An Ultrafast Light Gate

A simple technique is described for gating light on and off on the picosecond time scale. The gate is built in much the same fashion as traditional Kerr cells, the difference lying in the use of powerful optical pulses rather than electrical pulses to induce a birefringence in various liquids. The direct observation of the exponential decay (τ = 32 ± 6 psec) of the birefringence induced in nitrobenzene shows that orientational effects are largely responsible for the refractive index changes induced by light in this liquid.