A 459.317 nm narrow linewidth all-solid-state laser matched with cesium atom filter

Abstract

The application discloses a 459.317nm narrow linewidth all-solid-state laser based on a 1064.4nm pumped PPKTP crystal BWOPO and OPA technology. In view of the strict requirements of a cesium atom (Cs) filter on narrow linewidth and frequency stability, a "BWOPO-pre-frequency doubling-OPA amplification-terminal frequency doubling" composite architecture is innovatively provided. A 1064.4nm nanosecond pulse is used as a source, one road is pumped to the BWOPO, the distributed feedback mechanism is used to generate 1837.268nm narrow linewidth signal light, and 918.634nm seed light is obtained after frequency doubling; the other road is frequency-doubled to 532.2nm to synchronously pump the OPA to amplify the seed, and finally 459.317nm blue light is outputted after frequency doubling. The application realizes high-quality laser output accurately matched with the characteristic spectrum line of the cesium atom filter, and the wavelength is in the optimal waveband of ocean communication, and has important value in the fields of underwater optical communication, ocean detection and high-precision spectroscopy.

Description

Technical Field

[0001] This invention belongs to the fields of nonlinear optics, atomic physics and laser communication technology, and specifically relates to a narrow-linewidth 459.317nm all-solid-state laser based on backward optical parametric oscillation (BWOPO), optical parametric amplification (OPA) and frequency doubling technology using a 1064.4nm laser-pumped periodically polarized potassium titanate oxyphosphate (PPKTP). Technical Background Deep blue laser light in the 459nm band, positioned within the optical transmission window (450-490nm) of ocean water, possesses excellent penetration capabilities in offshore ocean waters, making it an important light source for applications such as underwater wireless optical communication, marine lidar, and high-precision spectroscopy. In particular, the 459.317nm blue light wavelength precisely matches the characteristic transition lines of cesium atoms (Cs). Using it as an emission source paired with a cesium atom filter significantly suppresses background noise from the solar radiation spectrum over a large receiving field of view, enhancing the all-weather performance of marine lidar and underwater laser communication systems. This makes it one of the ideal light sources for marine lidar and underwater wireless optical communication applications.

[0002] Currently, the main technical approaches to obtaining 459nm blue laser light include: direct output or frequency doubling of semiconductor lasers, but with low output power and poor beam quality; poor matrix material stability and low damage threshold of upconversion lasers; low efficiency, complex structure, and large size of ultraviolet-pumped parametric oscillators, posing a risk of damage to ultraviolet laser coatings; high cost, complex system, and complex maintenance of Ti:sapphire laser frequency doubling technology, with low conversion efficiency; and optical parametric oscillator (OPO) technology, which has attracted much attention due to its wide wavelength coverage. However, the laser linewidth output by traditional forward three-wave mixing OPO technology is usually very wide (hundreds of GHz or even wider), which cannot meet the narrow linewidth requirements of atomic filters. This usually requires the introduction of complex seed injection systems or intracavity etalons, which greatly increases the complexity and instability of the system.

[0003] Backward-wave optical parametric oscillation (BWOPO) is a special nonlinear frequency conversion technique in which the signal light and idler light propagate in opposite directions. Compared with traditional collinear OPO techniques, BWOPO has a naturally narrow linewidth due to its distributed feedback mechanism and does not require resonant cavity mirrors, making the system structure more compact and stable.

[0004] However, BWOPO technology still faces challenges in practical applications: on the one hand, due to the short gain length and high threshold of the backwave interaction, it is difficult to directly generate high-power lasers using BWOPO, and the crystal is at risk of optical damage when the pump energy is too high; on the other hand, for the specific wavelength of 459.317nm, if BWOPO is used for direct output followed by frequency doubling, a complex cascaded system is often required, limiting efficiency. Therefore, how to achieve efficient and high-power 459.317nm laser output while maintaining the narrow linewidth advantage of BWOPO remains a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0005] To overcome the shortcomings of existing technologies, this invention provides a 459.317nm narrow-linewidth all-solid-state laser matched with a cesium atom filter. This laser is based on PPKTP-BWOPO and OPA technologies and features a compact structure, narrow linewidth, high power, and high frequency stability.

[0006] To achieve the above objectives, this invention proposes an innovative composite architecture that utilizes a 1064.4 nm nanosecond pulsed laser as a single main pump source, combining the narrow linewidth advantage of BWOPO and the high gain advantage of OPA to obtain a narrow linewidth 459.317 nm laser output. The 1064.4 nm nanosecond pulsed laser is split into two paths using a beam splitter: the first path serves as the pump light for BWOPO, generating an 1837.268 nm backscattered signal light with naturally narrow linewidth characteristics and high beam quality in a submicron polarization period PPKTP crystal, which is then subjected to a first frequency doubling to obtain a 918.634 nm narrow linewidth seed light; the second path, after frequency doubling, generates 532.2 nm green light, which serves as the pump source for the OPA amplification stage, and the 918.634 nm seed light undergoes high-gain parametric amplification under precise time-domain synchronous control; the amplified 918.634 nm laser is then subjected to a second frequency doubling to finally output a 459.317 nm deep blue laser. This solution cleverly avoids the damage risks of direct high-power BWOPO, while using OPA to solve the power expansion problem, achieving blue light output with narrow linewidth, high power, and high frequency stability.

[0007] The technical solution of the present invention is as follows: A 459.317nm narrow-linewidth all-solid-state laser with matching cesium atom filters is provided, comprising four parts: a 1064.4nm fundamental frequency laser generation and beam splitting module, a BWOPO backward signal light generation module, a 532.2nm pump light generation and delay module, and an OPA parametric amplification and terminal frequency doubling module.

[0008] The 1064.4nm fundamental frequency laser generation and beam splitting module provides a high-beam-quality fundamental frequency pulsed laser and splits it into two paths according to a predetermined polarization state and energy ratio. It includes a 1064.4nm fundamental frequency pulsed laser, an optical isolator, a first half-wave plate, and a polarization beam splitter (PBS). The BWOPO backward signal light generation module uses the split S-polarized 1064.4nm light to pump a submicron periodic PPKTP crystal, generating a narrow-linewidth 1837.268nm backward signal light based on the backward optical parametric oscillation (BWOPO) effect. This signal light is then frequency-doubled to generate a 918.634nm seed light. The module includes a focusing lens group, a first beam splitter, a submicron periodic PPKTP crystal, a precision temperature-controlled furnace, a first beam-shaping lens group, a second half-wave plate, and a first... The system comprises a frequency-doubling crystal, a second beam splitter, and a third beam splitter. The 532.2nm pump light generation and delay module utilizes the split P-polarized 1064.4nm light to generate 532.2nm green light through frequency doubling, and precisely controls the green light in the time domain through an optical delay device. This module includes a second frequency-doubling crystal, a third beam splitter, an optical delay device, and a second beam-shaping lens group. The OPA parametric amplification and terminal frequency doubling module combines the delayed 532.2nm pump light with the 918.634nm seed light, performs optical parametric amplification in the OPA crystal, and then performs a second frequency doubling on the amplified 918.634nm laser to finally output a narrow-linewidth 459.317nm laser. This module includes a fourth beam splitter, an OPA crystal, a fifth beam splitter, a third half-wave plate, a terminal frequency-doubling crystal, and a sixth beam splitter.

[0009] The laser generated by the 1064.4nm fundamental frequency pulsed laser passes through an optical isolator, and then its polarization state is rotated by the first half-wave plate. Combined with a polarization beam splitter, the beam splitting ratio is precisely adjusted to split the laser into two paths: S-polarized light and P-polarized light.

[0010] The S-polarized light reflected by the polarization beam splitter passes through the focusing lens group and then through the first beam splitter to pump the submicron periodic PPKTP crystal in the precision temperature-controlled furnace. Based on the backward optical parametric oscillation (BWOPO) mechanism, a 1837.268nm backward signal light with a naturally narrow linewidth is generated in the Z-axis direction of the crystal. After being reflected by the first beam splitter, the light passes through the first beam shaping lens group and the second half-wave plate in sequence, and enters the first frequency doubling crystal for pre-frequency doubling to obtain a 918.634nm narrow linewidth seed light, which is then transmitted through the second beam splitter to the fourth beam splitter.

[0011] The P-polarized fundamental frequency light transmitted by the polarization beam splitter generates 532.2nm green light through the second frequency doubling crystal. After the remaining fundamental frequency light is filtered out by the third beam splitter, it enters the optical delay device consisting of an electric translation stage and a mirror mounted on it. By adjusting the optical path to compensate for the BWOPO settling time, the pump light and the seed light are precisely synchronized in the time domain. Then, after the spot pattern is adjusted by the second beam shaping lens group, it is output to the fourth beam splitter.

[0012] The 532.2nm pump light and the 918.634nm seed light are combined by the fourth beam splitter and injected into the OPA crystal for high-gain parametric amplification. The amplified 918.634nm signal light is filtered out by the fifth beam splitter, and its polarization direction is adjusted by the third half-wave plate. Finally, it is injected into the terminal frequency doubling crystal for secondary frequency doubling to generate a deep blue laser with a target wavelength of 459.317nm, which is then transmitted and output by the sixth beam splitter.

[0013] Furthermore, the 1064.4nm fundamental frequency pulsed laser is a pulsed laser oscillator or pulsed laser amplifier with neodymium-doped yttrium aluminum garnet (Nd:YAG) crystal or neodymium-doped yttrium vanadate (Nd:YVO4) crystal as the gain medium, with an output pulse width of 5-20ns and a repetition frequency of 1Hz-1kHz.

[0014] Furthermore, the optical isolator is a 1064.4nm wavelength optical isolator, used to prevent reflected light from returning to the laser from subsequent optical paths.

[0015] Furthermore, the first half-wave plate is a 1064.4nm half-wave plate, the second half-wave plate is a 1837.268nm half-wave plate, and the third half-wave plate is a 918.634nm half-wave plate, each half-wave plate being coated with an antireflection film of the corresponding wavelength.

[0016] Furthermore, the polarization beam splitter is a 1064.4nm wavelength polarization beam splitting cube, used to split the incident light into S-polarized light and P-polarized light with mutually perpendicular vibration directions.

[0017] Furthermore, the focusing lens group, the first beam shaping lens group, and the second beam shaping lens group are all composed of two plano-convex lenses. The focusing lens group focuses the 1064.4nm pump light into the PPKTP crystal, and the diameter of the focused spot is 100-200μm.

[0018] Furthermore, the front surface of the first beam splitter is coated with a 1064nm high-transmittance film and an 1837nm high-reflection film; the front surface of the second beam splitter is coated with a 918nm high-transmittance film and an 1837nm high-reflection film; the front surface of the third beam splitter is coated with a 532nm high-transmittance film and a 1064nm high-reflection film; the front surface of the fourth beam splitter is coated with a 532nm high-transmittance film and a 918nm high-reflection film; the front surface of the fifth beam splitter is coated with a 918nm high-transmittance film, a 532nm high-reflection film, and a 1265nm high-reflection film; and the front surface of the sixth beam splitter is coated with a 459nm high-transmittance film and a 918nm high-reflection film.

[0019] Furthermore, the PPKTP crystal employs type 0 quasi-phase matching, with the propagation directions of the pump light, signal light, and idler light all along the crystal's X-axis, and the polarization directions all along the crystal's Z-axis; the crystal's polarization period is 501.2 nm, used to achieve backward optical parametric oscillation from the 1064.4 nm pump light to the 1837.268 nm signal light.

[0020] Furthermore, the precision temperature control furnace has a temperature control accuracy of ±0.01℃ and an operating temperature range of 25-200℃.

[0021] Furthermore, the first frequency doubling crystal, the second frequency doubling crystal, the terminal frequency doubling crystal, and the OPA crystal are all type I phase-matched LBO crystals or BBO crystals. The light-transmitting surface of the first frequency doubling crystal is coated with 1837nm and 918nm anti-reflection films; the light-transmitting surface of the second frequency doubling crystal is coated with 1064nm and 532nm anti-reflection films; the light-transmitting surface of the OPA crystal is coated with 532nm, 918nm, and 1265nm anti-reflection films; and the light-transmitting surface of the terminal frequency doubling crystal is coated with 918nm and 459nm anti-reflection films.

[0022] Furthermore, in the optical delay device, two highly reflective mirrors form a folded optical path and are mounted on an electric translation stage. By adjusting the position of the translation stage, the optical path length of the 532.2nm optical path is precisely increased, with a delay adjustment range of 0-2ns and an accuracy of 1ps.

[0023] Compared with the prior art, the present invention has the following advantages: 1. The BWOPO technology is used to generate 1837.268nm signal light. By utilizing its natural narrow linewidth characteristics and distributed feedback mechanism, narrow linewidth seed light can be obtained without additional linewidth narrowing components, which simplifies the system structure and ensures high reliability. 2. A composite optical path architecture of "BWOPO-pre-frequency doubling-OPA amplification-terminal frequency doubling" is adopted. The seed light is amplified with high gain through the OPA amplification stage, which effectively improves the output power and conversion efficiency of the 459.317nm light generated by the final frequency doubling and avoids the crystal damage risk of direct high-power BWOPO. 3. Employing a single 1064.4nm main pump source, BWOPO pump light and OPA pump light are simultaneously obtained through beam splitting and frequency doubling techniques. The all-solid-state design results in a compact system structure and a stable and reliable optical path. 4. The output 459.317nm laser wavelength is precisely matched to the characteristic transition lines of cesium atoms. It has a narrow linewidth, high frequency stability, and is located in the optimal band for marine communication. It is suitable for underwater optical communication, marine exploration, atomic physics experiments, and quantum information technology. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the structure of the 459.317nm narrow linewidth all-solid-state laser based on PPKTP-BWOPO and OPA technologies of this invention.

[0025] In the diagram: A-1064.4nm fundamental frequency laser generation and beam splitting module, B-BWOPO backward signal light generation module, C-532.2nm pump light generation and delay module, D-OPA parametric amplification and terminal frequency doubling module; 1-1064.4nm fundamental frequency pulsed laser, 2-optical isolator, 3-first half-wave plate, 4-polarizing beam splitter, 5-focusing lens group, 6-first beam splitter, 7-submicron periodic PPKTP crystal, 8-precision temperature control furnace, 9-first beam shaping lens group, 10-second half-wave plate, 11-first frequency doubling crystal, 12-second beam splitter, 13-second frequency doubling crystal, 14-third beam splitter, 15-optical delay device, 16-second beam shaping lens group, 17-fourth beam splitter, 18-OPA crystal, 19-fifth beam splitter, 20-third half-wave plate, 21-terminal frequency doubling crystal, 22-sixth beam splitter. Detailed Implementation

[0026] The specific embodiments of the present invention will be further described below with reference to the accompanying drawings, but these should not be construed as limiting the scope of protection of the present invention.

[0027] like Figure 1 As shown, this invention relates to a 459.317nm narrow-linewidth all-solid-state laser based on PPKTP-BWOPO and OPA technologies, comprising four parts: a 1064nm fundamental frequency laser generation and beam splitting module A, a BWOPO backward signal light generation module B, a 532.2nm pump light generation and delay module C, and an OPA parametric amplification and terminal frequency doubling module D. Specific implementation details are as follows: The 1064.4nm fundamental frequency laser generation and beam splitting module A includes a 1064.4nm fundamental frequency pulsed laser 1, an optical isolator 2, a first half-wave plate 3, and a polarization beam splitter 4.

[0028] The 1064.4nm fundamental frequency pulsed laser 1 is a pulsed laser oscillator or pulsed laser amplifier with neodymium-doped yttrium aluminum garnet (Nd:YAG) crystal or neodymium-doped yttrium vanadate (Nd:YVO4) crystal as the gain medium. The output laser wavelength is 1064.4nm, the pulse width is about 10ns, the repetition frequency is 100Hz, and the single pulse energy is adjustable, up to a maximum of 20mJ. The optical isolator 2 is a 1064.4nm wavelength optical isolator, used to prevent reflected light from the subsequent optical path from returning to the laser and causing damage; The first half-wave plate 3 is a 1064.4nm half-wave plate coated with a 1064nm antireflection film; by rotating the angle of the half-wave plate 3, the splitting ratio of S-polarized light (reflected) and P-polarized light (transmitted) can be continuously adjusted; the polarization beam splitter 4 is a 1064.4nm wavelength polarization beam splitting cube used to split the incident light into S-polarized light (reflected light) and P-polarized light (transmitted light) with mutually perpendicular vibration directions; in this embodiment, considering that the threshold of BWOPO is approximately 100MW / cm 2 Furthermore, the seed light energy requirement is relatively small, while the OPA amplification stage requires high pump energy. Adjusting the half-wave plate allows approximately 10-20% of the energy (S light) to enter the BWOPO branch, and 80-90% of the energy (P light) to enter the OPA pump branch.

[0029] The BWOPO backward signal light generation module B includes a focusing lens group 5, a first beam splitter 6, a submicron periodic PPKTP crystal 7, a precision temperature control furnace 8, a first beam shaping lens group 9, a second half-wave plate 10, a first frequency doubling crystal 11, and a second beam splitter 12. The parameters of each component are as follows: The focusing lens group 5 consists of two plano-convex lenses, which are used to focus the 1064.4nm pump light into the PPKTP crystal 7, and the diameter of the focused spot is about 150μm. The front surface of the first beam splitter 6 is coated with a 1064nm high-transmittance film (HT@1064nm) and a 1837nm high-reflection film (HR@1837nm), and is placed at 45° to the optical axis; The submicron periodic PPKTP crystal 7 uses Type-0 quasi-phase matching (Type-0 QPM), i.e. ,in This represents extraordinary light whose polarization direction is along the crystal's Z-axis; all waves are polarized along the crystal's Z-axis. The crystal has a cross-section of 1mm × 3mm and a length of 10mm. Both light-transmitting surfaces are coated with anti-reflection films at 1064nm, 1837nm, and 2351nm, with an effective nonlinear coefficient. ,in The maximum nonlinear coefficient of the PPKTP crystal is approximately 13-15 pm / V. The refractive index is calculated using the Sellmeier equation for KTP crystals, based on the BWOPO phase-matching condition: That is, the requirement of conservation of momentum, in which, , , Let the vector magnitudes of the pump light, idler light, and signal light in the crystal be respectively, and the PPKTP polarization period be obtained as follows: ,in , , These represent the refractive indices of the pump light, idler light, and signal light along the Z-axis of the crystal, respectively. , , These are the wavelengths of the pump light, idler light, and signal light, respectively. =1064.4nm, =1837.268nm, =2351.7nm, substituting into the numerical calculation under room temperature conditions, yields... This belongs to submicron polarization and requires advanced high-voltage electric field polarization process for preparation. Due to the error of the Sellmeier equation, the actual processing cycle may be between 500nm and 502nm. It is necessary to adjust the temperature through a precision temperature-controlled furnace to accurately match 1837.268nm. The temperature control accuracy of the precision temperature control furnace 8 is ±0.01℃. The PPKTP crystal has a cross-section of 1mm×3mm and a length of 10mm. Both light-transmitting surfaces of the crystal are coated with anti-reflection films of 1064nm, 1837nm and 2351nm. The backlight beam generated by BWOPO has a naturally narrow linewidth characteristic, and the linewidth can approach the Fourier transform limit. The 1837.268nm backward signal light is reflected by the first beam splitter 6, and then passes through the first beam shaping lens group 9 and the second half-wave plate 10 in sequence before entering the first frequency doubling crystal 11 for pre-frequency doubling. The first beam shaping lens group 9 consists of two plano-convex lenses, used to adjust the spot size and divergence angle of the 1837.268nm signal light to a suitable range to match the mode requirements of the subsequent first frequency doubling crystal (11); the second half-wave plate 10 is an 1837nm half-wave plate coated with an 1837nm anti-reflection film. The first frequency doubling crystal 11 is a type I phase-matched LBO crystal, with a crystal cutting angle of [missing information]. The crystal has 1837nm and 918nm antireflection coatings on both light-transmitting surfaces, which are used to frequency double the 1837.268nm laser to generate a 918.634nm laser.

[0030] The front surface of the second beam splitter 12 is coated with a 918nm high-transmittance film (HT@918nm) and an 1837nm high-reflectance film (HR@1837nm), and is positioned at 45° to the laser axis. It is used to transmit the 918.634nm seed light and reflect the remaining 1837.268nm fundamental frequency light. The generated 918.634nm narrow-linewidth seed light is transmitted through the second beam splitter 12 and output to the OPA parametric amplification and terminal frequency doubling module D.

[0031] The 532.2nm pump light generation and delay module C includes a second frequency doubling crystal 13, a third beam splitter 14, an optical delay device 15, and a second beam shaping lens group 16. Wherein: The second frequency doubling crystal 13 is a type I phase-matched LBO crystal, with a crystal cutting angle of [missing information]. The crystal has 1064nm and 532nm antireflection coatings on both light-transmitting surfaces, which are used to frequency double the 1064.4nm laser to generate a 532.2nm laser. The front surface of the third beam splitter 14 is coated with a 532nm high-transmittance film (HT@532nm) and a 1064nm high-reflectance film (HR@1064nm), and is placed at a 45° angle to the laser axis; The optical delay device 15 consists of an electric translation stage and two high-reflectivity mirrors mounted on it. The two high-reflectivity mirrors form a folded optical path. By adjusting the position of the translation stage, the optical path of the 532.2nm optical path can be precisely increased. The delay adjustment range is 0-5ns, and the accuracy is 1ps. The second beam shaping lens group 16 consists of two plano-convex lenses, used to adjust the spot size and divergence angle of the 532.2nm pump light so that it matches the mode of the 918.634nm seed light at the OPA crystal 18.

[0032] The OPA parametric amplification and terminal frequency doubling module D includes a fourth beam splitter 17, an OPA crystal 18, a fifth beam splitter 19, a third half-wave plate 20, a terminal frequency doubling crystal 21, and a sixth beam splitter 22. Wherein: The front surface of the fourth beam splitter 17 is coated with a 532nm high-transmittance film (HT@532nm) and a 918nm high-reflectance film (HR@918nm), and is placed at a 45° angle to the laser axis; The OPA crystal 18 is a BBO crystal, and the crystal cutting angle is [missing information]. It is used to perform optical parametric amplification of 532.2nm pump light and 918nm seed light. Both light-transmitting surfaces of the crystal are coated with anti-reflection films of 532nm, 918nm and 1265nm. The front surface of the fifth beam splitter 19 is coated with a 918nm high-transmittance film (HT@918nm), a 532nm high-reflection film (HR@532nm), and a 1265nm high-reflection film (HR@1265nm). It is placed at 45° to the laser axis to transmit the amplified 918.634nm signal light and reflect the pump light and idler light. The third half-wave plate 20 is a 918.634nm half-wave plate coated with a 918nm antireflection film, used to adjust the polarization direction of the 918.634nm laser. The terminal frequency doubling crystal 21 is a type I phase-matched LBO crystal, and the crystal cutting angle is... It is used to generate 459.317nm laser by frequency doubling of 918.634nm laser. Both light-transmitting surfaces of the crystal are coated with 918nm and 459nm anti-reflection coatings. The front surface of the sixth beam splitter 22 is coated with a 459nm high-transmittance film (HT@459nm) and a 918nm high-reflection film (HR@918nm), and is placed at 45° to the laser axis to transmit the 459.317nm target laser and reflect the remaining 918.634nm fundamental frequency light.

[0033] In summary, this invention features a compact structure, narrow linewidth, high power, and high frequency stability. The output 459.317nm laser wavelength is located within the optical transmission window of ocean water and precisely matches the characteristic transition lines of cesium atoms, making it of significant application value in underwater communication and ocean exploration.

[0034] The above embodiments are only for illustrating the technical features of the present invention and should not be construed as limiting the scope of protection of the present invention. Any modifications or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this invention should be included within the scope of protection of this invention. Therefore, the scope of protection of this invention should be determined by the scope of the claims.

Claims

1. A 459.317nm narrow-linewidth all-solid-state laser matched with a cesium atom filter, characterized in that, It consists of four parts: a 1064.4nm fundamental frequency laser generation and beam splitting module (A), a BWOPO backward signal light generation module (B), a 532.2nm pump light generation and delay module (C), and an OPA parametric amplification and terminal frequency doubling module (D). The 1064.4nm fundamental frequency laser generation and beam splitting module (A) includes a 1064.4nm fundamental frequency pulsed laser (1), an optical isolator (2), a first half-wave plate (3), and a polarization beam splitter (4); The BWOPO backward signal light generation module (B) includes a focusing lens group (5), a first beam splitter (6), a submicron periodic PPKTP crystal (7), a precision temperature control furnace (8), a first beam shaping lens group (9), a second half-wave plate (10), a first frequency doubling crystal (11), and a second beam splitter (12). The 532.2nm pump light generation and delay module (C) includes a second frequency doubling crystal (13), a third beam splitter (14), an optical delay device (15), and a second beam shaping lens group (16); The OPA parametric amplification and terminal frequency doubling module (D) includes a fourth beam splitter (17), an OPA crystal (18), a fifth beam splitter (19), a third half-wave plate (20), a terminal frequency doubling crystal (21), and a sixth beam splitter (22); The laser generated by the 1064.4nm fundamental frequency pulsed laser (1) passes through the optical isolator (2), and then through the first half-wave plate (3) to rotate the polarization state. Combined with the polarization beam splitter (4) to precisely adjust the beam splitting ratio, it is split into two paths: S-polarized light and P-polarized light. Among them, the S-polarized light reflected by the polarization beam splitter (4) enters the BWOPO backward signal light generation module (B), passes through the focusing lens group (5), and then passes through the first beam splitter (6) to pump the submicron periodic PPKTP crystal (7) in the precision temperature control furnace (8). Based on the backward optical parameters, The BWOPO (Browser-Wave-Optics) mechanism generates a 1837.268nm backscattered signal light with a naturally narrow linewidth in the Z-axis direction of the crystal. This light is reflected by the first beam splitter (6) and then passes through the first beam-shaping lens group (9) and the second half-wave plate (10) in sequence. It then enters the first frequency-doubling crystal (11) for pre-frequency doubling to obtain a 918.634nm narrow linewidth seed light, which is then transmitted through the second beam splitter (12) and output to the OPA parametric amplification and terminal frequency doubling module (D). At the same time, the P-polarized fundamental frequency light transmitted by the polarization beam splitter (4) enters the OPA. The 532.2nm pump light is generated and delayed by the 532.2nm pump light generation and delay module (C). After the second frequency doubling crystal (13) generates 532.2nm green light, the remaining fundamental frequency light is filtered out by the third beam splitter (14). Then, it enters the optical delay device (15) consisting of an electric translation stage and a high-reflectivity mirror mounted on it. By adjusting the optical path to compensate for the BWOPO settling time, the pump light and the seed light are precisely synchronized in the time domain. After the spot mode is adjusted by the second beam shaping lens group (16), it enters the OPA parametric amplification and terminal frequency doubling module (D). In the amplification and terminal frequency doubling module (D), the 532.2nm pump light and the 918.634nm seed light are combined by the fourth beam splitter (17) and injected into the OPA crystal (18) for high-gain parametric amplification. After the amplified 918.634nm signal light is filtered by the fifth beam splitter (19) to remove waste light, the polarization direction is adjusted by the third half-wave plate (20), and finally injected into the terminal frequency doubling crystal (21) for secondary frequency doubling to generate a deep blue laser with a target wavelength of 459.317nm, which is then transmitted and output by the sixth beam splitter (22).

2. The 459.317nm narrow-linewidth all-solid-state laser with matched cesium atom filters according to claim 1, characterized in that, The 1064.4nm fundamental frequency pulsed laser (1) is a pulsed laser oscillator or pulsed laser amplifier with neodymium-doped yttrium aluminum garnet (Nd:YAG) crystal or neodymium-doped yttrium vanadate (Nd:YVO4) crystal as the gain medium. The output laser wavelength is 1064.4nm, the pulse width is 5-20ns, and the repetition frequency is 1Hz-1kHz.

3. The 459.317nm narrow-linewidth all-solid-state laser with matched cesium atom filters according to claim 1, characterized in that, The first half-wave plate is a 1064.4nm half-wave plate, the second half-wave plate is a 1837.268nm half-wave plate, and the third half-wave plate is a 918.634nm half-wave plate. Each half-wave plate is coated with an anti-reflection film of the corresponding wavelength.

4. A 459.317nm narrow-linewidth all-solid-state laser with a matched cesium atom filter according to claim 1, characterized in that, The polarization beam splitter (4) is a polarization beam splitting cube with a wavelength of 1064.4 nm, used to split the incident light into S-polarized light and P-polarized light with mutually perpendicular vibration directions.

5. A 459.317nm narrow-linewidth all-solid-state laser with a matched cesium atom filter according to claim 1, characterized in that, The focusing lens group (5), the first beam shaping lens group (9), and the second beam shaping lens group (16) are all composed of two plano-convex lenses. The focusing lens group (5) focuses the 1064.4nm pump light into the PPKTP crystal (7), and the diameter of the focused spot is 100-200μm.

6. A 459.317nm narrow-linewidth all-solid-state laser with a matched cesium atom filter according to claim 1, characterized in that, The front surface of the first beam splitter (6) is coated with a 1064nm high-transmittance film and an 1837nm high-reflectance film; the front surface of the second beam splitter (12) is coated with a 918nm high-transmittance film and an 1837nm high-reflectance film; the front surface of the third beam splitter (14) is coated with a 532nm high-transmittance film and a 1064nm high-reflectance film; the front surface of the fourth beam splitter (17) is coated with a 532nm high-transmittance film and a 918nm high-reflectance film; the front surface of the fifth beam splitter (19) is coated with a 918nm high-transmittance film, a 532nm high-reflectance film and a 1265nm high-reflectance film; and the front surface of the sixth beam splitter (22) is coated with a 459nm high-transmittance film and a 918nm high-reflectance film.

7. A 459.317nm narrow-linewidth all-solid-state laser with a matched cesium atom filter according to claim 1, characterized in that, The PPKTP crystal (7) adopts type 0 quasi-phase matching. The propagation directions of the pump light, signal light and idler light are all along the X-axis of the crystal, and the polarization directions are all along the Z-axis of the crystal. The polarization period of the crystal is 501.2nm, which is used to realize the backward optical parametric oscillation from 1064.4nm pump light to 1837.268nm signal light.

8. A 459.317nm narrow-linewidth all-solid-state laser with a matched cesium atom filter according to claim 1, characterized in that, The precision temperature control furnace (8) has a temperature control accuracy of ±0.01℃ and an operating temperature range of 25-200℃.

9. A 459.317nm narrow-linewidth all-solid-state laser with a matched cesium atom filter according to claim 1, characterized in that, The first frequency doubling crystal (11), the second frequency doubling crystal (13), the OPA crystal (18), and the terminal frequency doubling crystal (21) are all LBO or BBO crystals with type I phase matching. The first frequency doubling crystal (11) has 1837nm and 918nm anti-reflection coatings on its light-transmitting surface; the second frequency doubling crystal (13) has 1064nm and 532nm anti-reflection coatings on its light-transmitting surface; the OPA crystal (18) has 532nm, 918nm, and 1265nm anti-reflection coatings on its light-transmitting surface; and the terminal frequency doubling crystal (21) has 918nm and 459nm anti-reflection coatings on its light-transmitting surface.

10. A 459.317nm narrow-linewidth all-solid-state laser with a matched cesium atom filter according to claim 1, characterized in that, In the optical delay device (15), two highly reflective mirrors form a folded optical path, with a delay adjustment range of 0-2ns and an accuracy of 1ps.

Images