Optically pumped metastable noble gas laser employing laser induced preionization

Abstract

The application relates to a kind of optically pumped metastable noble gas lasers using laser-induced preionization, wherein a sample cell is arranged inside a noble gas metastable preparation chamber, a radio frequency electrode and a grounded electrode are arranged inside the noble gas metastable preparation chamber, the sample cell is arranged between the radio frequency electrode and the grounded electrode, a pump light source and a preionization light source are arranged outside the noble gas metastable preparation chamber, and the pump light source and the preionization light source are arranged to emit light perpendicularly and orthogonally to the sample cell, a first mirror is arranged between the pump light source and the noble gas metastable preparation chamber, a second mirror is arranged on the side of the noble gas metastable preparation chamber away from the pump light source, a lens is arranged between the preionization light source and the noble gas metastable preparation chamber, and a heating device is arranged outside the noble gas metastable preparation chamber. The application can quickly generate high-concentration metastable atoms based on laser-induced preionization and electron collision accelerated by an external electric field, and can directly avoid the problem of serious electromagnetic interference caused by the generation of metastable atoms in the traditional discharge mode at the mechanism level.

Description

Technical Field

[0001] This invention relates to the field of metastable inert gas laser technology, specifically to a laser-pumped metastable inert gas laser employing laser-induced pre-ionization. Background Technology

[0002] In recent years, the application of diode-pumped alkali lasers (DPALs) has developed rapidly. DPALs are three-level gas lasers that can output near-infrared wavelength lasers (K: 770nm, Rb: 795nm, Cs: 894nm), which has better practical performance than mid- and far-infrared wavelengths. Through gas circulation cooling, they can achieve good thermal management, resulting in excellent beam quality, making them particularly suitable for far-field applications. In addition, the alkali metal in this device has a large gain coefficient and excellent scaling amplification, enabling high-power output. According to publicly reported data, DPALs can already achieve power output in the kilowatt range. However, DPAL also faces many challenges in engineering applications, including: (1) Alkali metal atoms react chemically with alkane gases, and the decomposition and carbonization of alkane molecules will contaminate the window lens; (2) If only helium is used as a buffer gas, a higher gas pressure is required, which leads to a deterioration in beam quality and poses a great challenge to sealing, gas circulation, etc.; (3) Alkali metals are easily ionized, which leads to a decrease in the concentration of alkali metal atoms and quenching, which will limit the development of DPAL to higher power scales.

[0003] To address the challenges faced by DPAL, an optically pumped metastable rare gas laser (OPRGL) was proposed. This laser utilizes the similarity between the atomic structures of inert gases and alkali metals. Through discharge excitation, processes such as ionization, recombination, excited-state radiation, and relaxation excite the outermost electrons to form valence electrons, thus obtaining metastable particles. The metastable Rg* state in the inert gas has a long lifetime, equivalent to the ground state nS of alkali metals. The metastable state is then excited to a highly excited state by a diode pump, and the output laser wavelength is also in the near-infrared band. The optical pumping and laser output process of OPRGL is very similar to the three-level structure of DPAL, with the following differences: (1) Inert gases have excellent stability and there is no problem of chemical reaction; (2) OPRGL usually uses helium as a buffer gas, eliminating the need for alkane gases to accelerate the relaxation rate and avoiding carbonization problems; (3) OPRGL requires discharge to obtain a sufficient concentration of metastable particles.

[0004] Currently, to effectively expand the application areas and performance of high-power lasers, they generally need to be installed on mobile platforms such as vehicles and aircraft. Airborne platforms, in particular, place extremely stringent requirements on the size and weight of the lasers. Similar to high-power TEA CO2 lasers (TEA: Lateral Excitation Atmosphere), OPRGLs generate severe electromagnetic interference during the high-voltage discharge process of charging the capacitor. Airborne platforms are extremely sensitive to electromagnetic interference and electromagnetic compatibility. Shielding the electromagnetic interference generated by the discharge equipment requires a metal shielding box, resulting in a large and heavy laser system, posing a significant challenge to airborne platforms. Even so, it is difficult to completely avoid electromagnetic signal leakage, which limits the future application areas of high-power OPRGLs. Therefore, solving or avoiding electromagnetic interference problems through technological means will help promote the development of OPRGLs in the field of high-power lasers. Summary of the Invention

[0005] The purpose of this invention is to provide a laser-induced pre-ionization optically pumped metastable inert gas laser, which rapidly generates high concentrations of metastable atoms based on laser-induced pre-ionization and external electric field-accelerated electron collisions, thus directly avoiding the serious electromagnetic interference problem caused by traditional discharge methods in generating metastable atoms at the mechanistic level.

[0006] The objective of this invention is achieved through the following technical solution:

[0007] A laser-induced pre-ionization optically pumped metastable inert gas laser includes an inert gas metastable preparation chamber, a pump source, and a pre-ionization source. The inert gas metastable preparation chamber contains a sample cell, a radio frequency electrode, and a ground electrode, with the sample cell positioned between the radio frequency electrode and the ground electrode. Both the pump source and the pre-ionization source are located outside the inert gas metastable preparation chamber, with the emitted light from the pump source and the emitted light from the pre-ionization source perpendicular to each other in the sample cell. A first reflecting mirror is positioned between the pump source and the inert gas metastable preparation chamber, and a second reflecting mirror is positioned on the side of the inert gas metastable preparation chamber away from the pump source. A lens is positioned between the pre-ionization source and the inert gas metastable preparation chamber, and a heating device is positioned outside the inert gas metastable preparation chamber.

[0008] The radio frequency electrode is connected to the radio frequency source, and a matching network is provided between the radio frequency electrode and the radio frequency source. The electric field direction between the radio frequency electrode and the ground electrode is changed periodically.

[0009] The electrode plate of the radio frequency electrode is arranged parallel to the electrode plate of the ground electrode, and the sample cell is located between the electrode plates of the radio frequency electrode and the ground electrode.

[0010] Both the inert gas metastable preparation chamber and the sample cell have side windows on the side near the pre-ionization light source. The laser output from the pre-ionization light source is focused by a lens to form a focal line, and the focal line is located in the sample cell. The plane of the focal line is parallel to the electrode plates of the radio frequency electrode and the ground electrode, and the focal line is located on the side near the electrode plate of the radio frequency electrode.

[0011] The inert gas metastable preparation chamber includes an outer wall of the preparation chamber, one end of which is provided with a first end face window and the other end with a second end face window. One end of the sample cell is provided with an incident window facing the first end face window, and the other end is provided with an exit window facing the second end face window.

[0012] The surfaces of the first end face window, the second end face window, the incident window, and the exit window are all coated with a band anti-reflective coating.

[0013] The surface of the first reflector is coated with a band antireflection film and a band high reflection film, and the surface of the second reflector is coated with a band antireflection film and a band reflection film.

[0014] Both the first and second reflecting mirrors are concave reflecting mirrors, and the lens is a cylindrical convex lens.

[0015] The inert gas metastable preparation chamber includes an outer wall of the preparation chamber, and the heating device is located on the outer side of the outer wall of the preparation chamber and is connected to a temperature controller.

[0016] The sample cell is filled with alkali metals, inert gases for preparing metastable states, and buffer gases.

[0017] The advantages and positive effects of this invention are as follows:

[0018] 1. This invention utilizes laser-induced pre-ionization to generate high-density electrons while avoiding the strong electromagnetic interference problems caused by traditional discharge ionization.

[0019] 2. This invention uses alkali metals, whose atoms are easily ionized. The generated electrons collide with inert gas atoms, inducing their ionization and reducing the ionization threshold in the pre-ionization stage.

[0020] 3. The present invention uses alkali metals, and the vapors formed therefrom can be fully mixed with inert gases to form micro-ionization channels, which is beneficial for uniform ionization and collision during the pre-ionization stage.

[0021] 4. After pre-ionization, the present invention accelerates electrons to collide with inert gas atoms through an external radio frequency electric field, thereby obtaining a uniformly distributed, high-concentration metastable inert gas atom.

[0022] 5. This invention effectively reduces the size and weight of the laser, which helps to expand the application areas of this type of laser. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the structure of the present invention.

[0024] Figure 2 for Figure 1 A schematic diagram of the inert gas metastable preparation chamber structure.

[0025] Wherein, 1 is the pump light source, 2 is the first reflector, 3 is the inert gas metastable preparation chamber, 301 is the first end face window, 302 is the sample cell, 303 is the radio frequency electrode, 304 is the ground electrode, 305 is the outer wall of the preparation chamber, 306 is the second end face window, 4 is the pre-ionization light source, 5 is the lens, 6 is the heating device, 7 is the temperature controller, 8 is the matching network, 9 is the second reflector, and 10 is the radio frequency source. Detailed Implementation

[0026] The invention will now be described in further detail with reference to the accompanying drawings.

[0027] like Figures 1-2 As shown, the present invention includes an inert gas metastable preparation chamber 3, a pump light source 1, and a pre-ionization light source 4, wherein, as Figure 2 As shown, the inert gas metastable preparation chamber 3 is equipped with a sample cell 302, a radio frequency electrode 303, and a ground electrode 304, with the sample cell 302 located between the radio frequency electrode 303 and the ground electrode 304. Figure 1 As shown, both the pump light source 1 and the pre-ionization light source 4 are located outside the inert gas metastable preparation chamber 3, and the emitted light from the pump light source 1 and the emitted light from the pre-ionization light source 4 are perpendicular to each other in the sample cell 302. A first reflecting mirror 2 is provided between the pump light source 1 and the inert gas metastable preparation chamber 3, and a second reflecting mirror 9 is provided on the side of the inert gas metastable preparation chamber 3 away from the pump light source 1. A lens 5 is provided between the pre-ionization light source 4 and the inert gas metastable preparation chamber 3. The first reflecting mirror 2 and the second reflecting mirror 9 can be concave reflecting mirrors, and the lens 5 can be a cylindrical convex lens. Additionally, as shown... Figure 1 As shown, a heating device 6 is provided on the outside of the inert gas metastable preparation chamber 3, and the heating device 6 is connected to a temperature controller 7.

[0028] like Figure 2 As shown, the inert gas metastable preparation chamber 3 includes an outer wall 305. One end of the outer wall 305 has a first end face window 301, and the other end has a second end face window 306. The sample cell 302 has an incident window at one end facing the first end face window 301, and an exit window at the other end facing the second end face window 306. Figure 1As shown, the light emitted from the pump source 1 enters the sample cell 302 through the first end window 301 and exits through the second end window 306. The first end window 301 and the second end window 306 must be able to satisfy the transmission requirements of the laser output from the pump source, as well as the transmission requirements of the laser generated by the metastable inert gas laser system. The surfaces of the first end window 301, the second end window 306, the incident window, and the exit window are all coated with a band-specific anti-reflective coating; this is a well-known technique in the art.

[0029] like Figure 1 As shown, the first reflector 2 serves as a high-reflectivity cavity mirror, with its surface coated with a band-specific anti-reflection coating and a band-specific high-reflectivity coating. This surface coating achieves high transmittance for the pump laser band and high reflectivity for the metastable laser band. The second reflector 9 serves as an output coupling cavity mirror, with its surface coated with a band-specific anti-reflection coating and a band-specific reflectivity coating. This surface coating achieves high transmittance for the pump laser band and partial transmittance for the metastable laser band. The surface coating of the reflectors is a technique known in the art.

[0030] like Figure 1 As shown, the heating device 6 is located on the outer side of the preparation chamber 305. The sample cell 302 is filled with alkali metal and corresponding inert gases and buffer gases for preparing metastable states. The heating device 6 heats the outer wall 305 of the preparation chamber, and the heat is indirectly conducted to the interior of the sample cell 302 to generate a sufficient concentration of alkali metal vapor in the sample cell 302. The heating device 6 controls the heating temperature through a temperature controller 7. Both the heating device 6 and the temperature controller 7 are technologies known in the art and are commercially available products.

[0031] like Figure 1 As shown, the radio frequency electrode 303 is connected to the radio frequency source 10 via a circuit, and a matching network 8 is provided between the radio frequency electrode 303 and the radio frequency source 10. The low-voltage radio frequency electric field generated by the radio frequency source 10 periodically changes the direction of the electric field between the radio frequency electrode 303 and the ground electrode 304, thereby accelerating the reciprocating motion of electrons in the sample cell 302. The radio frequency source 10 and the matching network 8 are both technologies known in the art and are commercially available products. The radio frequency source 10 outputs a sinusoidal low-voltage radio frequency electric field with a repetition frequency on the order of MHz, thereby achieving periodic changes in the direction of the electric field.

[0032] like Figure 2 As shown, the electrode plate of the radio frequency electrode 303 is arranged parallel to the electrode plate of the ground electrode 304, the sample cell 302 is located between the electrode plate of the radio frequency electrode 303 and the electrode plate of the ground electrode 304, and a very small gap is left between the outer wall of the sample cell 302 and the adjacent electrode plate.

[0033] Both the inert gas metastable preparation chamber 3 and the sample cell 302 have side windows on the side near the pre-ionization light source 4. After the laser output from the pre-ionization light source 4 passes through the lens 5 (cylindrical convex lens), the laser spot is compressed and focused in the longitudinal direction, while the spot diameter remains unchanged in the transverse direction. Therefore, after the laser output from the pre-ionization light source 4 is focused by the lens 5, a focal line is generated in the transverse direction, and the focal line is located in the sample cell 302. The plane where the focal line is located is parallel to the electrode plate of the radio frequency electrode 303 and the electrode plate of the ground electrode 304, and the focal line is closer to the electrode plate of the radio frequency electrode 303. The laser output from the pre-ionization light source 4 is linearly focused by the lens 5 and acts on the alkali metal-inert gas mixture inside the sample cell 302 near the radio frequency electrode 303. The alkali metal is easily ionized, first undergoing multiphoton ionization, and then avalanche ionization, generating initial electrons. The accelerated electrons collide with inert gas atoms, triggering avalanche ionization. The number of electrons increases exponentially in nanosecond time. Pre-ionization will achieve a high electron density and a certain distribution range.

[0034] The working principle of this invention is as follows:

[0035] The sample cell 302 is filled with alkali metal and corresponding inert gas and buffer gas for preparing metastable states. The heating device 6 heats the outer wall 305 of the preparation chamber, and the heat is indirectly conducted to the interior of the sample cell 302 so that a sufficient concentration of alkali metal vapor is generated in the sample cell 302 and fully mixed with the inert gas and buffer gas.

[0036] Subsequently, metastable atoms are prepared. After the laser output from the pre-ionization source 4 passes through the lens 5 (cylindrical convex lens), the laser spot is compressed and focused in the longitudinal direction, while the spot diameter remains unchanged in the transverse direction. Therefore, after the laser output from the pre-ionization source 4 is focused by the lens 5, a focal line is generated in the transverse direction. The focal line is located in the sample cell 302. The plane where the focal line is located is parallel to the electrode plate of the radio frequency electrode 303 and the electrode plate of the ground electrode 304, and the focal line is closer to the side of the electrode plate of the radio frequency electrode 303. The laser output from the pre-ionization source 4 is linearly focused by the lens 5 and acts on the alkali metal-inert gas mixture inside the sample cell 302 near the radio frequency electrode 303. The alkali metal is easily ionized, first undergoing multiphoton ionization, and then avalanche ionization, generating initial electrons. The accelerated electrons collide with inert gas atoms, triggering avalanche ionization. The number of electrons increases exponentially in nanosecond time. Pre-ionization will achieve a high electron density and a certain distribution range. The low-voltage radio frequency electric field generated by the radio frequency source 10 periodically changes the direction of the electric field between the radio frequency electrode 303 and the ground electrode 304, thereby accelerating the reciprocating motion of electrons in the sample cell 302, realizing sufficient collisions between electrons and inert gas atoms, and generating metastable inert gas atoms with uniform distribution and sufficient concentration.

[0037] During the optical pumping stage, the laser output from the pump source 1 enters the sample cell 302 through the first end face window 301 and exits through the second end face window 306. The laser output from the pump source 1 excites the metastable atoms in the sample cell 302, and the emitted photons oscillate and amplify in the resonant cavity formed by the first reflector 2 and the second reflector 9. The laser directly generated is output from the second reflector 9.

[0038] The following are some application examples to further illustrate the working principle of the present invention. The laser wavelength output by the pump light source 1 will resonate and excite the metastable inert gas atoms located at the ns[3 / 2]2 energy level (Racah notation, corresponding Paschen notation is 1s5) to the np[5 / 2]3 energy level (Racah notation, corresponding Paschen notation is 2p9). For convenience, the Paschen notation will be used as the main term in the present invention.

[0039] Application Example 1:

[0040] In this application example, sample cell 302 is filled with sodium metal, and simultaneously, sample cell 302 is filled with neon gas to prepare metastable neon atoms. The neon gas filling pressure at room temperature is 60 torr (8.0 × 10⁻⁶). 3 It is also filled with helium as a buffer gas, and the helium filling pressure at room temperature is 650 torr (8.7 × 10⁻⁶ Pa). 4 The sample cell 302 is placed between the radio frequency electrode 303 and the ground electrode 304 inside the inert gas metastable preparation chamber 3. The heating device 6 heats the outer wall 305 of the preparation chamber, and the heat is indirectly conducted to the inside of the sample cell 302. The heating temperature is controlled by the temperature controller 7 to maintain at 150°C. At 150°C, the saturated vapor pressure of sodium metal in the sample cell 302 is 7.6 × 10⁻⁶ Pa. -6 torr(1.0×10 -3 (Pa), sodium vapor is thoroughly mixed with neon and helium.

[0041] Subsequently, metastable neon atoms are prepared. The 532nm laser output from the pre-ionization light source 4 is linearly focused by the lens 5 and acts on the sodium-neon-helium mixture inside the sample cell 302 near the radio frequency electrode 303 through the side window of the outer wall 305 of the preparation room. Sodium metal is easily ionized, and the initial electrons generated continue to collide with neon and helium atoms, triggering avalanche ionization of neon and helium atoms. Thus, high-density electrons with a certain distribution range are obtained through pre-ionization. The radio frequency source 10 is connected to the radio frequency electrode 303 through the matching network 8. The low-voltage radio frequency electric field generated by the radio frequency source 10 periodically changes the direction of the electric field between the radio frequency electrode 303 and the ground electrode 304, accelerating the reciprocating motion of electrons in the sample cell 302, realizing sufficient collisions between electrons and neon atoms, and ensuring the generation of 1s5 metastable neon atoms with uniform distribution and sufficient concentration.

[0042] During the optical pumping stage, the laser output from pump source 1 enters the sample cell 302 through the first end-face window 301 and exits through the second end-face window 306. The outer surfaces of the first end-face window 301, the second end-face window 306, and the two end windows of the sample cell 302 are coated with anti-reflection films in the 635–645 nm and 700–705 nm bands. The surface of the first reflector 2 is coated with an anti-reflection film in the 635–645 nm band and a high-reflection film in the 700–705 nm band. The surface of the second reflector 9 is coated with an anti-reflection film in the 635–645 nm band and a partial reflection film in the 700–705 nm band. The 640.2 nm laser output from pump source 1 excites the 1s5 metastable neon atoms in the sample cell 302 to the 2p9 energy level. Under the collision of helium atoms, the neon atoms in the 2p9 energy level rapidly relax to the 2p9 level. 10 Energy level, at 2p 10 A population inversion occurs between the 1s5 energy level and the radiated photons oscillate and amplify within a resonant cavity composed of the first reflector 2 and the second reflector 9. The directly generated 703.2nm laser is output from the second reflector 9.

[0043] Application Example 2:

[0044] In this application example, sample cell 302 is filled with potassium metal, and simultaneously filled with gas for preparing metastable argon atoms. The argon gas filling pressure at room temperature is 30 torr (4.0 × 10⁻⁶). 3 It is also filled with helium as a buffer gas, and the helium filling pressure at room temperature is 600 torr (8.0 × 10⁻⁶ Pa). 4 The sample cell 302 is placed between the radio frequency electrode 303 and the ground electrode 304 inside the inert gas metastable preparation chamber 3. The heating device 6 heats the outer wall 305 of the preparation chamber, and the heat is indirectly conducted to the inside of the sample cell 302. The heating temperature is controlled by the temperature controller 7 to maintain at 100°C. At 100°C, the saturated vapor pressure of potassium metal in the sample cell 302 is 2.2 × 10⁻⁶ Pa. -5 torr(3.0×10 -3 Potassium vapor is thoroughly mixed with argon and helium.

[0045] Subsequently, metastable argon atoms are prepared. The 532nm laser output from the pre-ionization light source 4 is linearly focused by the lens 5 and acts on the potassium-argon-helium mixture inside the sample cell 302 near the radio frequency electrode 303 through the side window of the outer wall 305 of the preparation room. Potassium metal is easily ionized, and the initial electrons generated continue to collide with argon and helium atoms, triggering avalanche ionization of argon and helium atoms. Thus, high-density electrons with a certain distribution range are obtained through pre-ionization. The radio frequency source 10 is connected to the radio frequency electrode 303 through the matching network 8. The low-voltage radio frequency electric field generated by the radio frequency source 10 periodically changes the direction of the electric field between the radio frequency electrode 303 and the ground electrode 304, accelerating the reciprocating motion of electrons in the sample cell 302, realizing sufficient collisions between electrons and argon atoms, and ensuring the generation of 1s5 metastable argon atoms with uniform distribution and sufficient concentration.

[0046] During the optical pumping stage, the laser output from pump source 1 enters the sample cell 302 through the first end-face window 301 and exits through the second end-face window 306. The outer surfaces of the first end-face window 301, the second end-face window 306, and the two end windows of the sample cell 302 are coated with anti-reflection films in the 810–815 nm and 910–915 nm bands, respectively. The surface of the first reflector 2 is coated with an anti-reflection film in the 810–815 nm band and a high-reflection film in the 910–915 nm band. The surface of the second reflector 9 is coated with an anti-reflection film in the 810–815 nm band and a partial-reflection film in the 910–915 nm band. The 811.5 nm laser output from pump source 1 excites the 1s5 metastable argon atoms in the sample cell 302 to the 2p9 energy level. Under the collision of helium atoms, the argon atoms in the 2p9 energy level rapidly relax to the 2p9 level. 10 Energy level, at 2p 10 A population inversion occurs between the 1s5 energy level and the radiated photons oscillate and amplify within a resonant cavity formed by the first reflector 2 and the second reflector 9. The directly generated 912.3nm laser is output from the second reflector 9.

[0047] Application Example 3:

[0048] In this application example, sample cell 302 is filled with rubidium metal, and simultaneously filled with a gas for preparing metastable krypton atoms. The krypton gas filling pressure at room temperature is 10 torr (1.3 × 10⁻⁶). 3 It is also filled with helium as a buffer gas, and the helium filling pressure at room temperature is 550 torr (7.3 × 10⁻⁶ Pa). 4 The sample cell 302 is placed between the radio frequency electrode 303 and the ground electrode 304 inside the inert gas metastable preparation chamber 3. The heating device 6 heats the outer wall 305 of the preparation chamber, and the heat is indirectly conducted to the inside of the sample cell 302. The heating temperature is controlled by the temperature controller 7 to maintain at 70°C. At 70°C, the saturated vapor pressure of rubidium metal in the sample cell 302 is 2.6 × 10⁻⁶ Pa. -5torr(3.5×10 -3 Pa), rubidium vapor is thoroughly mixed with krypton and helium.

[0049] Subsequently, metastable krypton atoms are prepared. The 532nm laser output from the pre-ionization light source 4 is linearly focused by the lens 5 and acts on the rubidium-krypton-helium mixture inside the sample cell 302 near the radio frequency electrode 303 through the side window of the outer wall 305 of the preparation room. Rubidium metal is easily ionized, and the initial electrons generated continue to collide with krypton and helium atoms, triggering avalanche ionization of krypton and helium atoms. Thus, high-density electrons with a certain distribution range are obtained through pre-ionization. The radio frequency source 10 is connected to the radio frequency electrode 303 through the matching network 8. The low-voltage radio frequency electric field generated by the radio frequency source 10 periodically changes the direction of the electric field between the radio frequency electrode 303 and the ground electrode 304, accelerating the reciprocating motion of electrons in the sample cell 302, realizing sufficient collisions between electrons and krypton atoms, and ensuring the generation of 1s5 metastable krypton atoms with uniform distribution and sufficient concentration.

[0050] During the optical pumping stage, the laser output from pump source 1 enters the sample cell 302 through the first end-face window 301 and exits through the second end-face window 306. The outer surfaces of the first end-face window 301, the second end-face window 306, and the two end windows of the sample cell 302 are coated with anti-reflection films in the 810–815 nm and 890–895 nm bands, respectively. The surface of the first reflector 2 is coated with an anti-reflection film in the 810–815 nm band and a high-reflection film in the 890–895 nm band. The surface of the second reflector 9 is coated with an anti-reflection film in the 810–815 nm band and a partial reflection film in the 890–895 nm band. The 813.3 nm laser output from pump source 1 excites the 1s5 metastable krypton atoms in the sample cell 302 to the 2p9 energy level. Under the collision of helium atoms, the krypton atoms in the 2p9 energy level rapidly relax to the 2p9 level. 10 Energy level, at 2p 10 A population inversion occurs between the 1s5 energy level and the radiated photons oscillate and amplify within a resonant cavity composed of the first reflector 2 and the second reflector 9. The directly generated 892.9nm laser is output from the second reflector 9.

[0051] Application Example 4:

[0052] In this application example, sample cell 302 is filled with cesium metal, and simultaneously filled with gas for preparing metastable xenon atoms. The xenon gas filling pressure at room temperature is 5 torr (6.7 × 10⁻⁶). 2 It is also filled with helium as a buffer gas, and the helium filling pressure at room temperature is 500 torr (6.7 × 10⁻⁶ Pa). 4The sample cell 302 is placed between the radio frequency electrode 303 and the ground electrode 304 inside the inert gas metastable preparation chamber 3. The heating device 6 heats the outer wall 305 of the preparation chamber, and the heat is indirectly conducted to the inside of the sample cell 302. The heating temperature is controlled by the temperature controller 7 to maintain at 50°C. At 50°C, the saturated vapor pressure of cesium metal in the sample cell 302 is 1.6 × 10⁻⁶ Pa. -5 torr(2.0×10 -3 Pa), cesium vapor is thoroughly mixed with xenon and helium.

[0053] Subsequently, metastable xenon atoms are prepared. The 532nm laser output from the pre-ionization light source 4 is linearly focused by the lens 5 and acts on the cesium-xenon-helium mixture inside the sample cell 302 near the radio frequency electrode 303 through the side window of the outer wall 305 of the preparation room. Cesium metal is easily ionized, and the initial electrons generated continue to collide with xenon and helium atoms, triggering avalanche ionization of xenon and helium atoms. Thus, high-density electrons with a certain distribution range are obtained through pre-ionization. The radio frequency source 10 is connected to the radio frequency electrode 303 through the matching network 8. The low-voltage radio frequency electric field generated by the radio frequency source 10 periodically changes the direction of the electric field between the radio frequency electrode 303 and the ground electrode 304, accelerating the reciprocating motion of electrons in the sample cell 302, realizing sufficient collisions between electrons and xenon atoms, and ensuring the generation of 1s5 metastable xenon atoms with uniform distribution and sufficient concentration.

[0054] During the optical pumping stage, the laser output from pump source 1 enters the sample cell 302 through the first end-face window 301 and exits through the second end-face window 306. The outer surfaces of the first end-face window 301, the second end-face window 306, and the two end windows of the sample cell 302 are coated with anti-reflection films in the 880–885 nm and 978–983 nm bands, respectively. The surface of the first reflector 2 is coated with an anti-reflection film in the 880–885 nm band and a high-reflection film in the 978–983 nm band. The surface of the second reflector 9 is coated with an anti-reflection film in the 880–885 nm band and a partial-reflection film in the 978–983 nm band. The 881.9 nm laser output from pump source 1 excites the 1s5 metastable xenon atoms in the sample cell 302 to the 2p9 energy level. Under the collision of helium atoms, the xenon atoms in the 2p9 energy level rapidly relax to the 2p9 level. 10 Energy level, at 2p 10 A population inversion occurs between the 1s5 energy level and the radiated photons oscillate and amplify within a resonant cavity composed of the first reflector 2 and the second reflector 9. The directly generated 980.0nm laser is output from the second reflector 9.

Claims

1. An optically pumped metastable noble gas laser employing laser induced pre-ionization, characterized by: The inert gas metastable state preparation chamber (3), the pumping light source (1) and the pre-ionization light source (4) are included, wherein the sample cell (302), the radio frequency electrode (303) and the grounding electrode (304) are arranged inside the inert gas metastable state preparation chamber (3), and the sample cell (302) is arranged between the radio frequency electrode (303) and the grounding electrode (304), the pumping light source (1) and the pre-ionization light source (4) are arranged outside the inert gas metastable state preparation chamber (3), and the light emitted by the pumping light source (1) and the light emitted by the pre-ionization light source (4) are perpendicular to the sample cell (302), the first reflector (2) is arranged between the pumping light source (1) and the inert gas metastable state preparation chamber (3), the second reflector (9) is arranged on the side of the inert gas metastable state preparation chamber (3) away from the pumping light source (1), the lens (5) is arranged between the pre-ionization light source (4) and the inert gas metastable state preparation chamber (3), and the heating device (6) is arranged outside the inert gas metastable state preparation chamber (3). The electrode plate of the radio frequency electrode (303) is arranged in parallel with the electrode plate of the grounding electrode (304), and the sample cell (302) is arranged between the electrode plate of the radio frequency electrode (303) and the electrode plate of the grounding electrode (304). The inert gas metastable state preparation chamber (3) and the sample cell (302) are provided with side windows on the side close to the pre-ionization light source (4), the pre-ionization light source (4) outputs laser light, the laser light is focused by the lens (5) to form a focus line, the focus line is located in the sample cell (302), the plane where the focus line is located is parallel to the electrode plate of the radio frequency electrode (303) and the electrode plate of the grounding electrode (304), and the focus line is close to the side of the electrode plate of the radio frequency electrode (303).

2. The optically pumped metastable noble gas laser employing laser induced pre-ionization of claim 1, wherein: The radio frequency electrode (303) is connected with the radio frequency source (10), a matching network (8) is arranged between the radio frequency electrode (303) and the radio frequency source (10), and the electric field direction between the radio frequency electrode (303) and the grounding electrode (304) is periodically changed.

3. The optically pumped metastable noble gas laser employing laser induced pre-ionization of claim 1, wherein: The inert gas metastable state preparation chamber (3) includes a preparation chamber outer wall (305), one end of the preparation chamber outer wall (305) is provided with a first end face window (301), the other end is provided with a second end face window (306), one end of the sample cell (302) is provided with an incident window opposite to the first end face window (301), and the other end is provided with an emission window opposite to the second end face window (306).

4. The optically pumped metastable noble gas laser employing laser induced pre-ionization of claim 3, wherein: The surfaces of the first end face window (301), the second end face window (306), the incident window and the emission window are coated with a waveband antireflection film.

5. The optically pumped metastable noble gas laser employing laser induced pre-ionization of claim 1, wherein: The surface of the first reflector (2) is coated with a waveband antireflection film and a waveband high-reflection film, and the surface of the second reflector (9) is coated with a waveband antireflection film and a waveband reflection film.

6. The optically pumped metastable noble gas laser employing laser induced pre-ionization of claim 1, wherein: The first reflector (2) and the second reflector (9) are both concave mirrors, and the lens (5) is a cylindrical convex lens.

7. The optically pumped metastable noble gas laser employing laser induced pre-ionization of claim 1, wherein: The inert gas metastable state preparation chamber (3) includes a preparation chamber outer wall (305), the heating device (6) is arranged outside the preparation chamber outer wall (305), and the heating device (6) is connected with the temperature controller (7).

8. The optically pumped metastable noble gas laser employing laser induced pre-ionization of claim 1, wherein: The sample cell (302) is filled with alkali metal and an inert gas for preparing metastable state and a buffer gas.

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