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

Abstract

Micro-filters fabricated using integration methods is now the trend for multichannel filters in imaging spectrum systems. Traditional multichannel bandpass filters are mainly fabricated separately by multilayered thin films and then glued together. This approach involves the complexity of precision cutting, dicing, and adhesive bonding; therefore, the possibility of miniaturization is quite limited. In this work, a dual channel bandpass thin film filter for the mid-infrared was fabricated by using the lift-off process. The structure of a 4-cavity Fabray–Perot (F-P) type filter was designed and optimized. The bandpass filter over the range 3.55–3.75 µm with full width at half maximum (FWHM) of 274 nm and the bandpass filter over the range 4.85–4.95 µm with FWHM of 246 nm were obtained with a 4.5 µm joint width. The average transmittance of the filters is more than 83.5% and optical density value of the cutoff is 3. The thickness of 3.55–3.75 µm bandpass filter was measured and the thickness error was analyzed. The results show that the thickness error, especially the thickness error of spacer layers, induces the degradations of peak transmission and bandwidth. This kind of mid-infrared filter has important application in space remote sensing, military, and civil fields.

Design and Fabrication of a patterned dual colour filter using Microwave plasma assisted Sputtering and Photolithography

“…Wavelength separation is required and is best achieved through the use of multiple filters based on thin film optical interference coatings. Microfabrication of these filter arrays reduces size and removes the need for a difficult and labor intensive dicing and gluing process [2].…”

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

“…Jeong and Mang proposed another visible-to-near-IR narrow bandpass filter with cholesteric liquid crystal materials . Mid-IR filters are more difficult to produce than visible/near-IR filters due to their greater thickness, which also makes striping the photoresist during the lift-off process challenging . Based on the Fabry–Perot interferometer, mid-IR filters have been developed by layering a fine-tuned thin film (nanometers) of semiconducting materials stacked on top of one another to form quantum well heterostructures or surface lattices.…”

“…99 Mid-IR filters are more difficult to produce than visible/near-IR filters due to their greater thickness, which also makes striping the photoresist during the lift-off process challenging. 100 Based on the Fabry−Perot interferometer, mid-IR filters have been developed by layering a fine-tuned thin film (nanometers) of semiconducting materials stacked on top of one another to form quantum well heterostructures or surface lattices. Sieger and Mizaikoff summarized the recent development of mid-IR transmitting materials for thin-film waveguide fabrication.…”

NIR to LWIR Dichroic Beamsplitter Designed and Manufactured for Space Optical Remote Sensor

“…As one of the main detection payloads on Earth observation satellites, the infrared multispectral imager has vast applications in meteorological analysis [2], environmental protection [3,4], the exploration of natural resources [5], and early warnings of geological disasters [6,7]. In recent years, because there has been a new generation of photoelectric detection technology that captures image data within specific wavelength ranges throughout the electromagnetic spectrum, multispectral imaging improves the dimension of image information and thus extends the function of traditional detection technology [8]. In a multi-channel infrared remote sensing imaging spectrometer, the spectral response is usually wide, and the instrument needs two or more detectors to detect optical signals of different bands [9].…”