A Study of Quasi-Phase-Matched Difference Frequency Generation of Infrared Radiation

• Main Authors: Shin Mou, 牟昕
• Other Authors: Ching-Fuh, Lin
• Format: Others
• Language: en_US
• Published: 2000
• Online Access: http://ndltd.ncl.edu.tw/handle/93357991762185785952

碩士 === 國立臺灣大學 === 光電工程學研究所 === 88 === Quasi-phase-matched difference frequency generation of mid-IR radiation have been studied from the numerical simulation to the real experiment in this thesis. In the numerical part, a quasi-3D IFD-BPM was proposed. It is improved from 2D model to a cylindrically symmetric 3D model named quasi-3D. This model is practical to simulate QPM DFG. A DFG experiment is simulated, and the simulation result of quasi-3D IFD-BPM is closer to it than that of 2D IFD-BPM. Some phenomena in QPM DFG are also surveyed with quasi-3D IFD-BPM. The most important one is that the DFG beam waist could be kept as constant inside the QPM crystal. This implies spatial soliton may be generated with QPM DFG. In the experimental part, a home-made tunable high power semiconductor laser is used as the pump source to carry out the DFG in PPLN. At first, the single layer AR coating on a tapered gain region semiconductor is investigated and carried out. This device is used for the tunable semiconductor laser with external-cavity grating feedback. After the AR coating, the threshold current is raised up slightly and the slope efficiency of L-I curve is lowered. The spectra get wider apparently. With grating external-cavity, the tuning range is 10nm for power from 300mW to 450mw. It is barely satisfactory to be the pump source of DFG. At last, the DFG pumped with tunable high power semiconductor laser is carried out. The maximal power is 3.4mW at 4.32mm. The efficiency is 7.32mW/cmW2, which is much smaller than the simulated estimation and others’ experimental results. This is caused by the large incident angle (48°) and maybe the bad optical field of semiconductor laser.