Double Doppler wavelength conversion of infrared optical pulses by moving grating of refractive index in semiconductors

摘要

A time-domain model of an excited semiconductor medium as a moving Bragg grating was used to investigate a double-Doppler wavelength conversion of an infrared (#lambda#_0 = 1.5 #mu#m) 0.8 ps width optical pulse. In order to calculate ultrafast electromagnetic transients, a time-domain Volterra integro-differential equation was used for simulations. It is shown here that the high drift velocity of carriers in an InAs semiconductor produces a 3.5 nm up and down (9.7 THz) conversion span. The converted pulse width and spectral density strongly depend on the contrast of permittivity modulation. The depth of modulation has to be at least 5 - 7. A - 3 dB conversion efficiency can be gained with a depth of modulation more than 7 and a length of semiconductor layer greater than 20 #mu#m.