Parallel sorting of orbital and spin angular momenta of light in a record large number of channels.

Parallel sorting of orbital and spin angular momentum components of structured optical beams is demonstrated. Both spin channels are multiplexed within the novel orbital angular momentum (OAM) sorter, reducing the size, weight, and number of elements. The sorted states are linearly spaced over 70 topological charge values. We experimentally and theoretically evaluate the operational range and crosstalk between neighboring channels and find that 30 orbital angular momentum states are available per spin channel for quantum communication or cryptography. This is achieved using an angular momentum sorter that we developed based on geometric phase optical elements. We present two devices consisting of liquid crystal polymer films photoaligned with complex two-dimensional patterns.

Beam shaping diffractive wave plates [Invited].

We present and discuss opportunities opened up by a new generation of beam shaping optical elements that combine capabilities of digital spatial light polarization converters and diffractive properties of thin liquid crystalline films with patterned orientation of anisotropy axis (diffractive wave plates). Several functions of the new generation beam shapers are demonstrated, among them converting a laser beam of a Gaussian profile into a ring profile in the far field, a flattop profile, and into complex images. We also describe electrically controlled beam shaping optical elements which can be turned off and on within milliseconds by applying a low external voltage. Optical, morphological, and electro-optical properties of the components are characterized.

Digital polarization holography advancing geometrical phase optics.

Geometrical phase or the fourth generation (4G) optics enables realization of optical components (lenses, prisms, gratings, spiral phase plates, etc.) by patterning the optical axis orientation in the plane of thin anisotropic films. Such components exhibit near 100% diffraction efficiency over a broadband of wavelengths. The films are obtained by coating liquid crystalline (LC) materials over substrates with patterned alignment conditions. Photo-anisotropic materials are used for producing desired alignment conditions at the substrate surface. We present and discuss here an opportunity of producing the widest variety of "free-form" 4G optical components with arbitrary spatial patterns of the optical anisotropy axis orientation with the aid of a digital spatial light polarization converter (DSLPC). The DSLPC is based on a reflective, high resolution spatial light modulator (SLM) combined with an "ad hoc" optical setup. The most attractive feature of the use of a DSLPC for photoalignment of nanometer thin photo-anisotropic coatings is that the orientation of the alignment layer, and therefore of the fabricated LC or LC polymer (LCP) components can be specified on a pixel-by-pixel basis with high spatial resolution. By varying the optical magnification or de-magnification the spatial resolution of the photoaligned layer can be adjusted to an optimum for each application. With a simple "click" it is possible to record different optical components as well as arbitrary patterns ranging from lenses to invisible labels and other transparent labels that reveal different images depending on the side from which they are viewed.

Broadband waveplate lenses.

We report on lenses that operate over the visible wavelength band from 450 nm to beyond 700 nm, and other lenses that operate over a wide region in the near-infrared from 650 nm to beyond 1000 nm. Lenses were recorded in liquid crystal polymer layers only a few micrometers thick, using laser-based photoalignment and UV photopolymerization. Waveplate lenses allowed focusing and defocusing laser beams depending on the sign of the circularity of laser beam polarization. Diffraction efficiency of recorded waveplate lenses was up to 90% and contrast ratio was up to 500:1.

Thin waveplate lenses of switchable focal length--new generation in optics.

We present new lenses - waveplate lenses created in liquid crystal and liquid crystal polymer materials. Using an electrically-switchable liquid-crystal half-wave retarder we realized switching between focused and defocused beams by the waveplate lens. A combination of two such lenses allowed the collimation of a laser beam as well as the change of focal length of optical system.