Farhyphen;infrared frequency modulation by optically induced gratings in silicon

摘要

Frequency modulation of 119 mgr;m (2.5 THz) H2O laser radiation by optically induced gratings in Si is reported. The gratings were excited using two diodehyphen;pumped, frequencyhyphen;tunable Nd:YAG lasers. Frequency shifts up to 15 MHz were generated. With 26 mW effective optical exitation power a maximal efficiency of 1.5times;10minus;3was achieved, with a 3 dB rollhyphen;off frequency of 35 kHz for the Si wafer used in the experiment. Results of numerical model calculations are presented, which show that efficiencies in the 10percnt; region should be achievable with moderate optical excitation power. It is pointed out that the principle of optically induced gratings offers a promising tool to transfer frequency modulation from the nearhyphen;infrared to the farhyphen;infrared spectral range.