third ytterbium-doped fiber 17. The power of the third pump laser 16 is adjusted at the first fiber connector 19 to obtain Stokes light with an average power of 700-900 mW. Its wavelength and repetition frequency are synchronized with the seed light, and the output pulse width is 1-20 ps.

[0080] Step 3: The other pulse light split by the first fiber beam splitter 14 passes through the third wavelength division multiplexer 20, and first enters the main amplifier stage composed of the second signal pump combiner 21, the fourth pump laser 22 and the fourth ytterbium-doped fiber 23 for amplification, and then generates four-wave mixing gain through the first photonic crystal fiber 24, and adjusts the second adjustable optical delay 26 to match the intrinsic repetition frequency of the fiber parametric oscillation resonator with the repetition frequency of the seed light, so that the signal light gain part formed by four-wave mixing is transmitted through the fiber coupler 25, the second adjustable optical delay 26 and the delay fiber 27 returns to the third wavelength division multiplexer 20 to generate fiber parametric oscillation, and at the same time, part of the pulse light is output from the fiber coupler 25. Then, the second fiber beam splitter 28 divides the light output from the fiber coupler 25 into two beams, one of which is output as the fifth pump light at the second fiber connector 29 in time-coordinated synchronization. Its wavelength is synchronously tuned with the wavelength of the seed light in the range of 730 to 1015 nm. The power of the fourth pump laser 22 is adjusted so that the average power of the pump light at the second fiber connector 29 is 100 mW to 150 mW, and the pulse width is 1 to 20 ps.

[0081] Step 4: The remaining light beam, split by the second optical fiber beam splitter 28, is first spectrally broadened using a second photonic crystal fiber 30. The picosecond pulse is then compressed into a femtosecond pulse using a second chirped fiber grating 31. A third adjustable optical delay 32 is then used to adjust the delay between the femtosecond and picosecond pulses, causing the femtosecond pulse to lag behind the picosecond pulse by a certain period, achieving time-shifted synchronization. The femtosecond pulse is then output at a third optical fiber connector 33. The wavelength of the resulting femtosecond pulse is synchronously tuned with the seed light within the range of 730 to 1015 nm, with an average power of 100 to 700 mW and a pulse width of 80 to 120 fs.

[0082] In summary, the present invention adopts an optical fiber structure to design a dual-band tuned optical fiber nonlinear microscopic spectroscopy hybrid excitation source. The excitation source device generates three beams of ultrashort pulses based on the same seed pulse and has natural synchronization. Among them, two beams of picosecond pulses that can achieve synchronous tuning of wavelength and repetition frequency are generated by means of passive mode locking technology and four-wave mixing nonlinear effect frequency conversion technology, and the two beams of pulses are always consistent in timing, while the other beam of femtosecond pulses is obtained after picosecond pulse compression and is output in a staggered synchronization manner that lags behind the picosecond pulse for a period of time. The application of co-synchronization and staggered synchronization of picosecond and femtosecond pulses can meet the excitation light requirements of different nonlinear imaging. Among them, two beams of time-co-synchronized picosecond pulses can be used for coherent Raman scattering microscopic spectroscopy imaging, while the time-staggered synchronized tunable femtosecond pulses can perform two-photon excitation fluorescence and second harmonic imaging of multiple components. This invention will greatly simplify the construction of nonlinear multimodal microspectral imaging systems, and has the characteristics of high stability, high reliability, high flexibility, and low maintenance costs. It will promote the promotion and application of portable nonlinear multimodal microspectral imagers.

[0083] It should be noted that although the present invention has been shown and described with reference to specific exemplary embodiments of the present invention, those skilled in the art should understand that the present invention is not limited to the above-mentioned embodiments and all kinds of changes to the present invention fall within the scope of protection of the present invention.

Claims

1. A dual-band tunable fiber nonlinear microscopic spectroscopy excitation source device, characterized in that: The device comprises a seed resonant cavity, a first optical fiber isolator (10), a pre-amplifier stage, a first optical fiber beam splitter (14), a main amplifier stage, a second optical fiber isolator (18), a first optical fiber connector (19), an optical fiber parametric oscillator resonant cavity, a fourth pump laser (22), a fourth pump laser (22), a second optical fiber beam splitter (28), a second optical fiber connector (29), a second photonic crystal fiber (30), a second chirped optical fiber grating (31), a third adjustable optical delay device (32) and a third optical fiber connector (33), which are connected in sequence; The seed resonant cavity comprises a saturable absorber (2), a first tunable optical delay device (3), a diffraction grating (4), an aspheric lens (5), a first ytterbium-doped optical fiber (6), a first wavelength division multiplexer (7), a first pump laser (8) and a first chirped fiber grating (9), which are connected in sequence; the pre-amplification stage comprises a second wavelength division multiplexer (11), a second pump laser (12) and a second ytterbium-doped optical fiber (13), which are connected in sequence; the main amplification stage comprises a first signal pump combiner (15), a third pump laser (16) and a third ytterbium-doped optical fiber (17), which are connected in sequence; and the fiber parametric oscillation resonant cavity comprises a third wavelength division multiplexer (20), a second signal pump combiner (21), a fourth ytterbium-doped optical fiber (23), a first photonic crystal fiber (24), a fiber coupler (25), a second tunable optical delay device (26) and a delay optical fiber (27), which are connected in sequence.

2. A method for realizing dual-band tunable fiber nonlinear microscopic spectroscopy excitation, characterized in that: The following steps are involved: Through the seed resonant cavity, the saturable absorber (2) achieves passive mode locking to generate picosecond pulses as seed light; The first adjustable optical delay device (3) controls the repetition frequency of the seed light, the diffraction grating (4) generates diffracted light from the collimated broadband spontaneous radiation light, the aspheric lens (5) collimates the broadband spontaneous radiation light onto the diffraction grating (4), the first pump laser (8) outputs the first pump light, the first ytterbium-doped optical fiber (6) serves as the gain medium in the seed resonant cavity, and generates broadband spontaneous radiation light through the first pump light, the first wavelength division multiplexer (7) combines the first pump light with the pulse light into the same optical fiber, namely the first ytterbium-doped optical fiber (6), and the first chirped fiber grating (9) partially reflects and transmits the pulse light in the range of 1010 to 1075 nm; The first optical fiber isolator (10) realizes unidirectional transmission of seed light; Through the pre-amplification stage, a second pump laser (12) generates a second pump light, and a second wavelength division multiplexer (11) combines the second pump light with the seed light into the same optical fiber, i.e., a second ytterbium-doped optical fiber (13). The second ytterbium-doped optical fiber (13) generates broadband spontaneous emission light through the second pump light, and pre-amplifies the incoming seed light; The pre-amplified seed light is evenly divided into two beams of pulsed light by the first optical fiber beam splitter (14); The third pump laser (16) generates a third pump light through the main amplifier stage, and the first signal pump combiner (15) combines the third pump light and the pulse light split after pre-amplification into the same optical fiber, i.e., the third ytterbium-doped optical fiber (17). The third ytterbium-doped optical fiber (17) generates broadband spontaneous radiation light through the third pump light, and performs main amplification on the pulse light split after pre-amplification; The second optical fiber isolator (18) realizes unidirectional transmission of the main amplified pulse light, the first optical fiber connector (19) outputs Stokes light, and the fourth pump laser (22) generates fourth pump light; Through the fiber parametric oscillation resonant cavity, the third wavelength division multiplexer (20) combines the pulse light after pre-amplification and the pulse light after fiber parametric frequency conversion into the same optical fiber, i.e., the input optical fiber of the second signal pump combiner (20); the second signal pump combiner (20) combines the fourth pump light, the pulse light after pre-amplification and the pulse light after fiber parametric frequency conversion into the same optical fiber, i.e., the fourth ytterbium-doped optical fiber (23); broadband spontaneous radiation light is generated by the fourth pump light, and the pulse light after pre-amplification and beam splitting is mainly amplified; the first photonic crystal fiber (24) forms a four-wave mixing gain; the fiber coupler (25) partially outputs the pulse light after four-wave mixing frequency conversion; the second adjustable optical delay (26) adjusts the intrinsic repetition frequency of the fiber parametric oscillation resonant cavity to be an integer multiple of the repetition frequency of the seed light; the delay optical fiber (27) increases the cavity length of the fiber parametric oscillation resonant cavity; The pulse light outputted by the fiber parametric oscillation resonant cavity is evenly divided into two beams of pulse light again by a second fiber beam splitter (28), wherein one beam of picosecond pulse light serves as the fifth pump light, the second fiber connector (29) outputs the fifth pump light, the second photonic crystal fiber (30) generates self-phase modulation, broadens the spectrum of the other beam of pulse light splitted by the second fiber beam splitter (28), the other beam of pulse light is compressed into a femtosecond pulse after passing through the second photonic crystal fiber (30) and the second chirped fiber grating (31) in sequence, the third adjustable optical delay device (32) adjusts the delay between the femtosecond pulse and the fifth pump light, and the third fiber connector (33) outputs the final femtosecond pulse light.

3. The method for realizing dual-band tunable fiber nonlinear microscopic spectroscopy excitation according to claim 2, characterized in that: The method further comprises the following steps: The output power of the first pump laser is controlled to achieve passive mode locking of the seed source, and the electrically controlled rotating stage and the first adjustable optical delay (3) are adjusted to tune the output wavelength and repetition frequency of the seed light within the range of 1010-1075 nm and 45 MHz-55 MHz respectively, with the output pulse width of the seed light being 1-20 ps and the average power being 1-10 mW.

4. The method for realizing dual-band tunable fiber nonlinear microscopic spectroscopy excitation according to claim 2, characterized in that: The method includes controlling the output power of the second pump laser so that the average power of the pre-amplified seed light is 30-100 mW.

5. The method for realizing dual-band tunable fiber nonlinear microscopic spectroscopy excitation according to claim 2, characterized in that: The power of the third pump laser (16) is adjusted to obtain Stokes light with an average power of 700mW to 900mW at the first optical fiber connector (19). The wavelength and repetition frequency are synchronized with the seed light, and the output pulse width is 1 to 20ps.

6. The method for realizing dual-band tunable fiber nonlinear microscopic spectroscopy excitation according to claim 2, characterized in that: The invention comprises a second optical fiber beam splitter (28) for evenly dividing the light outputted from the optical fiber coupler (25) into two beams, one of which is outputted as the fifth pump light at the second optical fiber connector (29) in a time-coordinated manner, and the wavelength thereof is synchronously tuned with the wavelength of the seed light within the range of 730 to 1015 nm. The power of the fourth pump laser (22) is adjusted so that the average power of the fifth pump light at the second optical fiber connector (29) is 100 mW to 150 mW, and the pulse width is 1 to 20 ps.

7. The method for realizing dual-band tunable fiber nonlinear microscopic spectroscopy excitation according to claim 2, characterized in that: The wavelength of the final femtosecond pulse is synchronously tuned with the seed light in the range of 730 to 1015 nm, with an average power of 100 to 700 mW and a pulse width of 80 to 120 fs.

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