Low-loss waveguides written with a femtosecond laser for flexible interconnection in a planar light-wave circuit

TLDR

The study aims to create a low‑loss single‑mode waveguide in boron‑phosphorus doped PLC glass, a material more challenging to write than pure‑silica glass. The waveguide is fabricated by femtosecond laser writing in the doped PLC glass. The laser‑written waveguide has a rectangular core, symmetric near‑field, a propagation loss of 0.35 dB cm⁻¹, a mismatch loss below 0.1 dB, and supports flexible 500‑µm connections with low coupling loss.

Abstract

We describe a low-loss single-mode waveguide in planar light-wave circuit (PLC) glass doped with boron and phosphorus, which is more difficult to write than pure-silica glass. The written waveguide has a rectangular core, a symmetric near-field pattern, and a propagation loss of 0.35?dB?cm. The loss that originates from the mode-field mismatch between the mode-field diameters of the written and the PLC waveguides is less than 0.1?dB?point. In addition, we successfully connected PLC waveguides with a 500-?m-long waveguide written with a laser. The laser-written waveguide can flexibly connect PLC waveguides with a low coupling loss.