Laser-assisted selective chemical etching for active trimming of GaAs waveguide devices

A technique for active trimming of GaAs channel waveguides using diode-laser-assisted wet chemical etching is described. Using this technique, the relative transmission through one leg of a 1.3 mu m directional coupler was varied from 0.1 to 0.8 in a controllable manner. The trimming process, which is carried out while a probe signal is transmitted through the device, can be used to correct for normal fabrication errors and can eliminate the requirement for DC bias voltages in devices such as modulators and switches.<>