The surface shape and optical thickness variation of a lithium niobate (LNB) wafer were measured simultaneously using a wavelength-tuning interferometer with a new phase-shifting algorithm. It is necessary to suppress the harmonic signals for testing a highly reflective sample such as a crystal wafer. The LNB wafer subjected to polishing, which is in optical contact with a fused-silica (FS) supporting plate, generates six different overlapping interference fringes. The reflectivity of the wafer is typically 15%, yielding significant harmonic signals. The new algorithm can flexibly select the phase-shift interval and effectively suppress the harmonic signals and crosstalk. Experimental results indicated that the optical thickness variation of the LNB wafer was measured with an accuracy of 2 nm.
© 2014 Optical Society of AmericaFull Article | PDF Article
Kenichi Hibino, Bozenko F. Oreb, Philip S. Fairman, and Jan Burke
Appl. Opt. 43(6) 1241-1249 (2004)
Kenichi Hibino, Ryohei Hanayama, Jan Burke, and Bozenko F. Oreb
Opt. Express 12(23) 5579-5594 (2004)
Yangjin Kim, Kenichi Hibino, Naohiko Sugita, and Mamoru Mitsuishi
Opt. Express 23(4) 4065-4073 (2015)