AbstractThermally induced dispersive and absorptive optical bistability of CdS is investigated in a temperature range of 20 K to RT. The influence of the geometry of the crystals, e. g., thickness, surface area size, and resonator structure, on the hysteresis feature and switching behavior is investigated. The quality of the thermal contact between the sample and the heat sink strongly influences switch‐back times. Further, starting temperature, light spot diameter, and pulse intensity are varied in order to find a set of optimization criteria for this kind of optical bistability. Experimental results are in good agreement with model calculations.