Record-low propagation losses of 154 dB/cm for substrate-type W1 photonic crystal waveguides by means of hole shape engineering

摘要

Large propagation losses in the order 600-1000 dB/cm were reported in the past for planar line-defect photonic crystal waveguides with a weak vertical refractive index contrast (substrate-type). Loss-relevant factors are a well-suited design of the photonic crystal pattern and a high-quality fabrication technology. Here, the focus is on the latter. Two methods—a thermally driven mass transport process and an ultra-slow, selective wet-etching process—are assessed with respect to their capability of enabling low-loss waveguides. With the resulting hole shape, we experimentally demonstrate record-low propagation losses of 154 dB/cm for W1 photonic crystal waveguides in the InP/InGaAsP system.