Patent ID: 7044636

Claim:
A method of measuring a fast time response of a sample by irradiating the sample using a fast pump light pulse, irradiating the sample using a probe light pulse, and observing a change of the probe light pulse reflected by the sample, corresponding to a response of the sample to the pump light pulse, said method comprising the steps of: preparing a first light source that emits a light pulse periodically for exciting the sample as the pump light pulse, and preparing a second light source, separate from the first light source, that emits a light pulse with the same period as the pump light pulse as the probe light pulse; and electrically controlling a time difference between a time at which the pump light pulse irradiates the sample and a time at which the probe light pulse irradiates the sample, thereby detecting a signal representative of the observed change based on the probe light pulse reflected by the sample, wherein the detected signal varies depending on the time difference of the pump light pulse and the probe light pulse, wherein temperature rise of the sample is detected by a thermoreflectance method, and wherein, in order to measure with high sensitivity a thermoreflectance signal, an intensity of the pump light pulse oscillated periodically per pulse is modulated with a slower period, and an intensity component of a signal synchronized with the slower period is lock-in detected.