Dual-wavelength pulse group Q-switched laser

Abstract

This invention relates to the field of solid-state laser technology, specifically providing a dual-wavelength pulse group Q-switched modulated laser, comprising: a pump source and a resonant cavity. The resonant cavity includes an input mirror, a first gain crystal, a Q-switching crystal, a second gain crystal, and an output mirror. The first gain crystal is a quasi-three-level gain medium, generating a first-wavelength laser under the pump light. The Q-switching crystal is used for passive Q-switching modulation of the first-wavelength laser, forming a first-wavelength laser pulse output. The second gain crystal is a four-level gain medium, partially absorbing the first-wavelength laser pulse and generating a second-wavelength laser pulse under the pump of the first-wavelength laser pulse. The first and second-wavelength laser pulses are output by the output mirror to form a dual-wavelength pulse group. This invention completely solves the gain competition problem caused by the shared gain medium in traditional technologies, improving the stability of output power and conversion efficiency.

Description

Technical Field

[0001] This invention belongs to the field of solid-state laser technology, and particularly relates to a dual-wavelength pulse group Q-switched modulated laser. Background Technology

[0002] Dual-wavelength lasers have wide applications in deep space and deep earth exploration, laser medicine, and environmental monitoring, but current technologies have significant limitations. Existing all-solid-state dual-wavelength laser output is mainly achieved through three methods: First, the fundamental frequency light and frequency-converted light oscillate simultaneously in a single-gain medium. However, this method suffers from intense gain competition, resulting in low output power and conversion efficiency. Second, output is achieved by combining the same medium's fluorescence spectral line with a frequency-selective element. Due to gain competition, efficient and stable oscillation is difficult to achieve, and delayed output is not possible. Third, the cavity-pumped method using dual-gain media avoids gain competition but can only achieve continuous laser output or novel band switching, without pulse group output. Furthermore, the resonant cavity structure design of existing dual-wavelength laser output devices is complex, making it difficult to adapt to the thermal stability requirements of dual-wavelength pulse groups and impossible to achieve multi-dimensional frequency, temporal, and spatial control of dual-wavelength pulse groups.

[0003] Therefore, there is an urgent need to design a scheme that can solve the dual-wavelength gain competition, output high repetition rate and narrow pulse width dual-wavelength pulse laser, and make the dual-wavelength pulse adjustable in the frequency domain, time domain and spatial domain. Summary of the Invention

[0004] In view of this, the present invention aims to provide a dual-wavelength pulse group Q-switched modulated laser, which introduces passive Q-switching and gain switching technology into the cavity pump structure, so that the two wavelengths are generated in independent gain media, solving the gain competition problem caused by the sharing of gain media in traditional technology, and establishing a multi-dimensional control mechanism in the frequency domain, time domain, and spatial domain.

[0005] To achieve the above objectives, the technical solution created by this invention is implemented as follows: This invention provides a dual-wavelength pulse group Q-switched laser, comprising: A pump source, which provides pump light; The resonant cavity includes an input mirror, a first gain crystal, a Q-switched crystal, a second gain crystal, and an output mirror arranged sequentially along the optical path. The first gain crystal is a quasi-three-level gain medium that generates a first-wavelength laser under the pump of a pump light. The Q-switched crystal is used to passively Q-modulate the first-wavelength laser to form a first-wavelength laser pulse output. The second gain crystal is a four-level gain medium that partially absorbs and pumps the first-wavelength laser pulse, generating a second-wavelength laser pulse under the pump of the first-wavelength laser pulse. The first-wavelength laser pulse and the second-wavelength laser pulse are output from the output mirror to form a dual-wavelength pulse group.

[0006] Preferably, the pump source is an 808nm laser diode, used to provide pump light with a wavelength of 808nm.

[0007] Preferably, the first gain crystal is an Nd:GdVO4 crystal, and the Nd:GdVO4 crystal is pumped by an 808nm pump light to generate a first wavelength laser of 912nm.

[0008] Preferably, the second gain crystal is an Nd:YVO4 crystal, and the Nd:YVO4 crystal is pumped by a first wavelength laser pulse of 912nm to generate a second wavelength laser pulse of 1064nm.

[0009] Preferably, the Q-switching crystal is Cr. 4+ YAG crystal or WS2 saturable absorber is used to pulse the first wavelength laser and as a gain switch for the second gain crystal.

[0010] Preferably, the resonant cavity is a straight cavity or an L-shaped cavity with a cavity length of 50mm to 100mm; the distance between the first gain crystal and the second gain crystal is 10mm to 20mm.

[0011] Preferably, the repetition frequency, pulse width, and delay of the dual-wavelength pulse group are adjusted by adjusting the initial transmittance of the Q-switched crystal, the length of the resonant cavity, the spacing between the first gain crystal and the second gain crystal, and the absorption efficiency of the second gain crystal for the first wavelength laser pulse.

[0012] Preferably, the repetition frequency of the first wavelength laser pulse and the second wavelength laser pulse in the dual-wavelength pulse group is 20±5kHz, the dual-pulse delay of the first wavelength laser pulse and the second wavelength laser pulse is 10±5ns, the pulse width of the first wavelength laser pulse is 50±2ns, and the pulse width of the second wavelength laser pulse is 40±2ns.

[0013] Preferably, the resonant cavity is designed with thermally stable cavity conditions based on the propagation circle diagram analysis method, so that the thermal lensing effect of the first gain crystal and the second gain crystal matches the stable region range of the resonant cavity.

[0014] Compared with the prior art, the present invention can achieve the following beneficial effects: This invention introduces passive Q-switching and gain switching technology into an intracavity pumping structure for the first time, achieving dual-wavelength pulse output with high repetition rate (20±5kHz) and narrow pulse width (approximately 50ns for 912nm and approximately 40ns for 1064nm). Furthermore, the two wavelength laser pulses are generated in two independent gain media. The first gain crystal serves as a quasi-three-level gain medium, and the second gain crystal as a four-level gain medium. Utilizing the partial absorption of the first wavelength laser pulse by the second gain crystal, the 912nm wavelength laser pulse is generated by pumping the first gain crystal with a pump light, and the 1064nm wavelength laser pulse is generated by pumping the second gain crystal with a 912nm wavelength laser pulse. This completely solves the gain competition problem caused by the shared gain medium in traditional technologies, improving the stability of output power and conversion efficiency.

[0015] Furthermore, this invention establishes a multi-dimensional control mechanism in the frequency, time, and spatial domains through passive Q-switching and gain switching, which can adjust the repetition frequency, pulse delay, and amplitude ratio of the dual-wavelength pulse group, and can flexibly adapt to various application scenarios such as deep space exploration, laser medicine, and environmental monitoring.

[0016] This invention employs a straight or L-shaped cavity, which is small in size, low in cost, and easy to integrate and apply; and achieves thermally stable cavity design based on the propagation circle diagram analysis method, ensuring stable operation of the system under the thermal lensing effect. Attached Figure Description

[0017] 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: Figure 1 This is a schematic diagram of the structure of a dual-wavelength pulse group Q-switched laser provided according to an embodiment of the present invention.

[0018] The reference numerals in the figures include: Pump source 1, coupling lens 2, input mirror 3, first gain crystal 4, Q-switching crystal 5, second gain crystal 6, output mirror 7. Detailed Implementation

[0019] 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.

[0020] 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.

[0021] 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.

[0022] 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.

[0023] The invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0024] Please see Figure 1 In one embodiment of the present invention, a dual-wavelength pulse group Q-switched laser is provided, comprising: Pump source 1, which is used to provide pump light; The resonant cavity includes an input mirror 3, a first gain crystal 4, a Q-switching crystal 5, a second gain crystal 6, and an output mirror 7 arranged sequentially along the optical path. The first gain crystal 4 is a quasi-three-level gain medium that generates a first-wavelength laser under the pump of the pump light. The Q-switching crystal 5 is used to passively Q-switch the first-wavelength laser to form a first-wavelength laser pulse output. The second gain crystal 6 is a four-level gain medium that has a partial absorption pumping effect on the first-wavelength laser pulse and generates a second-wavelength laser pulse under the pump of the first-wavelength laser pulse. The first-wavelength laser pulse and the second-wavelength laser pulse are output by the output mirror 7 to form a dual-wavelength pulse group.

[0025] Among them, the pump source 1 uses an 808nm laser diode to provide pump light with a wavelength of 808nm to continuously pump the first gain crystal 4 in the resonant cavity. The output power of the pump source 1 is adjustable, and the center wavelength is locked near 808nm, which is precisely matched with the absorption peak of the first gain crystal 4.

[0026] Since the pump light provided by pump source 1 has an initial scattering angle, a coupling lens 2 can be set between pump source 1 and resonant cavity. The pump light is focused and shaped by the coupling lens 2 to ensure that the pump light enters the resonant cavity efficiently.

[0027] Input mirror 3 and output mirror 7 are the two end mirrors of the resonant cavity. The resonant cavity can be a straight cavity or an L-shaped cavity. The pump-excited radiation photons oscillate between input mirror 3 and output mirror 7 to achieve laser output. After being shaped by coupling lens 2, pump source 1 enters the resonant cavity through input mirror 3. Input mirror 3 is a plano-concave lens. Coatings can be applied to both surfaces of input mirror 3 so that the surface of input mirror 3 closer to pump source 1 has high transmission effect for pump light of 808nm, while the surface of input mirror 3 farther from pump source 1 has high reflection effect for light of wavelengths of 808nm, 912nm, and 1064nm.

[0028] After passing through the input mirror 3, the pump light continues to enter the first gain crystal 4, which is a quasi-three-level gain medium, specifically an Nd:GdVO4 crystal. The Nd:GdVO4 crystal absorbs the pump light energy, causing particle energy transitions. The pump energy is stored in the form of population inversion, generating a first wavelength laser of 912nm. Simultaneously, the 912nm first wavelength laser also serves as the intracavity pump source for the second gain medium 6.

[0029] The 912nm wavelength laser generated by pumping the first gain crystal 4 continues to be transmitted to the Q-switched crystal 5, which can be made of Cr. 4+ YAG crystal or WS2 saturable absorber, specifically Cr in this embodiment of the invention. 4+ The YAG crystal, specifically the Q-switched crystal 5, acts as a passive Q-switching switch for the 912nm wavelength laser. It controls the periodic changes in cavity loss, converting continuous pump energy into pulsed output, thus achieving pulsed control of the 912nm wavelength laser. Furthermore, it serves as the gain switch for the second gain crystal 6. The transmittance of the Q-switched crystal 5 simultaneously determines the repetition frequency of the dual-wavelength pulse group. The initial transmittance of the Q-switched crystal 5 can be selected within the range of 20%-80%. By changing the thickness or doping concentration of the Q-switched crystal 5, the initial transmittance can be altered, thereby achieving frequency domain control. During operation, the Q-switched crystal 5 is subjected to periodically alternating high and low voltages, resulting in the periodic release of transitioned particles, forming laser pulses—the first wavelength laser pulse of 912nm.

[0030] The first wavelength laser pulse of 912nm continues to be incident on the second gain crystal 6. The second gain crystal 6 is an Nd:YVO4 crystal, which serves as the four-level gain medium for the first wavelength laser pulse of 912nm. The second gain crystal 6 has a partial absorption pumping effect on the first wavelength laser pulse of 912nm. That is, part of the first wavelength laser pulse of 912nm is transmitted through the second gain crystal 6 without being absorbed, forming the first wavelength laser pulse of 912nm in the dual-wavelength pulse group. The other part of the first wavelength laser pulse of 912nm is absorbed by the second gain crystal 6, realizing the pumping of the second gain crystal 6. When the first wavelength laser pulse of 912nm passes through the second gain crystal 6, some photons are absorbed, pumping the ions of the second gain crystal 6 to the upper energy level. Due to the extremely narrow pump pulse, the number of particles in the upper energy level accumulates rapidly within tens of nanoseconds. When the threshold is reached, stimulated emission of 1064nm begins, forming the second wavelength laser pulse of 1064nm. This process is known as the gain-switching effect, and the resulting pulse delay can be controlled by adjusting the power of the pump source 1, the doping concentration of the second gain crystal 6, or the distance d between the first gain medium 4 and the second gain crystal 6. The unabsorbed 912nm first wavelength laser pulse continues to propagate forward to the output mirror 7, with part of it being transmitted and the remainder reflected back into the cavity to maintain oscillation. The cavity surface of the output mirror 7 is coated to have a preset transmittance for 912nm and 1064nm wavelength light. The output mirror 7 outputs the portion of the 912nm first wavelength laser pulse and the 1064nm second wavelength laser pulse oscillating within the cavity, forming a dual-wavelength pulse group.

[0031] For the first gain crystal 4, the Q-switching crystal 5, and the second gain crystal 6, this embodiment of the invention employs a multi-domain control model, incorporating a quasi-three-level passive Q-switching with a "reabsorption" effect and a four-level gain switch. It integrates multi-dimensional control mechanisms in the time domain (gain switch controls pulse delay), frequency domain (passive Q-switching controls repetition frequency), and spatial domain (intracavity pump controls amplitude ratio) to fully control the dynamic behavior of particles within the cavity. By adjusting the initial transmittance of the Q-switching crystal 5, the length of the resonant cavity, the spacing between the first gain crystal 4 and the second gain crystal 6, and the absorption efficiency of the second gain crystal 6 for the first wavelength laser pulse, the repetition frequency, pulse width, and delay of the dual-wavelength pulse group are adjusted.

[0032] In the specific experimental testing process, the resonant cavity can be a straight cavity with an adjustable cavity length of 50mm to 100mm. The spacing between the first gain crystal 4 and the second gain crystal 6 is adjustable from 10mm to 20mm. The initial transmittance of the Q-switched crystal 5 is adjustable from 20% to 80%. It can achieve dual-wavelength pulse output of 912nm and 1064nm. The repetition frequency of the two wavelength pulses is 20±5kHz, the dual-pulse delay of the two wavelength pulses is 10±5ns, the pulse width of the first wavelength laser pulse is 50±2ns, and the pulse width of the second wavelength laser pulse is 40±2ns.

[0033] For the thermal stability design of the resonant cavity, this embodiment of the invention is based on the propagation circle diagram analysis method. The thermal lensing effect of the first gain crystal 4 and the second gain crystal 6 is equivalent to a lens, and an equivalent resonant cavity model with double thermal lenses is established. Through experimental measurement or theoretical calculation, the focal length variation range of the thermal lenses of the first gain crystal 4 and the second gain crystal 6 within the working pump power range is determined. Then, the thermal stability design of each component of the resonant cavity is carried out by the propagation circle diagram analysis method, so that the thermal lensing effect of the first gain crystal 4 and the second gain crystal 6 matches the stable range of the resonant cavity, ensuring the output stability of the dual-wavelength pulse group Q-switched laser when the pump power fluctuates or the thermal lensing effect changes.

[0034] 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.

[0035] 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.

[0036] 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.

[0037] 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 dual-wavelength pulse group Q-switched laser, characterized in that, include: A pump source, which provides pump light; The resonant cavity includes an input mirror, a first gain crystal, a Q-switched crystal, a second gain crystal, and an output mirror arranged sequentially along the optical path. The first gain crystal is a quasi-three-level gain medium that generates a first-wavelength laser under the pump light. The Q-switched crystal is used to passively Q-modulate the first-wavelength laser to form a first-wavelength laser pulse output. The second gain crystal is a four-level gain medium that partially absorbs and pumps the first-wavelength laser pulse, generating a second-wavelength laser pulse under the pump light. The first-wavelength laser pulse and the second-wavelength laser pulse are output from the output mirror to form a dual-wavelength pulse group.

2. The dual-wavelength pulse group Q-switched laser according to claim 1, characterized in that, The pump source is an 808nm laser diode, used to provide pump light with a wavelength of 808nm.

3. The dual-wavelength pulse group Q-switched modulated laser according to claim 2, characterized in that, The first gain crystal is an Nd:GdVO4 crystal, and the Nd:GdVO4 crystal is pumped by an 808nm pump light to generate a first wavelength laser of 912nm.

4. The dual-wavelength pulse group Q-switched modulated laser according to claim 3, characterized in that, The second gain crystal is an Nd:YVO4 crystal, and a first wavelength laser pulse of 912nm is used to pump the Nd:YVO4 crystal to generate a second wavelength laser pulse of 1064nm.

5. The dual-wavelength pulse group Q-switched modulated laser according to claim 1, characterized in that, The Q-switching crystal is Cr 4 + A YAG crystal or WS2 saturable absorber is used to pulse the first wavelength laser and to act as a gain switch for the second gain crystal.

6. The dual-wavelength pulse group Q-switched modulated laser according to claim 1, characterized in that, The resonant cavity is a straight cavity or an L-shaped cavity with a cavity length of 50mm to 100mm; the distance between the first gain crystal and the second gain crystal is 10mm to 20mm.

7. The dual-wavelength pulse group Q-switched modulated laser according to claim 1, characterized in that, By adjusting the initial transmittance of the Q-switched crystal, the length of the resonant cavity, the spacing between the first gain crystal and the second gain crystal, and the absorption efficiency of the second gain crystal for the first wavelength laser pulse, the repetition frequency, pulse width, and delay of the dual-wavelength pulse group can be adjusted.

8. The dual-wavelength pulse group Q-switched modulated laser according to claim 7, characterized in that, In the dual-wavelength pulse group, the repetition frequency of the first wavelength laser pulse and the second wavelength laser pulse is 20±5kHz, the dual-pulse delay of the first wavelength laser pulse and the second wavelength laser pulse is 10±5ns, the pulse width of the first wavelength laser pulse is 50±2ns, and the pulse width of the second wavelength laser pulse is 40±2ns.

9. The dual-wavelength pulse group Q-switched modulated laser according to claim 1, characterized in that, The resonant cavity is designed with thermal stability conditions based on the propagation circle diagram analysis method, so that the thermal lensing effect of the first gain crystal and the second gain crystal matches the stable region range of the resonant cavity.

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