Method and apparatus for measuring material properties using transient-grating spectroscopy

An apparatus for measuring a property of a sample, comprising:

• an excitation laser that generates an excitation laser beam;
• a beam-delivery system, aligned along an optical axis, that separates the excitation laser beam into at least two sub-beams;
• an imaging system aligned along the optical axis that collects at least two sub-beams and focuses them onto the sample to form an optical interference pattern that generates a time-dependent response in the sample;
• a probe laser that generates a probe laser beam oriented to diffract off the time-dependent response to form at least two signal beams;
• a beam-splitting optic oriented in the optical axis to transmit the excitation sub-beams, reflect the probe beam towards the sample, and reflect at least one signal beam;
• a detector that detects at least one signal beam and in response generates a radiation-induced electronic response;
• and
• a processor that processes the radiation-induced electronic response to determine the property of the sample.