Design and Preparation of a 6-Channel Fan-Shaped Integrated Narrow-Band Filter in the Mid-Infrared Band

Abstract

A six-channel fan-shaped integrated narrow-band filter on a silicon substrate was designed on the basis of the Fabray–Perot (FP) theory and was fabricated using e-beam thermal evaporation. The central wavelength was modulated by modifying the FP cavity thickness using the combination mask method. Germanium and zinc sulfide were selected as the high and low refractive index film materials, respectively. Its average peak transmission reached 83.3%, the cut-off transmittance was less than 1%, and the full width at half maximum (FWHM) changed from 55 and 94 nm, and the central wavelength positioning accuracy error was less than 0.35%. Furthermore, transmittance was also calculated inversely, using the thickness of each layer of films, in order to deduce the reason of the decrease in peak transmittance. Thickness deviation of each layer and interface scattering contributed to the decrease of peak transmittance. Compared with the same type of products in the market, our filter showed better properties than that of some published and commercial filter.

Review and Perspective: Gas Separation and Discrimination Technologies for Current Gas Sensors in Environmental Applications

“…IR interference filters can be fabricated using various methods, such as vacuum deposition, sputtering, and ion-assisted deposition, which has been recently reviewed by Lochbaum et al The thickness of each layer is carefully designed to create a specific interference pattern that selectively enhances the transmission of the desired wavelength range and reduces the transmission of other wavelengths . For example, Duan et al developed a six-channel integrated narrow-band mid-IR filter (3.6–4.4 μm) using different thicknesses of Ge film on Si, which is shown in Figure . Shi et al developed a tunable narrow-band mid-IR bandpass filter of 3.1–4.8 μm based on surface lattice resonance using different thicknesses of Ge–Sb–Te …”

“…Schematic structure of 6-channel fan-shaped integrated IR filters by Duan et al Reprinted (adapted or reprinted in part) with permission from ref . Duan, Y.; Cai, C.; Liang, H.; Jia, T.; Yin, S. Design and Preparation of a 6-Channel Fan-Shaped Integrated Narrow-Band Filter in the Mid-Infrared Band.…”

“…For example, a mid-IR QCL made of In-As/In-As-Sb provides wavelengths of 4.2 and 4.7 μm to detect carbon dioxide (CO) and carbon monoxide; an Al-In-As/In-As-Sb-based QCL emits 3.9–4.9 μm IR to detect CO 2 (4.2 μm), N 2 O (4.5 μm) and CO (4.6 μm); and an Al-In-Sb/In-Sb-based QCL is used for methane detection . Other IR QCLs include Ge-Sn/Si-Ge-Sn-based to provide wavelengths of 2.1–2.3, 2.9–3.2, and 4.35 μm. , …”

Design and Fabrication of an Integrated Dual-Channel Thin-Film Filter for the Mid-Infrared

“…For this application, much work has been done to fabricate the multichannel filter in the mid infrared spectral region. In the published work, the peak transmittance (Tmax) ranges from 30% to 65% [11,12]. A mid-IR dual-band filter, which consists of periodic gold grating and a CaF2 substrate, was prepared with the wavelength of ~3.8392 µm and the FWHM of 1.8 nm [13].…”

“…The filter has a passband width of 6 nm or 0.14% with peak transmission of 55% and a central wavelength of approximately 4.0 µm [14]. A six-channel fan-shaped integrated narrow-band filter on a silicon substrate was designed and fabricated [11]. Its average peak transmission reached 83.3%, the cut-off transmittance was less than 1% (optical density, OD = 2).…”