UC San Diego

The development of solid-state lasers with emission in the eye safe region of 1.5 μm is interesting for scientific and industrial purposes including laser cutting/manufacturing, communications and surgery. In this work I present the processing and characterization of erbium (Er:Al2O3) and erbium, chromium co-doped (Er:Cr:Al2O3) bulk aluminum oxide for laser gain media applications. These new gain media have excellent thermomechanical properties and are promising for laser power scaling.

In the first portion of this dissertation Current Activated Pressure Assisted Densification (CAPAD) is implemented to process and consolidate transparent bulk polycrystalline Er:Al2O3 ceramics via a simultaneous solid-state mixing and densification route. The materials have high transparency at the emission wavelength, and absorption lines characteristic of Er3+. Room temperature photoluminescence reveal broad emission peaks in the expected range of ~ 1.5 μm corresponding to intra-4f transitions in Er3+. The emission peaks are narrower at cryogenic temperatures (down to 10 K) revealing thermally broadened emission. In addition, ~ 1.5 μm emission has relatively long lifetimes that do not vary across a broad emission spectrum (1.5 - 1.6 μm), suggesting similar local environment of optically active Er ions responsible for the broad emission.

In the second portion of this dissertation, chromium ions are co-doped with erbium into the alumina matrix, as a sensitizer in order to increase the absorption cross-sections. The ~ 1.5 μm emission corresponding to Er3+ can be accessed through the broad and deep chromium absorption bands. The result is improved absorption and longer emission lifetimes compared to the singly doped Er alumina materials. The Cr:Er:Al2O3 is promising as a tunable near infrared laser gain material that can be pumped with 0.532 μm, a wavelength commonly used for pumping Ti:Sapphire, the most successful tunable short pulsed laser. A common theme of this work is the interplay between material processing, the material properties, and the development of optical devices using bulk polycrystalline transparent ceramics.