Abstract

Diffractive Optical Elements (DOEs) are used to manipulate the phase of a light beam in order to perform functions such as beam-steering, fan-out, wavelength discrimination and focusing. Typically, DOEs are fabricated by etching a structure into a piece of glass which generates a static phase profile being added to the input light beam. Dynamic diffractive optical elements which modulate the phase pattern of a beam can also be generated through the interaction of a liquid crystal with an electric field [1]. We report a more recent innovation [2] that uses an electrically addressed Multiple Quantum Well (MQW) structure incorporated into an asymmetric Fabry-Perot cavity to produce π phase modulation without any change in device reflectivity. The device relies on the change in absorption within the cavity to switch the dominance of the role played by one of the two Fabry-Perot mirrors thereby achieving the π phase change. Phase modulation is therefore obtained by electro-absorption modulation induced by the Quantum Confined Stark Effect (QCSE) which is acting in the MQW regions of the structure.

© 1997 Optical Society of America