Nanosecond transmission to total internal reflection switching has been demonstrated using a thin absorbing film of carbon microparticles suspended in ethanol. The switching results from laser-induced cavitation and the large refractive index mismatch that occurs when the vapor bubble meets the surrounding glass substrate. This extraordinarily large refractive index change (≳0.3) causes the incident beam to be totally internally reflected at the glass-vapor interface. Switching energies below 1 μJ have been measured using a 5 ns doubled Nd:YAG laser (λ=0.532 μm) pulse. We have investigated the effects that particle concentration, film thickness, and bias temperature have on switching performance.