This paper describes in a very easy and intelligible way, how the diffraction efficiencies of binary dielectric transmission gratings depend on the geometrical groove parameters and how a high efficiency can be obtained. The phenomenological explanation is based on the modal method. The mechanism of excitation of modes by the incident wave, their propagation constants and how they couple into the diffraction orders helps to understand the diffraction process of such gratings and enables a grating design without complicated numerical calculations.
Dielectric transmission gratings with a similar period as the wavelength of the incident light can exhibit strong polarization dependence. By optimizing the groove width of a negative first-order Littrow transmission grating it can be achieved that light is transmitted to the zeroth order for one polarization, regardless of the groove depth, while it is efficiently diffracted for the other polarization. An investigation of this remarkable effect, based on a modal field representation inside the grating, as well as experimental results are presented.
A new approach for the realization of highly dispersive dielectric transmission gratings is presented, which enables the suppression of any reflection losses and, thus, 100% diffraction efficiency. By applying a simple two-mode-model a comprehensible explanation as well as a theoretical design of such a reflection-free transmission grating is presented.
The ability of subwavelength structures to create an artificial effective index opens up new perspectives in designing highly efficient diffractive optical elements. We demonstrate a design approach for binary multi-phase level computer generated holograms based on the effective medium approach. The phase pattern is formed by various subwavelength structures that cause a certain phase delay to an incident light wave. This binary structure approach leads to a significant cost reduction by simplifying the fabrication process. For demonstration, a three-phase level element, operating in the visible range, is fabricated and experimentally evaluated.
The aim of this work is to measure the temperature variations by analyzing the plasmon signature on a metallic surface that is periodically structured and immersed in a liquid. A change in the temperature of the sample surface induces a modification of the local refractive index leading to a shift of the surface plasmon resonance (SPR) frequency due to the strong interaction between the evanescent electric field and the metallic surface. The experimental set-up used in this study to detect the refractive index changes is based on a metallic grating permitting a direct excitation of a plasmon wave, leading to a high sensibility, high-temperature range and contactless sensor within a very compact and simple device. The experimental set-up demonstrated that SPR could be used as a non-invasive, high-resolution temperature measurement method for metallic surfaces.
We present the design and realization of a highly dispersive dielectric transmission grating with 97.0% diffraction efficiency. This grating is embedded in fused silica, which allows for an efficient suppression of any reflection losses. It is very easy to handle and clean, and its monolithic layout gives rise to high resistance against laser-induced damage and long-term stability comparable to conventional fused silica components.