Mid-infrared waveguides in zinc sulfide crystal

Abstract

Depressed cladding optical waveguides have been fabricated in a zinc sulfide (ZnS) crystal by femtosecond laser inscription. The structures support single- or multi-mode guidance at the mid-infrared wavelength of ~4 μm. The two-dimensional refractive index profiles of the single-mode waveguides have been reconstructed, and the modal profiles of TE and TM modes were calculated numerically, that show very good agreement with the measured near-field modal profiles. The minimum propagation losses of the multimode cladding waveguides at 4 μm were ~1.1 dB/cm for the TE polarization and ~1.3 dB/cm for the TM polarization.