title: Multiple-surface interferometry of highly reflective wafer by wavelength tuning.
abstract: 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.
authors.forename: Yangjin
authors.initials: Y
authors.lastname: Kim
authors.forename: Kenichi
authors.initials: K
authors.lastname: Hibino
authors.forename: Ryohei
authors.initials: R
authors.lastname: Hanayama
authors.forename: Naohiko
authors.initials: N
authors.lastname: Sugita
authors.forename: Mamoru
authors.initials: M
authors.lastname: Mitsuishi