The switching response of a CdTe-InSb nonlinear etalon subject to an intense light beam is reported. The device is illuminated with a high intensity pulsed pump beam and a low intensity pulsed probe beam. The pump beam has a wavelength that corresponds to a negative slope of the low intensity reflectance spectrum of the etalon and has sufficient power to change the index of refraction in the etalon cavity. This causes a shift of the spectrum, a decrease in the reflectivity, and an increase in the electric field in the etalon cavity which further shifts the spectrum. This process continues until a minimum reflection level is reached. The output yields the convolution of the probe beam with the device response to the pump pulse. It appears that the switching response of the etalon is much faster than could be determined with the 100 ps pulses used.