Multi-pass amplifier technology has become the main development direction of high power solid-state laser devices. It is necessary to adjust and maintain the laser optical path,establish a mathematical model and adjustment scheme for optical path collimation,and set up six-pass amplification using matrix optics method. The mathematical model of the automatic collimation system is used to obtain the analytical expressions of the far and near-field laser spot offset and adjustment. The feasibility of the optical path principle and adjustment method of the auto-collimation system is verified.
The application of the solid state lasers has been greatly expanded in many domains. The laser system is required to be highly integrated. In this paper, an integrated design scheme of laser diode pumped solid state laser is proposed. The size of the device is reduced by integrating the laser power source with LD pump module. The MCU and low-temperature drift drive circuit is utilized as the hard core. The simplified effective pre-stage DC-DC power source and a quasiresonant full-bridge temperature control circuit are designed. The deep negative feedback for the discharge control loop is concluded in the design. The TEC is used and the control accuracy is ±0.5℃ by the using of predictive PID. The ripple and rise time of the current waveform is tested and the stability of the power supply operated at 20Hz is verified by the load test. The experiment results reveal that this system has good load capacity and stability. Compared with the previous power supply system, this system is small and compact. The power supply efficiency is improved by more than 10% and the size of device is greatly reduced.
A growing number of applications are calling for the compact high energy laser sources. In the last decade, significant progress has been made in the area of solid state lasers especially fiber lasers. The solid state laser is widely used in the processing industry, telecommunication systems at present. However, thermal effect, nonlinear effect and the damage of optical components limits the output power. We present a laser coherent combining technique based on heterodyne method in all-fiber feedback format. In this technique the feedback signals are coupled and transferred by fiber to simplify the system, while all factors of the signals such as the wavefront distribution, polarization state, power ratio of the sub-beams and the reference beam need to be considered and strictly controlled. Compared with the previous system, this technique brings another important advantage: Only the coupling side should meet stringent tolerance toward collimation. Phase detection for laser interferometry, phase control of sub-lasers is theoretically analysis and simulated to reveal the system control bandwidth, phase precision. A high speed phase detection circuit and a phase control circuit are developed. Proof of concept of this technique is experimentally demonstrated at 1.06μm. The experiment setup is shown. Stable results are obtained. The peak power rises up while the theoretical result is 2. Experiments reveal the validity of the technique in nanosecond pulse laser coherent combining.
We demonstrated a large face pumped double-sided liquid cooling Nd:YAG slab laser. The pump light incident from the large surface of the crystal, which are cooled by high-speed flowing cooling water, while the laser beam incident on to the end face, and travels in ZigZag path along the long direction in the crystal. The flat-flat resonant cavity was built, and the output coupler transmission was 30%. The Nd:YAG slab crystal with trapezoidal shape was used as the gain medium, the size of which was 190mm×12mm×4mm, one of the surfaces of 190mm×12mm was coated with antireflection film for 808nm and another was coated with reflection film for 808nm, and the end faces of 4mm×12mm were coated with antireflection film for 1064nm, the doping concentration of Nd3+ ion was 1.0at.%. The CW LD array and QCW LD array were used as the pump source to pump the slab crystal, the light emitting surfaces of which have the same size, and the pumping light passed through the pump windows made off used silica and incident into the crystal. Under CW LD pump, the maximum of 420W laser output was gotten, and under QCW LD pump, the maximum of 502W laser out put was gotten. Due to the much higher peak power of QCW laser diode, the small-signal gain was much higher, and induced the optical efficiency of QCW pumping system was much higher, and its thermal effect was relatively smaller because of the high extraction efficiency.
Side diode pumped electro-optical Q Switching Nd: YAG is demonstrated as master oscillator. F-P etalon and twisted-mode cavity combined configuration is introduced to select longitudinal modes. The seed light experiences a round trip through the two flash pump amplifiers, in this device, the 4f image transmission system and SBS phase conjugate mirror is adopted in order to improved beam quality, by compensating the heat depolarization effect and eliminate wave-front distortion. In the condition of 1 or 5 repetitions of the wavelength at 1064nm, it produces the pulse energy of 300mJ, pulse width of 12ns, and energy instability (RMS) below 3% in single longitudinal mode operation. With a type two-phase matched KTP crystal, 532nm green light is yielded, at 1 Hz repetition rate, the pulse energy of green light is more than 150mJ.
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