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[en] This study presents a pre-stress-assisted nanoimprint lithography (NIL) method for fabricating high-density flexible diffraction gratings. Compared to conventional NIL methods, this method offers the advantage of producing gratings with smaller periods than that of the master mould. First, a polydimethylsiloxane (PDMS) film is patterned by NIL, and is adhered to a flat PDMS substrate under pre-stress tension. Then, patterned PDMS gratings with small periods are obtained when the pre-stress tension is released. The grating periods can be controlled by the degree of the pre-stress tension. In the experiment, flexible diffraction gratings with periods of 3–4 µm are obtained, and the largest reduction ratio of the grating period is approximately 25%. Experimental results primarily verify the effectiveness of the proposed method for fabricating high-density diffraction gratings. Highlights (1) A pre-stress assisted NIL method for fabricating high-density diffraction gratings is proposed. (2) The periods of the diffraction gratings can be controlled by adjusting the degree of the pre-stress tension during the fabrication process. (3) A biggest grating-period reduction ratio of about 25% is obtained in the experiment. (paper)
[en] A wide bandpass double-grating polychromator with high rejection and high transmission has been designed and manufactured for laser-aided plasma diagnostics. The special mount utilizes subtractive dispersion in the second stage of the double polychromator such that the larger dispersion of the second stage is reduced by that of the first stage. This affects the intensity of the stray light background at the laser wavelength. The background at the edge of the laser line was measured at 10-5 of the light incident on the input slit. At the short end of the 200 nm bandpass, the stray light relative intensity approached 10-7
[en] We present a simple diffraction experiment with fractal gratings based on the triadic Cantor set. Diffraction by fractals is proposed as a motivating strategy for students of optics in the potential applications of optical processing. Fraunhofer diffraction patterns are obtained using standard equipment present in most undergraduate physics laboratories and compared with those obtained with conventional periodic gratings. It is shown that fractal gratings produce self-similar diffraction patterns which can be evaluated analytically. Good agreement is obtained between experimental and numerical results.
[en] A novel micro-electromechanical system (MEMS) technology-based grating laser scanner with a backside thinned grating platform has been successfully developed for high-speed laser scanning applications. The grating platform is thinned by a round cavity and reinforced by a circular frame, which are fabricated using a single mask delay etching (SMDE) technique. The SMDE technique, which utilizes the well-know loading effects of the deep reactive ion etching (DRIE) process, is a simple and low-cost methodology to regulate the etching rate of a prescribed area. It can be used in a silicon-on-insulator (SOI) micromachining process to form multilevel structures in a silicon device layer through a multi-step DRIE process from a wafer's backside. This paper presents the design, simulation, fabrication process and characterization of the high-speed MEMS grating scanner as well as the principle and applications of the SMDE technique. When illuminated with a 635 nm wavelength incident laser beam, the prototype scanner with a 1 mm diameter diffraction grating is capable of scanning at 50.192 kHz with an optical scan angle of 14.1°
[en] Presented in this article is an efficient design of lamellar multilayer grating (LMG) for the extreme ultraviolet/soft X-ray region near both the Si L-edge and B K-edge. The designs of LMGs have been performed by exploring different materials combinations, which are capable of providing high resolution and peak reflectivity. The performance analysis of the designed LMGs is made analytically using the coupled wave theory for single-order regime. That provides an estimation of diffraction efficiency and resolution. The effect of structural imperfections such as tapering of the lamellar profile and interfacial width on the optical properties are also analysed to describe non-ideal LMG structures
[en] Deep lamellar diffraction gratings fabricated by etching a transparent quartz plate are studied using spectroscopic ellipsometry. The rigorous coupled-wave analysis is used to calculate the optical response of the gratings. Three parameters of the rectangular profile are determined by utilizing the least-square method. Detailed investigation of the spectral dependences demonstrates the uniqueness of the solution. Observing the spectral dependences of Wood anomalies suggests that even complicated profiles can be fitted with high authenticity
[en] Complex diffraction patterns are formed by sophisticated diffraction gratings. However, the methods of synthesizing of such gratings are complicated and resource intensive. We propose a simple analytical approach to forming one- and two-dimensional quasiperiodic gratings supporting multiple diffraction consisting of a set of diffraction maxima with the specified spatial frequency of certain diffraction order. The structure of a quasiperiodic grating is a superposition of harmonic functions, which provide a discrete spatial spectrum. The number of diffraction maxima, their angular positions, and intensity distribution between them can be controlled by choosing appropriate reciprocal lattice vectors and their amplitudes. This effect confirmed by the experiment opens new possibilities for light shaping, imaging, and radiation coupling. (letter)
[en] The properties of diffraction gratings and multilayered systems constructed using 1D models of quasicrystals are considered based on numerical simulation. It is shown that there is a direct relationship between the self-similarity symmetry of quasicrystals and scaling in the characteristics of the above-mentioned optical devices. The degree of structural correspondence between the graphical representations of the geometric properties of crystals, light diffraction patterns of gratings, and the transmission spectra of multilayered systems is estimated. It is shown that certain types of self-similarity symmetry make the characteristics of aperiodic diffraction gratings highly stable to a change in the size ratio of forming elements.
[en] We propose a system of multiplexing and de-multiplexing, which uses a holographic diffraction grating to compel modulated light of different colors to be sent through an optical fiber. Diffraction gratings were fabricated specifically to pick the desired direction in which we wanted the light of different wavelengths to impinge the optic fiber, and also to be separated at the output. It was been found that the system preserves the polarization of light, which give us a one more freedom degree, allowing us to process twice the original information amount.
[en] We present and analyze a one-port sensor based on a single diffraction grating delineated over a planar optical waveguide. Distinct to previously reported devices, the grating we use here is used not only as I/O coupler, but also provides a built-in reference beam that is basically unaffected by the sensing process. The sensing process causes two effects simultaneously: a change in the angle of the out-coupled beam and a change in the phase accumulated by that beam. Both changes can be determined by their conjunction with the reference beam back-diffracted directly by the grating. These two effects are expected to have despair sensitivities, the angle changing effect being coarse and the interferometric phase-change effect being highly sensitive. Sensing simultaneously at two different scales enlarges to a great extent the sensing dynamic range. Theoretical analysis and simulations of a specific implementation example of the device are presented. (paper)