A New Waveguide Switch/Modulator using the Heterostructure Field Effect Transistor,

An optical waveguide switchmodulator is an important element for photonic switching systems. It is very important for these devices to be compatible with other electronic and optical components. In particular, it is desirable to have them monolithically integrated with lasers, transistors, and detectors. Implementation of a modulator is typically done using the Quantum Confined Stark EffectQCSE in a reverse biased PIN structure or using free carrier effects, both electrons and holes, in a forward biased PN structure. It has also been demonstrated that control of only electrons in a single quantum well via a gate electrode in an FET configuration can dramatically affect the optical absorption. A detailed analysis of the physical mechanisms controlling the changes in absorption due to the channel charge has also been given. Modulators using gate control of a channel charge benefit from both the high contrast available due to free carriers as well as high speed due to FET action. Recently the Heterostructure Field Effect Transistor HFET was reported as an ideal transistor for optoelectronic integration because of its unique waveguiding properties. We report here the operation of the HFET as an optical absorption modulator using its waveguiding capability.