Intermediate infrared wavelength conversion method and device of oxygen-iodine chemical laser

Abstract

The invention relates to the field of chemical oxygen-iodine lasers, in particular to a mid-infrared wavelength conversion method and device of a chemical oxygen-iodine laser. Firstly, a pair of pulsed magnetic field generators is placed on the upper side and the lower side of a gain area of an original continuous wave chemical oxygen-iodine laser; the hydrogen Raman pool is used as a magnetic gain switch to enable the laser to output laser pulses with higher peak power, then 1315nm wavelength laser output by the oxygen-iodine chemical laser is guided into the hydrogen Raman pool, the original 1315nm wavelength laser is converted into 2900nm wavelength laser through Raman scattering to be output, finally, the 2900nm wavelength laser is guided into the vacuum bin containing the iron-doped zinc selenide crystal, and the iron-doped zinc selenide crystal is obtained. And by pumping the iron-doped zinc selenide crystal, the laser with the wavelength of 2900 nm is further converted into intermediate infrared laser pulses with the wavelength of 4000-5000 nm. On the premise that the original laser structure is not influenced, the oxygen-iodine chemical laser has the possibility of being applied to the middle infrared band.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of oxygen-iodine chemical laser, in particular to a method and device for converting the mid-infrared wavelength of an oxygen-iodine chemical laser. BACKGROUND

[0002] Oxygen-iodine chemical laser has a very important position in high-energy laser due to its high chemical efficiency and good engineering amplification. However, the output wavelength of the oxygen-iodine chemical laser is determined by the iodine atomic energy level, which is fixed at 1315 nm, limiting the application occasions. At present, there are a large number of application requirements for high-power lasers in the 4000 to 5000 nm mid-infrared waveband in the fields of environmental monitoring, laser communication and photoelectric countermeasure. Therefore, converting the output wavelength of the oxygen-iodine chemical laser to the mid-infrared waveband can make the laser have more application occasions.

[0003] Wavelength conversion technology has always been one of the research hotspots in the field of laser, which is divided into linear wavelength conversion and nonlinear wavelength conversion. Linear wavelength conversion refers to using a laser crystal to input the original laser as pump light, and outputting new laser with longer wavelength through a resonant cavity. For example, Nd:YAG crystal can absorb 808 nm wavelength and output 1064 nm wavelength. Nonlinear wavelength conversion refers to using the nonlinear effect of optical materials to realize frequency doubling, difference frequency, sum frequency and Raman frequency conversion of input laser. However, the nonlinear coefficient of general materials is relatively low, and the damage threshold is limited. At present, neither of the two methods can directly convert the wavelength from 1315 nm to 4000 nm or above. SUMMARY

[0004] In order to solve the problem that the existing wavelength conversion technology cannot directly convert the wavelength from 1315 nm to 4000 nm or above, the purpose of the present application is to provide a method and device for converting the mid-infrared wavelength of an oxygen-iodine chemical laser, which can finally obtain laser output in the 4000 to 5000 nm mid-infrared waveband.

[0005] The purpose of the present application is achieved by the following technical solutions:

[0006] The method for converting the mid-infrared wavelength of an oxygen-iodine chemical laser comprises the following steps:

[0007] Periodic pulsed magnetic field is generated by a pulsed magnetic field generator placed outside the chemical oxygen iodine laser to change the output of the chemical oxygen iodine laser from continuous wave output to repeated pulsed output; then, 1315nm wavelength laser output by the chemical oxygen iodine laser is introduced into a Raman cell, and 1315nm wavelength laser is converted into 2900nm wavelength laser by stimulated Raman scattering of gas in the Raman cell; finally, 2900nm wavelength laser output by the Raman cell is introduced into a vacuum chamber in which an iron-doped zinc selenide crystal is placed, and 2900nm wavelength laser is converted into 4000-5000nm wavelength laser by pumping the iron-doped zinc selenide crystal.

[0008] A pair of pulsed magnetic field generators are placed on the upper and lower sides of the gain region of the chemical oxygen iodine laser, and the magnetic field is a pulsed magnetic field which is uniform in space and presents a square wave form in time in the gain region of the chemical oxygen iodine laser.

[0009] The 1315nm wavelength laser introduced into the Raman cell is repeated pulsed laser.

[0010] The gas in the Raman cell is hydrogen, and the pressure is 1.0-4.0MPa.

[0011] The pressure in the vacuum chamber is less than or equal to 0.1Pa.

[0012] The working temperature of the iron-doped zinc selenide crystal is less than or equal to 100K.

[0013] The conversion device for the mid-infrared wavelength conversion method of the chemical oxygen iodine laser comprises a chemical oxygen iodine laser, a pulsed magnetic field generator, a Raman frequency conversion module and a linear frequency conversion module, wherein the pulsed magnetic field generator is placed outside the chemical oxygen iodine laser, the continuous wave output of the chemical oxygen iodine laser is changed into repeated pulsed output by the periodic pulsed magnetic field generated by the pulsed magnetic field generator; the Raman frequency conversion module comprises a focusing lens A, a Raman cell and a dichroic mirror A which are sequentially arranged along the laser light path; the linear frequency conversion module comprises an output coupling mirror, a vacuum chamber and a focusing lens B, a dichroic mirror B, an iron-doped zinc selenide crystal and a high reflection mirror which are sequentially arranged along the laser light path, the focusing lens B, the dichroic mirror B and the output coupling mirror are all located outside the vacuum chamber, the output coupling mirror is located on one side of the dichroic mirror B, and the iron-doped zinc selenide crystal and the high reflection mirror are both arranged in the vacuum chamber.

[0014] A pair of pulsed magnetic field generators are symmetrically arranged on the upper and lower sides of the gain region of the chemical oxygen iodine laser.

[0015] A heat exchanger is further arranged in the vacuum chamber, liquid nitrogen is introduced into the heat exchanger, and the heat exchanger provides the required working environment temperature for the iron-doped zinc selenide crystal.

[0016] The iron-doped zinc selenide crystal is polished on both light transmission surfaces, and both light transmission surfaces are coated with an anti-reflection film.

[0017] The advantages and positive effects of the present application are as follows:

[0018] 1. The present application uses magnetic switch gain switching technology to change the output of the oxygen-iodine chemical laser from continuous wave output to repetitive pulse output, thereby improving the peak power of the laser and the photon conversion efficiency of stimulated Raman frequency conversion.

[0019] 2. The present application uses an iron-doped zinc selenide crystal as a linear conversion crystal, which has a wide absorption spectrum and emission spectrum, allowing the laser to have a certain tuning range.

[0020] 3. The present application uses hydrogen as a Raman medium, which has better thermal management, higher damage threshold, and larger Raman shift than nonlinear crystals.

[0021] 4. The Raman frequency conversion output of the present application is at a wavelength of 2900nm, which matches the absorption peak of the iron-doped zinc selenide crystal, reducing the energy loss between the two wavelength conversions. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 is a schematic diagram of the overall structure of the conversion device of the present application;

[0023] Figure 2 is a schematic diagram of the structure of the Raman frequency conversion module; Figure 1

[0024] is a schematic diagram of the structure of the linear frequency conversion module; Figure 3 Figure 1

[0025] wherein: 1 is an oxygen-iodine chemical laser, 2 is a pulse magnetic field generator, 3 is a Raman frequency conversion module, 4 is a linear frequency conversion module, 5 is a focusing lens A, 6 is a Raman cell, 7 is a dichroic mirror A, 8 is a focusing lens B, 9 is a dichroic mirror B, 10 is an output coupling mirror, 11 is a vacuum chamber, 12 is a heat exchanger, 13 is an iron-doped zinc selenide crystal, and 14 is a high-reflectivity mirror. DETAILED DESCRIPTION

[0026] The present application will be further described in detail below with reference to the accompanying drawings.

[0027] As Figures 1 to 3 ​​As shown, the mid-infrared wavelength conversion device of the present application includes an oxygen-iodine chemical laser 1, a Helmholtz coil 2, a Raman frequency conversion module 3 and a linear frequency conversion module 4, wherein the oxygen-iodine chemical laser 1 is provided with the pulse magnetic field generator 2, and the continuous wave output of the oxygen-iodine chemical laser 1 is changed into the repeated pulse output through the periodic pulse magnetic field generated by the pulse magnetic field generator 2; a pair of pulse magnetic field generators 2 are symmetrically arranged on the upper and lower sides of the gain region of the oxygen-iodine chemical laser 1 in the embodiment, and the pulse magnetic field generated by the pulse magnetic field generator 2 has a repetition frequency of 10 kHz, a duty cycle of 10% and a magnetic field amplitude of 300 Gauss.

[0028] The Raman frequency conversion module 3 of the embodiment is located between the oxygen-iodine chemical laser 1 and the linear frequency conversion module 4, and includes a focusing lens A 5, a Raman cell 6 and a dichroic mirror A 7 arranged in sequence along the laser light path. The dichroic mirror A 7 has high reflectivity to the 1315 nm wavelength laser and high transmissivity to the 2900 nm wavelength laser at the designed incident angle (45° in the embodiment).

[0029] The linear frequency conversion module 4 of the embodiment includes an output coupling mirror 10, a vacuum chamber 11 and a focusing lens B 8, a dichroic mirror B 9, a doped iron zinc selenide crystal 13 and a high reflectivity mirror 14 arranged in sequence along the laser light path. The focusing lens B 8, the dichroic mirror B 9 and the output coupling mirror 10 are located outside the vacuum chamber 11, the output coupling mirror 10 is located on one side of the dichroic mirror B 9, and the doped iron zinc selenide crystal 13 and the high reflectivity mirror 14 are arranged in the vacuum chamber 11. The vacuum chamber 11 of the embodiment is also provided with a heat exchanger 12, the inside of the heat exchanger 12 is filled with liquid nitrogen, the heat exchanger 12 provides the required working environment temperature for the doped iron zinc selenide crystal 13, and the minimum temperature of the heat exchanger 12 is 77 K. The dichroic mirror B 9 has high reflectivity to the 4000-5000 nm wavelength laser and high transmissivity to the 2900 nm wavelength laser at the designed incident angle (45° in the embodiment). The doped iron zinc selenide crystal 13 of the embodiment is polished on both light transmission surfaces and coated with an anti-reflection film (the anti-reflection film has anti-reflection effect on the 4000-5000 nm wavelength laser), and the doping concentration is 10 times 18.

[0030] The gas in the Raman cell 6 of the embodiment is hydrogen, and the pressure is 1.0-4.0 MPa (1.0 MPa in the embodiment). The pressure in the vacuum chamber 11 of the embodiment is less than or equal to 0.1 Pa. The working temperature of the doped iron zinc selenide crystal in the embodiment is 77-100 K.

[0031] The pulse magnetic field generator of the embodiment is a prior art, which will not be described here.

[0032] The mid-infrared wavelength conversion method of the oxygen-iodine chemical laser of the present application is as follows:

[0033] The magnetic field is generated by the pulse magnetic field generator 2 placed outside the oxygen-iodine chemical laser 1, and the output of the oxygen-iodine chemical laser 1 is changed from continuous wave output to repeated pulse output. Then, the 1315 nm wavelength laser output by the oxygen-iodine chemical laser 1 is introduced into the Raman cell 6, and the 1315 nm wavelength laser is converted into 2900 nm wavelength laser by stimulated Raman scattering of the gas in the Raman cell 6. Finally, the 2900 nm wavelength laser output by the Raman cell 6 is introduced into the vacuum chamber 11 in which the iron-doped zinc selenide crystal 13 is placed, and the 2900 nm wavelength laser is converted into 4000-5000 nm wavelength laser by pumping the iron-doped zinc selenide crystal 13. Specifically:

[0034] A pair of pulse magnetic field generators 2 is placed on the upper and lower sides of the gain region of the oxygen-iodine chemical laser 1, and a spatially uniform and temporally square-wave-form pulse magnetic field is generated in the gain region of the oxygen-iodine chemical laser 1. Under the action of the pulse magnetic field, the gain of iodine atoms changes periodically, so that the laser output is changed from continuous wave output to repeated pulse output. Then, the laser pulse is introduced into the Raman frequency conversion module 3, i.e., the 1315 nm wavelength laser introduced into the Raman cell 6 is repeated pulse laser. In the Raman frequency conversion module 3, the laser pulse is first focused by the focusing lens 5 into the Raman cell 6, and after Raman scattering of hydrogen, a part of the laser is converted into 2900 nm wavelength laser and transmitted through the dichroic mirror A7, and the remaining part of the unconverted 1315 nm wavelength laser is reflected by the dichroic mirror A7. Next, the 2900 nm wavelength laser emitted by the dichroic mirror A7 enters the linear frequency conversion module 4. In the linear frequency conversion module 4, the laser pulse is focused by the focusing lens B8 onto the iron-doped zinc selenide crystal 13, which is cooled to 77-100 K by the contact of the heat exchanger 12. At this temperature, the Fe ions in the iron-doped zinc selenide crystal 13 will absorb the 2900 nm wavelength laser and transition to the excited state, and at this temperature, the excited state energy level lifetime is tens of microseconds, which can form population inversion. Then, in the resonant cavity composed of the high reflector 14 and the output coupling mirror 10, laser emission is formed, and the emission wavelength range is 4000-5000 nm.

Claims

1. A method of mid-infrared wavelength conversion for an oxygen-iodine chemical laser, characterized by: Periodic pulsed magnetic field is generated by a pulsed magnetic field generator placed outside the chemical oxygen-iodine laser to change the output of the chemical oxygen-iodine laser from continuous wave output to repeated pulsed output; Then, the 1315 nm wavelength laser output by the chemical oxygen-iodine laser is introduced into a Raman cell, and the 1315 nm wavelength laser is converted into 2900 nm wavelength laser by stimulated Raman scattering of the gas in the Raman cell; finally, the 2900 nm wavelength laser output by the Raman cell is introduced into a vacuum chamber in which an iron-doped zinc selenide crystal is placed, and the 2900 nm wavelength laser is converted into 4000-5000 nm wavelength laser by pumping the iron-doped zinc selenide crystal.

2. The method of mid-infrared wavelength conversion of the chemical oxygen iodine laser according to claim 1, characterized in that: A pair of pulsed magnetic field generators are placed on the upper and lower sides of the gain region of the chemical oxygen-iodine laser, and the magnetic field is a pulsed magnetic field that is uniform in space and presents a square wave form in time in the gain region of the chemical oxygen-iodine laser.

3. The method of mid-infrared wavelength conversion for an oxygen-iodine chemical laser according to claim 1, wherein: The 1315 nm wavelength laser introduced into the Raman cell is repeated pulsed laser.

4. The method of mid-infrared wavelength conversion of the chemical oxygen iodine laser according to claim 1, characterized in that: The gas in the Raman cell is hydrogen, and the pressure is 1.0-4.0 MPa.

5. The method of mid-infrared wavelength conversion of the chemical oxygen iodine laser according to claim 1, characterized in that: The pressure in the vacuum chamber is less than or equal to 0.1 Pa.

6. The method of mid-infrared wavelength conversion of the chemical oxygen iodine laser according to claim 1, characterized in that: The working temperature of the iron-doped zinc selenide crystal is less than or equal to 100 K.

7. A conversion device for implementing the method of converting the wavelength of the mid-infrared wavelength of the chemical oxygen iodine laser according to any one of claims 1 to 6, characterized by: The system comprises a chemical oxygen-iodine laser (1), a pulsed magnetic field generator (2), a Raman frequency conversion module (3), and a linear frequency conversion module (4), wherein the pulsed magnetic field generator (2) is placed outside the chemical oxygen-iodine laser (1), the continuous wave output of the chemical oxygen-iodine laser (1) is changed into repeated pulsed output by the periodic pulsed magnetic field generated by the pulsed magnetic field generator (2); the Raman frequency conversion module (3) comprises a focusing lens A (5), a Raman cell (6), and a dichroic mirror A (7) arranged in sequence along the laser light path, and the linear frequency conversion module (4) comprises an output coupling mirror (10), a vacuum chamber (11), and a focusing lens B (8), a dichroic mirror B (9), an iron-doped zinc selenide crystal (13), and a high-reflectivity mirror (14) arranged in sequence along the laser light path, wherein the focusing lens B (8), the dichroic mirror B (9), and the output coupling mirror (10) are located outside the vacuum chamber (11), the output coupling mirror (10) is located on one side of the dichroic mirror B (9), and the iron-doped zinc selenide crystal (13) and the high-reflectivity mirror (14) are arranged in the vacuum chamber (11).

8. The conversion device of claim 7, wherein: A pair of pulsed magnetic field generators (2) are symmetrically arranged on the upper and lower sides of the gain region of the chemical oxygen-iodine laser (1).

9. The conversion device of claim 7, wherein: A heat exchanger (12) is further arranged in the vacuum chamber (11), liquid nitrogen is introduced into the heat exchanger (12), and the heat exchanger (12) provides the required working environment temperature for the iron-doped zinc selenide crystal (13).

10. The conversion device of claim 7, wherein: The iron-doped zinc selenide crystal (13) is polished on both light-transmitting surfaces and coated with an anti-reflection film.

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