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We propose a novel, high-contrast imager called a polarization interferometric nulling coronagraph (PINC) for direct detection of extrasolar planets. The PINC uses achromatic half-wave plates (HWPs) installed in a fully symmetric beam combiner based on polarizing beam splitters. Jones calculus suggests that a stellar halo suppression level of 10 10 can be achieved at 5 [lambda]/D for a broad wavelength range from 1.6 to 2.2 [micro]m by using Fresnel-rhomb HWPs made of BK7. Laboratory experiments on the PINC used two laser light sources (wavelengths of [lambda] = 532 and 671nm), and we obtained a halo suppression level of approximately [10.sup.-6] at 5 [lambda]/D for both wavelengths. OCIS codes: 350.1260, 120.3180, 260.5430, 260.3160, 050.5080.

An improved illumination system is proposed for creating a temporally coherent and spatially incoherent extended source to be used for spatial coherence control and reconstruction of a coherent hologram. Taking into account the fact that a rotating ground glass does not behave as an ideal Lambertian diffuser, the new illumination system tailors the directivity of the scattered lights to direct the lights efficiently into an interferometer so that a spatial coherence function can be better controlled and detected with higher fidelity. Experimental results are presented that demonstrate improved performance of the proposed system. OCIS codes: 030.1640, 120.1088.

The influence of tilted surfaces on the measurement of shape by spatial coherence profilometry is investigated. Based on theoretical analysis and experimental results, the systematic measurement error caused by surface tilt is determined. The systematic measurement error depends not only on the tilt angle but also on the parameters of the experimental setup. The theoretical analysis and the experiments show the similarities and differences between spatial coherence profilometry and white-light interferometry. We also suggest the conditions to obtain correct measurements by use of spatial coherence profilometry. [c] 2009 Optical Society of America OCIS codes: 030.1640, 030.1670, 120.3180, 120.6650.

To attain deeper nulling for an extended incoherent star disk a scheme for an achromatic interfero-coronagraph, incorporating two common-path interferometers in tandem, is proposed. Analytical and numerical predictions of the performance, which are in reasonably good agreement, are presented. The predicted performance improvement, by using two interferometers in tandem, is demonstrated by a preliminary experiment. A star coronagraph based on the proposed technique has the possibility to reach a [10.sup.-10] achromatic nulling contrast for an almost [10.sup.-2] [lambda]/D effective source size. OCIS codes: 260.3160, 260.5430, 050.5080.

A three-dimensional common-path interferometer is proposed, which can achromatically null out an on-axis source while maintaining the detectability of an off-axis source. A geometric phase in the three-dimensional interferometer introduces an achromatic [pi]-phase shift to the light from the on-axis source, such that destructive interference nulls out the axial light at one of the ports of the interferometer. Light from the off-axis source, which is exempt from destructive interference, comes out from both ports with equal intensity. The common-path scheme makes the system highly immune to environmental disturbances. In the described experiment, a 6 x [10.sup.-6] peak-to-peak nulling contrast was obtained. OCIS codes: 260.3160, 260.5430, 050.5080.

The optical path difference (OPD) and amplitude of a sinusoidal wavelength scanning (SWS) are controlled with a double feedback control system in an interferometer, so that a ruler marking every wavelength and a ruler with scales smaller than a wavelength are generated. These two rulers enable us to measure an OPD longer than a wavelength. A liquid-crystal Fabry-Perot interferometer (LC-FPI) is adopted as a wavelength-scanning device, and double sinusoidal phase modulation is incorporated in the SWS interferometer. Because of a high resolution of the LC-FPI, the upper limit of the measurement range can be extended to 280 [micro]m by the use of the phase lock where the amplitude of the SWS is doubled in the feedback control. The ruler marking every wavelength is generated between 80 [micro]m and 280 [micro]m, and distances are measured with a high accuracy of the order of a nanometer in real time. OCIS codes: 120.3180, 120.3930, 120.5050, 120.5060, 230.3720.