Highly Efficient Double-Layer Diffraction Microstructures Based on New Plastics and Molded Glasses

Abstract

Within the framework of rigorous diffraction theory, the maximum possible incidence angles of radiation on two-layer sawtooth relief-phase microstructures in the visible (0.4 ≤ λ ≤ 0.7 μm) spectral range are compared. Optical materials for the layers of these microstructures are selected from a database of 47 plastics and 165 molded glasses. It is shown that when the ratio of the spatial period of the microstructure to the effective depth of the relief is greater than 20, the achievable angles within which the diffraction efficiency exceeds 0.95 lie in a wide range from 18.5° to 40.5° for single-relief structures and 7.5° to 22.3° for structures with two internal reliefs. The best results for purely plastic microstructures are obtained when the plastic CMT and the indium tin oxide nanocomposite in polymethylmethacrylate are used.

Designing dual-band athermal refractive-lens IR objectives

“…Завершая параграф, проведём сравнительный анализ характеристик разработанного двухдиапазонного атермального рефракционно-линзового ИК-объектива с характеристиками представленного в работе [16] двухдиапазонного рефракционно-дифракционного ИК-объектива, включающего три рефракционные линзы, на плоской поверхности одной из которых размещена двухрельефная двух-или трехслойная дифракционная микроструктура. При сопоставимых рабочем спектральном диапазоне, фокусном расстоянии и угловом поле зрения данные объективы формируют сопоставимые по пространственному разрешению изображения.…”

Design of Ultra-High-Aperture Dual-Range Athermal Infrared Objectives

“…However, in this case, a real positive effect of using the DOE can be achieved only if the dependence of the diffraction efficiency (DE) of the element on the wavelength and angle of incidence of the radiation on it is suppressed. Therefore, the DOE microstructure is constructed as a double-relief two-or even three-layered structure [9,17]. The problem is exacerbated when we are using a refractive-diffractive lens in the conditions of a significant difference in its operating temperatures.…”

“…Its reliefs are made on the flat surfaces of the material substrates, which differ in their dispersion properties. Usually it is a pair of crownand flint-like optical materials [9,[17][18][19].…”

“…A significant inverse DOE dispersion, which is characterized by a negative dispersion coefficient, provides tangible advantages to refractive-diffraction schemes. Thus, in particular, a previous study [9] showed that in the double IR range, the required degree of correction of the longitudinal chromatism can be achieved with a three-lens high-aperture refractive-diffractive objective.…”

“…The chromatic aberrations of the optical systems operating in several spectral ranges can be corrected by using only refractive lenses in the optical scheme and by including a diffractive optical element (DOE) in the scheme. Such an element transforms the incident wavefront because of the effect of light diffraction on a relief sawtooth microstructure, which is experienced, for example, on the surface of a refractive lens [8,9]. A significant inverse DOE dispersion, which is characterized by a negative dispersion coefficient, provides tangible advantages to refractive-diffraction schemes.…”