DYNAMIC ETCH MASK TECHNIQUE FOR FABRICATING TAPERED SEMICONDUCTOR OPTICAL WAVE-GUIDES AND OTHER STRUCTURES

Using a novel dynamic etch mask technique and wet chemical etchants, we have produced semiconductor structures with tapered thicknesses, with horizontal slope angles as small as 0.9°. With this technique we have fabricated GaAs/GaAlAs rib optical waveguides in which the etch depth tapered from 0.2 to 1.0 μm over a distance of 50 μm, resulting in a 2× change in mode size, with an excess taper loss of less than 0.2 dB. The technique is capable of producing tapers in different orientations, at arbitrary locations on a sample, and appears to be useful for a wide variety of materials systems and devices.