Self-interferometric technique for visualization of phase patterns encoded onto a liquid-crystal display.

We report a new self-interferometric technique for visualizing phase patterns that are encoded onto a phase-only liquid-crystal display (LCD). In our approach, the LCD generates both the desired object beam as well as the reference beam. Normally the phase patterns are encoded with a phase depth of 2pi radians, and all of the incident energy is diffracted into the first-order beam. However, by reducing this phase depth, we can generate an additional zero-order diffracted beam, which acts as the reference beam. We work at distances such that these two patterns spatially interfere, producing an interference pattern that displays the encoded phase pattern. This approach was used recently to display the phase vortices of helical Ince-Gaussian beams. Here we show additional experimental results and analyze the process.

Generation of helical Ince-Gaussian beams with a liquid-crystal display.

We generate helical Ince-Gaussian (HIG) beams by using complex amplitude and phase masks encoded onto a liquid-crystal display (LCD). These beams display an intensity pattern consisting of elliptic rings, whose number and ellipticity can be controlled, and a phase exhibiting a number of in-line vortices, each with a unitary topological charge. We show experimental results that display the properties of these elliptic dark hollow beams. We introduce a novel interference technique for generating the object and reference beams by using a single LCD and show the vortex interference patterns. We expect that these HIG beams will be useful in optical trapping applications.

Azimuthal prism effect with partially blocked vortex-producing lenses.

We report a new effect in which the diffraction from a partially blocked angular phase pattern occupying half of the input plane produces a partial vortex output pattern that is rotated by 90 degrees compared with the input. The energy is sent into a different quadrant of the output plane from the input plane. The rotation direction depends on whether the angular phase pattern is clockwise or counterclockwise. When we combine clockwise and counterclockwise angular phase patterns on separate horizontal halves of the input plane, we create an interference effect in one half of the output plane, while the other half remains dark.