Optical characterization of the narrow-band filter with in-situ thickness monitoring at fixed wavelength

For application in the optical communication field, the narrow band TFF device with 4 cavities has been studied. By carefully analyzing the data, it was found that slight uncertainty of the optical thickness occurred at the turning point will cause phase errors that cannot be exactly corrected by the compensation algorithm and will deteriorate the spectral pattern. An improved method to in-situ monitor the film growth process in the full optical spectral range is suggested.