  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.
