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• Obtained >91 % diffraction efficiency for Littrow mounted dielectric gratings. • Dielectric stack and grating design gives near unit efficiency >20 nm spectrum. • Etch depth control allows grating filling factor lithography margins. • Precise control of the filling factor is forgiving for groove depth etching errors. • Patterns were produced via electron lithography and etching of simulated profiles. Diffraction efficiency (DE) and laser-induced damage threshold of Chirped pulse amplification (CPA) system diffraction gratings (DGs) are one of the main limiting factors for the anticipated progress of high peak power lasers. Optimization of a high reflectivity dielectric multilayer ZrO 2 /SiO 2 stack mirror with a DG etched in the top SiO 2 layer was carried out employing the Rigorous coupled wave analysis method. Two families of solutions possessing DE > 0.99 over the bandwidth of the 1030 nm wavelength ultrashort laser and withstanding different fabrication margins were identified for the Littrow configuration. DGs were produced and verified experimentally. Structures permitting variation in both the depth of the DG and filling factor without loss in DE were obtained for the 690 nm thick SiO 2 layer. While the 770 nm thick layer permitted separation of the two parameters requiring either rigorous control of the DG depth or filling factor. DG realization technology was proposed employing electron beam lithography and inductively coupled plasma reactive ion etching. Measurements of the fabricated structures demonstrated 0.91 DE for the first diffraction order over the 60 nm bandwidth and under a 6° mounting error from the Littrow configuration. Spectral angular reflectance DE simulations and respective measurements indicated quantitative agreement. The work provides an integrated overview of high DE periodic structure numerical optimization and manufacturing roadmap which could be applied for the high-peak-power laser CPA system development. [ABSTRACT FROM AUTHOR]

Abstract: In this work we present an optical refractive index sensor based on the Grating Light Reflection Spectroscopy (GLRS) method. The sensor consists of the finely spaced diffraction grating (sub micrometer region) that is in contact with the analyte (liquid or gas). Shining the polarized polychromatic light on the grating at the threshold angles of incidence and analysing the spectral response of the specular reflection we have observed steep changes of the reflection coefficient at certain wavelength values. We have shown that for the liquid analytes specular reflection spectra demonstrate double peak that can be used as one more parameter in the spectroscopic measurements. The detailed analysis of the spectral composition of the specular reflection illustrates ability of control of refractive index of analyte at least for two wavelengths at constant angle of incidence. [Copyright &y& Elsevier]

The article presents an experiment which examines the formation of periodical microstructures using interference lithography (IL) which aimed to document the degradation of grating performance to produce thermoembossed diffraction gratings. It is mentioned that IL is a technique for patterning regular arrays of fine features without the use of complex optical systems. The study revealed that microrelief recorded in photoresist is distorted during the following technological steps and the biggest changes of the grating geometry were found in the thermoembossing step. Several illustrations and graphs are also presented to further analyze the study.

Abstract: Imprint technique was successfully applied for the creation of optically variable diffractive images by combining direct imprint of single oriented grating, forming of desired graphic art with a set of polished stamps and reactive ion etching. Fidelity of the etching mask as well as shape of the grating transferred into the silicon substrate was analyzed by atomic force microscope. Problems, which occur during the fabrication process, are discussed. As a result, optically variable image composed of three orientations of gratings is presented. Proposed technique could find further application in the origination of not too complicated diffraction graphic arts suitable for document security applications. [Copyright &y& Elsevier]