The blazed convex grating is one of the key elements in Offner imaging spectrometers. In this paper the diffraction characteristics of the blazed convex grating is investigated by using rigorous coupled-wave analysis. The results indicate that within the wavelength from 1 μm to 2.5 μm, the first-order diffraction efficiency can be over 40% through controlling the blazed angle of blazed grating. Furthermore, when the blazed angle is 3.9 degree, the first-order diffraction efficiency is still over 40% with the vertex angles between 120 degree and 150 degree. The blazed convex grating with the spatial frequency of 73 L/mm in the center will be fabricated by holographic lithography-ion beam etching.
The echelle gratings with the ultra-high resolution are one of the key elements in spectroscopy, optical communications and other fields. Currently, the diamond ruling and the wet etching technique are two primary methods to fabricate echelle gratings. In this paper, we have adopted a new method of the echelle gratings fabrication. Firstly, the holographic lithography is used to form a photoresist grating mask. Then, reactive ion etching is adopted to fabricate the native substrate grating mask to replace the traditional photoresist grating mask, which allows more accurate control of the profile. Finally, the tilted ion-beam etching is used to etch the native substrate grating to ensure the precise control of the blazed angle and anti-blazed angle. A prototype of the echelle gratings with a line density of 80 lp/mm has been fabricated by above method.
In this paper, a sub-wavelength metal grating polarizer at visible region is designed by Finite Difference Time Domain (FDTD) method. We have analyzed the effects of the period, the thickness of metal layer and the duty cycle on the performance of the metal grating polarizer. Simulation results show that in order to increase the metal grating transmissivity and extinction ratio and to reduce the angle sensitivity (±30°), the period should be less than 200 nm; Therefore, the structure with 180nm period and an 120nm Al layer is chosen, and the transmission efficiency and extinction ratio is more than 75% and 25dB respectively. Finally, a prototype of the metal grating has been fabricated by holographic-immersion lithography and ion beam etching.
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