Ultra-low loss photonic integrated circuit with membrane-type photonic crystal waveguides

TLDR

The study designs and tests an SOI‑based photonic integrated circuit featuring two‑dimensional membrane‑type photonic crystal waveguides. The circuit uses spot‑size converters and butt‑couplers, with each optical interface optimized to minimize back‑reflections and suppress Fabry‑Perot noise. Measured transmission reveals propagation losses of 24 dB cm⁻¹, and the two‑stage coupling with ultra‑long waveguides reduces loss uncertainty to 3 dB cm⁻¹.

Abstract

We report the design and testing of an SOI-based photonic integrated circuit containing two-dimensional membrane-type photonic crystal waveguides. The circuit comprises spot-size converters to efficiently couple light from a fiber into single-mode strip waveguides and butt-couplers to couple from strip waveguides to photonic crystal waveguides. Each optical interface was optimized to minimize back-reflections and reduce the Fabry-Perot noise. The transmission characteristics of each component are measured and record low propagation losses in photonic crystal waveguides of 24dB/cm are reported. The combination of an efficient two-stage coupling scheme and utilization of ultra-long (up to 2mm) photonic crystal waveguides reduces the uncertainty in determining the loss figure to 3dB/cm.