All-solid-state Q-switched laser generation device and method

Abstract

The application provides a kind of all-solid-state Q-switched laser generating device and method.The device comprises: pump source, for emitting pump laser;Mother cavity, for realizing the oscillation and output of Q-switched laser with wavelength at main emission peak according to the main emission peak wavelength of the laser gain medium and the working wavelength of saturable absorber;Sub-cavity, for realizing the oscillation and output of Q-switched laser with wavelength at non-main emission peak according to the non-main emission peak wavelength of the laser gain medium.The application generates Q-switched laser at 1 μm common wavelength through mother cavity, and generates Q-switched laser of other wave band through sub-cavity;Sub-cavity can follow the state of mother cavity output Q-switched laser to realize output Q-switched laser, so that sub-cavity can realize the purpose of output Q-switched laser without saturable absorber.

Description

Technical Field

[0001] This invention relates to the field of all-solid-state Q-switched laser technology, and more particularly to an all-solid-state Q-switched laser generating device and method. Background Technology

[0002] All-solid-state Q-switched lasers are characterized by their compact structure, low cost, and high efficiency. They can output pulsed lasers with narrow pulse widths, high peak power, high repetition rates, and excellent beam quality, and are widely used in medical, military, industrial, and scientific research fields. Specifically, Q-switched lasers in different wavelength bands have their own application areas. For example, 1.0μm wavelength lasers can be used for metal cutting and welding; 2.0μm wavelength lasers can be used for cutting, welding, and engraving transparent plastics; 1.9-2.0μm wavelength lasers can be used for the removal of lesions such as tumors and polyps; 2.8-3.3μm wavelength lasers can be used for atmospheric molecule (haze) detection; and 3.0-5.0μm wavelength lasers can be used for space communication, etc. In particular, multi-band all-solid-state Q-switched lasers can simultaneously output multiple Q-switched lasers of different wavelengths, such as 1.0μm, 1.3μm, 1.5μm, 1.9μm, 2.0μm, and 3.0μm. These can be applied not only to various fields but also to terahertz generation, differential absorption lidar, wavelength division multiplexing lidar, laser ranging, and gas detection. Therefore, multi-band all-solid-state Q-switched lasers have become a research hotspot.

[0003] Currently, the main technologies for achieving Q-switching are active Q-switching and passive Q-switching. Active Q-switching relies primarily on acousto-optic or electro-optic Q-switching devices, all of which require additional control modules, undoubtedly increasing system complexity and cost. Passive Q-switching, on the other hand, only requires the effect of the saturable absorber itself to achieve Q-switching, eliminating the need for additional control modules. Therefore, passive Q-switching reduces system complexity, improves system compactness, and lowers costs. It is well known that the wavelength of Q-switched laser obtained using passive Q-switching technology is inextricably linked to the operating wavelength of the saturable absorber. Common commercially available saturable absorbers include: Cr:YAG crystals, with an operating wavelength of 1.064 μm; and semiconductor saturable absorbers, with operating wavelengths of 1.03 μm, 1.064 μm, 1.34 μm, 1.55 μm, 2.0 μm, and 2.8 μm, etc. However, since the operating wavelengths of these commercially available saturable absorbers are discrete, a single saturable absorber can only achieve Q-switching within one band, and it is impossible to achieve dual-band or even multi-band Q-switching with a single saturable absorber. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the prior art and provide a method and apparatus for achieving dual-band Q-switching using a single saturable absorber.

[0005] An all-solid-state Q-switched laser generating device, comprising:

[0006] Pump source, used to provide pump laser for the mother resonant cavity and the daughter resonant cavity;

[0007] The mother resonant cavity is used to realize the oscillation and output of Q-switched laser with the wavelength located at the main emission peak based on the main emission peak wavelength of the laser gain medium and the working wavelength of the saturable absorber;

[0008] The sub-resonant cavity is used to realize the oscillation and output of Q-switched laser with wavelength located at the non-main emission peak according to the non-main emission peak wavelength of the laser gain medium.

[0009] Furthermore, in the all-solid-state Q-switched laser generating device described above, the mother resonant cavity includes: a pump mirror, a laser gain medium, a saturable absorber, and a first output mirror;

[0010] The pump mirror, laser gain medium, saturable absorber, and first output mirror are arranged in sequence at the same height and coaxially.

[0011] Furthermore, in the all-solid-state Q-switched laser generating device described above, the pump mirror is used to transmit the pump laser and reflect the gain laser; the pump mirror is coated with a dielectric film having a certain transmittance to the pump laser and a dielectric film having a certain reflectance to the gain laser; the gain laser includes a gain laser with a wavelength located at the main emission peak and a gain laser with a wavelength located at a non-main emission peak.

[0012] Furthermore, in the all-solid-state Q-switched laser generating device described above, the first output mirror is used to reflect the gain laser with a wavelength located at the main emission peak and output the laser with a wavelength located at the main emission peak.

[0013] The first output mirror is coated with a dielectric film that has a certain transmittance for the gain laser whose wavelength is located at the main emission peak.

[0014] Furthermore, in the all-solid-state Q-switched laser generating device described above, the laser gain medium is used to absorb the pump laser and pump the ground-state particles to the upper energy level to generate the gain laser; the gain laser includes a gain laser with a wavelength located at the main emission peak and a gain laser with a wavelength located at a non-main emission peak.

[0015] Furthermore, in the all-solid-state Q-switched laser generating device described above, the saturable absorber is used to put the gain laser with a wavelength located at the main emission peak into a Q-switched state, and the operating wavelength of the saturable absorber is located at the main emission peak position of the laser gain medium.

[0016] Furthermore, in the all-solid-state Q-switched laser generating device described above, the sub-resonant cavity includes:

[0017] Pump mirror, laser gain medium, reflector, second output mirror; the reflector is tilted at 45 degrees.

[0018] The reflector is placed between the laser gain medium and the saturable absorber, forming a 45° angle with the gain laser emitted from the laser gain medium; the second output mirror is placed at the output end of the gain laser reflected by the reflector, perpendicular to the gain laser reflected by the reflector.

[0019] The reflector is used to receive the gain laser and split the gain laser into two parts: one part is the gain laser with a wavelength located at the main emission peak, and the other part is the gain laser with a wavelength located at a non-main emission peak; the reflector transmits the gain laser with a wavelength located at the main emission peak to the first output mirror, and at the same time reflects the gain laser with a wavelength located at a non-main emission peak to the second output mirror;

[0020] The second output mirror is used to reflect the gain laser with a wavelength located at a non-main emission peak and output the laser with a wavelength located at a non-main emission peak.

[0021] Furthermore, in the all-solid-state Q-switched laser generating device described above, the reflector is coated with a dielectric film having a certain transmittance for the gain laser with wavelengths located at the main emission peak and a dielectric film having a certain reflectance for the gain laser with wavelengths located at non-main emission peaks.

[0022] The second output mirror is coated with a dielectric film that has transmittance for gain laser light with wavelengths located at non-main emission peaks.

[0023] Furthermore, the all-solid-state Q-switched laser generating device described above includes multiple sub-resonant cavities, and multi-band Q-switched laser output is achieved through the main resonant cavity and the multiple sub-resonant cavities.

[0024] A method for generating an all-solid-state Q-switched laser includes:

[0025] Pump laser is emitted from a pump source;

[0026] The emitted pump laser is incident into a mother resonant cavity composed of a pump mirror, a laser gain medium, a saturable absorber, and a first output mirror, and a Q-switched laser with a wavelength located at the main emission peak is output through the mother resonant cavity.

[0027] A reflector is inserted between the laser gain medium and the saturable absorber, with the reflector forming a 45° angle with the gain laser emitted from the laser gain medium; the reflector reflects the gain laser whose wavelength is located at a non-main emission peak.

[0028] A second output mirror is added to the output end of the reflector, and the sub-resonant cavity is formed by the second output mirror, the pump mirror, the laser gain medium, and the reflector. By adjusting the position and angle of the second output mirror, the sub-resonant cavity outputs Q-switched laser with a wavelength located at the non-main emission peak.

[0029] The all-solid-state Q-switched laser generation device and method provided in this application utilize a commercially available saturable absorber to generate a common wavelength Q-switched laser at 1 μm in a mother resonant cavity, and generate Q-switched lasers of other wavelengths in a sub-resonant cavity. The sub-resonant cavity can follow the state of the Q-switched laser output from the mother resonant cavity to achieve Q-switched laser output. It can achieve dual-band Q-switching simply by controlling the cavity losses of the gain laser with wavelengths located at the main emission peak and the gain laser with wavelengths located at non-main emission peaks in the mother resonant cavity and the sub-resonant cavity, respectively. Thus, the sub-resonant cavity does not need to be saturable absorber to achieve the purpose of Q-switched laser output, and the device has a simple structure. Attached Figure Description

[0030] Figure 1 This is a schematic diagram of the dual-band all-solid-state Q-switched laser system provided by the present invention;

[0031] Figure 2 The graphs show the changes over time for the number of energy level particles (a), the number of particles in the saturable absorber (b), the number of photons at 1.06 μm (c), and the number of photons at 1.34 μm (d) on the laser gain medium when R1 = 97.0% and R2 = 99.5%.

[0032] Figure 3 The graphs show the changes over time for the number of energy level particles (a), the number of particles in the saturable absorber (b), the number of photons at 1.06 μm (c), and the number of photons at 1.34 μm (d) on the laser gain medium when R1 = 94.0% and R2 = 98.7%.

[0033] Figure 4 The graphs show the changes over time for the number of energy level particles (a), the number of particles in the saturable absorber (b), the number of photons at 1.06 μm (c), and the number of photons at 1.34 μm (d) on the laser gain medium when R1 = 90.0% and R2 = 97.7%.

[0034] Figure 5 The graphs show the changes over time for the number of energy level particles (a), the number of particles in the saturable absorber (b), the number of photons at 1.06 μm (c), and the number of photons at 1.34 μm (d) on the laser gain medium when R1 = 85.0% and R2 = 96.4%.

[0035] Figure 6 This is a schematic diagram of a three-band all-solid-state Q-switched laser system.

[0036] Figure 7 The graphs show the changes over time for the number of energy level particles (a), the number of particles in the saturable absorber (b), the number of photons at 1.06 μm (c), the number of photons at 1.34 μm (d), and the number of photons at 0.94 μm (e) in the laser gain medium when R1 = 97.0%, R2 = 99.5%, and R3 = 99.7%.

[0037] Figure 8 The graphs show the changes over time for the number of energy level particles (a), the number of particles in the saturable absorber (b), the number of photons at 1.06 μm (c), the number of photons at 1.34 μm (d), and the number of photons at 0.94 μm (e) on the laser gain medium when R1 = 94.0%, R2 = 98.7%, and R3 = 98.9%.

[0038] Figure 9 The graphs show the changes over time for the number of energy level particles (a), the number of particles in the saturable absorber (b), the number of photons at 1.06 μm (c), the number of photons at 1.34 μm (d), and the number of photons at 0.94 μm (e) in the laser gain medium when R1 = 90.0%, R3 = 97.7%, and R2 = 97.9%.

[0039] Figure 10 The graphs show the time-varying numbers of energy level particles (a), saturable absorber particles (b), 1.06 μm photons (c), 1.34 μm photons (d), and 0.94 μm photons (e) in the laser gain medium when R1 = 85.0%, R3 = 96.4%, and R2 = 96.5%.

[0040] Figure 11 This is a schematic diagram of a four-band all-solid-state Q-switched laser system. Detailed Implementation

[0041] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention are described clearly and completely below. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0042] Figure 1 This is a schematic diagram of the dual-band all-solid-state Q-switched laser system provided by the present invention, as shown below. Figure 1 As shown, the device includes:

[0043] Pump source 1 is used to emit pump laser, thereby providing excitation for the mother resonant cavity and the daughter resonant cavity;

[0044] The mother resonant cavity is used to realize the oscillation and output of Q-switched laser with wavelength located at the main emission peak based on the main emission peak wavelength of the laser gain medium and the operating wavelength of the saturable absorber.

[0045] The sub-resonant cavity is used to realize the oscillation and output of Q-switched laser with wavelength located at the non-main emission peak according to the non-main emission peak wavelength of the laser gain medium.

[0046] Specifically, the mother resonant cavity is used to realize the oscillation and output of Q-switched laser with wavelengths located at the main emission peak. Its operation depends primarily on the wavelength of the main emission peak of the laser gain medium and the operating wavelength of the saturable absorber; the operating wavelength of the saturable absorber must match the main emission peak. The sub-resonant cavity is used to realize the oscillation and output of Q-switched laser with wavelengths located at non-main emission peaks. Its operation depends primarily on the wavelength of the non-main emission peak of the laser gain medium. The device provided by this invention achieves the output of a dual-band Q-switched laser by controlling the photon losses of the gain laser with wavelengths located at the main emission peak and non-main emission peak within the mother and sub-resonant cavities, respectively.

[0047] The device provided in this application can control the reflectivity of the output mirrors of the mother and daughter resonators to make the form of the laser output from the daughter resonator follow that of the mother resonator. That is, when the mother resonator outputs a Q-switched laser, the daughter resonator also outputs a Q-switched laser, thereby realizing the output of a dual-band Q-switched laser.

[0048] Furthermore, such as Figure 1 As shown, the mother resonant cavity includes: a pump mirror 2, a laser gain medium 3, a saturable absorber 4, and a first output mirror 5; the pump mirror 2, laser gain medium 3, saturable absorber 4, and first output mirror 5 are arranged in sequence at the same height and coaxially. The sub-resonant cavity includes: a pump mirror 2, a laser gain medium 3, a reflector 6, and a second output mirror 7; the reflector 6 is tilted at 45 degrees. The reflector 6 is placed between the laser gain medium 3 and the saturable absorber 4, forming a 45° angle with the gain laser; the second output mirror 7 is placed at the laser output end of the reflector 6, forming a 45° angle with the reflector 6.

[0049] Specifically, this invention uses a resonant cavity and a laser gain medium as the mother resonant cavity and the daughter resonant cavity, respectively. The pump source provides excitation for the mother and daughter resonant cavities (and excitation for the laser gain medium). The pump mirror 2 has two functions: firstly, it allows the pump laser to pass through and be incident on the laser gain medium, providing excitation for the laser gain medium; secondly, it allows the gain laser to travel back and forth multiple times within the resonant cavity, passing through the laser gain medium each time, thereby amplifying the gain laser and achieving the purpose of outputting laser light. The pump mirror 2 serves as one end mirror of the mother and daughter resonant cavities, used for transmitting the pump laser and reflecting the gain laser. To achieve the function of transmitting the pump laser and reflecting the gain laser, the pump mirror 2 is coated with a narrow-band dielectric film with high transmittance for the pump laser and a broadband dielectric film with high reflectivity for the gain laser (including the emission spectrum range of the laser gain medium). The pump mirror 2 reflects the gain laser with wavelengths located at the main emission peak and the gain laser with wavelengths located at non-main emission peaks.

[0050] The laser gain medium 3 is used to absorb the pump laser, pump the ground-state particles to the upper energy level, and generate and emit gain laser.

[0051] The operating wavelength of the saturable absorber 4 is located at the main emission peak of the laser gain medium 3, and is used to generate Q-switched laser with the wavelength located at the main emission peak.

[0052] The first output mirror 5 serves as the other end mirror of the mother resonant cavity, forming the mother resonant cavity with the pump mirror 2. It is used to reflect the gain laser with a wavelength located at the main emission peak and output the laser with a wavelength located at the main emission peak. In order for the first output mirror 5 to have the function of reflecting the gain laser with a wavelength located at the main emission peak and outputting the laser with a wavelength located at the main emission peak, the first output mirror 5 is coated with a narrow-band dielectric film with a certain transmittance to the gain laser with a wavelength located at the main emission peak.

[0053] The working principle of the mother resonant cavity is as follows: Pump source 1 emits pump laser, which is incident on laser gain medium 3 through pump mirror 2. Laser gain medium 3 absorbs pump laser and emits gain laser. Gain laser first incident on pump mirror 2, which receives and reflects gain laser. The reflected gain laser then passes through laser gain medium 3 and saturable absorber and is incident on first output mirror 5. First output mirror 5 receives gain laser and only reflects gain laser with wavelength located at the main emission peak, so that gain laser with wavelength located at the main emission peak returns to pump mirror 2 through saturable absorber 4 and laser gain medium 3, forming a "I" type closed loop. After multiple round trips, gain laser with wavelength located at the main emission peak is output through first output mirror 5.

[0054] The reflector 6 receives the gain laser and splits it into two parts: one part is the gain laser with a wavelength located at the main emission peak, and the other part is the gain laser with a wavelength located at a non-main emission peak. The reflector 6 transmits the gain laser with a wavelength located at the main emission peak to the first output mirror 5, and reflects the gain laser with a wavelength located at a non-main emission peak to the second output mirror 7. The reflector 6 is coated with a dielectric film that is transmissive to the gain laser with a wavelength located at the main emission peak, and the dielectric film is reflective to the gain laser with a wavelength located at a non-main emission peak.

[0055] In this invention, the operating conditions of the reflector are as follows: the angle between the incident laser and the reflected laser is 90 degrees, wherein the incident laser is equivalent to the gain laser emitted by the laser gain medium, and the reflected laser is equivalent to the gain laser emitted by the reflector; or the incident laser and the reflected laser can be interchanged. When the angle between the incident laser and the reflected laser of the reflector 6 is 90 degrees, the loss of the reflected laser is minimized, which is beneficial to reducing laser loss.

[0056] The second output mirror 7 serves as the other end mirror of the sub-resonant cavity, forming a sub-resonant cavity with the pump mirror 1. It is used to reflect the gain laser with a wavelength located at the non-main emission peak and output the laser with a wavelength located at the non-main emission peak. The second output mirror 7 is coated with a narrow-band dielectric film with a certain transmittance for the gain laser with a wavelength located at the non-main emission peak, and the second output mirror 7 is perpendicular to the gain laser reflected by the reflecting mirror 6.

[0057] The working principle of the sub-resonator is as follows: Pump source 1 emits pump laser, which is incident on laser gain medium 3 through pump mirror 2. Laser gain medium 3 absorbs pump laser and emits gain laser. Gain laser is first incident on pump mirror 2, which receives and reflects the gain laser. The reflected gain laser is then incident on mirror 6 through laser gain medium 3. Mirror 6 transmits the gain laser with wavelength located at the main emission peak to the first output mirror 5 and reflects the gain laser with wavelength located at the non-main emission peak to the second output mirror 7. The second output mirror 7 then returns the gain laser with wavelength located at the non-main emission peak along the original path, that is, through mirror 6 and laser gain medium 3, back to pump mirror 2, forming a "7"-shaped closed loop. The gain laser with wavelength located at the non-main emission peak is finally output through the second output mirror 7 after multiple round trips.

[0058] This application constructs a mother-daughter resonator using a mother resonator and a daughter resonator, sharing a pump mirror 2 and a laser gain medium 3. The lasers from both resonators share the upper-level particle inversion number of the laser gain medium 3. The state of the laser output from the daughter resonator changes with the state of the laser output from the mother resonator; that is, when the mother resonator operates in Q-switched mode, it excites the daughter resonator to operate in Q-switched mode. The wavelength of the Q-switched laser output from the mother resonator depends on the main emission peak wavelength of the laser gain medium 3 and the operating wavelength of the saturable absorber 4. The wavelength of the Q-switched laser output from the daughter resonator depends only on the positions of the other emission peak wavelengths of the laser gain medium 3 and is independent of the operating wavelength of the saturable absorber 4. The transmittance of the first output mirror 5 and the second output mirror 7 is negatively correlated with the ratio of the emission cross-sections of the main emission peak gain laser to those of other emission peak gain lasers. The key factor for the simultaneous operation of the mother and daughter resonators and the output of Q-switched lasers in different wavelength bands is controlling the laser loss in the mother and daughter resonators, i.e., controlling the transmittance (transmittance ratio) of the output mirrors.

[0059] The theoretical model is as follows:

[0060]

[0061]

[0062]

[0063]

[0064] In the formula, subscript 1 represents the parameters of the mother resonant cavity, and subscript 2 represents the parameters of the child resonant cavity; N is the intracavity photon number density; g N represents the upper energy level particle number density of the laser gain medium. s and N s0 These represent the ground-state particle number density and the initial particle number density of a saturable absorber, respectively; σ g σ is the stimulated emission cross section of the laser gain medium; s The absorption cross section of a saturable absorber; γ g γ is the decay rate of the energy level particle density on the laser gain medium; s The decay rate of the particle number density of the saturable absorber; l g The optical transmission length of the laser gain medium; l s t is the light transmission length of the saturable absorber; c is the speed of light; R is the reflectivity of the output mirror; L is the round-trip photon loss within the cavity; r denoted as the intracavity photon round-trip time; P is the pump rate. By changing the reflectivity (which is also the transmittance, transmittance = 1 - reflectivity) of the output mirror, the mother and child resonators can simultaneously operate in Q-switched mode, outputting dual-band Q-switched laser light.

[0065] The device provided in this application achieves dual-band Q-switched laser output by controlling the intracavity losses of the gain lasers with wavelengths located at the main emission peak and non-main emission peak in the mother resonant cavity and the sub-resonant cavity, respectively. Controlling the intracavity losses of the gain lasers at the two wavelengths is actually achieved by controlling the reflectivity of the first output mirror 5 and the second output mirror 7. The advantage of this control method is that it does not require controlling the mode (size) matching degree of the two wavelength gain lasers and the pump laser in the gain medium. Therefore, the structural requirements for the resonant cavity are not high, allowing the device provided in this application to achieve dual-band Q-switched laser output using only the simplest flat-flat cavity. Furthermore, the advantage of a flat-flat cavity is that its cavity length can be arbitrarily adjusted, thus enabling the entire device to be miniaturized and integrated.

[0066] The dual-band all-solid-state Q-switched laser system provided in this application employs a master-slave resonator to generate dual-wavelength Q-switched lasers. Its key features are: the lasers in both the master and slave resonators share the upper-level particle inversion number of the laser gain medium; the state of the output laser from the slave resonator changes with the state of the output laser from the master resonator, meaning that when the master resonator operates in Q-switched mode, it excites the slave resonator to operate in Q-switched mode; the wavelength of the Q-switched laser output from the master resonator depends on the position of the main emission peak wavelength of the laser gain medium and the operating wavelength of the saturable absorber, typically placed at a common wavelength; the wavelength of the Q-switched laser output from the slave resonator depends only on the positions of the other emission peak wavelengths of the laser gain medium and is independent of the operating wavelength of the saturable absorber. Since the emission cross-section of the laser gain medium varies significantly at different wavelengths, simultaneously outputting dual-wavelength Q-switched lasers requires controlling the intracavity losses of the gain lasers at the two wavelengths in the master and slave resonators, respectively.

[0067] Specifically, this application utilizes a shared laser gain medium in a parent-child resonant cavity. By pumping a laser, particles in the ground state of the laser gain medium are transported to the excited state, resulting in inverted particles in the excited state. These particles transition to the ground state and emit laser light. The excited state itself splits into multiple energy levels, each corresponding to a different wavelength of laser radiation, potentially forming a multi-band laser. The sum of the number of particles in each energy level equals the total number of inverted particles, meaning that if one energy level has more particles, other energy levels will have fewer particles; however, under a fixed pumping condition, the total number of particles in the excited state is constant. The number of inverted particles in each energy level, i.e., the intensity of the laser output in different wavelength bands, is related to the cavity loss of the parent-child resonant cavity. The lower the cavity loss, the greater the output laser intensity under a fixed pumping condition. The morphology of the inverted particles, i.e. whether the output laser is a continuous laser or a Q-switched laser, is related to the form of the laser output from the mother resonator. If the mother resonator outputs a continuous laser, the daughter resonator can only output a continuous laser. Only when the mother resonator outputs a Q-switched laser can the daughter resonator output a Q-switched laser. In other words, only when the mother resonator outputs a Q-switched laser can the form of the laser output from the daughter resonator follow the mother resonator and also output a Q-switched laser, thus realizing the output of a dual-band Q-switched laser.

[0068] The dual-band all-solid-state Q-switched laser system structure provided in this application utilizes a commercially available saturable absorber to generate a Q-switched laser at a common wavelength of 1μm through a mother resonator. The sub-resonator follows the state of the Q-switched laser output from the mother resonator to achieve the output of the Q-switched laser. This allows the sub-resonator to achieve Q-switched laser output without the need for saturable absorption. The dual-band Q-switched laser can be achieved simply by controlling the intracavity losses of gain lasers with wavelengths located at two different emission peaks in the mother and sub-resonators, respectively. Furthermore, the structure of this device is simple.

[0069] Furthermore, there are currently no commercially available saturable absorbers that can operate at mid-infrared wavelengths (3-5 μm), which limits the realization of mid-infrared Q-switched lasers. The device provided in this application, however, can achieve Q-switched laser output in the 1- or 2-micron band by establishing a mother resonant cavity (because there are commercially available saturable absorbers with operating wavelengths at 1 or 2 microns), and can achieve Q-switched laser output in the 3-5 micron band by establishing a sub-resonant cavity. This allows for the output of mid-infrared (3-5 μm) Q-switched lasers even without a commercially available mid-infrared (3-5 μm) saturable absorber.

[0070] Figures 2-5This illustrates the formation process of a dual-band Q-switched laser. R1 represents the reflectivity of the output mirror in the mother resonator, and R2 represents the reflectivity of the output mirror in the daughter resonator. (a) shows the change in the number of particles in the excited state (total upper energy level) of the laser gain medium over time. As can be seen from the figure, a periodic change occurs over time: first, the number of photons increases (accumulating photon count; at this point, the resonator is in a high-loss state (determined by the saturable absorber), with no laser output); then, the number of photons decreases (the photon count accumulates to a certain level, the resonator is in a low-loss state (determined by the saturable absorber), the photon count decreases, and Q-switched laser output occurs); then, the number of photons continues to accumulate (no light output); then, the number of photons decreases again (Q-switched laser output occurs again), and this cycle repeats. The decrease in the number of particles indicates that a large number of particles have transitioned from the excited state to the ground state, at which point Q-switched laser output occurs. (b) The graph shows the change in the number of particles in the saturable absorber over time. As can be seen, a periodic pattern emerges: the number first increases (the resonant cavity is in a high-loss state), then decreases (the cavity loss suddenly decreases, resulting in Q-switched laser output), then increases again (the resonant cavity is in a high-loss state again), then decreases again (the cavity loss suddenly decreases, resulting in Q-switched laser output again), and so on. The decrease in the number of particles indicates that the saturable absorber causes a sudden decrease in cavity loss, at which point Q-switched laser output occurs. (c) The graph shows the trend of the intensity of the laser output from the mother resonant cavity over time. This not only confirms that the output laser is Q-switched, but also shows that the Q-switched laser output from the resonant cavity occurs when the number of particles in the excited state of the laser gain medium and the number of particles in the saturable absorber decreases. This also confirms that the output laser satisfies the principle of Q-switched laser operation. (d) The graph shows the trend of the intensity of the laser output from the sub-resonant cavity over time. It can be seen that the Q-switched laser output from the sub-resonator is synchronized with the Q-switched laser output from the mother resonator, that is, it occurs when the number of excited-state particles in the laser gain medium and the number of saturable absorber particles decrease. This reflects that the state of the sub-resonator follows the state of the mother resonator. Figures 2-5 The differences lie in the reflectivity of the output mirrors of the mother and child resonators and the intensity of the laser output from the mother and child resonators. Figures 2-5 It can be seen that dual-band Q-switched lasers can be achieved by controlling the reflectivity of the output mirror.

[0071] Furthermore, the all-solid-state Q-switched laser generating device provided by the present invention includes multiple sub-resonant cavities, and multi-band Q-switched laser output is realized through the main resonant cavity and the multiple sub-resonant cavities.

[0072] Specifically, the device includes two, three, or more sub-resonant cavities, which are used to realize the output of two-band, three-band, four-band, or multi-band Q-switched lasers, for example:

[0073] This invention also provides a three-band all-solid-state Q-switched laser generating device. Figure 6This is a schematic diagram of a three-band all-solid-state Q-switched laser system, as shown below. Figure 6 As shown, the three-band all-solid-state Q-switched laser generator includes a mother resonant cavity and two sub-resonant cavities; the mother resonant cavity outputs one band, and the two sub-resonant cavities each output two bands, so the three-band all-solid-state Q-switched laser generator outputs a total of three bands of Q-switched laser.

[0074] Similarly, the present invention also provides a four-band all-solid-state Q-switched laser generating device. Figure 11 This is a schematic diagram of a four-band all-solid-state Q-switched laser system, as shown below. Figure 11 As shown, the four-band all-solid-state Q-switched laser generator includes a mother resonant cavity and three sub-resonant cavities; the mother resonant cavity outputs one band, and the three sub-resonant cavities each output three bands, so the four-band all-solid-state Q-switched laser generator outputs a total of four bands of Q-switched laser.

[0075] Similarly, the present invention can also provide a multi-band all-solid-state Q-switched laser system that can generate N+1 bands of Q-switched laser; wherein the N bands of Q-switched laser are generated through sub-resonant cavities, and the Q-switched laser of one band is generated through a mother resonant cavity. Figures 7-10 This describes the formation process of a three-band Q-switched laser. Figures 7-10 The difference lies in the different reflectivity of the output mirrors of the mother and child resonant cavities, through Figures 7-10 It can be seen that three-band Q-switched lasers can be achieved by controlling the reflectivity of the output mirrors of the mother resonator and different sub-resonators.

[0076] This invention also provides a method for generating an all-solid-state Q-switched laser, comprising the following steps:

[0077] Step 1: A laser is emitted through pump source 1. The laser is incident on laser gain medium 3 through pump mirror 2, which provides excitation to the mother resonant cavity composed of pump mirror 2, laser gain medium 3, saturable absorber 4 and first output mirror 5, so that the mother resonant cavity works normally and outputs Q-switched laser with wavelength located at the main emission peak of laser gain medium 3 through the mother resonant cavity.

[0078] Step 2: Insert a reflector 6 between the laser gain medium 3 and the saturable absorber 4. The reflector 6 forms a 45° angle with the gain laser emitted from the laser gain medium 3. The reflector 6 reflects the gain laser whose wavelength is located at the non-main emission peak.

[0079] Step 3: Add a second output mirror 7, which, together with the second output mirror 7, the pump mirror 2, the laser gain medium 3, and the reflector 6, forms a sub-resonant cavity; the second output mirror 7 is placed at the laser output end of the reflector 6, forming a 45° angle with the reflector 6;

[0080] Step 4: Adjust the position and angle of the second output mirror 7 to enable the sub-resonant cavity to work normally and output Q-switched laser with a wavelength located at the non-main emission peak of the laser gain medium 3 through the sub-resonant cavity.

[0081] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. An all-solid-state Q-switched laser generating device, characterized in that, include: Pump source (1) is used to provide pump laser for the mother resonant cavity and the daughter resonant cavity; The mother resonant cavity is used to realize the oscillation and output of Q-switched laser with the wavelength located at the main emission peak based on the main emission peak wavelength of the laser gain medium and the working wavelength of the saturable absorber; Sub-resonant cavity, used to realize the oscillation and output of Q-switched laser with wavelength located at the non-main emission peak according to the non-main emission peak wavelength of the laser gain medium; The mother resonant cavity includes: a pump mirror (2), a laser gain medium (3), a saturable absorber (4), and a first output mirror (5); The pump mirror (2), laser gain medium (3), saturable absorber (4), and first output mirror (5) are arranged in sequence with equal height and coaxiality. The sub-resonant cavity includes: Pump mirror (2), laser gain medium (3), reflector (6), second output mirror (7); the reflector (6) is tilted at 45 degrees; The reflector (6) is placed between the laser gain medium (3) and the saturable absorber (4), forming a 45° angle with the gain laser emitted from the laser gain medium (3); the second output mirror (7) is placed at the output end of the gain laser reflected by the reflector (6), perpendicular to the gain laser reflected by the reflector (6); The reflector (6) is used to receive the gain laser and divide the gain laser into two parts: one part is the gain laser with a wavelength located at the main emission peak and the other part is the gain laser with a wavelength located at a non-main emission peak; the reflector (6) transmits the gain laser with a wavelength located at the main emission peak to the first output mirror (5) and reflects the gain laser with a wavelength located at a non-main emission peak to the second output mirror (7). The second output mirror (7) is used to reflect the gain laser with a wavelength located at the non-main emission peak and output the laser with a wavelength located at the non-main emission peak; It includes multiple sub-resonant cavities, and multi-band Q-switched laser output is achieved through the main resonant cavity and the multiple sub-resonant cavities.

2. The all-solid-state Q-switched laser generating device according to claim 1, characterized in that, The pump mirror (2) is used to transmit pump laser and reflect gain laser; the pump mirror (2) is coated with a dielectric film with a certain transmittance to the pump laser and a dielectric film with a certain reflectance to the gain laser; the gain laser includes a gain laser with a wavelength located at the main emission peak and a gain laser with a wavelength located at a non-main emission peak.

3. The all-solid-state Q-switched laser generating device according to claim 1, characterized in that, The first output mirror (5) is used to reflect the gain laser with a wavelength located at the main emission peak and output the laser with a wavelength located at the main emission peak; The first output mirror (5) is coated with a dielectric film that has a certain transmittance for the gain laser whose wavelength is located at the main emission peak.

4. The all-solid-state Q-switched laser generating device according to claim 1, characterized in that, The laser gain medium (3) is used to absorb the pump laser and pump the ground state particles to the upper energy level to generate the gain laser; the gain laser includes a gain laser with a wavelength located at the main emission peak and a gain laser with a wavelength located at a non-main emission peak.

5. The all-solid-state Q-switched laser generating device according to claim 1, characterized in that, The saturable absorber (4) is used to put the gain laser with the wavelength located at the main emission peak into a Q-switched state. The operating wavelength of the saturable absorber (4) is located at the main emission peak position of the laser gain medium (3).

6. The all-solid-state Q-switched laser generating device according to claim 1, characterized in that, The reflector (6) is coated with a dielectric film that has a certain transmittance for the gain laser with wavelength located at the main emission peak and a dielectric film that has a certain reflectance for the gain laser with wavelength located at the non-main emission peak. The second output mirror (7) is coated with a dielectric film that has transmittance for the gain laser whose wavelength is located at the non-main emission peak.

7. A method for generating an all-solid-state Q-switched laser, characterized in that, include: Pump laser is emitted through pump source (1); The emitted pump laser is incident into a mother resonant cavity composed of a pump mirror (2), a laser gain medium (3), a saturable absorber (4), and a first output mirror (5), and a Q-switched laser with a wavelength located at the main emission peak is output through the mother resonant cavity; A reflector (6) is inserted between the laser gain medium (3) and the saturable absorber (4), and the reflector (6) forms a 45° angle with the gain laser emitted from the laser gain medium (3); the reflector (6) reflects the gain laser whose wavelength is located at the non-main emission peak; A second output mirror (7) is added to the output end of the reflector (6), and the sub-resonant cavity is formed by the second output mirror (7), the pump mirror (2), the laser gain medium (3), and the reflector (6); by adjusting the position and angle of the second output mirror (7), the Q-switched laser with the output wavelength located at the non-main emission peak of the sub-resonant cavity is made to be emitted.

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