Low-loss waveguides in ultrafast laser-deposited As_2S_3 chalcogenide films

TLDR

Ultrafast pulsed laser deposition produced atomically smooth 5‑µm‑thick As₂S₃ films that are photosensitive near 520 nm, enabling waveguides to be directly patterned by photodarkening with an Ar‑ion or frequency‑doubled Nd:YAG laser, and their linear and nonlinear optical properties were characterized. Photodarkened waveguides exhibited optical losses below 0.2 dB cm⁻¹ beyond 1200 nm and below 0.1 dB cm⁻¹ in as‑deposited films, while the third‑order nonlinearity n₂ ranged from 100 to 200 times that of fused silica between 1100 and 1500 nm with low nonlinear absorption.

Abstract

Ultrafast pulsed laser deposition was used to successfully deposit atomically smooth 5-μm-thick As2S3 films. The as-deposited films were photosensitive at wavelengths close to the band edge (≈520 nm), and waveguides could be directly patterned into them by photodarkening using an argon-ion or frequency-doubled Nd:YAG laser. The linear and nonlinear optical properties of the films were measured as well as the photosensitivity of the material. The optical losses in photodarkened waveguides were <0.2 dB/cm at wavelengths beyond 1200 nm and <0.1 dB/cm in as-deposited films. The third-order nonlinearity, n2,As2S3, was measured using both four-wave mixing and the Z-scan technique and varied with wavelength from 100 to 200 times fused silica (n2,Silica≈3×10-16 cm2/W) between 1500 nm and 1100 nm with low nonlinear absorption.