Abstract
Porous silicon based rugate filters are emerging as interesting functionalized optical components in Micro-Opto-Electro-Mechanical Systems due to their specific nanostructures and superior optical properties. In this work, a cost-effective approach to generate a porous silicon based rugate filter wheel containing nine filter segments in the visible wavelength range suitable for multispectral imaging systems is presented. The filter wheel segments are patterned on a silicon wafer using silicon nitride insulating masks and generated using the anodization technique. Specific characteristics of filter segments are adjusted by the current squeezing effect during the anodization through the geometrical size of the filter segments, which results in local current redistributions and consequently porous silicon formation rate and porosity modifications. A finite element model made in COMSOL Multiphysics is also presented to study redistributions of the current density and the current squeezing effect during the anodization for the proposed filter wheel. The proposed filter wheel can be miniaturized and integrated into a portable multispectral imaging system.
Highlights
Porous Silicon Based Rugate Filter Wheel for Multispectral Imaging ApplicationsShervin Keshavarzi, 1,∗,z Andras Kovacs,[1] Mohammad Abdo,[2] Vlad Badilita,[2] Rui Zhu,[1] Jan G
Several types of optical biosensors operating with porous silicon (PSi)-based optical elements, such as Fabry-Perot layers,[10] Bragg reflectors,[11] rugate filters,[12] microcavities,[13] waveguides,[14] photonic crystals,[15] and diffraction gratings[16] have been so far reported
We present a cost-effective approach to generate a PSi rugate filter wheel containing nine filter segments in the visible wavelength range (570–820 nm) suitable for wavelength scanning multispectral imaging systems.[22]
Summary
Shervin Keshavarzi, 1,∗,z Andras Kovacs,[1] Mohammad Abdo,[2] Vlad Badilita,[2] Rui Zhu,[1] Jan G. Rugate filters are a class of optical filters, which are characterized by a sinusoidal continuous variation of the refractive index in a direction perpendicular to the plane of the filter.[17] The reflectance spectrum of a rugate filter shows a high reflectivity around a filter specific wavelength and a very low reflectivity elsewhere. We present a cost-effective approach to generate a PSi rugate filter wheel containing nine filter segments in the visible wavelength range (570–820 nm) suitable for wavelength scanning multispectral imaging systems.[22] In this approach, the filter wheel segments are patterned on a Si wafer covered by thin silicon nitride isolation layers and generated using the anodization technique. Redistribution subject to ECS terms of use (see ecsdl.org/site/terms_use) unless CC License in place (see abstract)
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