Optical characterization of femtosecond laser induced active channel waveguides in lithium fluoride crystals

Abstract

We successfully realized broad-band light-emitting color center waveguides buried in LiF crystals by using femtosecond laser pulses. The characterization of the waveguides was performed by optical microscopy, photoluminescence spectra, loss measurements and near-field profiling. The experimental results show that the direct-writing fabrication process induces low-index contrast active channel waveguides: their wavelength-dependent refractive index changes, estimated from 10−3 to 10−4 depending on the writing conditions, allow supporting few modes at visible and near-infrared wavelengths.