Patent ID: 9557267
Date: 2017-01-31
CPC Classifications: G01N

Claim:
1. A method for evaluating a substrate material having a substrate material surface and a substrate material sub-surface comprising the steps of: directing a first input beam comprising electromagnetic radiation onto a predetermined area of a substrate material having a substrate material surface and a substrate material sub-surface, the electromagnetic radiation of the first input beam having a wavelength of from about 1000 to about 300 nm; directing a second input beam comprising electromagnetic radiation onto the predetermined area of the substrate material surface, the electromagnetic radiation of the second input beam having a THz wavelength between about 0.3 mm and about 3 microns; mixing the first input beam and the second input beam at the substrate material surface to provide a sum frequency output beam; penetrating the substrate material surface to a predetermined depth of the substrate material sub-surface with the second input beam to provide a THz second harmonic output beam comprising a THz second harmonic signal of the second input beam; receiving the sum frequency output beam with a sum frequency output beam detector; receiving the THz second harmonic output beam with a THz second harmonic output beam detector; and measuring one or more characteristics of the substrate material sub-surface by evaluating the sum frequency output beam received by the sum frequency output beam detector.