A method and device for generating a 260nm wavelength low-noise all-solid-state ultraviolet laser

Abstract

A method and device for generating 260 nm wavelength low-noise all-solid-state ultraviolet laser, 808 nm laser pumps Nd:YVO4 crystal to generate 914 nm wavelength linearly polarized stimulated radiation fluorescence, the fluorescence is amplified and oscillated in the first laser oscillation cavity and realizes longitudinal mode compression by combining phase modulation longitudinal mode filter, generates 914 nm wavelength low-noise linearly polarized near-infrared laser, and is converted into 457 nm wavelength low-noise linearly polarized blue laser by intracavity frequency doubling; the 457 nm low-noise linearly polarized blue laser pumps Sm:YLF crystal in two directions to generate 605 nm wavelength linearly polarized orange-red stimulated radiation fluorescence, the fluorescence is amplified and oscillated in the second laser oscillation cavity and forms 605 nm wavelength low-noise linearly polarized orange-red laser after phase modulation filtering; the remaining 457 nm wavelength low-noise linearly polarized blue laser and the 605 nm wavelength low-noise linearly polarized orange-red laser of the pumped Sm:YLF crystal are nonlinearly frequency-converted by intracavity sum frequency, the polarization controller is used to optimize the polarization matching degree of the two lasers to improve the sum frequency efficiency, and 260 nm wavelength low-noise all-solid-state ultraviolet laser output is obtained.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of all-solid-state lasers, and particularly relates to a 260nm wavelength low-noise all-solid-state ultraviolet laser generation method and device. BACKGROUND

[0002] The ultraviolet laser with a wavelength near 260nm has important strategic application values in scientific research, industrial processing, biomedical medicine, environmental monitoring and other fields due to its short wavelength, high energy density, high focusing ability and strong absorption characteristics. In the field of biomedical detection and imaging, the absorption peak of nucleic acid molecules such as DNA and RNA is in the ultraviolet band near 260nm, so the 260nm ultraviolet laser is widely used in key technologies such as molecular diagnosis, fluorescence excitation, biochip imaging, etc. In the process of protein determination, gene amplification detection (PCR), etc., high monochromaticity and low-noise ultraviolet laser helps to improve the detection sensitivity and resolution. In the field of semiconductor and lithography processing, with the continuous reduction of integrated circuit process size, ultraviolet laser shows excellent performance in micro-nano lithography, wafer detection, defect identification and other processes, and 260nm ultraviolet laser is especially suitable for shallow etching and high-precision surface treatment. In the field of laser material surface modification and processing, 260nm ultraviolet laser has high linear absorption rate on the surface of many types of materials such as metals, ceramics and polymers, and can realize fine removal, non-thermal processing, surface activation and microstructure construction, and is widely used in flexible electronics, microfluidic chips and functional coating preparation. In the field of environmental monitoring and spectral analysis, 260nm ultraviolet laser can excite various pollutants, organic compounds and metal ions to produce characteristic fluorescence or Raman signals, which are used for trace substance detection, water quality analysis, food safety monitoring, etc. The above applications put forward multiple strict requirements on the laser output, such as high power density, high spatial and temporal stability, low intensity noise, high monochromaticity and good system integration capability, which promotes the continuous development of 260nm band low-noise linearly polarized ultraviolet laser technology.

[0003] At present, all-solid-state ultraviolet laser is the main development direction to realize 260nm wavelength output. Compared with traditional gas lasers (such as HeCd) or excimer lasers (such as ArF, KrCl), all-solid-state system has many advantages such as compact structure, long service life, flexible adjustment, low power consumption, stable output and the like. The most common all-solid-state ultraviolet laser generation method is based on 1064nm fundamental light output by a Nd:YAG laser, and two-stage frequency doubling is used to obtain 266nm wavelength ultraviolet laser output, i.e. 1064nm (fundamental light) → 532nm (two times frequency) → 266nm (four times frequency). This scheme has been commercialized for many years and has high maturity, and is often used in industrial marking, scientific research detection and instrument supporting system. However, this route still has the following key problems in performance and application aspects:

[0004] When Nd:YAG or Nd:YVO4 gain media operate in the 1064nm band, there are many intracavity multi-mode resonances, resulting in relatively high noise. After frequency doubling (532nm) and frequency quadrupling (266nm), the laser power noise is further amplified by the nonlinear frequency doubling mechanism, resulting in a low signal-to-noise ratio for the 266nm ultraviolet laser.

[0005] The 266nm laser is obtained by frequency doubling the 1064nm laser twice, and its total nonlinear conversion efficiency is usually no more than 10%. In particular, the conversion efficiency is even lower in the second stage (532nm→266nm) due to limitations such as material absorption, group velocity mismatch, and narrow phase matching window of frequency doubling.

[0006] Tiny fluctuations in pump light power accumulate as amplitude noise in the 1064nm stage. As the frequency doubling number increases, they eventually manifest as significant intensity fluctuations in the 266nm ultraviolet laser, which is particularly unfavorable for applications such as high-precision measurement and spectral imaging. Summary of the Invention

[0007] The technical problem to be solved by the present invention is to overcome the shortcomings of the prior art and provide a method and apparatus for generating a 260nm wavelength low-noise all-solid-state ultraviolet laser with good stability.

[0008] The technical solution adopted to solve the above-mentioned technical problems is: a method for generating 260nm wavelength low-noise all-solid-state ultraviolet laser, including the following steps:

[0009] Step 1. After beam expansion and quasi-shaping, the 808nm wavelength laser pumps the first laser crystal Nd:YVO4 crystal to generate 914nm wavelength linearly polarized near-infrared stimulated emission fluorescence. The 914nm wavelength linearly polarized near-infrared stimulated emission fluorescence is amplified by oscillation to form a 914nm wavelength linearly polarized near-infrared laser with no output.

[0010] Step 2. After passing the 914nm wavelength linearly polarized near-infrared laser with no output through the phase difference filtering of the first phase modulation longitudinal mode filter, a 914nm wavelength low-noise linearly polarized near-infrared laser with no output is generated.

[0011] Step 3. The 914nm wavelength low-noise linearly polarized near-infrared laser with no output is passed through the nonlinear frequency doubling effect of the frequency doubling crystal to generate a 457nm wavelength low-noise linearly polarized blue laser with no output.

[0012] Step 4. The 457nm wavelength low-noise linearly polarized blue laser with no output is bidirectionally end-pumped to the second laser crystal Sm:YLF crystal to generate 605nm wavelength linearly polarized orange-red stimulated emission fluorescence. After amplification by oscillation, 605nm wavelength linearly polarized orange-red laser is generated.

[0013] Step 5. After passing the 605nm wavelength linearly polarized orange-red laser through the phase difference filtering of the second phase modulation longitudinal mode filter, a 605nm wavelength low-noise linearly polarized orange-red laser is generated.

[0014] Step 6. Use a polarization controller to electro-optically modulate the polarization direction of the 605nm low-noise linearly polarized orange-red laser so that its polarization direction is parallel to that of the 457nm low-noise linearly polarized blue laser.

[0015] Step 7. Combine the remaining 457nm low-noise linearly polarized blue laser from pumping the second laser crystal in step 4 with the 605nm low-noise linearly polarized orange-red laser modulated in step 6. Then, in the sum-frequency crystal, generate a 260nm low-noise all-solid-state ultraviolet laser through nonlinear sum-frequency interaction.

[0016] As a preferred technical solution, in step 1, the exit surface of the first laser crystal Nd:YVO4 is cut at a tilt angle of 27° to generate linearly polarized light.

[0017] As a preferred technical solution, the first phase modulation longitudinal mode filter in step 2 is a single-axis quartz crystal;

[0018] The phase difference filtering method of the first phase modulation longitudinal mode filter is as follows: When the 914nm wavelength linearly polarized near-infrared laser passes through the uniaxial quartz crystal, it is decomposed into e-linearly polarized 914nm wavelength near-infrared laser and o-linearly polarized 914nm wavelength near-infrared laser. The angle between the optical axis of the uniaxial quartz crystal and the polarization plane of the 914nm wavelength linearly polarized near-infrared laser is adjusted so that the round-trip phase difference generated by the e-linearly polarized 914nm center wavelength near-infrared laser and the o-linearly polarized 914nm center wavelength near-infrared laser in the uniaxial quartz crystal is an integer multiple of 2π. When the 914nm wavelength linearly polarized near-infrared laser returns to the laser emission surface of the Nd:YVO4 crystal after a single round trip through the uniaxial quartz crystal, the longitudinal mode of the 914nm wavelength linearly polarized near-infrared laser, wherein the longitudinal mode that satisfies the condition that the round-trip phase difference is an integer multiple of 2π, has a transmittance of 100% through the Nd:YVO4 crystal, and the longitudinal mode that does not satisfy the condition that the round-trip phase difference is 2π is suppressed.

[0019] As a preferred technical solution, the frequency doubling crystal in step 3 is a type I angle-phase-matched LBO crystal, and the 914nm wavelength low-noise linearly polarized near-infrared laser is generated into a 457nm wavelength low-noise linearly polarized blue laser in the frequency doubling crystal according to the following formula:

[0020]

[0021] In the formula, λ 914nmThe wavelength of a low-noise linearly polarized near-infrared laser with a wavelength of 914 nm is λ. 457nm It is a low-noise linearly polarized blue laser with a wavelength of 457nm.

[0022] As a preferred technical solution, the exit surface of the second laser crystal Sm:YLF crystal is cut at a 35° tilt angle to generate linearly polarized light.

[0023] As a preferred technical solution, the second phase modulation longitudinal mode filter in step 5 is a uniaxial quartz crystal;

[0024] The phase difference filtering method of the second phase modulation longitudinal mode filter is as follows: When the 605nm wavelength linearly polarized orange-red laser passes through the uniaxial quartz crystal, it is decomposed into e-linearly polarized 605nm wavelength orange-red laser and o-linearly polarized 605nm wavelength orange-red laser. The angle between the optical axis of the uniaxial quartz crystal and the polarization plane of the 605nm wavelength linearly polarized orange-red laser is adjusted so that the round-trip phase difference generated by the e-linearly polarized 605nm center wavelength orange-red laser and the o-linearly polarized 605nm center wavelength orange-red laser in the uniaxial quartz crystal is an integer multiple of 2π. When the 605nm wavelength linearly polarized orange-red laser returns to the exit surface of the Sm:YLF crystal after a single round trip through the uniaxial quartz crystal, the longitudinal mode in the 605nm wavelength linearly polarized orange-red laser, wherein the longitudinal mode that satisfies the condition that the round-trip phase difference is an integer multiple of 2π has a transmittance of 100% through the Sm:YLF crystal, and the longitudinal mode that does not satisfy the condition that the round-trip phase difference is an integer multiple of 2π is suppressed.

[0025] As a preferred technical solution, in step 7, the sum-frequency crystal is a type I angle-phase-matched CLBO crystal, and the sum-frequency crystal generates a low-noise all-solid-state ultraviolet laser with a wavelength of 260nm according to the following formula:

[0026]

[0027] In the formula, λ 457nm The wavelength of a 457nm low-noise linearly polarized blue laser is λ. 605nm The wavelength of a 605nm low-noise linearly polarized orange-red laser is λ. 260nm This refers to the wavelength of a 260nm low-noise all-solid-state ultraviolet laser.

[0028] This invention also provides a 260nm wavelength low-noise all-solid-state ultraviolet laser generating device, comprising a laser diode, a beam expanding and focusing structure, a first laser crystal, a first phase modulation longitudinal mode filter, a frequency doubling crystal, a second laser crystal, a second phase modulation longitudinal mode filter, a polarization controller, a sum-frequency crystal, and an output mirror arranged sequentially along the optical path.

[0029] The laser diode is used to generate 808nm wavelength laser light;

[0030] The beam expanding and focusing structure is used to shape the 808nm wavelength laser into parallel light and focus it into the first laser crystal.

[0031] The first laser crystal is used to absorb the energy of an 808nm wavelength laser and pump it to generate a 914nm wavelength linearly polarized near-infrared stimulated emission fluorescence.

[0032] The first phase modulation longitudinal mode filter is used to adjust the round-trip phase difference of the 914nm wavelength linearly polarized near-infrared laser and generate a 914nm wavelength low-noise linearly polarized near-infrared laser.

[0033] The frequency doubling crystal is used to absorb 914nm wavelength low-noise linearly polarized near-infrared laser and generate 457nm wavelength low-noise linearly polarized blue laser through nonlinear frequency doubling.

[0034] The second laser crystal is used to absorb the energy of a 457nm wavelength low-noise linearly polarized blue laser and pump it to generate a 605nm wavelength linearly polarized orange-red stimulated emission fluorescence.

[0035] The second phase modulation longitudinal mode filter is used to adjust the round-trip phase difference of the 605nm wavelength linearly polarized orange-red laser and generate a 605nm wavelength low-noise linearly polarized orange-red laser.

[0036] The polarization controller is used to adjust the polarization direction of the 605nm wavelength low-noise linearly polarized orange-red laser to ensure that it is parallel to the polarization direction of the 457nm wavelength low-noise linearly polarized blue laser.

[0037] The sum-frequency crystal is used to absorb 605nm wavelength low-noise linearly polarized orange-red laser and 457nm wavelength low-noise linearly polarized blue laser, and generates 260nm wavelength low-noise all-solid-state ultraviolet laser through nonlinear sum-frequency action.

[0038] The output mirror is used for total reflection of three wavelength lasers: 914nm, 457nm and 605nm, while simultaneously transmitting a 260nm wavelength low-noise all-solid-state ultraviolet laser.

[0039] The first laser crystal, the first phase modulation longitudinal mode filter, the frequency doubling crystal, and the output mirror constitute the first laser oscillation cavity. The 914nm wavelength linearly polarized stimulated emission fluorescence oscillates and amplifies in the oscillation cavity to generate a 914nm wavelength low-noise linearly polarized near-infrared laser with no output. The 914nm wavelength low-noise linearly polarized near-infrared laser is multiplied by the nonlinear frequency doubling effect of the frequency doubling crystal to generate a 457nm wavelength low-noise linearly polarized blue laser with no output in the first laser oscillation cavity.

[0040] The second laser crystal, the second phase modulation longitudinal mode filter, the polarization controller, the sum-frequency crystal, and the output mirror constitute the second laser oscillation cavity. The 605nm wavelength linearly polarized orange-red stimulated emission fluorescence oscillates and amplifies in the oscillation cavity to generate a 605nm wavelength linearly polarized orange-red laser without output.

[0041] The first laser oscillation cavity and the second laser oscillation cavity share the same output mirror.

[0042] As a preferred technical solution, the first laser crystal is an Nd:YVO4 crystal, and the exit surface of the Nd:YVO4 crystal is cut at a tilt angle of 27° to generate linearly polarized light.

[0043] As a preferred technical solution, the second laser crystal is an Sm:YLF crystal, and the exit surface of the Sm:YLF crystal is cut at a 35° tilt angle to generate linearly polarized light.

[0044] The beneficial effects of this invention are as follows:

[0045] This invention effectively reduces the number of longitudinal modes of the laser by using a phase-modulated longitudinal mode filter and, in conjunction with the cutting angle of the right-side light-transmitting end face of the first and second laser crystals, alleviates mode competition within the laser resonator, thereby significantly reducing laser noise.

[0046] This invention utilizes stimulated emission of an Nd:YVO4 crystal to generate a 914nm low-noise linearly polarized near-infrared laser, which is then frequency-doubled within a cavity to generate a 457nm low-noise linearly polarized blue laser. The 457nm low-noise linearly polarized blue laser is further used as a pump source to bidirectionally pump an Sm:YLF crystal, generating a 605nm low-noise linearly polarized orange-red laser. Finally, the remaining 457nm low-noise linearly polarized blue laser pumped to a second laser crystal, along with the 605nm low-noise linearly polarized orange-red laser, are combined via intracavity summation to generate a 260nm low-noise all-solid-state ultraviolet laser, which is then output. Compared to the traditional fourth-harmonic generation method for obtaining ultraviolet lasers near 260nm, this method reduces energy loss during multiple frequency doubling operations, improves the nonlinear conversion efficiency and output stability of the ultraviolet laser near 260nm, and reduces its laser noise.

[0047] This invention has the advantages of compact laser structure, high energy efficiency, low laser noise, and low operating cost, and has strong practicality. Attached Figure Description

[0048] Figure 1 This is a schematic diagram of the structure of the 260nm wavelength low-noise all-solid-state ultraviolet laser generating device of the present invention.

[0049] Figure 2This is a schematic flowchart of the method for generating 260nm wavelength low-noise all-solid-state ultraviolet laser according to the present invention.

[0050] Figure 3 This is a spectral test diagram of a 260nm wavelength low-noise all-solid-state ultraviolet laser according to an embodiment of the present invention.

[0051] Figure 4 This is a test curve of the output power of the 260nm wavelength low-noise all-solid-state ultraviolet laser in Embodiment 2 of the present invention as a function of the pump current of the 808nm laser diode.

[0052] Figure 5 This is a stability test chart of the 260nm wavelength low-noise all-solid-state ultraviolet laser of the present invention at maximum output power for 4 hours.

[0053] Figure 6 This is a noise test curve of the 260nm wavelength low-noise all-solid-state ultraviolet laser in the embodiment of the present invention at maximum output power.

[0054] The components are: 1. laser diode, 2. beam expander collimator, 3. focusing lens, 4. first laser crystal, 5. first phase modulation longitudinal mode filter, 6. frequency doubling crystal, 7. second laser crystal, 8. second phase modulation longitudinal mode filter, 9. polarization controller, 10. sum frequency crystal, and 11. output mirror. Detailed Implementation

[0055] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments, but the present invention is not limited to the following embodiments.

[0056] exist Figure 1 In this embodiment, the 260nm wavelength low-noise all-solid-state ultraviolet laser generating device comprises a laser diode 1, a beam expander collimator 2, a focusing lens 3, a first laser crystal 4, a first phase modulation longitudinal mode filter 5, a frequency doubling crystal 6, a second laser crystal 7, a second phase modulation longitudinal mode filter 8, a polarization controller 9, a sum-frequency crystal 10, and an output mirror 11 arranged sequentially from left to right along the optical path.

[0057] Laser diode 1 is used to generate 808nm wavelength laser light. Beam expander collimator 2 and focusing lens 3 constitute a beam expander and focusing structure, which is used to shape the 808nm wavelength laser light into parallel light and focus it into the first laser crystal.

[0058] The first laser crystal 4 is an Nd:YVO4 crystal, and the pump end face of the Nd:YVO4 crystal is coated with an 808nm wavelength high transmission film (transmittance T). 808nm >99.5%), 1064nm wavelength high transmission film (transmittance T) 1064nm >95%), 1342nm wavelength high transmission film (transmittance T)1342nm >90%) and 914nm wavelength high reflectivity film (reflectivity R 914nm The Nd:YVO4 crystal, with a transmittance >99.5%, has its exit surface cut at a 27° angle and coated with a high-transmittance film at a wavelength of 914 nm (transmittance T). 914nm >99.5%). The Nd:YVO4 crystal absorbs the energy of an 808nm wavelength laser and is pumped to generate linearly polarized near-infrared stimulated emission fluorescence at a wavelength of 914nm.

[0059] The 914nm wavelength linearly polarized near-infrared stimulated emission fluorescence oscillates within the first laser oscillation cavity, which is composed of the first laser crystal 4, the first phase modulation longitudinal mode filter 5, the frequency doubling crystal 6, and the output mirror 11, generating a 914nm wavelength linearly polarized near-infrared laser with no output.

[0060] The first phase modulation longitudinal mode filter 5 is a single-axis quartz crystal used to adjust the round-trip phase difference of the 914nm wavelength linearly polarized near-infrared laser and generate a 914nm wavelength low-noise linearly polarized near-infrared laser with no output.

[0061] The left light-transmitting end face of the frequency doubling crystal 6 is coated with a 914nm wavelength high-transmission film (transmittance T). 914nm >99.7%), 605nm wavelength high transmission film (transmittance T) 605nm >99.5%), 266nm wavelength high reflectivity film (reflectivity R 457nm >99.0%); its right-side light-transmitting end face is coated with a 914nm wavelength high-transmittance film (transmittance T). 914nm >99.7%), 605nm wavelength high transmission film (transmittance T) 605nm >99.5%), 266nm wavelength high transmission film (transmittance T) 457nm >99.5%.

[0062] The frequency doubling crystal 6 is used to absorb low-noise linearly polarized near-infrared laser with a wavelength of 914nm and no output, and generates low-noise linearly polarized blue laser with a wavelength of 457nm and no output through nonlinear frequency doubling.

[0063] The second laser crystal 7 is an Sm:YLF crystal. The exit surface of the Sm:YLF crystal is cut at a 35° tilt angle. It is bidirectionally end-pumped by a 457nm wavelength low-noise linearly polarized blue laser with no output, generating 605nm wavelength linearly polarized orange-red stimulated emission fluorescence.

[0064] The 605nm wavelength linearly polarized orange-red stimulated emission fluorescence oscillates within the second laser oscillation cavity, which consists of the second laser crystal 7, the second phase modulation longitudinal mode filter 8, the polarization controller 9, the sum-frequency crystal 10, and the output mirror 11, generating a 605nm wavelength linearly polarized orange-red laser.

[0065] The second phase modulation longitudinal mode filter 8 is used to adjust the round-trip phase difference of the 605nm wavelength linearly polarized orange-red laser and generate a 605nm wavelength low-noise linearly polarized orange-red laser.

[0066] The polarization controller 9 is an electro-optic polarization controller made of LiTaO3 material and designed for a wavelength of 605nm. Both light-transmitting surfaces of the polarization controller 9 are perpendicular to the optical path of the 605nm low-noise linearly polarized orange-red laser. By changing the modulation voltage value of the polarization controller 9, the polarization direction of the 605nm low-noise linearly polarized orange-red laser is precisely rotated to ensure that it is parallel to the polarization direction of the 457nm low-noise linearly polarized blue laser.

[0067] The sum-frequency crystal 10 is a type I angle-phase-matched CLBO crystal used to absorb 605nm low-noise linearly polarized orange-red laser and 457nm low-noise linearly polarized blue laser, and to generate 260nm low-noise all-solid-state ultraviolet laser through nonlinear sum-frequency action.

[0068] The left optical transmission end face of the sum-frequency crystal is coated with a 914nm wavelength high-transmission film (transmittance T). 914nm >99.7%), 605nm wavelength high transmission film (transmittance T) 605nm >99.5%), 457nm wavelength high transmission film (transmittance T) 457nm >99.5%) and a 266nm wavelength high-reflectivity film (reflectivity R 457nm >99.0%); its right-side light-transmitting end face is coated with a 914nm wavelength high-transmittance film (transmittance T). 914nm >99.7%), 605nm wavelength high transmission film (transmittance T) 605nm >99.5%), 457nm wavelength high transmission film (transmittance T) 457nm >99.5%) and a high-transmittance film at 266nm wavelength (transmittance T) 457nm >99.5%). Output mirror 11 is used for total internal reflection of three wavelength lasers: 914nm, 457nm and 605nm, while simultaneously transmitting 260nm wavelength low-noise all-solid-state ultraviolet laser.

[0069] Output mirror 11 is a plano-concave mirror made of CaF2 material. Its left incident surface is concave, and its right exit surface is planar. The radius of curvature of the left incident surface is 580 mm. The left incident surface is coated with a high-reflectivity film with three wavelengths of 914 nm, 605 nm, and 457 nm (reflectivity R). 914nm >99.5%, reflectivity R 605nm >99.5%, reflectivity R 457nm >99%) and a high-transmittance film at a wavelength of 260nm (transmittance T) 266nm>99.5%. The right-end exit surface is coated with a high-transmission film with a wavelength of 260nm (transmittance T). 266nm >99.5%). Used for high-reflectivity 457nm wavelength low-noise linearly polarized blue laser and 605nm wavelength low-noise linearly polarized orange-red laser, while simultaneously transmitting 260nm wavelength low-noise all-solid-state ultraviolet laser.

[0070] exist Figure 2 The method for generating 260nm wavelength low-noise all-solid-state ultraviolet laser in this embodiment includes the following steps:

[0071] Step 1. After beam expansion and quasi-shaping, the 808nm wavelength laser pumps the first laser crystal Nd:YVO4 crystal to generate 914nm wavelength linearly polarized near-infrared stimulated emission fluorescence. The 914nm wavelength linearly polarized near-infrared stimulated emission fluorescence is amplified by oscillation through the first laser oscillation cavity to form a 914nm wavelength linearly polarized near-infrared laser with no output.

[0072] Step 2. After passing the 914nm wavelength linearly polarized near-infrared laser with no output through the phase difference filtering of the first phase modulation longitudinal mode filter, a 914nm wavelength low-noise linearly polarized near-infrared laser with no output is generated.

[0073] The first phase-modulated longitudinal mode filter is a uniaxial quartz crystal. Its phase difference filtering method is as follows: when the 914nm linearly polarized near-infrared laser passes through the uniaxial quartz crystal, it is decomposed into e-linearly polarized 914nm near-infrared laser and o-linearly polarized 914nm near-infrared laser. The angle between the optical axis of the uniaxial quartz crystal and the polarization plane of the 914nm linearly polarized near-infrared laser is adjusted so that the e-linearly polarized 914nm center wavelength near-infrared laser and the o-linearly polarized 914nm center wavelength near-infrared laser are separated by the uniaxial quartz crystal. The round-trip phase difference generated in the quartz crystal is an integer multiple of 2π. When the 914nm wavelength linearly polarized near-infrared laser returns to the laser emission surface of the Nd:YVO4 crystal after a single round trip through the uniaxial quartz crystal, the longitudinal mode of the 914nm wavelength linearly polarized near-infrared laser has a transmittance of 100% through the Nd:YVO4 crystal if the round-trip phase difference is an integer multiple of 2π. The longitudinal mode that does not meet the condition of a round-trip phase difference of 2π is suppressed by the first laser oscillation cavity after multiple round trips through the Nd:YVO4 crystal.

[0074] Step 3. The 914nm wavelength low-noise linearly polarized near-infrared laser with no output is passed through the nonlinear frequency doubling effect of the frequency doubling crystal to generate a 457nm wavelength low-noise linearly polarized blue laser with no output.

[0075] Step 4. The 457nm wavelength low-noise linearly polarized blue laser with no output is bidirectionally end-pumped to the second laser crystal Sm:YLF crystal to generate 605nm wavelength linearly polarized orange-red stimulated emission fluorescence. After being oscillated and amplified by the second laser oscillation cavity, 605nm wavelength linearly polarized orange-red laser is generated.

[0076] Step 5. After passing the 605nm wavelength linearly polarized orange-red laser through the phase difference filtering of the second phase modulation longitudinal mode filter, a 605nm wavelength low-noise linearly polarized orange-red laser is generated.

[0077] The second phase-modulated longitudinal mode filter is a single-axis quartz crystal. Its phase difference filtering method is as follows: when the 605nm linearly polarized orange-red laser passes through the single-axis quartz crystal, it is decomposed into e-linearly polarized 605nm orange-red laser and o-linearly polarized 605nm orange-red laser. The angle between the optical axis of the single-axis quartz crystal and the polarization plane of the 605nm linearly polarized orange-red laser is adjusted so that the e-linearly polarized 605nm center wavelength orange-red laser and the o-linearly polarized 605nm center wavelength orange-red laser are separated on the single axis. The round-trip phase difference generated in the quartz crystal is an integer multiple of 2π. When a 605nm wavelength linearly polarized orange-red laser returns to the exit surface of the Sm:YLF crystal after a single round trip through the uniaxial quartz crystal, the longitudinal mode of the 605nm wavelength linearly polarized orange-red laser has a transmittance of 100% through the Sm:YLF crystal if the round-trip phase difference is an integer multiple of 2π. The longitudinal mode that does not meet the condition of a round-trip phase difference of an integer multiple of 2π is suppressed by the second laser oscillation cavity after multiple round trips through the Sm:YLF crystal.

[0078] Step 6. Use a polarization controller to electro-optically modulate the polarization direction of the 605nm low-noise linearly polarized orange-red laser so that its polarization direction is parallel to that of the 457nm low-noise linearly polarized blue laser.

[0079] Step 7. Combine the remaining 457nm low-noise linearly polarized blue laser from pumping the second laser crystal in step 4 with the 605nm low-noise linearly polarized orange-red laser modulated in step 6, and generate a 260nm low-noise all-solid-state ultraviolet laser in the sum-frequency crystal through nonlinear sum-frequency action.

[0080] The sum-frequency crystal is a type I angle-phase-matched CLBO crystal, which generates a low-noise all-solid-state ultraviolet laser with a wavelength of 260nm according to the following formula:

[0081]

[0082] In the formula, λ 457nm The wavelength of a 457nm low-noise linearly polarized blue laser is λ. 605nmThe wavelength of a 605nm low-noise linearly polarized orange-red laser is λ. 260nm This refers to the wavelength of a 260nm low-noise all-solid-state ultraviolet laser. For example... Figures 3-6 As shown.

Claims

1. A method for generating a 260nm wavelength low-noise all-solid-state ultraviolet laser, characterized in that, Includes the following steps: Step 1. After beam expansion, collimation and shaping, the 808nm wavelength laser pumps the first laser crystal Nd:YVO4 crystal to generate 914nm wavelength linearly polarized near-infrared stimulated emission fluorescence. The 914nm wavelength linearly polarized near-infrared stimulated emission fluorescence is amplified by oscillation to form a 914nm wavelength linearly polarized near-infrared laser with no output. Step 2. After passing the 914nm wavelength linearly polarized near-infrared laser with no output through the phase difference filtering of the first phase modulation longitudinal mode filter, a 914nm wavelength low-noise linearly polarized near-infrared laser with no output is generated. Step 3. The 914nm wavelength low-noise linearly polarized near-infrared laser with no output is passed through the nonlinear frequency doubling effect of the frequency doubling crystal to generate a 457nm wavelength low-noise linearly polarized blue laser with no output. Step 4. The 457nm wavelength low-noise linearly polarized blue laser with no output is bidirectionally end-pumped to the second laser crystal Sm:YLF crystal to generate 605nm wavelength linearly polarized orange-red stimulated emission fluorescence. After amplification by oscillation, 605nm wavelength linearly polarized orange-red laser is generated. Step 5. After passing the 605nm wavelength linearly polarized orange-red laser through the phase difference filtering of the second phase modulation longitudinal mode filter, a 605nm wavelength low-noise linearly polarized orange-red laser is generated. Step 6. Use a polarization controller to electro-optically modulate the polarization direction of the 605nm low-noise linearly polarized orange-red laser so that its polarization direction is parallel to that of the 457nm low-noise linearly polarized blue laser. Step 7. Combine the remaining 457nm low-noise linearly polarized blue laser from pumping the second laser crystal in step 4 with the 605nm low-noise linearly polarized orange-red laser modulated in step 6. Then, in the sum-frequency crystal, generate a 260nm low-noise all-solid-state ultraviolet laser through nonlinear sum-frequency interaction.

2. The method for generating 260nm wavelength low-noise all-solid-state ultraviolet laser according to claim 1, characterized in that: In step 1, the exit surface of the first laser crystal, Nd:YVO4, is cut at a 27° tilt angle to generate linearly polarized light.

3. The method for generating 260nm wavelength low-noise all-solid-state ultraviolet laser according to claim 1, characterized in that: In step 2, the first phase modulation longitudinal mode filter is a single-axis quartz crystal; The phase difference filtering method of the first phase modulation longitudinal mode filter is as follows: When the 914nm wavelength linearly polarized near-infrared laser passes through the uniaxial quartz crystal, it is decomposed into e-linearly polarized 914nm wavelength near-infrared laser and o-linearly polarized 914nm wavelength near-infrared laser. The angle between the optical axis of the uniaxial quartz crystal and the polarization plane of the 914nm wavelength linearly polarized near-infrared laser is adjusted so that the round-trip phase difference generated by the e-linearly polarized 914nm center wavelength near-infrared laser and the o-linearly polarized 914nm center wavelength near-infrared laser in the uniaxial quartz crystal is an integer multiple of 2π. When the 914nm wavelength linearly polarized near-infrared laser returns to the laser emission surface of the Nd:YVO4 crystal after a single round trip through the uniaxial quartz crystal, the longitudinal mode of the 914nm wavelength linearly polarized near-infrared laser, wherein the longitudinal mode that satisfies the condition that the round-trip phase difference is an integer multiple of 2π, has a transmittance of 100% through the Nd:YVO4 crystal, and the longitudinal mode that does not satisfy the condition that the round-trip phase difference is 2π is suppressed.

4. The method for generating 260nm wavelength low-noise all-solid-state ultraviolet laser according to claim 1, characterized in that: The frequency doubling crystal in step 3 is a type I angle-phase-matched (LBO) crystal. The 914nm wavelength low-noise linearly polarized near-infrared laser is used in the frequency doubling crystal to generate a 457nm wavelength low-noise linearly polarized blue laser according to the following formula: In the formula, λ 914nm The wavelength of a low-noise linearly polarized near-infrared laser with a wavelength of 914 nm is λ. 457nm It is a low-noise linearly polarized blue laser with a wavelength of 457nm.

5. The method for generating 260nm wavelength low-noise all-solid-state ultraviolet laser according to claim 1, characterized in that: The second laser crystal, Sm:YLF crystal, has its exit surface cut at a 35° tilt angle to generate linearly polarized light.

6. The method for generating 260nm wavelength low-noise all-solid-state ultraviolet laser according to claim 1, characterized in that: In step 5, the second phase modulation longitudinal mode filter is a single-axis quartz crystal; The phase difference filtering method of the second phase modulation longitudinal mode filter is as follows: When the 605nm wavelength linearly polarized orange-red laser passes through the uniaxial quartz crystal, it is decomposed into e-linearly polarized 605nm wavelength orange-red laser and o-linearly polarized 605nm wavelength orange-red laser. The angle between the optical axis of the uniaxial quartz crystal and the polarization plane of the 605nm wavelength linearly polarized orange-red laser is adjusted so that the round-trip phase difference generated by the e-linearly polarized 605nm center wavelength orange-red laser and the o-linearly polarized 605nm center wavelength orange-red laser in the uniaxial quartz crystal is an integer multiple of 2π. When the 605nm wavelength linearly polarized orange-red laser returns to the exit surface of the Sm:YLF crystal after a single round trip through the uniaxial quartz crystal, the longitudinal mode of the 605nm wavelength linearly polarized orange-red laser, wherein the longitudinal mode that satisfies the condition that the round-trip phase difference is an integer multiple of 2π has a transmittance of 100% through the Sm:YLF crystal, and the longitudinal mode that does not satisfy the condition that the round-trip phase difference is an integer multiple of 2π is suppressed.

7. The method for generating 260nm wavelength low-noise all-solid-state ultraviolet laser according to claim 1, characterized in that: In step 7, the sum-frequency crystal is a type I angle-phase-matched CLBO crystal, which generates a low-noise all-solid-state ultraviolet laser with a wavelength of 260nm according to the following formula: In the formula, λ 457nm The wavelength of a 457nm low-noise linearly polarized blue laser is λ. 605nm The wavelength of a 605nm low-noise linearly polarized orange-red laser is λ. 260nm This refers to the wavelength of a 260nm low-noise all-solid-state ultraviolet laser.

8. A 260nm wavelength low-noise all-solid-state ultraviolet laser generating device, characterized in that, It comprises, in sequence along the optical path, a laser diode, a beam expander and focusing structure, a first laser crystal, a first phase-modulated longitudinal mode filter, a frequency doubling crystal, a second laser crystal, a second phase-modulated longitudinal mode filter, a polarization controller, a sum-frequency crystal, and an output mirror. The laser diode is used to generate 808nm wavelength laser light; The beam expanding and focusing structure is used to shape the 808nm wavelength laser into parallel light and focus it into the first laser crystal. The first laser crystal is used to absorb the energy of an 808nm wavelength laser and pump it to generate a 914nm wavelength linearly polarized near-infrared stimulated emission fluorescence. The first phase modulation longitudinal mode filter is used to adjust the round-trip phase difference of the 914nm wavelength linearly polarized near-infrared laser and generate a 914nm wavelength low-noise linearly polarized near-infrared laser. The frequency doubling crystal is used to absorb 914nm wavelength low-noise linearly polarized near-infrared laser and generate 457nm wavelength low-noise linearly polarized blue laser through nonlinear frequency doubling. The second laser crystal is used to absorb the energy of a 457nm wavelength low-noise linearly polarized blue laser and pump it to generate a 605nm wavelength linearly polarized orange-red stimulated emission fluorescence. The second phase modulation longitudinal mode filter is used to adjust the round-trip phase difference of the 605nm wavelength linearly polarized orange-red laser and generate a 605nm wavelength low-noise linearly polarized orange-red laser. The polarization controller is used to adjust the polarization direction of the 605nm wavelength low-noise linearly polarized orange-red laser to ensure that it is parallel to the polarization direction of the 457nm wavelength low-noise linearly polarized blue laser. The sum-frequency crystal is used to absorb 605nm wavelength low-noise linearly polarized orange-red laser and 457nm wavelength low-noise linearly polarized blue laser, and generates 260nm wavelength low-noise all-solid-state ultraviolet laser through nonlinear sum-frequency action. The output mirror is used for total reflection of three wavelength lasers: 914nm, 457nm and 605nm, while simultaneously transmitting a 260nm wavelength low-noise all-solid-state ultraviolet laser. The first laser crystal, the first phase modulation longitudinal mode filter, the frequency doubling crystal, and the output mirror constitute the first laser oscillation cavity. The 914nm wavelength linearly polarized stimulated emission fluorescence oscillates and amplifies in the oscillation cavity to generate a 914nm wavelength low-noise linearly polarized near-infrared laser with no output. The 914nm wavelength low-noise linearly polarized near-infrared laser is multiplied by the nonlinear frequency doubling effect of the frequency doubling crystal to generate a 457nm wavelength low-noise linearly polarized blue laser with no output in the first laser oscillation cavity. The second laser crystal, the second phase modulation longitudinal mode filter, the polarization controller, the sum-frequency crystal, and the output mirror constitute the second laser oscillation cavity. The 605nm wavelength linearly polarized orange-red stimulated emission fluorescence oscillates and amplifies in the oscillation cavity to generate a 605nm wavelength linearly polarized orange-red laser without output. The first laser oscillation cavity and the second laser oscillation cavity share the same output mirror.

9. The 260nm wavelength low-noise all-solid-state ultraviolet laser generating device according to claim 8, characterized in that, The first laser crystal is an Nd:YVO4 crystal, and the exit surface of the Nd:YVO4 crystal is cut at a 27° tilt angle to generate linearly polarized light.

10. The 260nm wavelength low-noise all-solid-state ultraviolet laser generating device according to claim 8, characterized in that, The second laser crystal is an Sm:YLF crystal, and the exit surface of the Sm:YLF crystal is cut at a 35° tilt angle to generate linearly polarized light.

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