A master-slave pulse delay controllable ultraviolet dual-wavelength dual-pulse laser

Abstract

This invention relates to the field of all-solid-state laser technology, specifically providing a master-slave pulse delay-controllable ultraviolet dual-wavelength dual-pulse laser, comprising: a pump source and a V-shaped folded resonator. The V-shaped folded resonator includes an input mirror, a gain medium, a Q-switched crystal, a total reflection mirror, a frequency doubling crystal, and an output mirror. The Q-switched crystal performs step modulation via a dual-step electrical signal. Within one modulation cycle, the dual-step electrical signal sequentially includes a high-voltage phase, a low-voltage phase, and a de-voltage phase. Within one pump cycle, it sequentially generates transitions from the high-voltage phase to the low-voltage phase and from the low-voltage phase to the de-voltage phase, respectively outputting a dual-wavelength master pulse and a dual-wavelength slave pulse. Furthermore, the delay between the dual-wavelength master pulses can be controlled by adjusting the duration of the low-voltage phase. This invention achieves ultraviolet dual-wavelength dual-pulse output with flexible and controllable master-slave pulse delay.

Description

Technical Field

[0001] This invention belongs to the field of all-solid-state laser technology, and particularly relates to an ultraviolet dual-wavelength dual-pulse laser with controllable master-slave pulse delay. Background Technology

[0002] With the deepening application of laser technology in biomedical imaging, precision micromachining, time-resolved spectroscopy, and photochemistry, more stringent requirements are being placed on the output characteristics of pulsed lasers. In particular, the demand for laser sources located in the ultraviolet band with precise timing control and multi-wavelength synchronous output capabilities is becoming increasingly urgent. In the biomedical field, ultraviolet dual-wavelength pulses can be used to excite different endogenous fluorophores or exogenous probes separately, achieving deeper multimodal microscopic imaging. In high-end precision machining, ultraviolet lasers, due to their high photon energy and small heat-affected zone, are suitable for cold processing of hard and brittle materials such as semiconductors and sapphire. The dual-pulse structure combined with controllable delay can optimize material removal mechanisms, further improving processing quality and efficiency. In basic scientific research, such as time-resolved fluorescence spectroscopy or pump-probe experiments, ultraviolet pulse pairs can serve as excitation or detection sources, enabling high spatiotemporal resolution analysis of ultrafast dynamic processes.

[0003] Currently, achieving laser output in the ultraviolet band mainly relies on nonlinear frequency transformations (such as frequency doubling and sum-frequency conversion) of near-infrared or visible lasers. However, publicly reported laser solutions that simultaneously achieve ultraviolet output, dual wavelengths, and controllable pulse delay are extremely rare. Existing technologies mostly focus on achieving a single wavelength or fixed delay. Existing technologies face the following main technical bottlenecks in achieving integrated ultraviolet, dual-wavelength, and controllable pulse delay laser output:

[0004] First, ultraviolet laser generation is inefficient and complex: the gain medium for directly emitting ultraviolet lasers is limited and inefficient. Mainstream solutions rely on nonlinear frequency conversion (such as frequency doubling and sum-frequency conversion) of near-infrared or visible lasers to generate ultraviolet light. This process requires the introduction of nonlinear crystals, precise temperature control, and complex phase-matching adjustment mechanisms, resulting in a large system, high stability requirements, and overall conversion efficiency constrained by multiple factors, making it difficult to balance high power with compact design.

[0005] Second, pulse delay is difficult to control flexibly in the ultraviolet band: existing ultraviolet pulsed lasers mostly output fixed repetition frequencies or single pulses. To obtain master-slave pulse pairs with precise and controllable delays, complex pulse timing segmentation and delay are usually required in the fundamental frequency stage, followed by nonlinear conversion, or external optical delay lines are needed. These methods introduce significant additional losses, timing jitter, and system complexity, making it difficult to achieve high-precision, programmable delay control at the microsecond level.

[0006] Third, achieving stable output of dual ultraviolet wavelengths is extremely challenging: generating two stable ultraviolet wavelengths in the same laser is very difficult. If two independent laser systems are used to generate different wavelengths and then combined, serious problems such as pulse synchronization, spatial overlap, and system complexity will arise. If a single nonlinear crystal is used to combine the dual-wavelength fundamental frequency light, the requirements for the power balance, spectral characteristics, and phase matching conditions of the fundamental frequency light are extremely stringent, making engineering implementation difficult and ensuring the stability of output energy and wavelength is challenging.

[0007] Therefore, there is an urgent need to design a laser that can output dual ultraviolet wavelengths and has flexible and controllable master-slave pulse delay. Summary of the Invention

[0008] In view of this, the present invention aims to provide a master-slave pulse delay controllable ultraviolet dual-wavelength dual-pulse laser. Through a dual-step drive signal Q-switching mechanism, two independent low-loss windows are created within a single energy storage cycle, enabling the output of two dual-wavelength ultraviolet laser pulses within the same working cycle, and the delay between the two pulses can be precisely and flexibly adjusted over a wide range.

[0009] To achieve the above objectives, the technical solution created by this invention is implemented as follows:

[0010] This invention provides a master-slave pulse delay controllable ultraviolet dual-wavelength dual-pulse laser, comprising:

[0011] Pump source, used to provide pump light;

[0012] The V-shaped folded resonant cavity includes a first resonant arm and a second resonant arm. The first resonant arm contains an input mirror, a gain medium, and a Q-switched crystal, which are used to generate and control the fundamental frequency laser in two visible bands.

[0013] The second resonant arm is equipped with a total reflection mirror, a frequency doubling crystal, and an output mirror, which are used to frequency double the two fundamental frequency lasers in the visible band into two ultraviolet lasers of different wavelengths.

[0014] The Q-switched crystal is also connected to a signal generator, which generates a double-step electrical signal. The double-step electrical signal includes a high-voltage stage, a low-voltage stage, and a de-voltage stage in sequence within one modulation cycle. The internal diffraction rate of the Q-switched crystal is modulated in a double-step manner through the double-step electrical signal. The transition from the high-voltage stage to the low-voltage stage and the transition from the low-voltage stage to the de-voltage stage are generated sequentially within one pump cycle to output a dual-wavelength master pulse and a dual-wavelength slave pulse, respectively.

[0015] Preferably, the pump source is a 444 nm blue light pump source.

[0016] Preferably, the input mirror is located at the rear end of the pump source, and the surface coating of the input mirror near the pump source has a transmittance of more than 95% for pump light, while the surface coating of the input mirror away from the pump source has a reflectance of more than 99.5% for the 600-650 nanometer wavelength band.

[0017] Preferably, the gain medium is placed in the rear optical path of the input mirror and mounted on a temperature-controlled water-cooled copper plane. The gain medium is a Pr:YLF crystal with a doping concentration of 0.5%.

[0018] Preferably, the Q-switching crystal is an acousto-optic Q-switching crystal or an electro-optic modulator. The Q-switching crystal is also connected to an RF driver, which is used to convert the bi-step electrical signal into an RF signal and transmit the RF signal to the Q-switching crystal.

[0019] Preferably, during the transition from the high-voltage stage to the low-voltage stage, the Q-switched crystal is in a partially open state to achieve dual-wavelength main pulse output; during the low-voltage stage, the Q-switched crystal accumulates the number of upper-level inversion particles under the influence of low voltage, and the delay between dual-wavelength main pulses is controlled by adjusting the duration of the low-voltage stage; during the transition from the low-voltage stage to the de-voltage stage, the Q-switched crystal is in a fully open state to achieve dual-wavelength slave pulse output.

[0020] Preferably, the Q-switched crystal has an angle with the optical axis of the first resonant arm, which is used to produce different diffraction effects for the fundamental frequency lasers in the two visible bands and adjust the intracavity loss difference of the fundamental frequency lasers in the two visible bands.

[0021] Preferably, the angle between the Q-switched crystal and the optical axis of the first resonant arm is 1 to 2 degrees.

[0022] Preferably, after the fundamental frequency laser is modulated by the Q-switched crystal, it is incident on the output mirror. The output mirror reflects the fundamental frequency laser towards the frequency doubling crystal. After passing through the frequency doubling crystal, it is incident on the total reflection mirror. The total reflection mirror has the effect of reflecting the two fundamental frequency lasers in the visible band and the two ultraviolet lasers of different wavelengths. The two ultraviolet lasers of different wavelengths obtained by frequency doubling are incident on the output mirror again and output by the output mirror.

[0023] The output mirror is a plano-concave mirror with a reflectivity of over 99.8% for the fundamental frequency laser and a transmittance of over 93% for two different wavelengths of ultraviolet laser.

[0024] Preferably, the wavelengths of the two fundamental frequency lasers in the visible band are 604 nm and 607 nm, respectively, and the wavelengths of the two ultraviolet lasers of different wavelengths are 302 nm and 303 nm, respectively.

[0025] Compared with the prior art, the present invention can achieve the following beneficial effects:

[0026] This invention employs a timing-dependent, two-order electrical signal step-modulation Q-switched crystal to create two independent low-loss windows within a single energy storage cycle, thereby sequentially generating master and slave dual-wavelength laser pulses. Precise pulse delay is achieved by adjusting the duration of the low voltage, solving the problem of existing ultraviolet pulsed lasers requiring complex pulse timing segmentation and delay in the fundamental frequency stage, followed by nonlinear conversion, or reliance on external optical delay lines to achieve dual-pulse output. Furthermore, a small tilt angle is set between the Q-switched crystal and the resonant cavity optical axis. This tilt angle differentially affects the diffraction efficiency of different wavelengths of laser light in the Q-switched crystal, actively balancing the intracavity net gain of the two transition lines at 604 nm and 607 nm in the gain medium, effectively suppressing gain competition and achieving stable synchronous output of dual wavelengths.

[0027] This invention uses a Pr:YLF crystal as the gain medium to generate 604nm and 607nm visible lasers under direct 444nm blue light pumping, eliminating the step of frequency doubling from mid-infrared to visible light; only a single frequency doubling is needed to generate 302nm and 303nm lasers. Combined with the aforementioned dual-step Q-switching and acousto-optic crystal tilt tuning techniques, ultraviolet dual-wavelength dual-pulse laser output is achieved. By adjusting the low-voltage duration of the dual-step electrical signal, the delay between the master and slave pulses can be precisely set over a wide range (e.g., from several microseconds to tens of microseconds), meeting the high timing accuracy requirements of time-resolved applications, and the control method is simple and low-cost.

[0028] This invention employs a V-shaped folded resonant cavity structure to achieve fundamental frequency optical oscillation and ultraviolet frequency-doubled light output within a compact space. Through the V-shaped resonant cavity design, it organically integrates acousto-optic Q-switching technology driven by a dual-step signal, dual-wavelength gain internal equalization technology based on crystal tilt angle, and intracavity frequency doubling technology. The system utilizes a single electronic control sequence to sequentially trigger two visible light dual-wavelength pulses with controllable delays within a single resonant cavity. A nonlinear crystal placed within the cavity synchronously converts the time and frequency domain characteristics of these two pulses to the ultraviolet band in real time. The final output is a precisely adjustable pulse delay and wavelength-stable ultraviolet dual-pulse sequence. This scheme features a compact structure and simple, efficient control logic, avoiding the challenges of multi-laser synchronization or complex external synthesis, providing a high-performance, high-reliability solution for applications requiring high-precision ultraviolet pulse pairs. Attached Figure Description

[0029] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments and descriptions of the invention are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0030] Figure 1This is an optical structure diagram of a master-slave pulse delay controllable ultraviolet dual-wavelength dual-pulse laser provided according to an embodiment of the present invention;

[0031] Figure 2 This is a schematic diagram of the master-slave pulse delay controllable principle provided by an embodiment of the present invention.

[0032] The reference numerals in the figures include:

[0033] 1. Pump source, 2. Focusing coupling mirror group, 3. Input mirror, 4. Gain medium, 5. Q-switched crystal, 6. RF driver, 7. Signal generator, 8. Total reflection mirror, 9. Frequency doubling crystal, 10. Output mirror. Detailed Implementation

[0034] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are only for explaining the invention and do not constitute a limitation thereof. Similar elements in different embodiments are referred to by associated similar element reference numerals. In the following embodiments, many details are described to facilitate a better understanding of the invention. However, those skilled in the art will readily recognize that some features may be omitted in different situations, or may be replaced by other elements, materials, or methods. In some cases, some operations related to the invention are not shown or described in the specification. This is to avoid obscuring the core parts of the invention with excessive description. For those skilled in the art, detailed description of these related operations is not necessary; the relevant operations can be fully understood based on the description in the specification and general technical knowledge in the art.

[0035] It should be noted that, unless otherwise specified, the embodiments and features described in this invention can be combined to form various implementations. Furthermore, the order of the steps or actions in the method description can be changed or adjusted in a manner readily apparent to those skilled in the art. Therefore, the various orders in the specification and drawings are merely for the clear description of a particular embodiment and do not imply a mandatory order, unless otherwise stated that a particular order must be followed.

[0036] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," and "counterclockwise," etc., indicating orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on this invention. Furthermore, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, features defined with "first," "second," etc., may explicitly or implicitly include one or more of that feature. In the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0037] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art will understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0038] The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0039] Please see Figure 1 In one embodiment of the present invention, a master-slave pulse delay controllable ultraviolet dual-wavelength dual-pulse laser is provided, comprising:

[0040] Pump source 1 is used to provide pump light;

[0041] The V-shaped folded resonant cavity includes a first resonant arm and a second resonant arm. The first resonant arm contains an input mirror 3, a gain medium 4, and a Q-switched crystal 5, which are used to generate and control the fundamental frequency lasers in two visible bands.

[0042] The second resonant arm is equipped with a total reflection mirror 8, a frequency doubling crystal 9, and an output mirror 10, which are used to frequency double the two fundamental frequency lasers in the visible band into two ultraviolet lasers of different wavelengths.

[0043] The Q-switched crystal 5 is also connected to a signal generator 7, which generates a double-step electrical signal. The double-step electrical signal includes a high-voltage stage, a low-voltage stage, and a de-voltage stage in sequence within one modulation cycle. The internal diffraction rate of the Q-switched crystal 5 is modulated in a double-step manner by the double-step electrical signal. The transition from the high-voltage stage to the low-voltage stage and the transition from the low-voltage stage to the de-voltage stage are generated sequentially within one pump cycle to output a dual-wavelength master pulse and a dual-wavelength slave pulse, respectively.

[0044] Pump source 1 employs a 444nm blue light pump source, positioned at the very front of the entire optical system. Its function is to provide pump light with a wavelength of 444nm. Specifically, pump source 1 can be a continuously output 444nm blue light semiconductor laser diode, with its center wavelength precisely matched to the absorption peak of a praseodymium-doped yttrium lithium fluoride laser crystal. This allows for the direct excitation of praseodymium ions within the crystal, serving as the energy source for visible light output.

[0045] As an alternative embodiment, pump source 1 can also employ other blue light sources capable of effectively absorbing and pumping the Pr:YLF crystal, such as blue laser diodes in other wavelength bands (e.g., 440-450 nm), or blue solid-state lasers generated through frequency doubling. The key is that the pump wavelength must match the absorption peak of the Pr:YLF crystal.

[0046] Since the pump light provided by pump source 1 has a certain divergence angle, a focusing coupling mirror group 2 is set at the rear end of pump source 1. The focusing coupling mirror group 2 is positioned between pump source 1 and V-shaped folded resonant cavity. The focusing coupling mirror group 2 refocuses and reshapes the pump light with the divergence angle into a small (radius of about 200 micrometers) and energy-concentrated spot. This ensures that the pump light can be efficiently coupled into the subsequent gain medium 4 and well matched with its internal laser mode, thereby improving pump efficiency and laying the foundation for generating high-brightness laser.

[0047] After being processed by the focusing coupling mirror group 2, the pump light enters the V-shaped folded resonant cavity. The V-shaped folded resonant cavity enables fundamental frequency oscillation and ultraviolet frequency-doubled light output within a compact space. The V-shaped folded resonant cavity includes a first resonant arm and a second resonant arm, with the optical element at the intersection of the two resonant arms being the output mirror 10. Firstly, the first resonant arm includes, sequentially arranged along the propagation of the pump light: an input mirror 3, a gain medium 4, and a Q-switching crystal 5. The input mirror 3 is located at the rear end of the focusing coupling mirror group 2, serving as the starting point of the resonant cavity. The input mirror 3 is a plane mirror with special optical thin films coated on its front and rear surfaces to facilitate the oscillation of excited photons within the resonant cavity. The surface of the input mirror 3 near the pump source 1 is coated with an optical thin film with high transmittance for 444 nm blue pump light; typically, this surface optical thin film has a transmittance of greater than 95% for 444 nm blue light. The surface of the input mirror 3, away from the pump source 1, is coated with an optical thin film with high reflectivity in the 600-650 nm wavelength band. Typically, the reflectivity of this optical thin film in the 600-650 nm wavelength band is greater than 99.5%. The input mirror 3 and the output mirror 10 at the other end together form an optical resonance.

[0048] After the pump light passes through the input mirror 3 and enters the V-shaped folded resonant cavity, it is incident on the gain medium 4, which is placed immediately behind the input mirror 3. The physical location of the gain medium 4 is at the center of the pump spot. The gain medium 4 is specifically a Pr:YLF crystal with a doping concentration of 0.5% and a size of 3×3×5 cubic centimeters. When pumped by 444 nm blue light, the praseodymium ions in the gain medium 4 are excited to a high-energy state, undergoing population inversion and acquiring the ability to emit laser light. There are two key emission wavelengths during the excitation process: 604 nm (π polarization) and 607 nm (σ polarization), both of which are in the orange-yellow light band visible to the human eye. Under the pumping action of the pump light, fundamental frequency lasers in the two visible bands of 604 nm and 607 nm can be generated.

[0049] As an optional embodiment, since heat is generated during the pumping process, in order to avoid the pumping heat from interfering with the laser performance, the gain medium 4 is mounted on a temperature-controlled water-cooled copper plane. Under normal circumstances, the water-cooled copper plane ensures that the temperature of the gain medium 4 is precisely controlled at 5°C. The water-cooled copper plane can ensure effective heat dissipation of the gain medium 4, further ensuring stable laser output and preventing the gain medium 4 from being damaged or its performance from degrading due to overheating.

[0050] After being pumped by gain medium 4 to generate a dual-wavelength fundamental frequency laser, the fundamental frequency laser is injected into Q-switched crystal 5. Q-switched crystal 5 is the core switch that realizes the "pulse" and "delay control" functions, and is generally also called a Q switch. Q-switched crystal 5 can be an acousto-optic Q-switched crystal (AOM) or an electro-optic modulator (such as a Pockels cell). Among them, acousto-optic Q-switched crystals usually have lower driving voltage and less thermal effect, making them more practical in the visible light band. Q-switched crystal 5 is used to modulate the fundamental frequency laser to generate dual-wavelength dual pulses in the visible light band, and it is necessary to ensure that the delay of the dual-wavelength master pulse and dual-wavelength slave pulse is controllable. To realize the modulation of Q-switched crystal 5, Q-switched crystal 5 is also connected to RF driver 6 and signal generator 7. RF driver 6 is electrically connected to Q-switched crystal 5, and signal generator 7 is electrically connected to RF driver 6.

[0051] Specifically, such as Figure 2 As shown, signal generator 7 generates a double-step electrical signal to perform double-step step modulation on the diffraction index inside Q-switched crystal 5. The double-step electrical signal generated by signal generator 7 needs to be converted into an RF signal by RF driver 6 before being transmitted to Q-switched crystal 5. The double-step electrical signal has a specific timing sequence, that is, it includes a high-voltage stage, a low-voltage stage, and a de-voltage stage in sequence within a modulation cycle, so that the acousto-optic voltage of each modulation cycle is controlled at the three positions of high voltage, low voltage, and de-voltage, and different action times are applied according to different positions to achieve loss modulation of laser Q-switching. Two independent low-loss windows are created within a single energy storage cycle, thereby sequentially generating master and slave laser pulses, wherein the dual-wavelength master pulse and the dual-wavelength slave pulse are in Figure 2The first and second wavelength components shown are 604 nm and 607 nm, respectively. The wavelength difference between the first and second wavelength components is the adjustable amplitude, and the adjustable interval between the dual-wavelength main pulse and the dual-wavelength slave pulse is the delay. Within one pump cycle, there are transitions from a high-voltage stage to a low-voltage stage and from a low-voltage stage to a de-voltage stage. During the transition from the high-voltage stage to the low-voltage stage, the Q-switched crystal 5 is in a partially open state. At this time, the number of energy level inversion particles accumulated in the high-voltage stage amplifies the pulse of the fundamental frequency laser, thereby modulating and generating dual-wavelength main pulses of 604 nm and 607 nm. After the dual-wavelength main pulses of 604 nm and 607 nm are successfully established, since the Q-switched crystal 5 is not fully open, it still has a high diffraction rate under the action of low voltage. At this time, by extending the duration of the low-voltage stage applied by the signal generator 7, the number of energy level inversion particles is further accumulated, ensuring that the dual-wavelength slave main pulses are fully amplified. During the transition from the low-voltage phase to the de-voltage phase, the Q-switched crystal 5 is fully on. At this time, the energy level inversion particles accumulated during the low-voltage phase again amplify the fundamental frequency laser pulse, thereby modulating and generating dual-wavelength slave pulses of 604 nm and 607 nm. Both the dual-wavelength master pulse and the dual-wavelength slave pulse are fundamental frequency laser pulses. Furthermore, the delay between the dual-wavelength master pulses can be controlled by adjusting the duration of the low-voltage phase. The continuous output of pump source 1, in conjunction with the periodic switching of the Q-switched crystal 5, achieves a continuous master-slave pulse sequence output.

[0052] As an optional embodiment, to achieve stable simultaneous output of two ultraviolet wavelengths, it is necessary to balance the competition between the two wavelengths caused by the inherent difference in gain of the gain medium 4. Without intervention, the wavelength with higher gain will oscillate preferentially, depleting the number of inverted particles and suppressing the oscillation of the wavelength with lower gain, ultimately resulting in the laser only outputting a single wavelength and failing to achieve dual-wavelength output. Therefore, this embodiment of the invention designs a gain balancing method. Since the diffraction efficiency of the Q-switched crystal 5 is sensitive to the angle and polarization state of the incident light, the Q-switched crystal 5 is fixed at an angle to the optical axis of the first resonant arm. This results in different actual optical path lengths for the two wavelengths within the Q-switched crystal 5, causing the Q-switched crystal 5 to produce different diffraction effects on the two fundamental frequency lasers in the visible band. Adjusting the difference in intracavity loss between the two fundamental frequency lasers in the visible band—that is, increasing the loss slightly for the high-gain wavelength and decreasing the loss slightly for the low-gain wavelength—minimizes the gain difference between the two wavelengths and optimally ensures that the net gain of the two wavelengths is equal. Experimental optimization revealed that the optimal balance range for the angle between the Q-switched crystal 5 and the optical axis of the first resonant arm is 1 to 2 degrees. This range effectively balances the gain without excessively increasing the intracavity loss.

[0053] As an alternative embodiment, the dual-step electrical signal does not have to be a square wave; any electrical signal waveform that can produce two distinguishable and time-interval-adjustable low-loss states is acceptable, such as two pulse sequences with adjustable pulse widths and intervals, or analog modulated waveforms with specific shapes.

[0054] After being modulated by the Q-switched crystal 5, the RF driver 6, and the signal generator 7, the generated dual-wavelength main pulses and dual-wavelength slave pulses of 604 nm and 607 nm are transmitted to the output mirror 10. The output mirror 10 serves as the other end face of the resonant cavity and is a plano-concave mirror with a radius of curvature of 100 mm. The inner surface of the output mirror 10 is coated with a specially designed film system, which makes the inner surface of the output mirror 10 highly reflective of the 604 nm and 607 nm fundamental frequency lasers in the visible light band, typically with a reflectivity greater than 99.8%, in order to maintain the high power density of the fundamental frequency laser in the cavity. The inner surface of the output mirror 10 has high transmittance of the 302 nm and 303 nm ultraviolet light bands, typically with a transmittance greater than 93%, thereby achieving efficient coupling and output of ultraviolet lasers. Therefore, the 604 nm and 607 nm fundamental frequency lasers are reflected by the output mirror 10 towards the frequency doubling crystal 9. The frequency doubling crystal 9 is a lithium triborate (LBO) nonlinear optical crystal used to frequency double the 604 nm and 607 nm fundamental frequency lasers. The frequency doubling crystal 9 has dimensions of 3 × 3 × 10 cubic millimeters and uses type I noncritical phase matching (θ = 90°, φ = 61.7°) to frequency double the 604 nm and 607 nm fundamental frequency lasers circulating in the cavity to generate 302 nm and 303 nm ultraviolet lasers, respectively. The frequency doubling crystal 9 also requires a heat dissipation and temperature control device, which can be placed in a water-cooled heater to ensure stable phase matching temperature. After being frequency doubled by the frequency doubling crystal 9, the 604 nm and 607 nm fundamental frequency lasers form 302 nm and 303 nm ultraviolet lasers. After being emitted from the frequency doubling crystal 9, the ultraviolet lasers are directed towards the total reflection mirror 8. The total reflection mirror 8 reflects both the 604 nm and 607 nm fundamental frequency lasers and the 302 nm and 303 nm ultraviolet lasers, with a reflectivity greater than 99.5%. This allows it to efficiently reflect both the fundamental frequency laser and the frequency-doubled ultraviolet laser to the output mirror 10, achieving dual-wavelength dual-pulse ultraviolet laser output.

[0055] As an optional embodiment, in addition to using an LBO crystal, the frequency doubling crystal 9 can also be other nonlinear optical crystals suitable for the 604 nm and 607 nm wavelength bands and possessing phase-matching capabilities. Common alternatives include barium β-borate (BBO), potassium dihydrogen phosphate and its deuterated products (KDP / KD). Cesium triborate (CeBBO), lithium cesium triborate (CeBBO), and bismuth borate (BiBBO), etc.

[0056] Based on the above description of the laser structure, the use of the laser and the process of ultraviolet dual-wavelength dual-pulse output are described in the embodiments of the present invention as follows:

[0057] First, the laser is started, and pump source 1 continuously outputs 444 nm blue pump light. This blue pump light is focused by focusing coupling mirror group 2 and then passes through input mirror 3, where it is absorbed by gain medium 4. Pr³⁺ ions in gain medium 4 are excited to the upper energy level. Simultaneously, signal generator 7 outputs a high-voltage control signal (i.e., the high-voltage phase) to RF driver 6. RF driver 6 converts this signal into an RF signal to drive Q-switched crystal 5 to operate in a high diffraction efficiency state. At this time, Q-switched crystal 5 introduces significant additional losses within the resonant cavity, resulting in an extremely low Q value and complete suppression of laser oscillation. Gain medium 4 is in a purely "energy storage" state, and the number of inverted particles in its upper energy level accumulates linearly over time.

[0058] When the number of inverted particles accumulated in the gain medium 4 reaches saturation, the output signal of the signal generator 7 undergoes its first step, dropping from high voltage to low voltage. The output power of the RF driver 6 then drops sharply, causing a dramatic decrease in the diffraction efficiency of the Q-switched crystal 5. This is equivalent to a sudden and significant reduction in cavity loss, rapidly increasing the Q-value of the resonant cavity. Subsequently, the large number of inverted particles stored in the high-voltage stage avalanche-like transition to the lower energy level through stimulated emission in a very short time, forming a strong laser oscillation and outputting a giant laser pulse, the main pulse. This pulse propagates within the V-shaped cavity and contains dual-wavelength components at 604 nm and 607 nm.

[0059] The control signal is maintained at a low voltage for a preset time. This stage is the critical delay and re-energy storage stage. Although the Q-switched crystal 5 is still in a low-loss state, the net gain in the cavity is below the threshold because the main pulse has consumed most of the inverted particle number, and the laser oscillation temporarily stops. However, the pumping process continues, and the gain medium 4 reabsorbs pump energy, and the particle number in its upper energy level begins to accumulate again. The duration of this low voltage is the time delay between the main pulse and the slave pulse set in the program. By adjusting the parameters of the signal generator 7, the delay time can be precisely digitally set in the range of several microseconds to tens of microseconds, thereby achieving flexible control of the pulse interval. When the low voltage transitions to the de-voltage process, this transient process creates another brief low-loss window in the cavity, which is sufficient for the re-accumulated inverted particle number to undergo a second stimulated emission avalanche, thereby generating and outputting a second giant laser pulse, i.e., the slave pulse, through the output mirror 10.

[0060] In the process described above, each visible light master pulse and slave pulse, during its circulation within the V-shaped resonant cavity, undergoes a nonlinear frequency transformation of the 604 nm and 607 nm lasers contained within the frequency doubling crystal 9 each time it passes through the crystal. The 604 nm laser is frequency-doubled to generate a 302 nm ultraviolet laser, and the 607 nm laser is frequency-doubled to generate a 303 nm ultraviolet laser. Due to the high ultraviolet light transmittance of the output mirror 10, these ultraviolet photons are directly coupled out of the output cavity. Therefore, each visible light master-slave pulse pair corresponds to the generation of an ultraviolet dual-wavelength pulse pair with the same delay relationship. By repeating the above process, a series of ultraviolet dual-wavelength master-slave pulse pairs with strictly controllable pulse intervals can be obtained.

[0061] As an alternative embodiment, in addition to using a Pr:YLF crystal, other praseodymium-doped crystals such as Pr:YAG and Pr:LiLuF4 can also generate different visible light wavelengths under blue light pumping. Other ion-doped crystals that directly emit visible light, such as erbium-doped (Er3+) or thulium-doped (Tm3+) crystals combined with a double-step modulation scheme, can also be considered, but the efficiency and emitted laser wavelength may differ.

[0062] In summary, the above description is merely a preferred embodiment of this specification and is not intended to limit the scope of protection of this specification. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this specification should be included within the scope of protection of this specification.

[0063] The systems, apparatuses, modules, or units described in one or more of the above embodiments may be implemented by a computer chip or entity, or by a product having a certain function. A typical implementation device is a computer. Specifically, a computer may be, for example, a personal computer, a laptop computer, a cellular phone, a camera phone, a smartphone, a personal digital assistant, a media player, a navigation device, an email device, a game console, a tablet computer, a wearable device, or any combination of these devices.

[0064] It should also be noted that the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0065] The various embodiments in this specification are described in a progressive manner. Similar or identical parts between embodiments can be referred to interchangeably. Each embodiment focuses on describing the differences from other embodiments. In particular, the system embodiments are basically similar to the method embodiments, so the description is relatively simple; relevant parts can be referred to the descriptions in the method embodiments.

Claims

1. A master-slave pulse delay controllable ultraviolet dual-wavelength dual-pulse laser, characterized in that, include: The pump source is used to provide pump light; the pump source is a 444 nm blue light pump source. The V-shaped folded resonant cavity includes a first resonant arm and a second resonant arm. An input mirror, a gain medium, and a Q-switched crystal are disposed in the first resonant arm for generating and controlling the fundamental frequency laser in two visible bands. The gain medium is a Pr:YLF crystal with a doping concentration of 0.5%. The second resonant arm is equipped with a total reflection mirror, a frequency doubling crystal, and an output mirror, which are used to frequency double two fundamental frequency lasers in the visible band into two ultraviolet lasers of different wavelengths; the wavelengths of the two fundamental frequency lasers in the visible band are 604 nm and 607 nm, respectively, and the wavelengths of the two ultraviolet lasers of different wavelengths are 302 nm and 303 nm, respectively. The Q-switched crystal is also connected to a signal generator, which generates a double-step electrical signal. The double-step electrical signal includes a high-voltage stage, a low-voltage stage, and a de-voltage stage in sequence within one modulation cycle. The internal diffraction rate of the Q-switched crystal is modulated in a double-step manner by the double-step electrical signal. The transition from the high-voltage stage to the low-voltage stage and the transition from the low-voltage stage to the de-voltage stage are generated sequentially within one pump cycle to output a dual-wavelength master pulse and a dual-wavelength slave pulse, respectively. After being modulated by the Q-switched crystal, the fundamental frequency laser is incident on the output mirror. The output mirror reflects the fundamental frequency laser toward the frequency doubling crystal. After passing through the frequency doubling crystal, the laser is incident on the total reflection mirror. The total reflection mirror reflects both fundamental frequency lasers in the visible band and two ultraviolet lasers of different wavelengths. The two ultraviolet lasers of different wavelengths obtained after frequency doubling are incident on the output mirror again and output by the output mirror. The output mirror is a plano-concave mirror, the reflectivity of the output mirror for the fundamental frequency laser is greater than 99.8%, and the transmittance of the output mirror for two ultraviolet lasers of different wavelengths is greater than 93%.

2. The master-slave pulse delay controllable ultraviolet dual-wavelength dual-pulse laser according to claim 1, characterized in that, The input mirror is disposed at the rear end of the pump source. The surface coating of the input mirror near the pump source has a transmittance of more than 95% for pump light, and the surface coating of the input mirror away from the pump source has a reflectance of more than 99.5% for the 600-650 nanometer wavelength band.

3. The master-slave pulse delay controllable ultraviolet dual-wavelength dual-pulse laser according to claim 2, characterized in that, The gain medium is placed in the optical path at the rear end of the input mirror and mounted on a temperature-controlled water-cooled copper plane.

4. The master-slave pulse delay controllable ultraviolet dual-wavelength dual-pulse laser according to claim 1, characterized in that, The Q-switched crystal is an acousto-optic Q-switched crystal or an electro-optic modulator. The Q-switched crystal is also connected to a radio frequency driver, which is used to convert the bi-step electrical signal into a radio frequency signal and transmit the radio frequency signal to the Q-switched crystal.

5. The master-slave pulse delay controllable ultraviolet dual-wavelength dual-pulse laser according to claim 1, characterized in that, During the transition from the high-voltage stage to the low-voltage stage, the Q-switched crystal is in a partially open state, realizing dual-wavelength main pulse output; during the low-voltage stage, the Q-switched crystal accumulates the upper energy level inversion particle number under the action of low voltage, and the delay between dual-wavelength main pulses is controlled by adjusting the duration of the low-voltage stage; during the transition from the low-voltage stage to the de-voltage stage, the Q-switched crystal is in a fully open state, realizing dual-wavelength slave pulse output.

6. The master-slave pulse delay controllable ultraviolet dual-wavelength dual-pulse laser according to claim 1, characterized in that, The Q-switching crystal has an angle with the optical axis of the first resonant arm, which is used for producing different diffraction effects on the base frequency lasers of two visible bands, and adjusting the difference of the in-cavity loss of the base frequency lasers of the two visible bands.

7. The master-slave pulse delay controllable ultraviolet dual-wavelength dual-pulse laser according to claim 1, characterized in that, The angle of the Q-switching crystal with the optical axis of the first resonant arm is 1-2 degrees.

Images