Optimization of retardance for a complete Stokes polarimeter.

We present two figures of merit based on singular value decomposition, which can be used to assess the noise immunity of a complete Stokes polarimeter. These are used to optimize a polarimeter featuring a rotatable retarder and a fixed polarizer. A retardance of 132 degrees (approximately three-eighths wave) and retarder orientation angles of +/-51.7 degrees and +/-15.1 degrees are found to be optimal when four measurements are used. Use of this retardance affords a factor-of-1.5 improvement in signal-to-noise ratio over systems employing a quarter-wave plate. A geometric means of visualizing the optimization process is discussed, and the advantages of the use of additional measurements are investigated. No advantage of using retarder orientation angles spaced uniformly through 360 degrees is found over repeated measurements made at the four retarder orientation angles.

Microtags with 150-nm line gratings fabricated by use of extreme-ultraviolet lithography.

The microtag concept is an anticounterfeiting and security measure. Microtags are computer-generated holograms (CGH's) consisting of 150-nm lines arranged to form 300-nm-period gratings. The microtags that we describe were designed for readout at 442nm . The smallest microtag measures 56micromx80 microm when viewed at normal incidence. The CGH design process uses a modified iterative Fourier-transform algorithm to create either phase-only or phase-and-amplitude microtags. We also report on a simple and compact readout system for recording the diffraction pattern formed by a microtag. The measured diffraction patterns agree very well with predictions.

Mass-producible microscopic computer-generated holograms: microtags.

We have developed a method for encoding phase and amplitude in microscopic computer-generated holograms (microtags) for security applications. An 8 x 8 cell phase-only and an 8 x 8 cell phase-and-amplitude microtag design has been exposed in photoresist by the extreme-ultraviolet (13.4-nm) lithography tool developed at Sandia National Laboratories. Each microtag measures 80 microm x 160 microm and contains features that are 0.2 microm wide. Fraunhofer zone diffraction patterns can be obtained from fabricated microtags without any intervening optics and compare favorably with predicted diffraction patterns.

Nonwalk-off multipass Twyman-Green interferometer.

A modification of the multipass Twyman-Green interferometer is suggested that avoids the walk-off problem. Also, a data reduction scheme has been developed that permits most of the aberrations of the ancillary optics to be separated from those of the test piece.

Physical optics modeling in soft-x-ray projection lithography.

We develop a diffraction-based tool that can predict the image quality in projection lithography systems. The effects of partial coherence and source variations and imaging defects in both the condenser and the camera optics can all be determined.

Soft-x-ray projection lithography experiments using Schwarzschild imaging optics.

Soft-x-ray projection imaging is demonstrated by the use of 14-nm radiation from a laser plasma source and a single-surface multilayer-coated ellipsoidal condenser. Aberrations in the condenser and the Schwarzschild imaging objective are characterized and correlated with imaging performance. A new Schwarzschild housing, designed for improved alignment stability, is described.

Designing and constructing thick holographic optical elements.

Previously, holographic optical elements have been constructed with two spherical waves. Better image quality and efficiency can be achieved by constructing thick HOE's with spherically aberrated wavefronts. We include an exact lens equivalent for a HOE to allow computer optimization of such systems. The effect of changes in the index of refraction and thickness of the emulsion are considered along with the quality of the substrate. Optical systems to construct such HOE's are discussed and analytically described. Many examples are presented.

Achromatic triplet using holographic optical elements.

An achromatic optical system can be made using three holographic optical elements. A very simple design scheme is presented, and the properties of the system are discussed.