Abstract

The mobility of photoexcited charge carriers in photorefractive insulators can be measured with a holographic time-of-flight technique.¹ By illuminating the crystal with two interfering 30 ps laser pulses at the wavelength of 532 nm, we create an instantanuous sinusoidal pattern of photoexcited charge carriers. A strong electric field E₀ is applied across the crystal causing the sinusoidal pattern of charge carriers to drift with a velocity μE₀, where μ is the mobility. With a proper choice of the interference fringe spacing Λ, the superposition of this drifting charge pattern on the complementary pattern of photo-ionized traps creates an observable oscillating space charge field. We probe this oscillation by diffracting a weak cw He-Ne beam from the refractive index grating that is created via the electro-optic effect. The period P_t of the observed oscillation is the time required for photoexcited charge carriers to drift over one spatial period Λ.

© 1991 Optical Society of America