Light guiding and optical resonances in ZnS microstructures doped with Ga or In.

The high refractive index of ZnS (about 2.4 in the visible range) makes ZnS microstructures good candidates for the fabrication of light guides and resonant microcavities. Light guiding behaviour has been studied in several ZnS structures. In particular, in this work the behavior of rods and plates has been investigated and it is has been shown that the morphology of the studied structures plays a determinant role on the supported resonant modes. In ZnS:Ga and ZnS:In structures investigated in the present work Fabry-Perot as well as Whispering Gallery resonant modes are supported. A good agreement has been found between the experimental results and the theoretical model used to describe both types of resonances, which have been used to estimate the refractive index of the doped material. In ZnS:Ga wires with triangular cross-section a lasing effect has been observed in the blue-green range. To our knowledge, it is the first time that resonant modes in visible region have been studied in doped ZnS.