SEPARATION OF OPTICAL THIN-FILM AND SUBSTRATE ABSORPTION BY OBLIQUELY-CROSSED PHOTOTHERMAL DEFLECTION - THEORY

An explicit three-dimensional calculation of c.w. modulated phototherm al deflection (PTD) with obliquely crossed geometry, including optical thin film and substrate absorption, has been presented. Theoretical r esults show that the obliquely crossed PTD technique is feasible to se parate the thin film and substrate absorption, and to measure low thin film absorption under high substrate absorption by appropriately adju sting the cross-point position of the excitation and probe beams. Meas urement of the thin film absorption is not affected by the thermal pro perties of the substrate. The obliquely crossed PTD also provides a me thod for real-time monitoring of thin film generation.