Abstract

The switching properties of the zero-gap directional coupler were investigated by using a picosecond mode-locked cavity-dumped Styryl-9M dye laser in a pump-probe configuration. Both pump and probe were collinear and focused onto one side of the overmoded waveguide structures. When the pump beam was completely blocked, the probe beam emerged from the one side of the coupler. When the probe pulses arrived just before (~20 ps) the pump pulses, the probe beam remained in the same side of the waveguide. However, when the probe delay was changed so that the probe pulses arrived slightly later than the pump pulses, the probe pulses were switched into the adjacent side of the output of the waveguide. The ratios of the intensities of the output spots were about 1:9 in both the switched and unswitched state. The probe delay was scanned in small steps in order to time resolve the switch times. The signal in the low channel was observed to rise while that in the other channel decreased within 1-2 ps. By scanning the probe delay over 6.7 ns, the recovery time of the nonlinear coupler was found to obey an exponential decay with a time constant of about 1 ns.

© 1990 Optical Society of America