Integrated lasers in crystalline double tungstates with focused-ion-beam nanostructured photonic cavities

摘要

Deeply etched Bragg gratings were fabricated by focused ion beam (FIB) milling in KgdxLu_(1-x)(WO_4)_2:Yb~(3+) to obtain photonic cavity structures. By optimizing parameters such as dose per area, dwell time and pixel resolution the redeposition effects were minimized and grating structures more than 4 μm in depth with an improved sidewall angle of ～5° were achieved. Fabry-Perot microcavities were defined and used to assess the optical performance of the grating structures at ～1530 nm. An on-chip integrated laser cavity at ～980 nm was achieved by defining a FIB reflective grating and FIB polished waveguide end-facet. With this cavity, an onchip integrated waveguide laser in crystalline potassium double tungstate was demonstrated.