Multispectral Detection with Metal-Dielectric Filters: An Investigation in Several Wavelength Bands with Temporal Coupled-Mode Theory EMELINE LESMANNE, 1,2 ROCH ESPIAU DE LAMAESTRE, 1 SALIM BOUTAMI, 1 CE ´ DRIC DURANTIN, 1 LAURENT DUSSOPT, 1 and GIACOMO BADANO 1,3 1.—Univ. Grenoble Alpes, CEA, LETI, MINATEC campus, 38054 Grenoble, France. 2.—e-mail: emeline.lesmanne@cea.fr. 3.—e-mail: giacomo.badano@cea.fr Multispectral infrared (IR) detection is of great interest to enhance our ability to gather information from a scene. Filtering is a low-cost alternative to the complex multispectral device architectures to which the IR community has devoted much attention. Multilayer dielectric filters are standard in industry, but they require changing the thickness of at least one layer to tune the wavelength. Here, we pursue an approach based on apertures in a metallic layer of fixed thickness, in which the filtered wavelengths are selected by varying the aperture geometry. In particular, we study filters made of at least one sheet of resonating apertures in metal embedded in dielectrics. We will discuss two interesting problems that arise when one attempts to design such filters. First, metallic absorption must be taken into account. Second, the form and size of the pattern is limited by lithography. We will present some design examples and an attempt at explaining the filtering behavior based on the temporal coupled mode theory. That theory models the filter as a resonator interacting with the environment via loss channels. The transmission is solely determined by the loss rates associated with those channels. This model allows us to give a general picture of the filtering performance and compare their characteristics at different wavelength bands. Key words: Infrared detection, filter, metal, temporal coupled-mode theory INTRODUCTION Infrared multispectral detection has drawn a lot of attention in recent years as many applications in spectroscopy (for example, gas detection) or color imaging are emerging. In order to miniaturize the detector, as well as to reduce its power consumption and sensitivity to vibrations, multispectral detec- tion can be performed at the pixel level instead of being external, as it is the case with a filter wheel. Multicolor HgCdTe detectors are described in the review of Rogalski et al., 1 but these solutions are complex and expensive. Another option is to use wideband detectors associated with pixel-level filters tuned to specific wavelengths. Multilayer dielectric filters have been studied, 2 but their resonance wavelength is determined by the layers’ thicknesses so that the fabrication of a multispectral imager is quite complex. Moreover, such a filter is thick compared to the wavelength, which can induce unwanted mechanical stress. Pixel-level filters must preferably be composed of multiple layers of fixed thicknesses and tuned to a specific wavelength by the geometry of the metallic/dielectric patterns, so that adjacent pixels can be tuned to a different wavelength without impacting the complexity of fabrication. Several types of filters with a fixed thickness have been demonstrated. Filters based on the surface plasmon properties of a metallic layer have been presented. 3 Plasmons are responsible for the (Received October 19, 2015; accepted March 19, 2016; published online April 7, 2016) Journal of ELECTRONIC MATERIALS, Vol. 45, No. 9, 2016 DOI: 10.1007/s11664-016-4475-8 Ó 2016 The Minerals, Metals & Materials Society 4603