High-energy heavy-ratio counterflow type alkali metal vapor laser master oscillator power amplifier system

Abstract

The application discloses a high-energy-weight-ratio alkali metal vapor laser master oscillator power amplifier system, which comprises a transverse flow type alkali metal vapor cell, an alkali metal laser resonant cavity mirror, a 45-degree dichroic mirror and a semiconductor laser pumping source; the transverse flow type alkali metal vapor cell is used for providing a gain medium for the alkali metal vapor laser master oscillator power amplifier system; the alkali metal laser resonant cavity mirror provides a seed light source for the master oscillator power amplifier system; one end surface of the 45-degree dichroic mirror is coated with a full reflection film with a central wavelength being a laser wavelength and an anti-reflection film with a central wavelength being a pumping wavelength, and the other end surface is coated with an anti-reflection film with a central wavelength being the pumping wavelength; and the semiconductor laser pumping source comprises at least two semiconductor lasers, which are used as pumping sources of seed and amplification stages of the transverse flow type alkali metal vapor laser master oscillator power amplifier system respectively. The application has a small demand for heat dissipation equipment, can greatly reduce the volume and weight of the system and has a high-energy-weight-ratio advantage.

Description

Technical Field

[0001] This invention belongs to the field of alkali metal vapor laser technology and relates to a high energy-to-weight ratio transverse flow alkali metal vapor laser master oscillation amplification system. Background Technology

[0002] Alkali metal lasers are three-level lasers that utilize alkali metal vapor as the gain medium and a narrow-linewidth semiconductor laser as the pump source. They are also often referred to as diode-pumped alkali lasers (DPAL). Due to a series of outstanding advantages, including high Stokes efficiency, low heat generation, good beam quality, compact structure, non-toxic laser medium, low cost and high reusability of the vapor pool, high system reliability, and laser wavelengths (cesium (Cs): 894.95 nm; rubidium (Rb): 794.98 nm; potassium (K): 770.11 nm) falling within the atmospheric window, alkali metal lasers are considered a reliable, high energy-to-weight ratio, compact, high average power (≥1 MW) laser source.

[0003] Currently, to obtain laser sources with high beam quality and high output power, a common approach is to amplify a single-mode low-power seed laser source by constructing a laser master oscillator amplification system. In high-power laser master oscillator amplification systems, the gain media of the seed stage and amplification stage are typically solid-state or fiber-optic and are separate, leading to significant difficulties in assembling and adjusting the optical path and requiring sophisticated and complex heat dissipation equipment. Furthermore, laser master oscillator amplification systems using solid-state or fiber-optic gain media generate a high amount of heat. As output power increases, the number of heat dissipation devices required in the amplification system increases, leading to a larger system size and weight, a lower energy-to-weight ratio, and difficulties in mounting on mobile platforms for engineering applications.

[0004] Because the mixed gas (composed of alkali metal vapor and buffer gas) in the alkali metal vapor cell has low thermal conductivity, high-power laser pumping easily leads to localized high temperatures within the cell. This causes a rapid increase in the alkali metal vapor concentration, primarily manifested as a high concentration of particles in the third energy level (relaxation level) of alkali metal atoms. This directly reduces the absorption rate of the pump light by the vapor cell, further decreasing the optical-to-optical efficiency of the alkali metal laser. Simultaneously, high temperatures can also cause alkali metal consumption within the vapor cell, decreased laser power or even cessation of oscillation, contamination and damage to the vapor cell's optical window. Therefore, timely removal of the heat generated within the alkali metal vapor cell during high-power laser pumping, preventing photochemical reactions, alkali metal consumption, thermal effects, and vapor cell damage caused by localized high temperatures, is one of the main problems that urgently need to be solved in high-power alkali metal laser development. Summary of the Invention

[0005] (I) Purpose of the Invention

[0006] The purpose of this invention is to address the current situation where high-power laser sources have low energy-to-weight ratios and large size and weight, making them difficult to mount on mobile platforms for engineering applications. This invention proposes a high energy-to-weight ratio transverse-flow alkali metal vapor laser master oscillation amplification system. The aim is to solve the problems of low energy-to-weight ratios and large size and weight in high-power solid-state or fiber laser master oscillation amplification systems due to the use of discrete gain media layouts, as well as the problems faced by alkali metal lasers during high-power pumping, such as localized high temperatures leading to laser power reduction or even oscillation cessation, optical window contamination, and damage.

[0007] (II) Technical Solution

[0008] To solve the above-mentioned technical problems, the present invention provides a high energy-to-weight ratio transverse flow alkali metal vapor laser master oscillation amplification system, comprising: a semiconductor laser pump source 1, a laser total reflection mirror 3, an optical window 4, a laser output coupling mirror 5, a 45° dichroic mirror 7, and a transverse flow alkali metal vapor cell 11.

[0009] The semiconductor laser pump source 1 includes at least two semiconductor lasers, which are used to pump the gain media of the seed stage 8 and the amplification stage 9 of the transverse flow alkali metal vapor laser master oscillation amplification system, respectively. Together with the semiconductor laser pump source 1, the laser total reflection mirror 3, the transverse flow alkali metal vapor cell 11, and the laser output coupling mirror 5, it constitutes the seed stage of the entire laser master oscillation amplification system, providing the system with a seed laser source with good beam quality. Together with the seed laser 6, the semiconductor laser pump source 1, and the transverse flow alkali metal vapor cell 11, it constitutes the amplification stage of the laser master oscillation amplification system, generating high-power laser.

[0010] Among them, the laser total reflection mirror 3, together with the semiconductor laser pump source 1, the cross-flow alkali metal vapor cell 11, and the laser output coupling mirror 5, constitute the seed stage of the laser master oscillation amplification system, which is used to generate the seed laser source. The surface of the laser source is coated with an anti-reflection film with the center wavelength of the pump laser at one end, and the surface of the laser source is coated with an anti-reflection film with the center wavelength of the pump laser and a total reflection film with the center wavelength of the seed laser at the other end.

[0011] The optical window 4 is located on both end faces of the cross-flow alkali metal vapor pool 11 and includes at least two sets, which are used for pumping the laser and transmitting the laser, respectively. The connection between the optical window 4 and the cross-flow alkali metal vapor pool 11 must be sealed with a suitable sealing method to prevent impurities such as oxygen and water vapor in the air from entering the cross-flow alkali metal vapor pool 11 and causing alkali metal consumption, which would affect the normal operation of the laser main oscillation amplification system.

[0012] Among them, the laser output coupling mirror 5, together with the semiconductor laser pump source 1, the laser total reflection mirror 3, and the cross-flow alkali metal vapor cell 11, constitute the seed stage of the laser master oscillation amplification system, which is used to generate seed laser. The surface of the laser output coupling mirror 5 near the cross-flow alkali metal vapor cell 11 is coated with a reflective film with a center wavelength of the laser wavelength and a high reflective film with a pump laser wavelength, and the surface of the other end is coated with an anti-reflection film with a center wavelength of the laser wavelength.

[0013] Among them, the 45° dichroic mirror 7 is used to fold the pump and laser optical paths. One end of its surface is coated with a 45° incident antireflection film with a center wavelength of the pump laser wavelength, and the other end of its surface is coated with a 45° incident antireflection film with a center wavelength of the pump laser wavelength and a 45° incident total reflection film with a center wavelength of the laser wavelength.

[0014] The transverse-flow alkali metal vapor pool 11 is a container for alkali metal vapor and buffer gas, providing gain media for the seed stage and amplification stage of the laser master oscillation amplification system. It adopts a metal-glass composite structure and incorporates a built-in metal fan to homogenize the temperature field, driving the flow of the mixed gas within the vapor pool to avoid localized high temperatures during high-power pumping. The transverse-flow alkali metal vapor pool 11, together with the semiconductor laser pump source 1, the laser total reflection mirror 3, and the laser output coupling mirror 5, constitute the seed stage of the laser master oscillation amplification system. Together with the semiconductor laser pump source 1 and the seed laser 6, it constitutes the amplification stage of the laser master oscillation amplification system.

[0015] (III) Beneficial Effects

[0016] The high-energy-to-weight ratio transverse-flow alkali metal vapor laser master oscillation amplification system provided by the above technical solution has the following beneficial effects:

[0017] (1) In this invention, the optical path assembly and adjustment of the transverse flow alkali metal vapor laser master oscillation amplification system is simple and the energy-to-weight ratio is high. The gain medium of the seed stage and the amplification stage of the laser master oscillation amplification system is provided by a transverse flow alkali metal vapor pool. Moreover, the alkali metal itself generates little heat, which can reduce the demand for optical components and heat dissipation equipment, and significantly reduce the size and weight of the system.

[0018] (2) In this invention, the high-power alkali metal laser beam generated by the transverse flow alkali metal vapor laser master oscillation amplification system has excellent beam quality.

[0019] (3) In this invention, the high-power alkali metal laser beam generated by the transverse flow alkali metal vapor laser master oscillation amplification system has a narrow frequency linewidth. Without considering the external dispersive element, the laser output frequency linewidth is usually ≤20GHz.

[0020] (4) In this invention, the transverse flow alkali metal vapor laser master oscillation amplification system can output multiple high-power alkali metal lasers. Potassium, rubidium, cesium and other alkali metal vapors can be injected into the transverse flow vapor pool at the same time. With a suitable pump structure, at least three different wavelengths of high-power alkali metal lasers can be generated.

[0021] (5) In this invention, the transverse flow alkali metal vapor laser master oscillation amplification system has a high damage resistance threshold. The transverse flow alkali metal vapor pool used in the system drives the mixed gas in the vapor pool to flow laterally through the built-in fan, which can homogenize the temperature field, increase the gas heat exchange efficiency, reduce the temperature difference in the pool, avoid local high temperature, prevent thermal phenomena such as alkali metal atom consumption in the alkali metal vapor pool, laser power reduction, and optical window contamination and damage during high-power pumping, and achieve the purpose of improving the optical window threshold.

[0022] (6) In this invention, the optimization cost of the transverse flow alkali metal vapor laser master oscillation amplification system is low and the time consumption is short. The transverse flow alkali metal vapor cell used in the system has a low reusability rate, the proportion or type of atmosphere in the cell can be easily changed, the system optimization cost is low, no crystal material growth is required, and the time consumption is short.

[0023] (7) In this invention, the laser output performance of the transverse flow alkali metal vapor laser master oscillation amplification system is stable and reliable. The flow field and temperature field inside the transverse flow alkali metal vapor cell used in the system are stable, and the laser output power fluctuation is small. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of a high-energy-to-weight-ratio transverse-flow alkali metal vapor laser master oscillation amplification system. Detailed Implementation

[0025] To make the objectives, contents, and advantages of the present invention clearer, the specific embodiments of the present invention will be described in further detail below with reference to the accompanying drawings and examples.

[0026] To address the issues of complex optical path assembly, large size and weight, and low energy-to-weight ratio in current solid-state or fiber laser master oscillation amplification systems due to the separate layout of gain media, as well as the localized high temperature and other thermal phenomena that occur in the vapor pool of alkali metal vapor laser systems during high-power pumping, this invention proposes a high energy-to-weight ratio transverse flow alkali metal vapor laser master oscillation amplification system, taking into account the high efficiency and low heat generation of alkali metal Stokes lasers. Figure 1This is a schematic diagram of a high energy-to-weight ratio transverse-flow alkali metal vapor laser master oscillation amplification system related to an embodiment of the present invention, including: a semiconductor laser pump source 1, a pump laser beam 2, a laser total reflection mirror 3, an optical window 4, a laser output coupling mirror 5, a seed laser 6, a 45° dichroic mirror 7, a seed stage of the transverse-flow alkali metal vapor laser master oscillation amplification system 8, an amplification stage of the transverse-flow alkali metal vapor laser master oscillation amplification system 9, a laser beam 10, and a transverse-flow alkali metal vapor cell 11.

[0027] The semiconductor laser pump source 1 serves as the pump source for the seed stage 8 and the amplification stage 9 of the transverse flow alkali metal vapor laser master oscillation amplification system. Its wavelength linewidth needs to be narrowed. The narrowed linewidth should match the linewidth of the D2 line broadened by the buffer gas in the vapor cell to improve the utilization rate of the pump laser. Generally, the linewidth is about 0.1 nm.

[0028] The pump laser beam 2 is generated by the semiconductor laser source 1. The beam spot in its geometric space should be subjected to beam shaping processing to improve the mode matching efficiency of the pump light and the laser, and increase the optical-optical efficiency of the laser master oscillation amplification system.

[0029] The laser total reflection mirror 3 serves as a laser resonant cavity mirror, used to generate the seed laser 6 of the transverse flow alkali metal vapor laser master oscillation amplification system. Its surface near the pump laser source is coated with an anti-reflection film with a center wavelength of the pump laser wavelength, and its other surface is coated with an anti-reflection film with a center wavelength of the pump laser wavelength and a total reflection film with a center wavelength of the seed laser wavelength.

[0030] The optical window 4 is located at both end faces of the transverse flow alkali metal vapor cell 11, and includes at least two sets of pump light and laser transmission for the seed stage 8 and amplification stage 9 of the transverse flow alkali metal vapor laser master oscillation amplification system, respectively. Special attention should be paid to sealing the optical window to the transverse flow alkali metal vapor cell to prevent impurities such as oxygen and water vapor from entering the cavity and to prevent leakage of the mixed gas inside the cavity, which could lead to oxidation of the alkali metal and affect the performance of the laser system. Generally, the ultimate vacuum at the sealed optical window should be <10⁻³ Pa.

[0031] The laser output coupling mirror 5 serves as a laser resonant cavity mirror, used to generate the seed laser 6 of the transverse flow alkali metal vapor laser master oscillation amplification system. Its surface near the transverse flow alkali metal vapor pool 11 is coated with a reflective film with a center wavelength of the laser wavelength and a high reflective film with a pump laser wavelength, while the surface of the other end is coated with an anti-reflection film with a center wavelength of the laser wavelength.

[0032] The seed laser 6 is generated by the seed stage 8 of the transverse flow alkali metal vapor laser master oscillation amplification system, providing a low-power seed laser source with excellent beam quality for the amplification stage 9 of the transverse flow alkali metal vapor laser master oscillation amplification system, and is used to generate a high-power alkali metal laser with excellent beam quality.

[0033] The 45° dichroic mirror 7 is used to fold the pump light and laser light path. One end of its surface is coated with a 45° incident antireflection film with a center wavelength of the pump laser wavelength, and the other end of its surface is coated with a 45° antireflection film with a center wavelength of the pump laser wavelength and a 45° incident total reflection film with a center wavelength of the laser wavelength.

[0034] The transverse flow alkali metal vapor laser master oscillation amplification system 8 consists of a semiconductor laser pump source 1, a laser total reflection mirror 3, a transverse flow alkali metal vapor cell 11, and a laser output coupling mirror 5, and is used to provide seed laser 6 for the amplification stage 9 of the transverse flow alkali metal vapor laser master oscillation amplification system.

[0035] The transverse flow alkali metal vapor laser master oscillation amplification system 9 consists of a seed laser 6, a semiconductor laser pump source 1, and a transverse flow alkali metal vapor cell 11, and is used to generate high-power alkali metal lasers with excellent beam quality.

[0036] The laser beam 10 is generated by a transverse flow alkali metal vapor laser main amplification system.

[0037] The cross-flow alkali metal vapor cell 11 adopts a metal-glass composite structure. An internal fan drives the mixed gas within the vapor cell to flow in a cross-flow manner, homogenizing the internal temperature field, reducing temperature differences, lowering the maximum temperature, and preventing thermal phenomena such as photochemical reactions, alkali metal consumption, laser power reduction or even oscillation cessation, optical window contamination or damage, and low beam quality that may occur during high-power pumping. The vapor cell cavity should avoid using components that release oil fumes, and the sealing performance of all seals should be considered in light of the impact of high-temperature corrosive environments. Special attention should be paid to the sealing performance of the internal fan to ensure that under high-speed, high-wind-speed operation, there is no gas leakage or oil fumes affecting the cavity's airtightness and the laser system's performance.

[0038] The mixed gas consists of alkali metal vapor and a buffer gas. The alkali metal vapor is usually potassium vapor, rubidium vapor, cesium vapor, or the above-mentioned mixed gas. The buffer gas can be methane, ethane, helium, argon, or a mixture of the above-mentioned gases.

[0039] In this embodiment, a module of the semiconductor laser pump source 1, after linewidth narrowing, emits a pump laser beam. This beam is shaped into a pump laser beam 2, transmitted through a total internal reflection mirror 3, and reaches a set of optical windows 4 of a transverse flow alkali metal vapor cell 11. The pump laser beam is then absorbed by the alkali metal vapor atoms, and the remaining pump laser exits from the optical windows 4 of the transverse flow alkali metal vapor cell 11, reaches the surface of the laser output coupling mirror 5, and is reflected back into the transverse flow alkali metal vapor cell 11. The laser, composed of the semiconductor laser source 1, the total internal reflection mirror 3, the transverse flow alkali metal vapor cell 11, and the laser output coupling mirror 5, serves as the seed stage 8 of the transverse flow alkali metal vapor laser master oscillation amplification system, used to generate a low-power seed laser 6 with excellent beam quality. The seed laser 6 is reflected by two 45° dichroic mirrors 7 and passes through another set of optical windows 4 of the transverse flow alkali metal vapor cell 11. Another module of the semiconductor laser pump source 1 emits a high-power pump laser, which is transmitted through a 45° dichroic mirror and enters the transverse flow alkali metal vapor cell 11 through another set of optical windows 4, pumping alkali metal vapor atoms. The amplification stage 9 of the transverse flow alkali metal vapor laser master oscillation amplification system, composed of the seed laser 6, the semiconductor laser pump source 1, and the transverse flow alkali metal vapor cell 11, ultimately generates a high-power alkali metal laser 10.

[0040] As can be seen from the above technical solution, the present invention has the following significant features:

[0041] 1. The seed stage and amplification stage of the transverse flow alkali metal vapor laser main amplification system proposed in this invention use alkali metal vapor as the gain medium, which is provided by a transverse flow alkali metal vapor cell. This avoids the use of separate gain medium layouts and features simple optical path assembly and adjustment, compact structure, and high energy-to-weight ratio.

[0042] 2. The transverse flow alkali metal vapor laser master oscillation amplification system proposed in this invention uses alkali metal vapor as the gain medium, which has high beam quality and is superior to solid-state laser master oscillation amplification systems.

[0043] 3. The transverse flow alkali metal vapor cell of the transverse flow alkali metal vapor laser master oscillation amplification system proposed in this invention can homogenize the temperature field, improve the heat exchange efficiency of the mixed gas in the cell, reduce the temperature difference, reduce the maximum temperature in the cell, suppress optical window contamination, increase the optical window damage threshold, and avoid photochemical reactions of alkali metals.

[0044] 4. The cross-flow alkali metal vapor laser master oscillation amplification system proposed in this invention has stable temperature field, stable flow field, and stable output performance of the laser system within the cross-flow alkali metal vapor cell.

[0045] 5. The transverse-flow alkali metal vapor laser master amplification system proposed in this invention has the advantage of narrow laser frequency linewidth. The D1 line emission cross-section of alkali metal vapor atoms is relatively narrow, and the output frequency linewidth is typically ≤20GHz without the addition of external dispersive elements.

[0046] 6. The transverse alkali metal vapor cell of the transverse alkali metal vapor laser master oscillation amplification system proposed in this invention adopts a metal-glass composite structure, which can arbitrarily change the type and proportion of atmosphere in the vapor cell, and the system optimization cost is low and the time consumption is short.

[0047] 7. The transverse flow alkali metal vapor laser master oscillation amplification system proposed in this invention can simultaneously realize the output of high-power alkali metal lasers of multiple wavelengths. The transverse flow alkali metal vapor pool can be simultaneously injected with mixed alkali metal vapors containing potassium, rubidium, cesium and other metals, which can realize high-power alkali metal lasers of at least three wavelengths.

[0048] 8. The transverse flow alkali metal vapor laser master oscillation amplification system proposed in this invention can realize a multi-stage amplification scheme, which can be achieved by setting multiple sets of optical windows at both ends of the transverse flow alkali metal vapor cell in combination with 45° dichroic mirrors.

[0049] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A high-energy-to-weight-ratio transverse-flow alkali metal vapor laser master oscillation amplification system, characterized in that, include: The system includes a semiconductor laser pump source, a laser total reflection mirror, optical windows, a laser output coupler, a 45° dichroic mirror, and a transverse flow alkali metal vapor cell. At least two sets of optical windows are provided on the transverse flow alkali metal vapor cell. A 45° dichroic mirror is arranged on one side of one set of optical windows, while a laser total reflection mirror and a laser output coupler are arranged on the other two sides of the other optical windows, respectively. A semiconductor laser pump source is arranged outside the laser total reflection mirror, and a 45° dichroic mirror is arranged outside the laser output coupler. All 45° dichroic mirrors are arranged on the same side of the transverse flow alkali metal vapor cell. A semiconductor laser pump source is arranged on the outside of a 45° dichroic mirror on one side of one of the optical windows. The transverse flow alkali metal vapor cell, laser output coupling mirror, laser total reflection mirror, and semiconductor laser pump source outside the laser total reflection mirror constitute the seed stage of the main oscillation amplification system; the transverse flow alkali metal vapor cell, 45° dichroic mirror, and semiconductor laser pump source outside the 45° dichroic mirror constitute the amplification stage of the main oscillation amplification system.

2. The high energy-to-weight ratio transverse flow alkali metal vapor laser master oscillation amplification system as described in claim 1, characterized in that, The laser total reflection mirror is coated with an antireflection film with a center wavelength of the pump laser wavelength on the surface near the pump laser incident end, and the other end surface is coated with a total reflection film with a center wavelength of the laser wavelength and an antireflection film with the pump laser wavelength.

3. The high energy-to-weight ratio transverse flow alkali metal vapor laser master oscillation amplification system as described in claim 2, characterized in that, At least two sets of optical windows, one set for the pump beam transmission of the seed stage of the main oscillator amplification system, and the other set for the laser beam transmission of the amplification stage of the main oscillator amplification system.

4. The high energy-to-weight ratio transverse flow alkali metal vapor laser master oscillation amplification system as described in claim 3, characterized in that, The laser output coupling mirror is coated with a reflective film with a center wavelength of the laser wavelength and a high reflective film with a pump laser wavelength on the end surface near the cross-flow alkali metal vapor cell, and an anti-reflective film with a center wavelength of the laser wavelength on the other end surface.

5. The high energy-to-weight ratio transverse-flow alkali metal vapor laser master oscillation amplification system as described in claim 4, characterized in that, The 45° dichroic mirror is used to fold the alkali metal vapor laser optical path. One end of the mirror is coated with a 45° incident total reflection film with a center wavelength of the laser wavelength and a 45° incident antireflection film with a center wavelength of the pump laser wavelength. The other end is coated with a 45° incident antireflection film with a center wavelength of the pump laser wavelength.

6. The high energy-to-weight ratio transverse flow alkali metal vapor laser master oscillation amplification system as described in claim 5, characterized in that, The cross-flow alkali metal vapor pool provides the gain medium for the seed stage and amplification stage of the main oscillation amplification system. The cross-flow alkali metal vapor pool adopts a metal-glass composite structure, and an internal fan drives the mixed gas in the vapor pool to flow in a cross-flow manner.

7. The high energy-to-weight ratio transverse flow alkali metal vapor laser master oscillation amplification system as described in claim 6, characterized in that, The mixed gas in the crossflow alkali metal vapor pool includes alkali metal vapor and buffer gas.

8. The high energy-to-weight ratio transverse flow alkali metal vapor laser master oscillation amplification system as described in claim 7, characterized in that, The alkali metal vapor is one or a mixture of potassium vapor, rubidium vapor, and cesium vapor, and the buffer gas is one or a mixture of methane, ethane, helium, and argon.

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