Modified Lead-zirconate-titanate for Pyroelectric Sensors

Pyroelectric sensors based on ceramic materials have found applications in IR detectionin defence and civil systems. To develop suitable ceramic material for IR detector applications,a modified PZT system with compositional formula Pb1-xSmx(Zr0.58Fe0.18Mn0.02Nb0.2Ti0.02)O3  where0  x  0.025 was synthesised by conventional solid state reaction method. The materials werecharacterised for their properties like dielectric and pyroelectric coefficient. Hysteresis loop wasrecorded at room temperature. The sample with 2 mole per cent samarium (Sm) substitutions wasfound to be more promising for sensor application based on its high material's figure of merit(FOM). Sensors fabricated with this material were integrated with FET amplifier. The devicesconfigured with compensating element were evaluated for different chopping frequencies.  Thevalue of material's FOM, FD, and detectivity, D*, were determined from measured parameters andwere,  3.6 x 10-5 Pa-1/2 and 2 x 108 cmHz1/2/W, respectively

Polarization-Tunable Antenna-Coupled Infrared Detector

An antenna-coupled infrared detector with polarization tuning over approximately 90 degrees by application of a bias voltage in the range of a few hundred millivolts. This mechanism of polarization tuning eliminates the need for bulk-optical polarization filters. When integrated into focal plane arrays, these detectors can be used in remote-sensing systems to facilitate enhanced image recognition, feature extraction and image-clutter removal. A preferred version of the antenna has longitudinal metal antenna arms extending outward from an infrared(IR) sensor in a spiral pattern, polarization tuning devices connected between the antenna arms, and a voltage for controlling the polarization tuning devices, wherein the polarization tuning devices enable real-time control of current distribution in the arms. The infrared(IR) sensors can be tunnel diodes, schottky diodes, photovoltaics, photoconductors, and pyroelectrics. Application areas can include earth-resource mapping, pollution monito

Evaluation of commercial pyroelectric detectors

A series of commercially available pyroelectric detectors made from PVF2, LTO, SBN, and TGS were evaluated in terms of responsivity and detectivity as a function of frequency. The performance of the detectors evaluated was very different, depending upon the manufacturer of the detector, and this dependency was primarily related to the thickness of the various detectors. The best detectors of each material were comparable in performance at frequencies around 10 Hz but differed radically at frequencies above 100 Hz

Multispectral Multpolarization Antenna-Coupled Infrared Focal Plane Array

Adjacent pixels of an infrared focal plane array (IR FPA) can be configured to have different spectral or polarization responses by adjustment of the lengths or orientations of the antenna arms which couple radiation into the sensors. The manufacturing costs of such an antenna-coupled IR FPA would be much less than integration of spectral or polarization filters onto each pixel, or fabrication of adjacent pixels with materials of different bandgaps. The antenna-coupled pixels can be made smaller than usual pixels, allowing this diversity of spectral or polarization information on the FPA without losing spatial resolution. The infrared (IR) sensors can be tunnel diodes, schottky diodes, photovoltaics, photoconductors, bolometers, and pyroelectrics. Application areas can include military and civilian remote sensing, automotive driving aids, industrial sensing, medical imaging, and general surveillance

Pyroelectric Materials for Uncooled Infrared Detectors: Processing, Properties, and Applications

Uncooled pyroelectric detectors find applications in diverse and wide areas such as industrial production; automotive; aerospace applications for satellite-borne ozone sensors assembled with an infrared spectrometer; health care; space exploration; imaging systems for ships, cars, and aircraft; and military and security surveillance systems. These detectors are the prime candidates for NASA s thermal infrared detector requirements. In this Technical Memorandum, the physical phenomena underlying the operation and advantages of pyroelectric infrared detectors is introduced. A list and applications of important ferroelectrics is given, which is a subclass of pyroelectrics. The basic concepts of processing of important pyroelectrics in various forms are described: single crystal growth, ceramic processing, polymer-composites preparation, and thin- and thick-film fabrications. The present status of materials and their characteristics and detectors figures-of-merit are presented in detail. In the end, the unique techniques demonstrated for improving/enhancing the performance of pyroelectric detectors are illustrated. Emphasis is placed on recent advances and emerging technologies such as thin-film array devices and novel single crystal sensors

PVF pyroelectric radiometer

Polyvinylfluoride (PVF) plastic film was found to be a good pyroelectric material. Radiometers using PVF were developed that exhibit high sensitivity and frequency response. Normalized detectivities of greater than 10 to the 8th power cm/Hz/w and responsivities on the order of 100,000 V/W were measured (500 C BB source, 0.1 Hz chopping frequency and 1 Hz bandwidth.

Sensor requirements for Earth and planetary observations

Future generations of Earth and planetary remote sensing instruments will require extensive developments of new long-wave and very long-wave infrared detectors. The upcoming NASA Earth Observing System (EOS) will carry a suite of instruments to monitor a wide range of atmospheric and surface parameters with an unprecedented degree of accuracy for a period of 10 to 15 years. These instruments will observe Earth over a wide spectral range extending from the visible to nearly 17 micrometers with a moderate to high spectral and spacial resolution. In addition to expected improvements in communication bandwidth and both ground and on-board computing power, these new sensor systems will need large two-dimensional detector arrays. Such arrays exist for visible wavelengths and, to a lesser extent, for short wavelength infrared systems. The most dramatic need is for new Long Wavelength Infrared (LWIR) and Very Long Wavelength Infrared (VLWIR) detector technologies that are compatible with area array readout devices and can operate in the temperature range supported by long life, low power refrigerators. A scientific need for radiometric and calibration accuracies approaching 1 percent translates into a requirement for detectors with excellent linearity, stability and insensitivity to operating conditions and space radiation. Current examples of the kind of scientific missions these new thermal IR detectors would enhance in the future include instruments for Earth science such as Orbital Volcanological Observations (OVO), Atmospheric Infrared Sounder (AIRS), Moderate Resolution Imaging Spectrometer (MODIS), and Spectroscopy in the Atmosphere using Far Infrared Emission (SAFIRE). Planetary exploration missions such as Cassini also provide examples of instrument concepts that could be enhanced by new IR detector technologies

Planar multimode detector arrays for infrared and millimeter-wave applications

A new type of detector array is described. By means of a suitably designed metallic network, many detector elements (each individually small compared to wavelength) are assembled into an impedance-matched termination for radiation incident normally on the plane of the device. Residual reactance is tuned out by means of a movable backshort. An array of 400 bismuth-film microbolometers with a total area of 1 cm^2 has been tested at 215 GHz. A coupling efficiency of approximately 60 percent was observed. The detector has a D^* of 4 x 10^8 cm · Hz^(1/2)/W at room temperature with response time on the order of 2 x 10^-7 s. Similar arrays of Schottky and SIS diodes can probably be constructed

Ultrathin 2 nm gold as ideal impedance-matched absorber for infrared light

Thermal detectors are a cornerstone of infrared (IR) and terahertz (THz) technology due to their broad spectral range. These detectors call for suitable broad spectral absorbers with minimalthermal mass. Often this is realized by plasmonic absorbers, which ensure a high absorptivity butonly for a narrow spectral band. Alternativly, a common approach is based on impedance-matching the sheet resistance of a thin metallic film to half the free-space impedance. Thereby, it is possible to achieve a wavelength-independent absorptivity of up to 50 %, depending on the dielectric properties of the underlying substrate. However, existing absorber films typicallyrequire a thickness of the order of tens of nanometers, such as titanium nitride (14 nm), whichcan significantly deteriorate the response of a thermal transducers. Here, we present the application of ultrathin gold (2 nm) on top of a 1.2 nm copper oxide seed layer as an effective IR absorber. An almost wavelength-independent and long-time stable absorptivity of 47(3) %, ranging from 2 $\mu$m to 20 $\mu$m, could be obtained and is further discussed. The presented gold thin-film represents analmost ideal impedance-matched IR absorber that allows a significant improvement of state-of-the-art thermal detector technology