Fabrication and characterization of photonic devices directly written in glass using femtosecond laser pulses

TLDR

Near‑IR femtosecond laser pulses are used to write single‑mode straight and curved waveguides in silicate glasses, with parameters tuned for smooth mode profiles, refractive index changes reconstructed from near‑field data, propagation losses measured by throughput and Fabry‑Perot resonators, and both coarse and fine period gratings fabricated and thermally characterized. The technique’s usefulness is shown by creating an optical interleaver.

Abstract

Both straight and curved waveguides are written in a variety of silicate glasses using near-IR femtosecond laser pulses. Writing parameters are identified that produce waveguides that support only a single mode and yield smooth-mode profiles. The laser pulse-induced refractive index change is reconstructed from near-field mode profile data using the scalar wave equation and by refractive near-field profiling. Waveguide propagation losses are determined by throughput and Fabry-Perot resonator measurements. Both coarse and fine period gratings are written and characterized, and the thermal stability of these gratings is investigated. The utility of the femtosecond writing technique is demonstrated by fabricating an optical interleaver.