The temperature dependent refractive index of amorphous silicon has been measured at a wavelength of 820 nm from room temperature up to nearly the melting point close to 1200 °C. The method employed is to use a single pulse from a XeCl excimer laser to heat the silicon without crystallizing it and to measure the transient reflectivity. This is then modeled by converting a calculated temperature profile into an effective multilayer structure and calculating the reflectivity using a transfer matrix formulation. The refractive index is optimized using simulated annealing. The real part of the refractive index is found to vary linearly with a temperature coefficient of 3.85×10-4 while the extinction coefficient is found to vary as exp(3.82×10-3T), with T=0 at room temperature.