Stress-induced optical waveguides written by an ultrafast laser in Nd³⁺, Y³⁺ co-doped SrF₂ crystals

Abstract

High refractive index contrast, birefringence and luminescence properties of written channel waveguides inside fluoride crystals written by femtosecond (fs) laser have been studied. Herein, fs laser-induced stress affected zone is an efficient tool to create birefringence and high refractive index contrast in Nd 3+ , Y 3+ codoped SrF 2 crystal for wide range of pulse energies and repetition rates. In fabricating the waveguides at high repetition rate (typ. 500 kHz), we avoided too much heat accumulation, and thus they exhibit lower propagation loss in codoped SrF 2 crystal (1.63 ± 0.21 dB/cm for TM-polarization). The measured retardance can be interpreted as related to stress-induced birefringence in response to free of stress volume expansion photoinduced in the non-spherical irradiated zone. The photoluminescence and lifetime measurements are also carried out in order to understand local changes of the network in and around femtosecond laser induced waveguides written in codoped SrF 2 crystal.

Optical Fiber Sensors by Direct Laser Processing: A Review

“…There are several works reporting waveguides inscribed by femtosecond lasers in bulk glasses [20,33,82,[115][116][117]. However, the number of studies reporting waveguides inscribed in optical fibers is significantly lower.…”