Femtosecond oscillator and femtosecond laser source for two-photon printing
By using a combination of a linear Mamyshev oscillator and holmium-doped fluoride fiber in a femtosecond oscillator, the structure of a two-photon printing femtosecond laser source is simplified, directly outputting high-energy lasers in the 700 nm ~ 800 nm and 500 nm ~ 560 nm bands. This solves the problem of system complexity in the prior art and improves the efficiency and applicability of the laser source.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- QIANYUAN NATIONAL LABORATORY
- Filing Date
- 2026-02-25
- Publication Date
- 2026-05-12
AI Technical Summary
In the existing technology, the femtosecond laser source for two-photon printing has a complex structure, which requires an infrared femtosecond laser seed source, a seed source pulse width stretcher, an amplification system, a pulse width compressor, and a frequency doubling system, resulting in a long link and a complex overall structure.
Employing a pump source system and a femtosecond oscillation module, including a linear Mamyshev oscillator, holmium-doped fluoride fiber, and tapered fiber, laser gain is generated by the pump beam from the linear Mamyshev oscillator incident on the holmium-doped fluoride fiber, and spectral broadening is achieved in the tapered fiber. Combined with the self-phase modulation effect of the Mamyshev oscillator, femtosecond lasers in the 700 nm ~ 800 nm and 500 nm ~ 560 nm bands are directly output, simplifying the system structure.
It achieves high-energy femtosecond laser output without the need for multi-stage amplification and frequency doubling systems, simplifies the laser system structure, improves the efficiency and reliability of the laser source, and is suitable for two-photon printing.
Smart Images
Figure CN122008703A_ABST
Abstract
Description
Technical Field
[0001] This application relates to the field of laser application technology, and more specifically, to a femtosecond oscillator and a femtosecond laser source for two-photon printing. Background Technology
[0002] The fundamental principle of two-photon polymerization printing originates from the two-photon absorption theory proposed by Maria Goeppert-Mayer in 1931. However, it wasn't until 1997, when Japanese scientist S. Maruo first used a femtosecond laser to achieve micron-scale three-dimensional structure printing in photoresist, that the application of two-photon technology truly began. Two-photon printing is based on nonlinear optical effects: when a femtosecond laser is focused on photosensitive resin, the resin molecules simultaneously absorb two near-infrared photons. When the total absorbed energy exceeds the polymerization threshold, the resin undergoes cross-linking and curing within a very small volume of the laser focus. Because the nonlinear effect is activated only in the high-intensity region, its processing resolution breaks through the optical diffraction limit, reaching below 100 nm.
[0003] The wavelengths of femtosecond laser sources used for two-photon printing are generally in the visible and near-infrared bands. Among them, laser sources in the 780 nm and 532 nm bands have low scattering and absorption rates in photosensitive resins and can penetrate to a depth of hundreds of micrometers, which is conducive to realizing the internal printing of deep structures. Therefore, the 700 nm ~ 800 nm band and the 500 nm ~ 560 nm visible light band are most widely used in two-photon printing.
[0004] Currently, laser sources in the 700 nm ~ 800 nm band and the 500 nm ~ 560 nm visible light band are mainly obtained through nonlinear frequency doubling technology. The laser system links in these two bands are relatively long and the overall structure is relatively complex. They typically include five parts: an infrared femtosecond laser seed source, a seed source pulse width stretcher, a single or multi-stage amplification system, a pulse width compressor, and a frequency doubling system. Summary of the Invention
[0005] This application provides a femtosecond oscillator and a femtosecond laser source for two-photon printing. The femtosecond oscillator does not require pulse width broadening, multi-stage amplification and frequency doubling systems, and can directly emit high-energy short-pulse femtosecond lasers in the 700 nm ~ 800 nm band or the 500 nm ~ 560 nm band, which greatly simplifies the structural complexity of the femtosecond laser source for two-photon printing.
[0006] To achieve the above objectives, the technical solutions adopted in the embodiments of this application are as follows: One aspect of this application provides a femtosecond oscillator, including a pump source system and a femtosecond oscillation module. The femtosecond oscillation module includes a linear Mamyshev oscillator, and a holmium-doped fluoride fiber and a tapered fiber disposed between the linear Mamyshev oscillator. The linear Mamyshev oscillator is composed of a first reflective diffraction grating and a second reflective diffraction grating respectively arranged at a Littoral angle. A pump beam coupled by the pump source system is incident on the holmium-doped fluoride fiber to generate laser gain. The gain laser oscillates and broadens its spectrum between the first and second reflective diffraction gratings through the tapered fiber, so that the broadened laser beam covers the reflection wavelengths of the first and second reflective diffraction gratings.
[0007] In one feasible embodiment of this application, the pump source system includes a signal generator, a laser diode driver, and a visible light band laser diode. The signal generator outputs a periodic signal to the laser diode driver to drive the visible light band laser diode to output pulses, or the signal generator outputs a DC signal to the laser diode driver to drive the visible light band laser diode to output a continuous wave.
[0008] In one feasible implementation of the embodiments of this application, the visible light band laser diode is a blue laser diode.
[0009] In one feasible embodiment of this application, the femtosecond oscillator further includes a pump optical coupling module disposed between the pump source system and the femtosecond oscillation module. The pump optical coupling module includes at least one convex lens, and the femtosecond oscillation module is also provided with a dichroic mirror. After the pump beam is collimated and focused by the pump optical coupling module, it is coupled into the holmium fluoride-doped fiber through the dichroic mirror.
[0010] In one feasible embodiment of this application, the femtosecond oscillation module further includes an output coupling device, which includes a first half-wave plate and a polarization beam splitter. The polarization transmission axis of the first half-wave plate is adjusted to reflect a portion of the laser beam out through the polarization beam splitter.
[0011] In one feasible embodiment of this application, the reflection wavelength of the first reflective diffraction grating is 745nm, the reflection wavelength of the second reflective diffraction grating is 752nm, the length of the holmium-doped fluoride fiber is 1.5m, and the length of the tapered fiber is 0.5m.
[0012] Another aspect of the embodiments of this application provides a femtosecond laser source, including a femtosecond oscillator of any of the foregoing, and a pulse width compression system, wherein the laser beam emitted after spectral broadening by the femtosecond oscillator is emitted after the pulse width is compressed in the pulse width compression system.
[0013] In one feasible embodiment of this application, the pulse width compression system includes a second half-wave plate, a Treacy type compressor, and a roof prism reflector. The laser beam emitted after spectral broadening by the femtosecond oscillator is polarized by the second half-wave plate and then incident on the Treacy type compressor to compress the laser pulse width. The resulting compressed pulse width laser beam is emitted through the roof prism reflector.
[0014] In one feasible embodiment of this application, the Treacy type compressor includes a first transmission diffraction grating and a second transmission diffraction grating arranged in parallel opposite directions. After the laser beam compresses its pulse width within the Treacy type compressor, it exits toward the roof prism reflector.
[0015] In one feasible embodiment of this application, the femtosecond laser source of this application further includes a high reflectivity plane mirror. The high reflectivity plane mirror is disposed in the optical path of the reflection direction of the roof prism reflector. The compressed pulse width laser beam reflected by the roof prism reflector is reflected out through the high reflectivity plane mirror.
[0016] The femtosecond oscillator provided in this application embodiment includes a pump source system and a femtosecond oscillation module. The femtosecond oscillation module includes a linear Mamyshev oscillator and a holmium-doped fluoride fiber and a tapered fiber disposed between the linear Mamyshev oscillator. The linear Mamyshev oscillator is composed of a first reflective diffraction grating and a second reflective diffraction grating respectively arranged at a Littoral angle. The pump beam coupled by the pump source system is incident on the holmium-doped fluoride fiber to generate laser gain. The gain laser oscillates and broadens its spectrum between the first reflective diffraction grating and the second reflective diffraction grating through the tapered fiber, so that the broadened laser beam covers the reflection wavelength of the first reflective diffraction grating and the second reflective diffraction grating. Holmium-doped fluoride fiber, when excited by pump light emitted from a pump source system, exhibits emission gain in the near-infrared 700 nm-800 nm band and the visible light 500 nm-560 nm band. This gain laser, combined with the self-phase modulation effect of the tapered fiber in the Mamyshev oscillator, achieves spectral broadening. The broadened spectrum covers the reflection wavelength λ1 of the first reflective diffraction grating and the reflection wavelength λ2 of the second reflective diffraction grating. Stable laser oscillation is formed by reflection between the first and second reflective diffraction gratings. Thus, the femtosecond oscillator in this embodiment of the application does not require the complex setup of a multi-stage amplification system and a frequency doubling system to meet the requirements for high single-pulse energy femtosecond laser output in the 700 nm-800 nm band and the 500 nm-560 nm visible light band for two-photon printing. Attached Figure Description
[0017] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.
[0018] Figure 1 This is one of the structural schematic diagrams of a femtosecond oscillator provided in an embodiment of this application; Figure 2 A schematic diagram of energy level transitions in a fluoride-doped optical fiber in a femtosecond oscillator after being excited by visible light pump light, provided as an embodiment of this application; Figure 3 This is a second schematic diagram of the structure of a femtosecond oscillator provided in an embodiment of this application; Figure 4 This is the third schematic diagram of a femtosecond oscillator provided in the embodiments of this application; Figure 5 This is the fourth schematic diagram of a femtosecond oscillator provided in the embodiments of this application; Figure 6 Fifth schematic diagram of a femtosecond oscillator provided in the embodiments of this application; Figure 7 A schematic diagram of a femtosecond oscillator provided in this application embodiment is shown in Figure 6. Figure 8 A schematic diagram of the laser spectrum output by a femtosecond oscillator provided in an embodiment of this application; Figure 9 A pulsed laser sequence diagram of a femtosecond oscillator output provided in an embodiment of this application; Figure 10 A schematic diagram of the laser pulse width output by a femtosecond oscillator is provided for an embodiment of this application; Figure 11 A schematic diagram of the pulse width of a laser pulse output from a femtosecond oscillator after compression by a pulse width compression system, provided as an embodiment of this application; Figure 12 This is a schematic diagram of the printing effect of two-photon printing using the femtosecond laser source provided in the embodiments of this application.
[0019] Icons: 10-Pump source system; 11-Signal generator; 12-Laser diode driver; 13-Visible light band laser diode; 20-Femtosecond oscillation module; 21-Holmium-doped fluoride fiber; 22-Tap-fiber; 23-First reflective diffraction grating; 24-Second reflective diffraction grating; 25-Dichroic mirror; 26-Output coupling device; 261-First half-wave plate; 262-Polarization beam splitter; 30-Pump light coupling module; 40-Pulse width compression system; 41-Second half-wave plate; 42-Treacy type compressor; 421-First transmission diffraction grating; 422-Second transmission diffraction grating; 43-Roof prism reflector; 44-High reflectivity plane mirror. Detailed Implementation
[0020] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. It should be noted that, in the absence of conflict, the various features in the embodiments of this application can be combined with each other, and the combined embodiments are still within the protection scope of this application.
[0021] In the description of this application, it should be noted that the terms "upper," "lower," "left," "right," "inner," and "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 application and simplifying the description, and therefore should not be construed as limiting this application. In addition, the terms "first," "second," and "third," etc., are only used to distinguish descriptions and should not be construed as indicating or implying relative importance.
[0022] Femtosecond laser light sources used for two-photon printing typically have wavelengths in the visible and near-infrared bands. Currently, the 700 nm to 800 nm and 500 nm to 560 nm wavelength ranges are the most widely used in two-photon printing. In particular, laser light sources with wavelengths of 780 nm and 532 nm are more suitable for two-photon printing due to their higher light penetration and lower scattering and absorption rates in photosensitive resins, resulting in better performance in printing deep structures. Limited by the inability of conventional gain media to cover the 700 nm ~ 800 nm band and the 500 nm ~ 560 nm visible light band, as well as the light wave splitting caused by nonlinear effects, existing technologies can only obtain laser sources for the 700 nm ~ 800 nm band and the 500 nm ~ 560 nm visible light band through nonlinear frequency doubling technology. This requires five indispensable parts, including an infrared femtosecond laser seed source, a seed source pulse width stretcher, an amplification system, a pulse width compressor, and a frequency doubling system, resulting in a long laser system link and a complex overall structure.
[0023] Based on this, one aspect of the embodiments of this application provides a femtosecond oscillator, such as... Figure 1 As shown, the femtosecond oscillator includes a pump source system 10 and a femtosecond oscillation module 20. The femtosecond oscillation module 20 includes a linear Mamyshev oscillator, and a holmium-doped fluoride fiber 21 and a tapered fiber 22 disposed between the linear Mamyshev oscillator.
[0024] The linear Mamyshev oscillator consists of a first reflective diffraction grating 23 and a second reflective diffraction grating 24 respectively arranged at a Littoral angle. A pump beam coupled to the pump source system 10 is incident on the holmium fluoride-doped fiber 21 to generate laser gain. The gain laser oscillates and broadens its spectrum between the first reflective diffraction grating 23 and the second reflective diffraction grating 24 through the tapered fiber 22, so that the broadened laser beam covers the reflection wavelengths of the first reflective diffraction grating 23 and the second reflective diffraction grating 24.
[0025] The pump laser beam emitted from the pump source system 10 is coupled into a linear Mamyshev oscillator. The coupled pump laser beam first enters a holmium-doped fluoride fiber 21, which serves as the gain medium in the linear Mamyshev oscillator and generates laser gain after being excited by the pump light. The holmium-doped fluoride fiber 21 is obtained by doping holmium with fluoride as the substrate material. For example, the holmium-doped fluoride fiber 21 can be selected from Ho:ZBLAN, Ho:ZrF4, Ho:InF3, etc.
[0026] For example, when the incident pump laser beam is approximately 450 nm blue light, after the holmium fluoride-doped fiber 21 is excited, please refer to... Figure 2 As shown, the ground state energy level 5 Particle absorption pump photons on I8 transition to energy levels 5 F 5 1+ 5 At G6, this energy level is metastable, therefore the particle will continue to relax to the level. 5 F4+ 5 On S2, the energy level 5 F4+ 5 Number of particles and energy levels on S2 5 I7 and ground state energy level 5 The I8 pairs form a population inversion, corresponding to laser emission lines of 740 nm ~ 757 nm and 536 nm ~ 553 nm, respectively.
[0027] The linear Mamyshev oscillator is composed of a first reflective diffraction grating 23 and a second reflective diffraction grating 24 respectively set at a Littoral angle. The first reflective diffraction grating 23 is set at a Littoral angle of wavelength λ1, and the second reflective diffraction grating 24 is set at a Littoral angle of wavelength λ2. This makes the angles of the incident light and the diffracted light the same, that is, the diffracted light passing through the first reflective diffraction grating 23 or the second reflective diffraction grating 24 will return along the original path of the incident light. This makes the first reflective diffraction grating 23 and the second reflective diffraction grating 24 serve as the two end mirrors of the linear Mamyshev oscillator. The first reflective diffraction grating 23 reflects the laser light of wavelength λ1, and the second reflective diffraction grating 24 reflects the laser light of wavelength λ2.
[0028] It should be noted that the reflection wavelength λ1 of the first reflective diffraction grating 23 and the reflection wavelength λ2 of the second reflective diffraction grating 24 can be selected and set accordingly based on the laser band that the femtosecond oscillator of this application needs to emit.
[0029] Since the reflection wavelength λ1 of the first reflective diffraction grating 23 is different from the reflection wavelength λ2 of the second reflective diffraction grating 24, a highly nonlinear medium needs to be placed inside the linear Mamyshev oscillator to ensure successful laser oscillation. This allows the laser light passing through the highly nonlinear medium to achieve spectral broadening that covers both the reflection wavelengths λ1 of the first reflective diffraction grating 23 and λ2 of the second reflective diffraction grating 24. In this embodiment, the highly nonlinear medium is a tapered optical fiber 22.
[0030] After laser amplification, the gained laser beam, due to its self-phase modulation effect within the tapered fiber 22, achieves spectral broadening to cover the reflection wavelength λ1 of the first reflective diffraction grating 23 and the reflection wavelength λ2 of the second reflective diffraction grating 24. This allows reflection between the first and second reflective diffraction gratings 23 and 24, resulting in stable laser oscillation. Compared to conventional nonlinear fibers, the tapered fiber 22 has a smaller core diameter, thus creating a stronger nonlinear effect. Even with a shorter tapered fiber 22 (0.5 m), sufficient spectral broadening is provided, ensuring a high repetition rate for the mode-locked pulse. Furthermore, the nonlinear Mamyshev mode-locked oscillator cavity based on the self-phase modulation effect of the tapered fiber 22 has a modulation depth approaching 100% compared to traditional mode-locked cavities, exhibiting greater tolerance to nonlinear phase shifts. This further facilitates the direct output of high-energy femtosecond lasers from femtosecond laser sources used for two-photon printing, including the femtosecond oscillator of this embodiment.
[0031] This application provides a femtosecond oscillator, including a pump source system 10 and a femtosecond oscillation module 20. The femtosecond oscillation module 20 includes a linear Mamyshev oscillator, and a holmium-doped fluoride fiber 21 and a tapered fiber 22 disposed between the linear Mamyshev oscillator. The linear Mamyshev oscillator is composed of a first reflective diffraction grating 23 and a second reflective diffraction grating 24 respectively arranged at a Littoral angle. A pump beam coupled into the pump source system 10 is incident on the holmium-doped fluoride fiber 21 to generate laser gain. The gain laser oscillates and broadens its spectrum between the first reflective diffraction grating 23 and the second reflective diffraction grating 24 through the tapered fiber 22, so that the broadened laser beam covers the reflection wavelengths of the first reflective diffraction grating 23 and the second reflective diffraction grating 24. The holmium-doped fluoride fiber 21, under the excitation of pump light emitted from the pump source system 10, exhibits emission gain in the near-infrared 700 nm-800 nm band and the visible light 500 nm-560 nm band. The gain laser, combined with the self-phase modulation effect of the tapered fiber 22 in the Mamyshev oscillator, achieves spectral broadening. The broadened spectrum covers the reflection wavelength λ1 of the first reflective diffraction grating 23 and the reflection wavelength λ2 of the second reflective diffraction grating 24. Stable laser oscillation is formed by reflection between the first reflective diffraction grating 23 and the second reflective diffraction grating 24. Thus, the femtosecond oscillator of this embodiment does not require the complex setup of a multi-stage amplification system and a frequency doubling system to meet the requirements for high single-pulse energy femtosecond laser output in the 700 nm-800 nm band and the 500 nm-560 nm visible light band for two-photon printing.
[0032] In one feasible implementation of the embodiments of this application, such as Figure 3As shown, the pump source system 10 includes a signal generator 11, a laser diode driver 12, and a visible light band laser diode 13. The signal generator 11 outputs a periodic signal to the laser diode driver 12 to drive the visible light band laser diode 13 to output pulses, or the signal generator 11 outputs a DC signal to the laser diode driver 12 to drive the visible light band laser diode 13 to output a continuous wave.
[0033] The pump source system 10 of this application embodiment has two output modes: pulsed laser and continuous laser. Specifically, during the initial startup of the femtosecond oscillator in this application embodiment, the signal generator 11, laser diode driver 12, and visible light laser diode 13 of the pump source system 10 are connected. The signal generator 11 outputs a periodic signal to the laser diode driver 12, driving the visible light laser diode 13 to output pulsed light. The output pulsed pump light is coupled into a holmium fluoride-doped fiber 21. Excited by the pump light, the holmium fluoride-doped fiber 21 generates a laser gain output. The first reflective diffraction grating 23 and the second reflective diffraction grating 24 have specific reflection wavelengths λ1 and λ2, respectively. The gain laser is spectrally broadened in the tapered fiber 22 so that the broadened laser spectrum covers the reflection wavelengths λ1 and λ2 of the first and second reflective diffraction gratings 23 and 24, thereby reflecting the broadened laser between the first and second reflective diffraction gratings 23 and 24 until stable laser oscillation is formed.
[0034] After a stable laser oscillation is formed in the linear Mamyshev oscillator, the signal generator 11 outputs a DC signal to the laser diode driver 12 to drive the visible light band laser diode 13 to output a continuous wave, switching to the continuous wave working mode.
[0035] In one feasible implementation of the embodiments of this application, the visible light band laser diode 13 is a blue light laser diode.
[0036] The visible light laser diode 13 is a blue laser diode. Driven by the laser diode driver 12, the blue laser diode emits blue light with a wavelength of about 450 nm. After the blue light of about 450 nm is incident on the holmium fluoride-doped fiber 21 for excitation, the pump photons undergo transitions and population inversion, which can output laser beams corresponding to the near-infrared band of 740 nm ~ 757 nm and the visible green band of 536 nm ~ 553 nm. After modulation processing such as spectral broadening and compression, it can be used for two-photon printing.
[0037] In one feasible implementation of the embodiments of this application, such as Figure 4As shown, the femtosecond oscillator in this embodiment of the application further includes a pump light coupling module 30 disposed between the pump source system 10 and the femtosecond oscillation module 20. The pump light coupling module 30 includes at least one convex lens. The femtosecond oscillation module 20 is also provided with a dichroic mirror 25. After the pump beam is collimated and focused by the pump light coupling module 30, it is coupled into the holmium fluoride-doped fiber 21 through the dichroic mirror 25.
[0038] Dichroic mirror 25 is used to couple the pump beam into the holmium fluoride-doped fiber 21. Dichroic mirror 25 has high reflectivity for pump beams in the visible light band and high transmittance for the laser wavelength oscillating in the femtosecond oscillation module 20. Therefore, setting dichroic mirror 25 in the oscillation reflection optical path of the femtosecond oscillation module 20 will not affect the formation and maintenance of the oscillation optical path.
[0039] For example, such as Figure 4 As shown, Figure 4 The pump light coupling module 30 shown includes two biconvex lenses. The signal generator 11 of the pump source system 10 outputs a periodic signal to the blue laser diode driver 12 to drive the blue laser diode to output pulses. The output pulsed 450 nm pump light is collimated and focused by the two biconvex lenses with a focal length of 12.7 mm, and then reflected by the dichroic mirror 25 into the oscillation optical path of the femtosecond oscillation module 20, and coupled into the holmium fluoride-doped fiber 21.
[0040] After adjusting parameters such as pump light power, duty cycle, and pulse repetition frequency of the pump source system 10 pulse output until mode-locked pulse is achieved in the femtosecond oscillation module 20, the signal generator 11 of the pump source system 10 adjusts the signal and converts the periodic signal into a DC signal to drive the blue laser diode driver 12 to output a continuous wave of the blue laser diode. After the signal mode change of the signal generator 11, the mode-locked pulse state is still maintained in the femtosecond oscillation module 20.
[0041] In one feasible implementation of the embodiments of this application, such as Figure 5 As shown, the femtosecond oscillation module 20 also includes an output coupling device 26, which includes a first half-wave plate 261 and a polarization beam splitter 262. The polarization transmission axis of the first half-wave plate 261 is adjusted to reflect part of the laser beam through the polarization beam splitter 262.
[0042] like Figure 5As shown, the output coupling device 26 includes a first half-wave plate 261 and a polarization beam splitter 262 disposed in the oscillation optical path of the femtosecond oscillation module 20. After the laser reflected between the first reflective diffraction grating 23 and the second reflective diffraction grating 24 of the femtosecond oscillation module 20 forms a stable laser oscillation, the first half-wave plate 261 is rotated to adjust the direction of its polarization transmission axis. This changes the polarization direction of the laser beam passing through the first half-wave plate 261. For example, if the original laser beam was P-polarized, after the rotation of the first half-wave plate 261, it is no longer strictly P-polarized. A portion of the light energy from the laser beam reflected back from the first reflective diffraction grating 23 or the second reflective diffraction grating 24 is split and reflected by the polarization beam splitter 262 and output outside the femtosecond oscillation module 20. Figure 5 The output is emitted upwards as shown.
[0043] It should be noted that those skilled in the art should know that by adjusting the angle of the first half-wave plate 261, the proportion of light energy of the reflected laser beam can be adjusted and selected.
[0044] like Figure 8 The image shown is a laser spectrum output by a femtosecond oscillator according to an embodiment of this application. Figure 8 As can be seen, the center wavelength of the output laser beam is 748 nm, and the spectral width at 10dB is 65.40206 nm.
[0045] In one feasible embodiment of this application, the reflection wavelength of the first reflective diffraction grating 23 is 745nm, and the reflection wavelength of the second reflective diffraction grating 24 is 752nm.
[0046] The visible light laser diode 13 is a blue laser diode. Correspondingly, the reflection wavelength of the first reflective diffraction grating 23 is 745 nm, and the reflection wavelength of the second reflective diffraction grating 24 is 752 nm. The holmium-doped fluoride fiber 21 has a length of 1.5 m and a core diameter of 1 μm. The tapered fiber 22 has a length of 0.5 m, and its core size is in the nanometer or submicrometer range. This significantly improves the nonlinear effect of the femtosecond oscillation module 20, ensuring sufficient intensity of the self-phase modulation effect within the oscillation cavity even with a relatively short operating length. Furthermore, it allows the laser spectrum within the oscillation cavity to achieve spectral broadening covering the reflection wavelengths of the first and second reflective diffraction gratings 23 and 24 after passing through the tapered fiber 22. Simultaneously, it ensures that the short-sized femtosecond oscillation module 20 generates high repetition frequency (>30 MHz) pulses.
[0047] Another aspect of this application provides a femtosecond laser source, such as... Figure 6As shown, the laser beam includes any of the aforementioned components, a femtosecond oscillator, and a pulse width compression system 40. The laser beam emitted after spectral broadening by the femtosecond oscillator is then emitted after its pulse width is compressed in the pulse width compression system 40.
[0048] The femtosecond laser source for two-photon printing provided in this application embodiment includes the aforementioned femtosecond oscillator, and further includes a pulse width compression system 40 for further processing the spectrally broadened laser beam emitted from the femtosecond oscillator for use as a light source for two-photon printing. The pulse width compression system 40 is used to compress the pulse width of the laser beam emitted after spectrally broadening by the femtosecond oscillator before emission.
[0049] Please refer to Figure 9 As shown, the pulsed laser sequence output by the femtosecond oscillator has a pulse repetition frequency of approximately 54 MHz, corresponding to a linear oscillator cavity length of 2.8 m. Figure 10 This is a schematic diagram of the pulse width of a laser pulse output from a femtosecond oscillator, which is approximately 318 fs. (Refer to...) Figure 11 The image shows a schematic diagram of the pulsed laser pulse width output after compression by the pulse width compression system 40. Figure 11 As can be seen, after compression, the pulse width of the laser is approximately 116 fs.
[0050] like Figure 12 As shown in the figure, the printing effect of two-photon printing is achieved by using a laser with a pulse width compressed by a pulse width compression system of 40. It can be seen that a better two-photon printing effect can be achieved.
[0051] In one feasible implementation of the embodiments of this application, such as Figure 6 As shown, the pulse width compression system 40 includes a second half-wave plate 41, a Treacy type compressor 42, and a roof prism reflector 43. The beam emitted after spectral broadening by the femtosecond oscillator is polarized by the second half-wave plate 41 and then enters the Treacy type compressor 42 to compress the laser pulse width. The resulting compressed pulse width beam is emitted through the roof prism reflector 43.
[0052] In one feasible implementation of the embodiments of this application, such as Figure 6 As shown, the Treacy type compressor 42 includes a first transmission diffraction grating 421 and a second transmission diffraction grating 422 arranged in parallel opposite directions. After the laser beam is compressed in the Treacy type compressor 42, it is emitted toward the roof prism reflector 43.
[0053] like Figure 6As shown, the laser beam emitted after spectral broadening by the femtosecond oscillator first has its polarization direction adjusted by the second half-wave plate 41. The polarized laser beam then enters the Treacy compressor 42 to compress its pulse width. The Treacy compressor 42 includes a first transmission diffraction grating 421 and a second transmission diffraction grating 422 arranged parallel to each other. By adjusting the rotation angle of the second half-wave plate 41, the light energy of the laser beam incident on the Treacy compressor 42 can be adjusted. Adjusting the distance between the first and second transmission diffraction gratings 421 and 422 can adjust the pulse width range of the emitted laser beam after pulse width compression. Therefore, by adjusting the distance between the second half-wave plate 41 and the first and second transmission diffraction gratings 421 and 422 until the narrowest compressed pulse width is obtained, the diffracted laser beam is reflected by the roof prism reflector 43.
[0054] In one feasible implementation of the embodiments of this application, such as Figure 7 As shown, the pulse width compression system 40 also includes a high reflectivity plane mirror 44. The high reflectivity plane mirror 44 is disposed in the optical path of the reflection direction of the roof prism reflector 43. The compressed pulse width laser beam reflected by the roof prism reflector 43 is reflected out through the high reflectivity plane mirror 44.
[0055] like Figure 7 As shown, a high-reflectivity plane mirror 44 is also provided in the optical path of the roof prism reflector 43 in the direction of reflection. After the diffracted laser beam is reflected by the roof prism reflector 43, it passes through the Treacy type compressor 42 along the original path and is then reflected out by the high-reflectivity plane mirror 44.
[0056] The laser beam emitted from the femtosecond oscillation module 20 passes through the back of the high-reflectivity plane mirror 44 and is incident on the Treacy type compressor 42. After being reflected by the roof prism reflector 43, it returns along the same path and is reflected out by the high-reflectivity plane mirror 44 from the front. The high-reflectivity plane mirror 44 has a high reflectivity, so the loss of the diffracted laser beam in the reflection of the high-reflectivity plane mirror 44 can be almost ignored.
[0057] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.
Claims
1. A femtosecond oscillator, characterized in that, The system includes a pump source system and a femtosecond oscillation module. The femtosecond oscillation module includes a linear Mamyshev oscillator and a holmium-doped fluoride fiber and a tapered fiber disposed between the linear Mamyshev oscillator. The linear Mamyshev oscillator is composed of a first reflective diffraction grating and a second reflective diffraction grating respectively arranged at a Littoral angle. A pump beam coupled by the pump source system is incident on the holmium-doped fluoride fiber to generate laser gain. The gain laser oscillates and broadens its spectrum between the first reflective diffraction grating and the second reflective diffraction grating through the tapered fiber, so that the broadened laser beam covers the reflection wavelengths of the first reflective diffraction grating and the second reflective diffraction grating.
2. The femtosecond oscillator according to claim 1, characterized in that, The pump source system includes a signal generator, a laser diode driver, and a visible light band laser diode. The signal generator outputs a periodic signal to the laser diode driver to drive the visible light band laser diode to output pulses, or the signal generator outputs a DC signal to the laser diode driver to drive the visible light band laser diode to output a continuous wave.
3. The femtosecond oscillator according to claim 2, characterized in that, The visible light band laser diode is a blue laser diode.
4. The femtosecond oscillator according to claim 2, characterized in that, It also includes a pump light coupling module disposed between the pump source system and the femtosecond oscillation module. The pump light coupling module includes at least one convex lens. The femtosecond oscillation module is also provided with a dichroic mirror. After the pump beam is collimated and focused by the pump light coupling module, it is coupled into the holmium-doped fluoride fiber through the dichroic mirror.
5. The femtosecond oscillator according to any one of claims 1-4, characterized in that, The femtosecond oscillation module also includes an output coupling device, which includes a first half-wave plate and a polarization beam splitter. The polarization transmission axis of the first half-wave plate is adjusted to reflect a portion of the laser beam through the polarization beam splitter.
6. The femtosecond oscillator according to claim 1, characterized in that, The reflection wavelength of the first reflective diffraction grating is 745 nm, and the reflection wavelength of the second reflective diffraction grating is 752 nm. The length of the holmium-doped fluoride optical fiber is 1.5m; the length of the tapered optical fiber is 0.5m.
7. A femtosecond laser source, characterized in that, The system includes a femtosecond oscillator as described in any one of claims 1-6, and a pulse width compression system, wherein the laser beam emitted after spectral broadening by the femtosecond oscillator is pulse-width compressed in the pulse width compression system before being emitted.
8. The femtosecond laser source according to claim 7, characterized in that, The pulse width compression system includes a second half-wave plate, a Treacy-type compressor, and a roof prism reflector. The laser beam emitted after spectral broadening by the femtosecond oscillator is polarized by the second half-wave plate and then enters the Treacy-type compressor to compress the laser pulse width. The compressed pulse width laser beam is then emitted through the roof prism reflector.
9. The femtosecond laser source according to claim 8, characterized in that, The Treacy-type compressor includes a first transmission diffraction grating and a second transmission diffraction grating arranged in parallel opposite directions. The laser beam is compressed in the Treacy-type compressor and then emitted toward the roof prism reflector.
10. The femtosecond laser source according to claim 9, characterized in that, It also includes a high-reflectivity plane mirror, which is disposed in the optical path of the reflection direction of the roof prism reflector. The compressed pulse width laser beam reflected by the roof prism reflector is reflected out through the high-reflectivity plane mirror.