Transient thermal measurements using the index of refraction as a temperature sensitive parameter

Two techniques for transient thermal measurements are presented. One measurement technique employs the change of optical index of refraction with temperature, which is usually referred to as the thermooptic effect in optics. Even though this change is very small, in the range of 10^-5/°C, its effect can be transformed into large variations in optical signals by proper design. The other method utilizes the thermoresistive effect of electrical resistance change with temperature. This change is in the range of 4×10^-3/°C, which is adequate to provide a signal for measurement. The intrinsic response time of both techniques is a few nanoseconds, thus providing the means to study the rapid initial temperature rise caused by a step source power. The measured thermal responses are compared with the response calculated using a three-dimensional transient temperature solution derived previously. The measured responses agree well with the calculated one