Stable and flexible ring-shaped optical-lattice generation by use of axially symmetric polarization elements.

To overcome a trade-off issue between stability and flexibility in the generation of ring-shaped optical lattices, we proposed and demonstrated a novel generation method by using axially symmetric polarization elements. While two optical vortices were coaxially generated, electrically controlled phase difference between them by an electro-optic modulator enabled a precise rotation of the lattice. Our method has the capability to fulfill the high stability and rapid rotation.

Design and laboratory demonstration of an achromatic vector vortex coronagraph.

A vector vortex coronagraph (VVC) is one of promising means for imaging extremely faint objects around bright stars such as exoplanets. We present a design of an achromatic VVC, in which an axially-symmetric half-wave plate (AHP) is placed between crossed polarization filters (circular polarizer and analyzer). The circular polarizer and the analyzer are both composed of a polarizer and a quarter-wave plate (QWP).

Lateral shearing with a pair of double Fresnel rhombs for nulling interferometry.

A lateral-shearing interferometer with a pair of double Fresnel rhombs is proposed. Use of Fresnel rhombs enables us to accomplish simultaneously lateral shearing and achromatic nulling. Nulling interferometry with lateral shearing is one of the basic methods for searching directly for extrasolar planets with a segmented-mirror telescope.

Speckle level suppression using an unbalanced nulling interferometer in a high-contrast imaging system.

High-contrast imaging systems with a stellar halo suppression level of 10(-10) are required for direct detection of Earth-like extra-solar planets. We investigated a novel high-contrast imaging system with an unbalanced nulling interferometer (UNI) followed by phase and amplitude correction (PAC), which not only can reduce starlight but also can suppress the speckle level caused by wavefront aberrations. We successfully demonstrated that wavefront aberrations were sufficiently magnified by the UNI and the magnified aberrations were effectively corrected in amplitude and phase with two deformable mirrors.

Common-path lateral-shearing nulling interferometry with a Savart plate for exoplanet detection.

We propose a common-path lateral-shearing nulling interferometer for direct detection of exoplanets. A Savart plate is placed between crossed polarizers to produce a lateral shear and realize fully achromatic and highly stable nulling interference for starlight. We construct a double-shearing interferometer using two Savart plates for implementing orthogonal x and y shears.

Polarization interferometric nulling coronagraph for high-contrast imaging.

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.

Polarimetric stellar interferometry by use of birefringent retarders.

We propose a polarimetric technique for a stellar interferometer that uses two birefringent retarders inserted into each arm of the interferometer. The retarders shift the interference fringes of the two orthogonal polarizations to opposite directions along an optical path difference (OPD), which enables us to measure the polarized fringe visibilities separately. Laboratory demonstrations were carried out using quartz retarders with a thickness of 1.

Achromatic deep nulling with a three-dimensional Sagnac interferometer.

A 3-D Sagnac interferometer can null out light from an on-axis source achromatically. The 3-D Sagnac interferometer can make stable and achromatic pi phase shifts, because it has a common path structure. The achromaticity of the interferometer is theoretically proved by Jones calculus.

Polarization interferometric stellar coronagraph.

A nulling stellar coronagraph based on polarization interferometry is proposed that has achromatic characteristics. The principle and the optical setup of the nulling stellar coronagraph are described. Experimental results with monochromatic and white light show the usefulness of the proposed method.