Suppression of the Talbot effect in Fourier transform acousto-optic imaging.

We report on the observation and correction of an imaging artifact attributed to the Talbot effect in the context of acousto-optic imaging using structured acoustic waves. When ultrasound waves are emitted with a periodic structure, the Talbot effect produces -phase shifts of that periodic structure at every half of the Talbot distance in propagation. This unwanted artifact is detrimental to the image reconstruction, which assumes near-field diffraction is negligible.

Optical coherent detection through multi-scattering media by wave-mixing cleaning effect in liquid-crystal OASLM.

Liquid-crystal (LC) optically addressable spatial light modulators (OASLMs) allow control of the phase and amplitude of optical beams. By performing wave mixing in an OASLM, we show that coherent phase detection can be achieved for light beams passing through highly scattering media, such as foam layers with several cm thicknesses. Thanks to the adaptive response of our OASLM, the phase information on the speckle signal is transferred at the output of the OASLM to the plane wave reference beam, allowing the cleaning of optical distortions and the direct measurement of amplitude phase modulations with a small diameter single photodiode.

kHz-speed optically induced phase gratings with liquid crystal light valves in transient dynamic mode.

Liquid crystal light valves (LCLV) are optically addressable spatial light modulators that allow controlling the phase and amplitude properties of optical beams. We show that sub-milliseconds phase and amplitude modulations can be obtained when operating the LCLV in the transient dynamic mode by setting the working point close to the saturation of the response. Thanks to the large birefringence of the liquid crystals, this condition provides enough phase shifts to respond to the needs of several methods for optical measurement, dynamic holography, interferometry, and imaging through phase disturbing media, while providing kilohertz (kHz) speed.

Shear-enhanced diffraction from thin permanent gratings in dye-doped nematic liquid crystal cells.

Permanent gratings are recorded in planar-aligned dye-doped nematic liquid crystal cells under visible light illumination. By increasing the irradiation intensity and exposure time, several diffraction orders of the recorded gratings are obtained in the Raman-Nath diffraction regime. By applying a dynamic transverse shear on one of the confining plates of the cell, an enhancement of the diffraction efficiency is achieved, which follows the period of the grating.