Wolfgang Dultz

Direct observation of Berry's topological phase by using an optical fiber ring interferometer

Abstract This paper describes a simple interferometric arrangement, which allows a direct observation of Berrys topological phase in optical fibers. The interferometer consists of a single mode, low birefringent fiber ring that involves a non-coplanar path (a helix). The fringe shift observed by changing the helix pitch permits the measurement of the geometrical phase.

Rotation of the polarization plane in optical fibers

The rotation of the polarization plane of a light wave traveling in an optical fiber that lies on a space curve based on parallel transport is described. An estimation of the effect due to winding the fiber is presented.

Optical fiber vibration sensor using (Pancharatnam) phase step interferometry

A fiber-optic vibration sensor based on polarization and phase-step interferometry is reported. Left- and right-circularly polarized light coming back from the reference and signal arms of a modified Michelson fiber interferometer is processed with an array of five linear analyzers separated angular steps of /spl pi//4 (rad) from each other. Thus, five interference patterns are acquired simultaneously and the dynamical phase retrieval problem is reduced to five-step interferometry in the time-domain. A vibration sensor as described above was built by the authors and its performance was investigated.

The Bust of the Tyrant: an optical illusion

The spectacular optical illusion of the hollow mask is considerably improved by filling the mask with a transparent medium. The mask seems to stare more directly at the onlooker and its deceptive motions follow his movements over a wider field. The history of the illusion of the hollow mask is outlined and the legend of the Bust of the Tyrant is invented. Other ways of making a bust which follows the moving onlooker face to face are discussed.

Novel liquid crystal spatial light modulators for adaptive optics and image processing

We have developed laboratory prototypes of nematic and ferroelectric liquid crystal optically addressed spatial light modulators with photosensitive layers based on ZnSe, alpha-SiH, pin alpha-SiH, alpha-SiCH, and pin alpha-SiCH. The SLM performance characteristics measured using standard projection and holographic techniques are presented. The advantages and shortcoming of different SLM design versions are analyzed for the use in the wavefront correction and dynamic hologram recording systems. The examples are given for specific implementation of the SLMs in these systems.

Development of the optically addressed spatial light modulators for dynamic holography applications using deformed-helix ferroelectric liquid crystals

The basic characteristics of the optically addressed spatial light modulators are presented based on ferroelectric liquid crystal (FLC) as a light modulating media and amorphous hydrogenated silicon carbide a-SiC:H and dye-doped polyimide films as photoconducting layers. The parameters of the constituent parts are described, among them: photoconductivity of photosensitive layers, data about newly developed light blocking layers, characteristics of the FLC materials, utilizing the deformed helix ferroelectric effect. The dynamics of the response in hundreds Hz region, the diffraction efficiency of 20% at spatial resolution better than 501 p/mm, and sensitivity in range of microWatt/cm2 are obtained.

Measurement of the spin-redirection phase using Pancharatnam's theorem

A Michelson interferometer is presented which enables a direct measurement of Berrys geometric phase (spin-redirection phase) resulting from light propagating through a helically wound optical single-mode fibre. The operation of the interferometer is interpreted in terms of Pancharatnams theorem. In addition, we put the spin-redirection phase into the context of Pancharatnams phase.

Complex self-coherence function determination using geometric phase techniques

A method to determine the complex coherence function is proposed. The usual approach to obtain information about the coherence function is interferometric. Our method is based on the concept of geometric phase, which has the property of achromaticity. This characteristic will enable us to add phase delays to the entire interferogram. Taking simultaneously two delayed interferograms, a complete reconstruction of the complex coherence function is possible.

Polarization-based tunable interferometric filter

A polarization-based tunable interferometric filter essentially consisting of a two-beam interferometer with birefringence elements is described. The analysis of the filter is done through the concept of a geometric phase in optics-namely, the Pancharatnam phase. The transmission characteristics of the filter can be controlled through three parameters: the thickness of the birefringent elements, the optical path difference, and the orientation angle of an analyzer placed at the interferometer output. It is demonstrated theoretically that, with a particular choice of these parameters, the chromatic dispersion of the filter is compensated in a given spectral range. Some properties of the device are confirmed by an experimental demonstration.

Local Optical Limiting Devices Based on Photoaddressed Spatial Light Modulators, Using Ferroelectric Liquid Crystals

Abstract The devices for local light discrimination in the field of view of eye or light-sensitive devices (videocamera, etc.) are discussed, using optically addressed spatial light modulators. The deformed helical ferroelectric (DHF) effect in FLCs is considered. Different optical schemes of local optical limiting devices with corresponding driving conditions are discussed and the transmission of devices in dependence on FLC parameters (molecular tilt angle) is estimated. The operation ofdevice prototype for local protection of video camera using OASLM and FLC shutter is shown.