This paper presents a theoretical and experimental discussion of reflectance and transmittance for S and P-polarized radiation at 250 GHz for silicon and gallium arsenide wafers irradiated by a 6 ns pulsed, 532 nm laser to determine absorption. A two-layer stratified medium theory was developed relying on the Vogel model for carrier lifetime and the Drude model for permittivity. These results contribute to the potential future commercialization of laser-driven semiconductor switch applications such as coupling to a resonant ring or storage cavity.