Single-mode sapphire fiber Bragg grating

TL;DR

This paper demonstrates the fabrication of single-mode sapphire fiber Bragg gratings with a novel multi-layer cladding design, narrow bandwidth, high-temperature resilience, and potential for remote sensing in extreme environments.

Contribution

It introduces a new method for inscribing single-mode sapphire fiber Bragg gratings using femtosecond laser direct writing with adaptive beam shaping.

Findings

Narrow bandwidth (<0.5 nm) of the gratings

Survival after annealing at 1000°C

Successful inscription within 425 μm sapphire fiber

Abstract

We present here the inscription of single-mode waveguides with Bragg gratings in sapphire. The waveguide Bragg gratings have a novel multi-layer depressed cladding design in the 1550 nm telecommunications waveband. The Bragg gratings have a narrow bandwidth (<0.5 nm) and have survived annealing at 1000{\deg}C. The structures are inscribed with femtosecond laser direct writing, using adaptive beam shaping with a non-immersion objective. A single-mode sapphire fiber Bragg grating is created by writing a waveguide with a Bragg grating within a 425 {\mu}m diameter sapphire optical fiber, providing significant potential for accurate remote sensing in ultra-extreme environments.