A mJ-level pulsed laser generating device

Abstract

This invention discloses a mJ-level pulsed laser generation device, comprising a pump laser, a collimating mirror, a focusing mirror, an input mirror, a gain medium, and an output mirror arranged sequentially. The pump laser outputs a divergent pump laser, the collimating mirror converts the divergent pump laser into a collimated laser, the focusing mirror converts the collimated laser into a focused laser, and the focused laser is transmitted to the gain medium through the input mirror. The gain medium amplifies the focused laser to obtain an amplified laser beam. The gain medium is a crystal doped with rare-earth ions. The side of the output mirror facing the gain medium is coated with an anti-saturable absorption material including a ground state energy level, an excited state energy level, and higher energy levels. The band gap between the excited state energy level and the ground state energy level is zero, and there is a band gap with the higher energy levels that is smaller than the target energy. The output mirror outputs a target energy pulsed laser generated by passive Q-switching based on the anti-saturable absorption material. This invention achieves the generation of high-energy pulses by combining an anti-saturable absorption material and a suitable gain medium.

Description

Technical Field

[0001] This invention belongs to the field of energy pulse technology, specifically relating to a mJ-level pulsed laser generating device. Background Technology

[0002] Pulsed lasers, especially high-energy pulsed lasers, have important applications in information transmission and laser shock enhancement. Currently, obtaining high-energy pulsed lasers is mainly achieved through pulsed laser amplification, with the seed laser playing a decisive role in the overall amplification effect. If the seed laser can achieve higher energy, the overall amplification order and complexity can be reduced in subsequent amplification stages. Furthermore, the shape of the pulse may deform during amplification, making the direct generation of a high-energy pulsed laser source crucial. Pulse energy depends on both the average output power and the pulse repetition frequency of the laser. Improving the average output power mainly involves increasing the efficiency of the pump laser, increasing the gain of the gain medium, and improving the heat dissipation of the gain medium. Reducing the laser repetition frequency primarily involves using low-repetition-rate active modulation devices (acousto-optic Q-switching, electro-optic Q-switching, etc.) or high-saturation-flux rare-earth ion-doped crystals as absorbers in passive Q-switching systems. The Q-value represents the laser loss and is an important method for generating pulsed lasers. Q-switching can achieve narrower pulse widths and higher peak power compared to electrical control, and lower repetition rates compared to mode-locked lasers. However, the repetition rates of pulsed lasers obtained by various Q-switching methods are typically in the kHz range, and the pulse energies are usually in the μJ or even nJ range, while the single-pulse energies of current high-energy lasers rarely reach the mJ range.

[0003] Therefore, providing a device and method capable of generating pulsed lasers in the mJ range is an urgent technical problem that needs to be solved. Summary of the Invention

[0004] In view of the shortcomings of the prior art, the purpose of this invention is to provide a mJ-level pulsed laser generating device, which solves the problem of low pulse energy levels in the prior art.

[0005] This application discloses a mJ-level pulsed laser generation device. The device includes a pump laser, a collimating mirror, a focusing mirror, an input mirror, a gain medium, and an output mirror arranged sequentially. The pump laser is used to output a divergent pump laser with divergent characteristics. The collimating mirror is used to convert the divergent pump laser into a collimated laser. The focusing mirror is used to convert the collimated laser into a focused laser. The focused laser is transmitted to the gain medium through the input mirror. The gain medium is used to amplify the focused laser to obtain an amplified laser beam. The input mirror has target coatings on two opposite sides. The target coating opposite the focusing mirror has target transmittance for the focused laser, and the target coating opposite the gain medium has target reflectivity for the amplified laser beam. The gain medium is Cr-doped. 3+ The crystal of ions; the output mirror is coated with an anti-saturable absorption material on the side facing the gain medium. The anti-saturable absorption material includes a ground state energy level, an excited state energy level, and a higher state energy level. The band gap between the ground state energy level and the excited state energy level is zero. There is a band gap between the excited state energy level and the higher state energy level that is smaller than the target energy, exhibiting a second saturation characteristic. The output mirror is used to output a target energy pulsed laser generated by passive Q-switching based on the anti-saturable absorption material.

[0006] In some embodiments, a band gap with a target energy of 1 eV exists between the excited state level and the higher state level.

[0007] In some embodiments, the anti-saturation absorber is a two-dimensional HfTe2 material.

[0008] In some embodiments, the collimating lens is a plano-convex lens, including a collimating lens plane and a collimating lens convex surface, and the focusing lens is a plano-convex lens, including a focusing lens plane and a focusing lens convex surface, wherein the collimating lens convex surface is opposite to the focusing lens convex surface.

[0009] In some embodiments, the input mirror is configured as a plano-lens with two flat surfaces or as a plano-concave lens with one flat surface and the other concave surface, wherein the concave surface of the plano-concave lens faces the gain medium, and the output mirror is configured as a plano-lens.

[0010] In some embodiments, the pump laser is a semiconductor laser emitting a wavelength of 638 nm, and the gain medium is a semiconductor laser with a target Cr content. 3+ The ion-doped chrysoberyl crystal has a target energy pulse laser output by the output mirror with a wavelength of 755 nm and a pulse energy greater than 10 mJ.

[0011] In some embodiments, both the pump laser and the gain medium are cooled by water.

[0012] In some embodiments, the pump laser is a semiconductor laser with an emission wavelength of 976 nm, the gain medium is a Yb:YAG crystal, and the wavelength of the target energy pulsed laser output by the output mirror is 1064 nm with a pulse energy greater than 10 mJ.

[0013] In some embodiments, the pump laser is cooled by air, and the gain medium is cooled by water.

[0014] In some embodiments, a etalon is further disposed between the pump laser and the collimating lens, the etalon being used to tune the laser wavelength emitted by the pump laser.

[0015] The present invention includes, but is not limited to, the following beneficial effects: (1) This scheme achieves the generation of large-energy pulses by combining anti-saturable absorption materials and suitable gain media; (2) The target coating design on the input mirror ensures that the focused laser enters the gain medium with the target transmittance, further improving the efficiency of laser amplification; (3) The specific coating design on the input mirror enables the focused laser to be effectively transmitted to the gain medium, while the amplified laser beam can also be reflected efficiently. This design helps to improve energy conversion efficiency and reduce energy loss; (4) The use of Cr-doped 3+ (5) The ion crystal is used as the gain medium. Cr ions have good laser working characteristics and can achieve efficient laser amplification in a variety of wavelength ranges; (6) The band gap between the ground state and excited state of the anti-saturated absorber is zero, while there is a band gap for the target energy between the excited state and higher states. This design helps to achieve oversaturation of the ground state energy level and saturation of the excited state energy level, achieving the effect of secondary saturation and increasing the saturation intensity of the absorber; (7) This scheme generates target energy pulsed laser based on the passive Q-switching method of the anti-saturated absorber. Since the generation of passive Q-switched pulsed laser does not depend on the external modulator, the whole system can be more stable and reduce fluctuations caused by external factors. At the same time, by changing the characteristics of the gain medium or the anti-saturated absorber, the parameters of the pulsed laser can be adjusted to improve the flexibility of the system. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below.

[0017] Figure 1 This is a schematic diagram illustrating the principle of anti-saturation absorption of the anti-saturation absorption material according to an embodiment of the present invention;

[0018] Figure 2 This is a schematic diagram of the structure of the mJ-level pulsed laser generating device according to an embodiment of the present invention;

[0019] Figure 3This is a diagram showing the band structure and electronic density of states of the HfTe2 material according to an embodiment of the present invention;

[0020] Figure 4 This is a schematic diagram of the pulse sequence and pulse shape of the mJ-level pulsed laser output according to an embodiment of the present invention;

[0021] In the diagram, 1-pump laser, 2-collimating lens, 3-focusing lens, 4-input mirror, 5-gain medium, 6-output mirror. Detailed Implementation

[0022] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. All other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0023] For details, please refer to Figure 2 As shown, a mJ-level pulsed laser generation device is disclosed. The device includes a pump laser 1, a collimating mirror 2, a focusing mirror 3, an input mirror 4, a gain medium 5, and an output mirror 6 arranged sequentially. The pump laser is used to output a divergent pump laser with divergent characteristics. The collimating mirror 2 is used to convert the divergent pump laser into a collimated laser. The focusing mirror 3 is used to convert the collimated laser into a focused laser. The focused laser is transmitted to the gain medium 5 through the input mirror 4. The gain medium 5 is used to amplify the focused laser to obtain an amplified laser beam. The input mirror 4 has target coatings on two opposite sides. The target coating opposite the focusing mirror 3 has a transmittance greater than 99% for the focused laser, and the target coating opposite the gain medium 5 has a transmittance greater than 99% for the target laser beam. The gain medium 5 is Cr-doped. 3+ The output mirror 6 is a crystal of ions; an anti-saturation absorption material is drop-coated on the side of the output mirror 6 facing the gain medium 5. The anti-saturation absorption material includes a ground state energy level, an excited state energy level, and higher energy levels. The band gap between the ground state energy level and the excited state energy level is zero, and there is a band gap between the excited state energy level and the higher energy level that is lower than the target energy, exhibiting secondary saturation characteristics. The output mirror 6 is used to output the target energy higher than 10 mJ generated by the passive Q-switching method based on the anti-saturation absorption material.

[0024] It's important to note that the ground state refers to the lowest energy level an atom is in under normal conditions, where electrons move in orbits closest to the nucleus. The ground state and excited state are two important concepts describing the electronic states of atoms or molecules. The ground state refers to the lowest energy stable state of an atom or molecule under normal conditions, where the electron configuration follows the Fermi-Dirac distribution and the Pauli exclusion principle. The excited state, on the other hand, refers to the state where electrons in an atom or molecule are excited to a higher energy level after absorbing a certain amount of energy, but are not yet ionized.

[0025] Electrons in an atom are always arranged to occupy the lowest possible energy levels, and each energy level can only hold a certain number of electrons. This arrangement ensures the atom is in its most stable state. Specifically, electrons fill energy levels sequentially according to their principal quantum numbers, from smallest to largest. Under each principal quantum number, electrons first fill energy levels with smaller angular momentum quantum numbers, such as the s level, and then fill energy levels with larger angular momentum quantum numbers, such as p, d, and f. When the number of electrons in a certain energy level reaches its maximum capacity, electrons begin to fill the next energy level. From an energy state perspective, the main difference between the ground state and excited states lies in their energy levels. The ground state is the lowest energy stable state of an atom or molecule, while the excited state is the state where an atom or molecule absorbs energy and transitions to a higher energy level. This energy change can be calculated using quantum mechanics; if the energy of a molecule or atom is higher than the ground state energy, then it is in an excited state.

[0026] Furthermore, the drop-coating step for the anti-saturable absorber material on the side of the output mirror 6 facing the gain medium 5 can be as follows: 5 mg of HfTe2 two-dimensional material powder is placed in a 10 mL centrifuge tube, which is then filled with alcohol. The centrifuge tube containing the HfTe2 powder and alcohol is placed in an ultrasonic cleaner and ultrasonically treated for 12 hours, using ultrasonic vibration to separate a monolayer of HfTe2 mixture. The ultrasonically treated mixture is then centrifuged to remove large particles, and the supernatant is removed and placed in a new centrifuge tube for further centrifugation. The solution after the second centrifugation is then drop-coated onto the output mirror 6 and dried at room temperature for 12 hours to obtain the output mirror 6 coated with HfTe2 two-dimensional material.

[0027] Specifically, the energy level relationships of antisaturated absorber materials are as follows: Figure 1 As shown, in one example, the saturated absorber can be a two-dimensional HfTe2 material, such as... Figure 3 As shown, Figure 3This is a schematic diagram of the band structure (left) and electronic density of states (right) of a two-dimensional HfTe2 material. The gap between the excited state and the ground state is 0 eV, making it easier for electrons in the ground state to transition to the excited state. However, a 1 eV band gap exists between the excited state and higher states, hindering the spontaneous transition of electrons from higher states to the excited state, making the process slower. Specifically, the saturation process of an anti-saturable absorber involves the following: when laser light is incident on the surface of the HfTe2 two-dimensional material, if the photon energy of the laser is greater than the band gap between the ground and excited states, it can excite electrons in the ground state to transition to the excited state, and the laser light is absorbed. According to the Pauli exclusion principle, each position in the excited state can only accommodate one transitioning electron. Therefore, when enough electrons occupy the positions in the excited state, the excited state cannot accommodate more electrons, and the HfTe2 two-dimensional material no longer absorbs laser light; that is, the absorber reaches saturation. At this point, more laser light can pass through the HfTe2 two-dimensional material. The phenomenon of the absorption rate of the HfTe2 two-dimensional material gradually increasing under high-energy laser excitation is called saturation absorption. During this process, excited-state particles spontaneously transition from the excited state to the ground state, but this process is slower than the excitation rate. The anti-saturation absorption process is as follows: when a sufficient number of excited-state particles accumulate, if the pump laser energy is greater than the energy between the excited state and a higher state, it can excite the excited-state electrons to transition to a higher energy level again, which is the secondary absorption of laser light by the HfTe2 two-dimensional material. At this time, the absorption rate of the HfTe2 two-dimensional material to laser light increases again, so this process is called anti-saturation absorption, also known as secondary absorption. Because the excited-state electrons are emptied during secondary absorption, a certain amount of energy is needed to maintain the saturation of the excited state. Therefore, secondary absorption requires higher energy to reach saturation, and the material has a higher saturation flux. Thus, based on the anti-saturation absorption material of this scheme, after the laser starts working, the anti-saturation absorption material absorbs laser energy to reach secondary saturation, and more energy accumulates in the laser cavity. The instantaneous release of the accumulated energy is larger, resulting in a high-peak-value, high-energy laser pulse. For example, the pulse sequence and pulse shape of the obtained high-energy laser pulse are as follows... Figure 4 As shown in the figure, the pulse repetition frequency is 262 Hz and the pulse width is 454 ns. The corresponding high-energy laser pulse is 5.8 mJ.

[0028] Understandably, this scheme achieves the generation of high-energy pulses by combining anti-saturable absorber materials and a suitable gain medium; furthermore, the target coating design on the input mirror ensures that the focused laser enters the gain medium with the target transmittance, improving the efficiency of laser amplification; additionally, the specific coating design on the input mirror allows the focused laser to be effectively transmitted to the gain medium, while the amplified laser beam can also be reflected efficiently. This design helps to improve energy conversion efficiency and reduce energy loss; furthermore, the use of Cr-doped... 3+ ion crystals as gain media, Cr3+ Ions possess excellent laser operating characteristics, enabling efficient laser amplification across multiple wavelength ranges. Furthermore, the antisaturable absorber material exhibits a zero band gap between its ground and excited states, while a band gap smaller than the target energy exists between the excited and higher states. This design facilitates oversaturation of the ground state energy level and saturation of the excited state energy level, achieving a secondary saturation effect and increasing the saturation intensity of the absorber. Moreover, this scheme generates target energy pulsed lasers based on passive Q-switching of the antisaturable absorber material. Since the generation of passively Q-switched pulsed lasers does not depend on an external modulator, the entire system is more stable, reducing fluctuations caused by external factors. Simultaneously, by changing the properties of the gain medium or the antisaturable absorber material, the parameters of the pulsed laser can be adjusted, improving the system's flexibility.

[0029] In some embodiments, the collimating lens 2 is a plano-convex lens, including a collimating lens plane and a collimating lens convex surface, and the focusing lens 3 is a plano-convex lens, including a focusing lens plane and a focusing lens convex surface, with the collimating lens convex surface and the focusing lens convex surface facing each other.

[0030] In some embodiments, the input mirror 4 is configured as a plano-plane lens with two flat surfaces or as a plano-concave lens with one flat surface and the other concave surface, the concave surface of the plano-concave lens being the gain medium 5, and the output mirror 6 is configured as a plano-plane lens.

[0031] Understandably, the gain medium 5, which matches the anti-saturable absorber HfTe2 two-dimensional material, is also crucial. Since high-energy pulsed lasers require the gain medium 5 to store more energy, it needs a wider upper laser energy level and must emit photons of appropriate wavelengths (wavelength corresponds to energy, requiring suitable energy) to ensure the transition positions satisfy the band gap from the ground state to the excited state and higher states. Furthermore, the gain medium 5 needs to have sufficiently strong gain to emit enough photons to saturate the two-dimensional material. To reduce thermal effects in the gain medium 5 and increase pump power, the pump laser and the emitted laser must have similar wavelengths. Therefore, the gain medium 5 in this scheme can be Cr-doped. 3+ A laser crystal with chromium (Cr) composition, wherein the laser crystal emits wavelengths in the visible light range up to 800 nm. Exemplarily, the gain medium 5 can be chrysoberyl or titanium sapphire. In one example, the gain medium 5 can also be a laser crystal with a Yb composition, such as Yb:YAG or Yb:YAP.

[0032] In some embodiments, the pump laser 1 is selected as a semiconductor laser with an emission wavelength of 638 nm, and the gain medium 5 is selected as having the target Cr... 3+The ion-doped chrysoberyl crystal outputs a target energy pulsed laser with a wavelength of 755 nm and a pulse energy greater than 10 mJ from the output mirror 6. Preferably, the Cr concentration can be 0.2-2 at.%, and both the pump laser and the gain medium 5 are cooled by water.

[0033] In some embodiments, the pump laser 1 can emit a semiconductor laser with a wavelength of 976 nm, the gain medium 5 can be a Yb:YAG crystal (ytterbium-doped yttrium aluminum garnet), the output mirror 6 outputs a target energy pulsed laser with a wavelength of 1064 nm and a pulse energy greater than 10 mJ, the pump laser is cooled by air, and the gain medium 5 is cooled by water.

[0034] In some embodiments, a etalon is further provided between the pump laser 1 and the collimating lens 2, and the etalon is used to tune the laser wavelength emitted by the pump laser 1.

[0035] Furthermore, in another example, high-energy vortex pulsed lasers or higher-order mode pulsed lasers can also be generated by ring-pumping, oblique pumping, and cavity mirror etching. Anti-saturable absorption materials are not limited to two-dimensional HfTe2 materials; other two-dimensional materials with similar energy levels can also be used to generate high-energy pulsed lasers.

[0036] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the claimed invention.

Claims

1. A mJ-level pulsed laser generating device, characterized in that, The device includes a pump laser (1), a collimating lens (2), a focusing lens (3), an input lens (4), a gain medium (5), and an output lens (6) arranged sequentially. The pump laser is used to output a divergent pump laser with divergent characteristics. The collimating lens (2) is used to convert the divergent pump laser into a collimated laser. The focusing lens (3) is used to convert the collimated laser into a focused laser. The focused laser is transmitted to the gain medium (5) through the input lens (4). The gain medium (5) is used to amplify the focused laser to obtain an amplified laser beam. The input lens (4) has target coatings on two opposite sides. The target coating opposite the focusing lens (3) has target transmittance for the focused laser, and the target coating opposite the gain medium (5) has target reflectivity for the amplified laser beam. The gain medium (5) is Cr-doped. 3+ The crystal of ions; the output mirror (6) is coated with an anti-saturable absorption material on the side facing the gain medium (5). The anti-saturable absorption material has a ground state energy level, an excited state energy level and a higher state energy level. The band gap between the ground state energy level and the excited state energy level is zero. There is a band gap between the excited state energy level and the higher state energy level that is smaller than the target energy, exhibiting a second saturation characteristic. The output mirror (6) is used to output the target energy pulsed laser generated by the passive Q-switching method based on the anti-saturable absorption material.

2. The pulsed laser generating device according to claim 1, characterized in that, There is a band gap with a target energy of 1 eV between the excited state level and the higher state level.

3. The mJ-level pulsed laser generating device according to claim 1, characterized in that, The anti-saturation absorber is a two-dimensional HfTe2 material.

4. The mJ-level pulsed laser generating device according to claim 1, characterized in that, The collimating lens (2) is a plano-convex lens, including a collimating lens plane and a collimating lens convex surface. The focusing lens (3) is a plano-convex lens, including a focusing lens plane and a focusing lens convex surface. The collimating lens convex surface is opposite to the focusing lens convex surface.

5. The mJ-level pulsed laser generating device according to claim 1, characterized in that, The input mirror (4) is constructed as a plano lens with two flat surfaces or as a plano-concave lens with one flat surface and the other concave surface, the concave surface of the plano-concave lens facing the gain medium (5), and the output mirror (6) is constructed as a plano lens.

6. The mJ-level pulsed laser generating device according to claim 1, characterized in that, The pump laser (1) is a semiconductor laser with an emission wavelength of 638 nm, and the gain medium (5) is a semiconductor laser with a target Cr content. 3+ The ion-doped chrysoberyl crystal has a target energy pulse laser output by the output mirror (6) with a wavelength of 755 nm and a pulse energy greater than 10 mJ.

7. The mJ-level pulsed laser generating device according to claim 6, characterized in that, Both the pump laser and the gain medium (5) are cooled by water.

8. The mJ-level pulsed laser generating device according to claim 1, characterized in that, The pump laser (1) is a semiconductor laser with an emission wavelength of 976nm, the gain medium (5) is a Yb:YAG crystal, and the output mirror (6) outputs a target energy pulse laser with a wavelength of 1064nm and a pulse energy greater than 10mJ.

9. The mJ-level pulsed laser generating device according to claim 8, characterized in that, The pump laser is cooled by air, and the gain medium (5) is cooled by water.

10. The mJ-level pulsed laser generating device according to claim 6 or 8, characterized in that, A datum is also provided between the pump laser (1) and the collimating mirror (2), and the datum is used to tune the laser wavelength emitted by the pump laser (1).

Images