Investigation On Nd:YAG 1319nm/1338nm Dual-wavelength Laser Used For Achieving Terahertz Radiation

Terahertz radiation has important applications because of many frontiers in medical imaging, physical detection and astronomical observation; it has been widespread concern of scholars so far. Currently terahertz radiation is difficult to directly apply to practical production, scientific research and other fields because of its poor performance of output laser. This paper aims to research on LD end-pumped Nd:YAG crystal to achieve high power 1319nm/1338 nm dual-wavelength laser output and provide theoretical and experimental basis for high-power terahertz radiation.In this paper, the dual-wavelength laser output characteristics were researched by combining both theoretical and experimental. The thermodynamically and the optical stable laser resonators was theoretical studied and achieved for the first time. The high power, high beam quality LD end-pumped 1319nm/1338 nm dual-wavelength laser output for continuous laser and AO Q-switched laser were obtained, and the output power of the dual-wavelength laser into terahertz radiation was researched on this basis. The main research contents are as follows:(1) Based on CW LD end-pumped Nd:YAG crystal, combined rate equations for 1319nm/1338 nm dual-wavelength laser, the simulation expression and results of the dual-wavelength laser average output power, the laser pulse peak power and laser linewidth are given;(2) The temperature distribution of LD end-pumped non-bonded Nd:YAG crystal and bonded Nd:YAG crystals were established and comparative analyzed, the effective plan of thermal effects compensation scheme have been proposed. The thermal lens focal length of the laser crystal under working conditions was simulated to provide the basis for design of laser resonator. Combined thermal lens focal length of laser crystal and end-pumped approach, thermodynamic and optical stability dual-wavelength laser cavity was designed;(3) Carried out the experiments of LD end-pumped 1319nm/1338 nm dual-wavelength laser output for continuous laser and AO Q-switched laser, finally, got continuous output of 5.77 W, the beam quality of M2=1.13, the proportion of dual-wavelength was close to 1:1, the pulse output peak power of 4300 W under the repetition frequency of 10 k Hz;(4) Physical processes of obtaining terahertz radiation used dual-wavelength laser through the process of nonlinear difference frequency were analyzed. Combined with the physical properties of the difference frequency crystal DAST, model of difference frequency energy conversion process was established, the power of terahertz radiation for theoretically possible output was 15.34 m W of 3.23 THz.