Diffraction efficiency

About: Diffraction efficiency is a research topic. Over the lifetime, 10320 publications have been published within this topic receiving 158298 citations.

Electrically Controllable Domains in Nematic Liquid Crystals

Abstract: It is reported here that it was observed that in suitable nematic liquid crystals in very thin sandwich cells from the threshold of domain formation up to the highest practicable field strength, the inverse domain width is proportional to the applied dc electric field, while dynamic scattering does not occur. Since such a cell performs as an electrically controllable optical grating which can be made to have very high diffraction efficiency, this effect may also be of practical interest.

Fourth-order partial-coherence effects in the formation of integrated-intensity gratings with pulsed light sources

Abstract: We performed theoretical calculations of the relative diffraction efficiency of partially coherent light-induced integrated-intensity gratings using pulsed sources, paying particular attention to thermal gratings. We provided a simple intuitive picture of the phenomenon and then calculated exact expressions that, unlike instantaneous-intensity-grating results, necessarily require the use of fourth-order coherence functions. Assuming several radiation models, we evaluated these expressions and found that the results proved to be insensitive to the specific radiation model assumed. The application of these results to a previously performed pulsed-laser experiment yielded a better fit to the data than an expression involving only second-order coherence, which is valid only in the cw limit. We included the effects of grating decay and, in addition, compared the use of integrated-intensity gratings for ultrashort-pulse-length measurement with standard techniques. Finally, we calculated expressions for the relative diffraction efficiency of integrated-intensity gratings created with excitation beams from two separate and independent sources of different frequency, and we report an experiment whose results were found to agree with this theory.

Orbital angular momentum generation and mode transformation with high efficiency using forked polarization gratings.

Abstract: We present a novel optical element that efficiently generates orbital angular momentum (OAM) of light and transforms light between OAM modes based on a polarization grating with a fork-shaped singularity This forked polarization grating (FPG) is composed of liquid crystalline materials, and can be made either static or switchable with high diffraction efficiency (ie, 100% theoretically) into a single order By spatially varying the Pancharatnam–Berry phase, FPGs shape the wavefront and thus control the OAM mode We demonstrate theoretically and empirically that a charge lg FPG creates helical modes with OAM charge ±lg when a Gaussian beam is input, and more generally, transforms the incident helical mode with OAM charge lin into output modes with OAM charge lin±lg We also show for the first time that this conversion into a single mode can be very efficient (ie, ∼95% experimentally) at visible wavelengths, and the relative power between the two possible output modes is polarization-controllable from 0% to ∼100% We developed a fabrication method that substantially improves FPG quality and efficiency over prior work We also successfully fabricated switchable FPGs, which can be electrically switched between an OAM generating/transforming state and a transmissive state Our experimental results showed >92% conversion efficiency for both configurations at 633 nm These holographically fabricated elements are compact (ie, thin glass plates), lightweight, and easily optimized for nearly any wavelength from ultraviolet to infrared, for a wide range of OAM charge, and for large or small clear apertures They are ideal elements for enhanced control of OAM, eg, in optical trapping and high-capacity information

Modulation transfer function measurements for thin layers of azo dyes in PVA matrix used as an optical recording material.

Abstract: Diffraction efficiencies and characteristic erasure times were measured for two recording materials suitable for real-time holography and four-wave mixing. A study of real-time transmission volume grating formation was done in conjunction with polarization states of the writing beams for 30-microm thick layers. Modulation transfer function curves presented were obtained using a versatile device for which the spatial frequency domain was 500-4000 cycles/mm.