Asymmetric Probe, Planar Transient Grating Spectroscopy System

A method of using transient grating spectroscopy, comprising:

• separating a pulsed pump electromagnetic radiation along a pump incident path into pump components;
• separating probe electromagnetic radiation traveling along a probe incident path, angularly offset from the pump incident path, into a reference component and a probe component, the reference component, and the probe component being substantially in a common plane;
• directing the pump components to an inspection location on an inspection surface at a sample;
• directing the reference component and the probe component to the inspection location at the sample from a forward path side of a plane that intersects the inspection surface, the pump components forming a sample transient grating at the inspection location and the reference component and at least portion of the probe component forming a homodyned signal in a detection path as a function of interaction with the sample transient grating, the detection path being at a reverse path side of the plane, at least a portion of the homodyned signal being substantially in the common plane;
• and
• detecting the homodyned signal for use in collecting data for characterizing the sample.

A method of using transient grating spectroscopy, comprising:

• illuminating an inspection location on an inspection surface with pump electromagnetic radiation along a first pump incident path and a second pump incident path to form a sample transient grating at the inspection location, the first pump incident path and the second pump incident path being symmetric about a plane that intersects with the inspection location;
• illuminating the inspection location with reference electromagnetic radiation along a reference incident path and with probe electromagnetic radiation along a probe incident path, the reference incident path and the probe incident path being incident from a forward path side of the plane that intersects with the inspection surface;
• and
• detecting collected electromagnetic radiation that propagates along a collection path, the collected electromagnetic radiation resulting from interactions of the reference electromagnetic radiation, the probe electromagnetic radiation, and the sample transient grating, the collection path being at a reverse path side of the plane that intersects with the inspection surface.