Sheet laser amplifierTechnical Field
The invention belongs to the field of high-power solid lasers, and particularly relates to a novel sheet-shaped laser amplifier.
Background
In the development history of the high-power solid laser driver 30 for more than one year, the technology of the laser driver has been rapidly developed, and particularly under the excitation of the laser inertial confinement fusion technology, important units and laboratories in many countries of the world have conducted a great deal of research on ultra-high-power laser drivers of various scales and levels, such as the us lifmor laboratory, the france mel laboratory, the university of osaka japan laser engineering center, the Shanghai optical engine institute of china, and the eight places of the middle-aged material.
In ultra high power laser drivers, one very important module is a slab laser amplifier, which provides 99% of the energy of the entire device, the core of the entire driver.
Important parameters for measuring the sheet-shaped amplifier include light transmission aperture, small signal gain coefficient, gain uniformity, energy storage efficiency and the like. At present, the common weakness of the chip laser amplifiers at home and abroad is low gain coefficient of small signals. To solve this problem, the prior art generally increases the number of xenon lamps and increases the pumping intensity, but this measure increases the size of the amplifier, reduces the efficiency and even the reliability of the device, thereby affecting the practicality and stability of the system, and the prior art cannot solve this problem well.
Disclosure of Invention
The invention provides a chip laser amplifier with large small signal gain coefficient, higher efficiency and good compactness from the aspects of parameter optimization and structural design.
The sheet laser amplifier comprises a frame unit, a lamp box I, a lamp box II, a sheet box, an end mirror I and an end mirror II, wherein the sheet box is fixed at the center of the frame unit, the lamp box I and the lamp box II are respectively fixed at the left side and the right side of the frame unit, the end mirror I and the end mirror II are respectively fixed at the front end and the rear end of the frame unit, and the lamp box I and the lamp box II are staggered and overlapped with the sheet box.
The xenon lamp groups in the lamp box I and the lamp box II are composed of 14 xenon lamps, each 7 xenon lamps are connected in series to form a loop, and each xenon lamp is distributed at equal intervals and symmetrically distributed relative to the sheet box.
The working voltage of the xenon lamp discharge loop is 23.5kV, the capacitance is 234 mu F/loop, the inductance is 69 mu H/loop, and the resistance is less than or equal to 120mΩ/loop.
In the lamp box I and the lamp box II, except for a partition glass surface, reflectors are arranged on the remaining inner side surfaces, the back reflectors of the xenon lamps in the lamp box I and the lamp box II are short-wing involute reflectors, the reflectors at the two ends of the xenon lamps are flat reflectors, the reflectors at the top and the bottom of the sheet box are v-shaped flat reflectors, and the opening faces the middle of the sheet box.
The baffle glass of the lamp box is plated with a double-sided anti-reflection broadband chemical film.
The slice box comprises a slice gain medium, a supporting part and a cooling airflow channel, wherein the included angle between the normal direction of the surface of the slice gain medium and the direction of the incident laser is Brewster angle theta, and the horizontal dimension of the slice gain medium is larger than the sum of the laser caliber and the laser horizontal direction offset generated by the refraction factor.
The end mirror I and the end mirror II comprise window glass and mechanical structures, dielectric films for anti-reflection to incident laser are plated on the surfaces of the window glass of the end mirror I and the window glass of the end mirror II, the included angle between the normal direction of the surfaces of the dielectric films and the direction of the incident laser is 1 DEG plus or minus 0.2 DEG, and the front end mirror and the rear end mirror are distributed in an eight shape.
The beneficial effects are that:
The invention obviously improves the gain coefficient and efficiency of the amplifier, reduces the working parameters of components and improves the reliability, the xenon lamps are distributed at equal intervals, the pumping energy is increased under the condition of ensuring the reliable and stable operation of the pumping of the xenon lamps based on the optimized working parameters, the efficiency and the uniformity of the distribution of the radiation light of the xenon lamps on the surface of a gain medium are improved, the gain uniformity of the sheet-shaped amplifier is further improved, the light box sheet boxes are staggered and overlapped, the volume of the module is reduced under the condition of ensuring the performance of the module, the length of the amplifier is reduced to 780mm, the transmission efficiency of the pumping cavity is obviously improved by using the short-wing involute-imitating silver-plated reflector, and the transmission efficiency of the pumping cavity is further obviously improved by arranging the reflector at the top of the light box as a V-shaped light-gathering triangular reflector.
Drawings
Fig. 1 is a structural diagram of a slab laser amplifier.
Fig. 2 is a schematic diagram of the transmission of an incident laser light.
Fig. 3 is a schematic view of the mounting position of the end mirror.
Fig. 4 is a schematic diagram of an exemplary patch amplifier operating light path.
Fig. 5 is an amplifier pumping structure.
Fig. 6 is an amplifier pumping chamber.
The reference numerals indicate 1-frame mounting unit, 2-sheet box, 3-lamp box I, 4-lamp box II, 5-end mirror I, 6-end mirror II, 7-xenon lamp, 8-reflector, 9-partition glass, 10-gain medium, 11-sheet box supporting component, 12-laser to be amplified, 13-amplified laser, 14-beam expanding unit, 15-involute reflector and 16-V type triangular reflector.
Detailed Description
The novel chip laser amplifier disclosed in the present invention is designed and embodied in principle by combining the embodiments and the drawings, but the protection scope of the present invention should not be limited thereto.
The embodiment will be described with respect to a specific embodiment of a sheet-shaped neodymium glass laser amplifier having a light transmission aperture of 400mm×400 mm.
Fig. 1 is a schematic diagram of a sheet-like laser amplifier in an embodiment of the present invention, which is composed of a frame unit 1, a sheet case 2, a lamp box I3, a lamp box II4, an end mirror I5, and an end mirror II 6. The frame unit is an outer frame of the amplifier, the whole frame unit is a relatively closed environment, a cooling nitrogen inflow port is arranged on the upper surface of the frame unit, a cooling nitrogen outflow port and an electrical interface are arranged on the lower surface of the frame unit, the lamp box I3 and the lamp box II4 form a sealed environment by 14 xenon lamps 7, reflectors 8 and partition glass 9, nitrogen channels are reserved on the upper side and the lower side, and the sheet box comprises neodymium glass sheets 10 and supporting parts 11.
The dimensions of the neodymium glass sheet 10 in the illustrated embodiment are selected to take into account the laser caliber and the horizontal offset of the neodymium glass sheet refractive index from the laser. Fig. 2 is a schematic diagram illustrating transmission of laser light to be amplified when the laser light is incident on a neodymium glass sheet, where the incident laser light is incident on the neodymium glass sheet at brewster angle θ=arctan (n), and the refractive index of the neodymium glass sheet causes the incident laser light to shift in the horizontal direction, and the magnitude of the shift Δ is:
where d is the thickness of the neodymium glass sheet and n is the refractive index of the neodymium glass sheet.
Then, according to fig. 2, considering that the installed neodymium glass sheet is a hemmed dimension, the length l of the neodymium glass sheet may be obtained to satisfy the following relation:
Where a is the horizontal dimension of the laser aperture. The dimensions (length. Times. Width. Times. Thickness) of the neodymium glass in this example were selected to be 810 mm. Times.460 mm. Times.40 mm (with a binding). The neodymium glass sheet is placed in the main light path at Brewster angle, and the installation environment cleanliness is better than that of 100 grades, so that laser damage caused by the fact that impurity particles adhere to the surface is avoided.
In the embodiment, the arrangement mode of the xenon lamps is shown in fig. 2, each lamp box consists of 14 lamps, each 7 xenon lamps are connected in series to form a loop, and the xenon lamps of the two lamp boxes are symmetrically arranged. The size parameters of the xenon lamp are that the outer diameter is phi 37mm, the inner diameter is 31mm, the total length is 740mm, the arc length is 440mm, the inflation pressure of the xenon lamp is 160-165 torr, the voltage of a discharge loop of the xenon lamp is 23.5kV, the capacitance is 234 mu F/loop, the inductance is 69 mu H/loop, and the resistance is 120mΩ/loop. The 14 xenon lamps are distributed at equal intervals in the length direction (598 mm).
In the embodiment, the surfaces of all reflectors in the lamp box are plated with silver, the thickness of the plating layer is not less than 40 mu m, the plating layer is required to be firm, so that the plating layer is prevented from falling off in the processes of strong xenon lamp light irradiation, lamp box maintenance and the like, the surfaces of the plated silver are polished to mirror surfaces, the plated silver reflectors are coated with SiO2 protective films, and the reduction of reflectivity caused by vulcanization of the plated silver layers is prevented. The lamp box reflector is required to be insulated from the box body, led out from the cable and grounded. Reflectors are designed on the inner sides of the other surfaces except the glass surface of the partition board in the lamp box so as to ensure the uniformity of pumping of the xenon lamp in the length direction, namely, the reflector is used for mapping the mirror image of the xenon lamp pumping source into an infinitely long light source.
In the embodiment, the window glass surfaces of the end mirror I and the end mirror II are plated with dielectric films for enhancing the reflection of incident laser, and the geometric dimensions (length multiplied by width multiplied by thickness) of the end mirror are selected to be 440mm multiplied by 34mm. The installation position relationship between the end mirror I and the end mirror II is shown in fig. 3, so as to inhibit self-oscillation caused by residual reflection of the end mirror, and the transmittance of the incident laser is not obviously affected, and the angles between the surface normal directions of the end mirror I and the end mirror II and the main light path direction are 1 degrees, so that the end mirror I and the end mirror II are distributed in an eight shape.
The sheet box 2 is fixed at the center of the frame unit, the lamp box I3 and the lamp box II4 are respectively fixed at the left side and the right side of the frame unit, and the end mirror I5 and the end mirror II6 are respectively fixed at the front end and the rear end of the frame unit.
The reflector arrangement of the sheet laser amplifier in this embodiment is shown in fig. 4, 5 and 6. The involute reflectors 15 shown in fig. 5 are positioned behind the xenon lamps, and a corresponding involute reflector is positioned behind each xenon lamp. The involute peak is 3mm from the xenon lamp. The V-shaped triangular reflectors 16 are positioned on the upper and lower surfaces of the pumping chamber with an angular arrangement as shown in fig. 6.
In this embodiment, as shown in fig. 4, the simple working light path of the novel sheet laser amplifier is that the laser 12 to be amplified is first expanded into the laser with the aperture of 400mm×400mm by the beam expanding unit 14, the laser after the beam expansion enters the novel sheet laser amplifier from the end mirror I5, and the amplified laser is output from the end mirror II 6.
The working process of the sheet laser amplifier comprises the steps of firstly charging a power supply module of the laser amplifier, discharging a xenon lamp loop by the power supply module after the charged electric quantity meets the requirement, converting electric energy into light energy by the xenon lamp to irradiate the neodymium glass sheet, absorbing the light energy of the xenon lamp by neodymium ions through radiation transition, forming particle number inversion between upper and lower energy levels of laser in a medium, enabling the neodymium glass sheet to obtain enough energy storage, and enabling neodymium ions to be stimulated to radiate transition from high energy level to low energy level when laser pulses pass through the neodymium glass sheet, so that the amplifying process of laser is realized.
After the laser amplifier is operated, nitrogen with cleanliness better than 100 grades is adopted for sweeping the neodymium glass sheet, so that heat distortion recovery is promoted, attachment of aerosol on the surface of the neodymium glass sheet is avoided, and meanwhile, air is used for sweeping the lamp box, so that heat recovery is promoted.