Diffraction efficiency

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

Dye-doped liquid crystals as high-resolution recording media.

Abstract: Light-induced anchoring of the molecular director is reported to be an efficient method for writing permanent holographic gratings in dye-doped liquid crystals. We have achieved higher sensitivity and spatial resolution in these materials with other methods. An energy density as low as 10(-1) J/cm(2) was sufficient to write gratings with a resolution higher than 100 lines/mm.

Large-scale resonance amplification of optical sensing of volatile compounds with chemoresponsive visible-region diffraction gratings.

Abstract: Micropatterning of the vapochromic charge-transfer salt, [Pt(CNC6H4C10H21)4][Pd(CN)4], on transparent platforms yields transmissive chemoresponsive diffraction gratings. Exposure of the gratings to volatile organic compounds (VOCs) such as chloroform and methanol leads to VOC uptake by the porous material comprising the grating lattice or framework, and a change in the material's complex refractive index, n. The index change is accompanied by a change in the degree of index contrast between the lattice and the surrounding medium (in this case, air), and a change in the diffraction efficiency of the grating. When a monochromatic light source that is not absorbed by the lattice material is employed as a probe beam, only changes in the real component of n are sensed. Under these conditions, the grating behaves as a nonselective, but moderately sensitive, sensor for those VOCs capable of permeating the porous lattice material. When a probe color is shifted to a wavelength coincident with the vapochromic charge-transfer transition of the lattice material, the sensor response is selectively amplified by up to 3.5 orders of magnitude, resulting in greatly enhanced sensitivity and some degree of chemical specificity. On the basis of studies at four probe wavelengths, the amplification effect is dominated by resonant changes in the imaginary component of the refractive index. The observed wavelength- and analyte-dependent amplification effects are quantitatively well described by a model that combines a Kramers-Kronig analysis with an effective-medium treatment of dielectric effects.

Electromagnetic analysis of diffraction gratings by the finite-difference time-domain method

Abstract: Diffraction gratings with feature sizes comparable to the wavelength are analyzed with a finite-difference time-domain method, which is a unique approach to electromagnetic problems in the time domain. The diffraction efficiencies obtained are in good agreement with other commonly used numerical methods in the frequency domain. As a further application, diffraction problems with pulsed light are also investigated.

Switchable two-dimensional gratings based on field-induced layer undulations in cholesteric liquid crystals

Abstract: We propose switchable two-dimensional (2D) diffractive gratings with periodic refractive-index modulation arising from layer undulations in cholesteric liquid crystals. The cholesteric cell can be switched between two states: (1) flat layers of a planar cholesteric texture and (2) a square lattice of periodic director modulation associated with layer undulations that produces 2D diffraction patterns. The intensities of the diffraction maxima can be tuned by changing the applied field. The diffractive properties can be optimized for different wavelengths by appropriately choosing cholesteric pitch, cell thickness, and surface treatment.

152 W average power Tm-doped fiber CPA system

Abstract: A high-power thulium (Tm)-doped fiber chirped-pulse amplification system emitting a record compressed average output power of 152 W and 4 MW peak power is demonstrated. This result is enabled by utilizing Tm-doped photonic crystal fibers with mode-field diameters of 35 μm, which mitigate detrimental nonlinearities, exhibit slope efficiencies of more than 50%, and allow for reaching a pump-power-limited average output power of 241 W. The high-compression efficiency has been achieved by using multilayer dielectric gratings with diffraction efficiencies higher than 98%.