Silicon diffractive optical element with piecewise continuous profile to focus high-power terahertz radiation into a square area

Abstract

A technique of high-frequency laser ablation using a 2D beam scanner has been designed and applied to creation of a silicon diffractive optical element (DOE) with a continuous profile to focus a terahertz Gaussian beam into a square region. The microrelief of the resulting silicon DOE has been analyzed with a white-light interferometer and a scanning electron microscope. The distribution of radiation behind the DOE illuminated by a high-power beam of the Novosibirsk free-electron laser at a wavelength of 130 µm, recorded with a pyroelectric camera, has been demonstrated. The measured diffraction efficiency of the DOE is equal to 97 ± 2 % .

Direct search method of double-layer diffractive optical elements

“…11,12 The history of DOE research has been characterized by a relentless pursuit of increased diffraction efficiency. 13 Currently, single-layer DOEs can attain a diffraction efficiency of 100% at a designated design wavelength, whereas double layer DOEs (DLDOEs) can achieve the same level of diffraction efficiency at two design wavelengths. [14][15][16] This distinctive property of DLDOEs endows them with a wideband diffraction efficiency.…”

“…There has been an impressive increase in DOE performance associated with their improved diffraction efficiency 11 , 12 . The history of DOE research has been characterized by a relentless pursuit of increased diffraction efficiency 13 …”

Optimization, fabrication and characterization of a binary subwavelength cylindrical terahertz lens

“…Появление источников мощного терагерцового излучения, таких как лазеры на свободных электронах [1], привело к необходимости формирования элементной базы для управления характеристиками мощных пучков терагерцового излучения. Известны результаты исследования пропускающих [2 -5] и отражающих [6] элементов, предназначенных для фокусировки мощного терагерцового пучка в заданные двумерные [4] и трёхмерные [7] области, а также для формирования мощных терагерцовых пучков с заданными поперечно-модовым составом [8] и поляризационным состоянием [9]. В качестве материала подложки пропускающих силовых терагерцовых эле-ментов в [2 -5, 7 -9] использовался высокорезистивный кремний [10].…”