Abstract : A model has been developed for mass transport of two-dimensional surface profiles for which a Cartesian coordinate system can be conveniently used. Simple analytical solutions have been obtained that provide valuable insights for the fabrication of microoptical structures. A mode of laser operation has been discovered that allows a single Nd:YAG laser with an intracavity nonlinear crystal to stably generate light at the 589-nm sum frequency of the 1064- and 1320-nm outputs. The dynamics of this new mode of operation has been investigated experimentally. The frequency response of the microchip laser to pump-power modulation has been derived in closed form. It is shown that pump-power modulation is a viable technique to change the output frequency of microchip lasers. Strained InGaAs/A1GaAs quantum-well diode lasers have been fabricated on Si substrates for the first time, with the objective of improving laser reliability by incorporating in the active layer to inhibit the propagation of dark-line defects. One graded-index separate-confinement heterostructure single-quantum-well laser with an In0.05Ga0.95As active layer has operated CW for 56.5 h, a record lifetime for GaAs-based diode lasers on Si. Thin films of polysilyne have been patterned by exposure with 193-nm radiation followed by selective etching of the unexposed areas in a HBr plasma. Patterns with 0.2microns resolution and high aspect ratio were obtained when this dry development process was applied to bilayers consisting of polysilyne on an organic planarizing layer.