Brian Monacelli

Infrared frequency selective surface based on circuit-analog square loop design

A frequency selective surface (FSS) was designed to have a resonant spectral signature in the infrared. The lithographically composed, layered structure of this infrared FSS yields a resonant response in absorption to infrared radiation at a wavelength determined by its FSS element structure and the structure of its substrate layers. The infrared spectral characteristics of this surface are studied via Fourier transform infrared spectroscopy and spectral radiometry in the 3 to 15 /spl mu/m region of the spectrum. The design is based on circuit-analog resonant behavior of square loop conducting elements.

Optical resonances in periodic surface arrays of metallic patches

The transmission of light along the surface normal through an air-quartz-glass interface covered with a periodic array of thin, rectangular gold patches has been studied over the visible to infrared range. The various structures that are observed can be qualitatively understood as arising from standing-wave resonances set by the size and surroundings of the metal patches. A method-of-moments calculational scheme provides simulations in good quantitative agreement with the data. It is shown how the standing-wave picture provides a useful conceptual framework to understand and exploit such systems.

Design, fabrication, and characterization of antenna-coupled metal-oxide-metal diodes for dual-band detection

Two designs for antenna-coupled Ni-NiO-Ni diodes are fabricated and tested for dual-band detection in the millimeter-wave (MMW), 94-GHz, and infrared (IR), 28.3-THz, frequencies. The detector noise, antenna receiving properties, and noise equivalent power (NEP) are measured. The simultaneous dual-band response is verified.

Uncertainty analysis in the measurement of the spatial responsivity of infrared antennas

The measurement of a two-dimensional spatial responsivity map of infrared antennas can be accomplished by use of an iterative deconvolution algorithm. The inputs of this algorithm are the spatial distribution of the laser beam irradiance illuminating the antenna-coupled detector and a map of the measured detector response as it moves through the illuminating beam. The beam irradiance distribution is obtained from knife-edge measurements of the beam waist region; this data set is fitted to a model of the beam. The uncertainties, errors, and artifacts of the measurement procedure are analyzed by principal-component analysis. This study has made it possible to refine the measurement protocol and to identify, classify, and filter undesirable sources of noise. The iterative deconvolution algorithm stops when a well-defined threshold is reached. Spatial maps of mean values and uncertainties have been obtained for the beam irradiance distribution, the scanned spatial response data, and the resultant spatial responsivity of the infrared antenna. Signal-to-noise ratios have been defined and compared, and the beam irradiance distribution characterization has been identified as the statistically weakest part of the measurement procedure.

Infrared frequency selective surfaces: design, fabrication, and measurement

A frequency selective surface (FSS) is designed and fabricated to resonate in the infrared. This IR FSS is designed using Periodic Method of Moments (PMM) software and is based on circuit-analog resonance of square loop conducting elements. The FSS is fabricated via electron beam lithography. The spectral characteristics of this surface are studied in the mid-infrared employing a spectral radiometer. The IR FSS may operate as an emissive narrowband source or reflective bandpass filter centered at a wavelength of 6.5μm, sharply cutting off short wavelength radiation and gradually filtering longer wavelengths. The addition of a superstrate layer, intended to further shape the FSS spectral signature, is also studied and the results discussed.

Wavelength tuning of an antenna-coupled infrared microbolometer

Wavelength tuning is demonstrated in an antenna-coupled infrared microbolometer. With a 300-mV control voltage, we observed a tuning range of 0.15 μm near 10 μm. A metal-oxide-semiconductor capacitor underneath the antenna arms causes the shift of resonance wavelength with applied voltage. We develop a device model that agrees with measured results.

Characterization of a wavelength-tunable antenna-coupled infrared microbolometer

Wavelength tuning is demonstrated in an antenna-coupled infrared microbolometer. With a 300-mV control voltage, we observed a tuning range of 0.5 µm near 10 µm. A metal-oxide-semiconductor capacitor underneath the antenna arms causes the shift of resonance wavelength with applied voltage. We develop a device model that agrees well with measured results.

Characterization of digital-micromirror device-based infrared scene projector

A test procedure is developed for an infrared laser scene projector, and applied to a projection system that we develop based on digital micromirror technology. The intended use will be for simulation and target training. Resolution and noise are significant parameters for target perception models of infrared imaging systems. System resolution is normally measured as the modulation transfer function (MTF), and its noise modeled through an appropriate signal standard deviation metric. We compare MTF measurements for both mid-wave (MWIR) and long-wave IR (LWIR) bands for an infrared laser scene projector based on the digital micromirror device (DMD). Moreover, we use two complimentary models to characterize imaging camera noise. This provides a quantitative image-quality criterion of system performance.

Infrared frequency selective surfaces

A frequency selective surface (FSS) is designed and fabricated to resonate in the infrared. The FSS is designed via periodic method of moments (PMM) software and is based on circuit-analog resonance of square loop elements. The lithographically composed FSS resonates at the absorption of infrared radiation. The spectral characteristics of this surface are studied from 3 to 15 /spl mu/m.

Infrared targets for testing and training

We present a design for an IR scene projector for live-fire training applications, based on modification of a commercial-off-the-air laser-light-scene scanner retrofitted with a CO2 laser and associated IR optics. Design goals include a reusable or at least very inexpensive shoot- through projection screen. This application calls for a wide projection field as compared to typical IR scene-projection systems intended for hardware in the loop testing.