Optical Measurement/Evaluation Method And Optical Measurement/Evaluation Apparatus

摘要

A high-sensitivity evaluation technique for optical anisotropy. An optical measurement/evaluation apparatus A has an optical pulse generator 1 which generates optical pulses, half mirror 3 , first mirror 5 , second mirror 7 , third mirror 9 , retroreflector 11 , wave plate 15 , lens 17 , spectroscope 21 , and controller (PC) 23 . An optical pulse L 1 emitted from the optical pulse generator 1 is separated into two pulsed lights L 2 and L 3 by the half mirror 3. The pulsed light L 2 is reflected by the mirrors 5 and 7 (pulsed lights L 4 and L 5 ) and polarized light of the optical pulse is rotated by the half-wave phase plate 15 installed on a rotary stage 15 a and is focused on a surface of a specimen S by the lens 17 (L 8 ). The optical pulse L 3 is reflected by the retroreflector 11 which returns light parallel to incident light and non-coaxially (L 6 ), and reflected by the mirror 9 . Then polarized light of the optical pulse is rotated by the half-wave phase plate 15 installed on the rotary stage 15 a and is focused on the same position on the surface of the specimen S by the lens 17 through an optical path L 7 different from L 8 above. In so doing, the linearly polarized lights of the two optical pulses are directed at the specimen S by being aligned approximately parallel to each other and being rotated simultaneously. A phenomenon known as four-wave mixing occurs when a wave number k₁ is given to the optical pulse L 8 and a wave number k₂ is given to the optical pulse L 7 . Presence of anisotropic changes due to uniaxial strain or the like in an isotropic thin film causes large anisotropy in the intensity of diffracted light (2k₂-k₁).