Room temperature low-loss etchless alumina ridge waveguides fabricated by pulsed laser deposition and lift-off

Alumina is a remarkable material for integrated photonics thanks to its broad transparency window spanning from ultraviolet to infrared, its low propagation losses, and its high solubility for rare-earth elements. However, conventional device fabrication processes, particularly those involving etching, often introduce significant optical losses, hindering the performance of high-quality alumina components. Pulsed laser deposition combined with a lift-off process offers an effective alternative, addressing the limitations of etching-based methods. In this paper, we present low-loss alumina waveguides in the visible and infrared spectral ranges, characterized using two distinct approaches. By evaluating the propagation losses in alumina thin films deposited under varying conditions and across different waveguide widths, we achieve losses as low as 2.0 dB/cm. This work demonstrates the potential of this technique for precise alumina structuring, paving the way for innovative rare-earth-doped alumina photonic devices.