Femtosecond laser direct-written fiber Bragg gratings with high reflectivity and low loss at wavelengths beyond 4 µm
Abstract
We report on the fabrication of, to the best of our knowledge, the first highly reflective fiber Bragg gratings for the 4 µm wavelength range. A second-order grating with a coupling coefficient ( κ ) of 230 m − 1 , losses 0.25 d B / c m , and a bandwidth of approximately 3 nm was inscribed into the core of a passive indium fluoride ( I n F 3 ) fiber using a femtosecond (fs) laser. Thermal annealing of this grating at a temperature of 150°C for 90 min resulted in the enhancement of κ to 275 m − 1 . Further, we show that I n F 3 fibers respond very differently to irradiation with fs laser pulses as compared to ZBLAN fibers and that this difference manifests itself in a significantly larger process window for inscription and in the formation of a more complex refractive index profile that is believed to be caused by the larger nonlinearity of I n F 3 . This Letter paves the way to the development of new wavelength stabilized all-fiber mid-infrared lasers beyond 4 µm.
Document Details
- Document Type
- Pub Defense Publication
- Publication Date
- Jul 29, 2020
- Source ID
- 10.1364/ol.399329
Entities
People
- Alexander Fuerbach
- Gayathri Bharathan
- Jean-yves Carrée
- Marcel Poulain
- Martin Ams
- Samuel Poulain
- Toney Teddy Fernandez
Organizations
- Air Force Office of Scientific Research