Self-, cross-, and induced-phase modulations in condensed matter

Abstract

When an intense laser pulse propagates through a medium, it changes the refractive index. This in turn changes the phase, amplitude, and frequency of the incident laser pulse. If an additional coherent light pulse is present, coupled phase modulation occurs. Three types of coupled phase mode are presented. Comparison of the spectral broadening of the Raman line produced in an optical fiber with the spectral width of the pump laser line has shown evidence for cross-phase modulation. Induced-phase modulation occurs when a weak picosecond laser pulse of frequency ω1 propagates in a glass together with another intense laser pulse of frequency ω2. Induced spectral broadening about a weak nonphase matched second harmonic at 527-nm pulse is observed by propagating an intense primary 1054-nm picosecond laser pulse through ZnSe crystals. Induced spectral broadened pulses with wavelengths spanned from 500 to 570 nm generated in ZnSe appear to have about the same propagation time as the pump 1054-nm pulse. The apparent dispersionlesslike propagation of the induced spectral broadened pulses is discussed.