InGaP/AlInGaP quantum well waveguide modulators for visible wavelengths

Recent advances in visible wavelength semiconductor lasers (<700 nm) [1] have spurred interest in modulators operating at these wavelengths. This wavelength range is of enormous interest in the areas of plastic fiber communications, displays and optical storage. Although multiple quantum well (MQW) waveguide modulators have been successfully demonstrated in the IR wavelength range [2], development of visible MQW modulators has been severely limited by material constraints [3]. II-VI materials, such as CdZnTe/ZnTe MQWs [4] and ZnSe/ZnSSe bulk layers [5] have been used to fabricate waveguide modulators at operating at 640 nm and 488 nm, respectively. In this letter, we report a first MQW GaInP/AlGaInP waveguide modulator. Use of this material system automatically assures compatibility and integrability with the most promising visible semiconductor lasers, which also consist of GaInP/AlGaInP layers. Integration of such modulators with compatible lasers could result in much faster switching than direct modulation of the active devices, as well as chirp free operation. Switching speeds of modulators are RC limited, because they rely on field effects for operation. These switching speed can be reduced by lowering device capacitance, which depends on the device size and can be made as small as technologically viable. In contrast, lasers rely on carrier injection and therefore their switching speeds are limited by carrier lifetimes. Furthermore, modulator switching requires far less power, since no current is drawn. These two considerations make integration attractive for plastic fiber communications and displays.