Dissertation Defense

Reconfigurable Optical Devices Utilizing Chalcogenide Phase Change Materials

Mohsen Jafari


There is a great demand for tunable integrated photonic devices for the visible and near infrared region. Applications of such devices include time keeping, communication, imaging, sensing, and displays systems. Using a chalcogenide glass, Germanium Telluride (GeTe), within a sub-wavelength layered optical cavity, tunable integrated optical devices with reliable and reversible operations were developed. GeTe has proven to have an outstanding reliability and has been used in phase change memories that have been developed in recent decades for ultra-low power storage systems. By employing two distinct index of refraction values of the thin GeTe films at their glassy amorphous and metallic crystalline states at optical wavelengths, we demonstrated an optical shutter with noteworthy contrast of up to 40 dB at 1.55 um, 1.1 um, and 780 nm for the use in an integrated chip-scale atomic clock. Moreover, a multi-color filter working at visible range (400 nm-750 nm) with four interchangeable colors is shown in a sub-wavelength film coating (thickness<300 nm) that included two GeTe layers with only a single integrated joule heater element. Using this optimized design, the tunable color filter showed reversible blue, red, orange, and green colors. The low static power consumption of these devices, due to reliable memory-based phase transitioning of GeTe, makes them prime candidates for a number of portable consumer electronic applications.

Sponsored by

Professor Mina Rais-Zadeh & Professor L. Jay Guo