Development of Field-Controlled Smart Optic Materials (ScN, AlN) with Rare Earth Dopants

Abstract

Development of the fundamental materials for field-controlled spectrally active optics is essential for new concept of optics, such as: membrane optics, filters for LIDARs, windows for sensors and probes, telescopes, spectroscopes, cameras, light valves, light switches, flat-panel displays, etc. The dopants of rare earth elements create a number of absorption and emission band structures and can easily be incorporated into many high quality crystalline and amorphous hosts. In wide band-gap semiconductors, like ScN and AlN with rare earth dopants, the existing deep levels can capture or emit the mobile charges, and can be ionized with the loss or capture of the carriers. This is a fundamental basis for smart optic materials. ScN and AlN doped with rare earth elements (Er, Ho) were tested under an applied electric field to characterize spectral and refractive index shifts by the Stark Effect. Decrease in refractive index under an applied electric field was observed as a shift in absorption coefficient using a variable angle spectroscopic ellipsometer. Under an electric field, mobile carriers are redistributed within the space charge region (SCR) to reveal this electro-refractive effect. The main research goal is to facilitate concept demonstration and testing of field-controlled spectrally smart active optics for optical multi-functional capabilities in a selected spectral range.