Pixel Scale Fabry-Perot Filter Array for Chemical-Agent Vapor Detection

Spectral sensing in the long-wave infrared (LWIR) region is crucial for applications such as chemical and gas detection, environmental monitoring, and security. These applications require the ability to accurately identify and quantify various chemical vapors and trace gases in diverse environments. The demand for compact, portable, and efficient spectral sensors has grown, driven by the need to integrate these capabilities into micro-uncrewed aerial vehicles (micro-UAVs), wearable devices, and other mobile platforms. Effective spectral sensors enable real-time analysis and decision-making, enhancing safety and operational efficiency in both civilian and defense sectors. Current approaches to LWIR spectral sensing often rely on bulky and power-intensive Fourier-transform infrared (FTIR) spectrometers, which are not well-suited for integration into small or portable systems. These traditional systems suffer from high size, weight, and power (SWAP) requirements, limiting their deployment in constrained environments. Additionally, existing filter technologies face challenges in balancing spectral resolution with signal-to-noise ratio, leading to compromises in detection sensitivity and accuracy. Fabrication complexities and spatial inhomogeneities in filter arrays further hinder the scalability and performance of current sensors. As a result, there is a pressing need for more compact, lightweight, and efficient spectral sensing solutions that can deliver high performance without the drawbacks of conventional methods.

Technology Description

The spectral sensor system is designed for compact chemical and gas detection, integrating a 160 × 120 long-wave infrared (LWIR) detector array with a 32 × 24 Fabry-Pérot filter array on a single substrate. Each filter covers a 5 × 5 block of detectors, enabling the detection of up to 768 wavelength bands, with practical applications focusing on 132 unique bands between 7.36 to 12.64 microns. The Fabry-Pérot filters feature resonant cavities formed by Bragg mirrors made from alternating layers of germanium and zinc sulfide. The optical system includes random phase plates to ensure uniform radiance distribution across the detector array. Fabrication utilizes grayscale photolithography and etching techniques compatible with microelectronic processes, allowing integration into various form factors such as micro-UAVs, wearable devices, and pen-sized spectrometers. The system supports autonomous operation with onboard power, controller, and memory components, making it versatile for applications ranging from personal protection to environmental monitoring.

This technology is differentiated by its exceptional compactness and integration capabilities, achieving a balance between high spectral resolution and optimal signal-to-noise ratio through precise mirror reflectivity control. The use of grayscale photolithography allows for accurate cavity thickness variations, while the pseudo-random arrangement of filters minimizes spatial inhomogeneity, enhancing detection fidelity. Advanced signal processing techniques, including overlapping filter passbands and spectrum deconvolution, further improve measurement accuracy. Compared to traditional bulky FTIR-based systems, the sensor offers significant advantages in size, weight, and power (SWaP), enabling portable and versatile deployments. Its adaptability to various platforms and wavelength ranges, coupled with lower costs and enhanced performance, makes it a superior solution for trace gas detection and chemical analysis across multiple environments and applications.