Weak measurements of light chirality with a plasmonic slit.

We examine, both experimentally and theoretically, an interaction of tightly focused polarized light with a slit on a metal surface supporting plasmon-polariton modes. Remarkably, this simple system can be highly sensitive to the polarization of the incident light and offers a perfect quantum weak measurement tool with a built-in postselection in the plasmon-polariton mode. We observe the plasmonic spin Hall effect in both coordinate and momentum spaces which is interpreted as weak measurements of the helicity of light with real and imaginary weak values determined by the input polarization. Our experiment combines the advantages of (i) quantum weak measurements, (ii) near-field plasmonic systems, and (iii) high-numerical aperture microscopy in employing the spin-orbit interaction of light and probing light chirality.

Observation of the spin-based plasmonic effect in nanoscale structures.

Observation of surface-plasmon phenomena that are dependent upon the handedness of the circularly polarized incident light (spin) is presented. The polarization-dependent near-field intensity distribution obtained in our experiment is attributed to the presence of a geometric phase arising from the interaction of light with an anisotropic and inhomogeneous nanoscale structure. A near-field vortex surface mode with a spin-dependent topological charge was obtained in a plasmonic microcavity. The remarkable phenomenon of polarization-sensitive focusing in a plasmonic structure was also demonstrated.

Color-coded optical profilometry with >10(6) resolved depth steps.

A novel, to our knowledge, approach to light-stripe triangulation configuration that allows for parallel, fast, real-time three-dimensional surface topography with an extremely large number of optically resolved depth steps is presented, analyzed, and experimentally demonstrated. The method is based on a color-coding and decoding arrangement that exploits polychromatic illumination and axially dispersing optical elements. This leads to an increase of the depth-measuring range without any decrease in the axial or the lateral resolution. Our experiments yield three-dimensional surface measurements with lateral and depth optical resolutions of <40 nm, for a depth of focus of 48 mm, resulting in 1.2 x 10(6) resolving depth steps.

High-resolution spectrometry for diffuse light by use of anamorphic concentration.

A new scheme to improve the spectral resolution of grating-based spectrometers for diffuse light is proposed and demonstrated. It exploits an anamorphic transformation that reduces the beam divergence in the direction of the grating grooves while increasing the divergence in the orthogonal direction to improve the spectral resolution without any loss of light. Up to 12-fold improvement in the spectral resolution was obtained.

Anamorphic concentration of solar radiation beyond the one-dimensional thermodynamic limit.

We propose and demonstrate a new scheme for anamorphic concentration of a big (40 cm x 40 cm) diffuse light source to achieve an extremely high concentration in one lateral direction at the expense of that in the other direction, to preserve the total (two-dimensional) optical brightness. Such anamorphic concentration is achieved by a combination of two conventional two-dimensional concentrators and a properly designed retroreflector array. Our experiments in search of a diffuse white-light source with properties comparable with those of solar radiation have yielded 28-fold improvement of the one-dimensional concentration ratio compared with those of conventional concentrators and 14-fold improvement compared with the one-dimensional thermodynamic limit.

Computer-generated space-variant polarization elements with subwavelength metal stripes.

A novel method of performing two-dimensional space-variant polarization operations is presented. The method is based on determining the local direction and period of subwavelength metal-stripe gratings by use of vectorial optics to obtain any desired continuous polarization change. We demonstrate our approach with specific computer-generated space-variant polarization elements for laser radiation at 10.6mum. The polarization properties are verified with complete space-variant polarization analysis and measurement.

Pancharatnam--Berry phase in space-variant polarization-state manipulations with subwavelength gratings.

We report the appearance of a geometrical phase in space-variant polarization-state manipulations. This phase is related to the classic Pancharatnam-Berry phase. We show a method with which to calculate it and experimentally demonstrate its effect, using subwavelength metal stripe space-variant gratings. The experiment is based on a unique grating for converting circularly polarized light at a wavelength of 10.6 mum into an azimuthally polarized beam. Our experimental evidence relies on analysis of far-field images of the resultant polarization.

Analytic design of hybrid diffractive-refractive achromats.

An analytic design of hybrid achromats that combine refractive and diffractive elements is presented. The design procedure does not rely on paraxial approximations and involves two separate stages. In the first stage the chromatic aberrations are corrected for the paraxial rays, and in the second stage the spherical aberrations are corrected by addition of an aspherical phase function to the diffractive element. The residual spherochromatic aberrations of the achromat are evaluated both analytically and numerically, with good agreement between the results. Finally, we illustrate the design procedure by designing a plano-convex achromat for IR radiation with little chromatic dispersion.

Efficient multilevel phase holograms for CO(2) lasers.

Multilevel phase holograms for monochromatic radiation at a wavelength of 10.6 microm are recorded as surface relief gratings with multilevel discrete binary steps. Our experiments show that diffraction efficiencies close to 90% can be achieved both for transmissive and reflective elements. The reduction of efficiency due to errors in the depth and the width of the step levels is considered.

Holographic axilens: high resolution and long focal depth.

We report a novel aspheric holographic optical element, the holographic axilens, for achieving extended focal depth while keeping high lateral resolution. The element is designed according to special optimization techniques and recorded as a computer-generated hologram. The results for a specific element, which has a depth of focus of 30 mm, a lateral resolution of 80 microm, a focal length of 1250 mm, and a diameter of 12.5 mm at a wavelength of 633 nm, are presented.

Heterostructure multilevel binary optics.

A method for forming multilevel diffractive elements (kinoforms) that have highly accurate level heights so as to obtain high diffraction efficiencies is presented. The method, which leads to heterostructure multilevel binary optical elements, relies on conventional deposition technology, selective etching, and multimask lithography. As an illustration, a reflective multilevel element for 10.6-microm radiation is designed, recorded, and tested.

Reflective and refractive systems for general two-dimensional beam transformations.

A method for designing reflective and refractive surfaces that perform general transformations on two-dimensional beams is presented. In some cases the shape of the surfaces is represented by a simple integral of an analytic expression, whereas in other specific cases it is represented as a solution of a Poisson-like equation. Finally, the possible use of noncontinuous surfaces (facets) is discussed and evaluated quantitatively. Some of the novel techniques developed are also applicable for beam transformations that are realized with diffractive systems.

Optical coordinate transformations.

A novel technique for designing holographic optical elements that can perform general types of coordinate transformation is presented. The design is based on analytic ray-tracing techniques for finding the grating vector of the element, from which the holographic grating function is obtained as a solution of a Poissonlike equation. The grating function can be formed either as a computer-generated or as a computer-originated hologram. The design and realization procedure are illustrated for a specific holographic element that performs a logarithmic coordinate transformation on two-dimensional patterns.

Realization of perfect shuffle and inverse perfect shuffle transforms with holographic elements.

Techniques for implementing perfect shuffle and inverse perfect shuffle operations with the aid of a single holographic optical element are presented. The element is composed of subholographic lenses which operate on a different input area. For the inverse perfect shuffle operation, polarization coding is added in order to separate the input into distinct groups. Experimental results illustrating the effectiveness of the proposed techniques are given.

On the limits of optical interconnects.

The density capabilities of free-space optical interconnects are analyzed by applying Gabor's theory of information. It is shown that it is possible to increase the space-bandwidth product capabilities of space-variant interconnect schemes if they have symmetry properties. Several examples of such symmetries (locality, separability and smoothness) are discussed in detail, together with some experimental results.

Three-dimensional optical metrology with color-coded extended depth of focus.

A novel method of rapid three-dimensional optical metrology that is based on triangulation of a configuration of color-coded light stripes is presented. The method exploits polychromatic illumination and a combined diffractive-refractive element, so the incident light is focused upon a stripe that is axially dispersed, greatly increasing the depth-measuring range without any decrease in the axial or the lateral resolution. The discrimination of each color stripe is further improved by spectral coding and decoding techniques. An 18-fold increase in the depth of focus was experimentally obtained while diffraction-limited light stripes were completely maintained.

Continuous-phase elements can improve laser beam quality.

Siegman [Opt. Lett. 18, 675 (1993)] showed that binary-phase plates cannot improve laser beam quality. We demonstrate that continuous spiral phase elements can improve the quality of beams that originate from a laser operating with a pure high-order transverse mode. A theoretical analysis is presented, along with experimental results obtained with a CO(2) laser. The results reveal that a nearly optimal Gaussian output beam can be obtained with only a small decrease in the output power.

Spatial Fourier-transform polarimetry using space-variant subwavelength metal-stripe polarizers.

A novel method for rapid polarization measurement is suggested. The method is based on a periodic space-variant polarizer that can be realized by use of subwavelength metal-stripe gratings. The Stokes parameters of the incident beam are determined by Fourier analysis of the space-variant intensity transmitted through the grating, thus permitting real-time polarization measurement. We discuss the design and realization of such polarizers and demonstrate our technique with polarization measurements of CO(2)-laser radiation at a wavelength of 10.6mum.

Efficient formation of a high-quality beam from a pure high-order Hermite-Gaussian mode.

We present a relatively simple method for efficiently transforming a single high-order mode into a nearly Gaussian beam of much higher quality. The method is based on dividing the mode into equal parts that are then combined coherently. We illustrate the method by transforming a Hermite-Gaussian (1, 0) mode with M(x)(2)=3 into a nearly Gaussian beam with M(x)(2)=1. 045 . Experimental results are presented and compared with theoretical results.

Conversion of a high-order mode beam into a nearly Gaussian beam by use of a single interferometric element.

We present a new, compact, and practical optical mode converter that efficiently transforms a high-order Hermite-Gaussian (HG) laser beam into a nearly Gaussian beam. The mode converter is based on coherently adding different transverse parts of the high-order mode beam by use of a single planar interferometric element. The method, configuration, and experimental results obtained with a pulsed Nd:YAG HG TEM10 laser beam are presented. The results reveal that the efficiency of conversion of a HG beam to a nearly Gaussian beam can be as high as 90%.