Terahertz double-Doppler wavelength shifting of infrared optical pulses in excited semiconductor medium

A time-domain model of an excited semiconductor medium as a moving Bragg grating is used to investigate a double-Doppler wavelength conversion of an infrared (/spl lambda//sub 0/=15 /spl mu/m) 0.8 ps optical pulse. In order to investigate ultrafast electromagnetic transients, a time-domain integro-differential equation has been used for simulations. It is shown that the high drift velocity of carriers in InAs semiconductor produces a 10 THz conversion span. The converted pulse width and spectral density depend on contrast of permittivity modulation and have to be as high, as possible.