Micromachined Infrared Spectometer

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This proposal proposes to utilize the principal investigator's expertise in micromachined uncooled infrared detectors to develop miniature, micromachined optical spectrometers whose total dimensions are on the order of millimeters that are capable of operating up to the long-wave infrared region (1-15 m). The miniaturization of an optical spectrometer is challenging because high spectral resolution generally requires large optical paths. In the case of a micromachined optical spectrometer, the optical paths will be relatively short limiting the spectral resolution. However, micromachining offers the ability to mass-produce the devices at low cost. Some applications such as gas monitoring do not require high spectral resolution; at least as a first line of defense, local early warning sensor for monitoring the presence of a toxic gas in a controlled working environment. The ability to have wearable, low cost optical spectrometers would be advantageous to environmental safety and maintaining a safe work place. Micromachined spectrometers could also monitor carbon dioxide in buildings, serving as a sensor for ventilation systems.Intellectual Merit: This investigation will develop micromachined infrared spectrometers operating in the 1-15 m wavelength range. Micromachined microbolometers will be used to detect the radiation such that a single class of detector can measure the radiant energy over the entire spectrum. Fabry-Perot and cavity interferometers will be investigated through numerical simulation and experimental characterization. The infrared microspectrometers will be designed and simulated using the CorningIntellisense Intellisuite CAE tool. The performance limits and design trade-offs for different spectrometer geometries will be investigated. The infrared microspectrometers will be fabricated using the Kronos Foundry Service and the fabrication facilities at the UTA Nanofab. A relatively new material family, GeOx and SixGe1-xOy, will be investigated as the thermometer employed in the microbolometer. Researchers at Univeridad Politecnica de Madrid, Spain have measured the temperature coefficient of resistance (R -1 dR/dT) in these materials to be as high as 4.2%/K and demonstrated good performance in bulk micromachined microbolometers. These materials have the advantage of being easily deposited by rf sputtering at room temperature and being oxides of conventional integrated circuit materials. This investigation will seek to further the investigation of the application of GeOx and SixGe1-xOy to uncooled infrared detection and the use of surface micromachining with polyimide sacrificial layers to demonstrate higher performance in the microbolometers (detectivity goal of 10 8 to 10 9 cm Hz 1/2 /W). The results of this part of the investigation will also impact microbolometer applications in night vision, in addition to optical spectrometers applications.Broader Impact: The results of the investigation will be distributed widely through traditional conference presentations and journal articles as well as by publishing a web-based tutorial on micromachined spectrometers that is written to target the general public rather than scientists and engineers.