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We propose a new technique for achromatic 3-D field correlation that makes use of the characteristics of both axial and lateral magnifications of imaging through a common-path Sagnac shearing interferometer. With this technique, we experimentally demonstrate, for the first time to our knowledge, 3-D image reconstruction of coherence holography with generic thermal light. By virtue of the achromatic axial shearing implemented by the difference in axial magnifications in imaging, the technique enables coherence holography to reconstruct a 3-D object with an axial depth beyond the short coherence length of the thermal light.

Coherence holography capable of real-time recording and reconstruction is proposed and experimentally demonstrated with a generic Leith-type coherence hologram. The coherence hologram is optically generated in real-time using a Mach-Zehnder interferometer and reconstructed using a Sagnac radial shearing interferometer. With this method one can create an optical field distribution with a desired spatial coherence function, and visualize the coherence function in real-time as the contrast and phase variations in an interference fringe pattern. The reconstructed image of the complex coherence function has been quantified with the Fourier transform method of fringe-pattern analysis.

A new image reconstruction scheme for coherence holography using a modified Sagnac-type radial shearing interferometer with geometric phase shift is proposed, and the first experimental demonstration of generic Leith-type coherence holography, which reconstructs off-axis 3-D objects with depth information, is presented. The reconstructed image, represented by a coherence function, can be visualized with a controllable magnification, which opens up a new possibility for a coherence imaging microscope.

A novel wavefront measurement interferometer is developed that enables the user to evaluate the wavefronts of multi-wavelength optical pickups. In this interferometer, instead of transparent pinholes used in Mach-Zehnder interferometers, reflection dot pinhole mirrors are used to generate reference wavefronts for different wavelengths which make the optical system very flexible and simple compared with those using transparent pinholes. The interferometer is designed to operate at wavelengths of 405 nm, 650 nm and 780 nm over an NA range of up to 0.95, which is very difficult to realize when transparent pinholes are used for generating reference wavefronts. The three-beam problem is solved and the optics of the interferometer is simplified by employing a software filter instead of using spatial filters in the optics of the interferometer. The instrument has an equal optical path length that enables the user to measure pickups with a very short coherence length. A new method by which asymmetric aberration components, such as astigmatic and coma aberrations, can be calibrated by rotating the measured lens with 90 and 180 degrees is proposed and the calibration results are verified by using a high precision reference point source. System accuracy is also evaluated by comparing with the measurement results obtained by commercial Fizeau type interferometer and a good agreement is achieved.

A new instrument for terahertz time-domain spectroscopy (THz-TDS) has been developed. It consists of a composite THz-TDS system and a high throughput (Martin-Puplett) interferometer. The instrument is for use in the qualitative study of optoelectronic constants of materials. The spectral transmission intensity and phase shift related to phonon-polariton dispersion have been measured between 100 cm(-1) and 3 cm(-1) on ferroelectric crystals of industrial interest. These include bismuth titanate Bi4Ti3O12 (a key material for FeRAM), lithium niobate LiNbO3 (a typical nonlinear crystal for parametric oscillator applications) and lithium heptagermanate Li2Ge7O15 for surface elastic wave filter applications. The complex dielectric constants are well reproduced by the phonon-polariton dispersion relation based on the Kurosawa formula. The instrument details and phonon-polariton dispersion results are described.

Abstract: The phase-crossing algorithm is proposed for white-light interferometry, which uses the multi-color phase information of spectrally decomposed interferograms recorded simultaneously with color-sensitive image sensors. The location of zero optical path difference is identified as the singular point at which the phase becomes color invariant, and is determined accurately with a sub-sampling-interval resolution from the crossing point of the multi-color phase distributions obtained by the Fourier transform method. An experimental result is presented that demonstrates the performance of the phase-crossing algorithm. [Copyright &y& Elsevier]