Phase-Change Materials for Photonic Limiters

Limiters, with their optical properties highly dependent on the wavelength and intensity of the incoming light, are often used to protect sensitive optical components. Currently most limiters are sacrificial, destroyed after a single high intensity exposure. As an alternative, this work focuses on photonic limiters because they significantly increase the cost-efficiency by their high damage threshold and reusability. We study a photonic limiter design with phase-change material (PCM) as a key component. To incorporate PCM in the limiter design, we use ellipsometry to characterize PCM optical property at a wide range of wavelength and temperature. An example of such materials is GeSbTe (GST), an alloy consisting of germanium, antimony and tellurium. Around a critical temperature, GST transforms from amorphous to crystalline, thereby switching its optical properties. Besides GST, we also examine the optical properties of other semiconductors such as ZnO and GaAs as possible material for other limiter designs.