Broadband sub-millimeter wave technology has received significant attention for potential applications in security, medical, and military imaging. Despite theoretical advantages of reduced size, weight, and power compared to current millimeter wave systems, sub-millimeter wave systems have been hampered by a fundamental lack of amplification with sufficient gain and noise figure properties. We report a broadband pixel operating from 300 to 340 GHz, biased off a single 2 V power supply. Over this frequency range, the amplifiers provide > 40 dB gain and <8 dB noise figure, representing the current state-of-art performance capabilities. This pixel is enabled by revolutionary enhancements to indium phosphide (InP) high electron mobility transistor technology, based on a sub-50 nm gate and indium arsenide composite channel with a projected maximum oscillation frequency fmax>1.0 THz. The first sub-millimeter wave-based images using active amplification are demonstrated as part of the Joint Improvised Explosive Device Defeat Organization Longe Range Personnel Imager Program. This development and demonstration may bring to life future sub-millimeter-wave and THz applications such as solutions to brownout problems, ultra-high bandwidth satellite communication cross-links, and future planetary exploration missions.
We discuss the methods and design considerations required in engineering a high-resolution camera for use at 94 GHz
(~3mm wavelength) to yield the best compromise between optical resolution, field of view, object distance, depth of
focus, image acquisition time, and system cost. This application is one in which only the blackbody radiation emitted by
the body is a light source, i.e., a passive system. Several critical design parameters were optimized in this design,
including, the point spread function size upon the detector array, optical losses, and depth of focus. The metric for
characterization of the optical design was the Huygen's wavelet calculation that correlated well with measured
performance. Measurements of the PSF and MTF agreed with the model within measurement error. Sample imagery of
hidden objects demonstrate that this prototype design is capable of resolving objects with feature sizes as small as 0.50
inch and further show the utility of this millimeter wavelength camera.
A system for characterizing polarization controllers and other fiber components with Mueller matrices is presented. Most polarization controllers, such as lithium niobate modulators or PLZT electro-optical modulators, exhibit a wide range of polarization behaviors at constant drive voltage including elliptical retardance, polarization dependant loss (PDL), and depolarization. Specifying the half wave voltage for such devices describes their desired characteristic, an electrically addressable retardance, but not the undesired characteristics. Devices with complex polarization behaviors require a similarly comprehensive description of their polarization effects. We present example measurements that demonstrate how the Mueller matrix as a function of voltage provides a complete description of the desired retardance and the undesired PDL. Such polarization controller Mueller matrices can be multiplied with Mueller matrices for other photonic components to quantify how component polarizations interact.
Retinal vessel oxygen saturation has been suggested as a parameter for monitoring a wide range of conditions including occult blood los and a variety of ophthalmic diseases. We have developed an Eye Oximeter (EOX), that noninvasively measures the oxygen saturation of the blood in individual large retinal vessels using scanning lasers. 1D vessel extinction profiles are obtained at four wavelengths (629, 678, 821 and 899 nm), and the vessel transmittances computed. The oxygen saturation of blood within the vessel is then calculated from the transmittance data. We have performed an in vitro experiment on human blood which demonstrates the calibration of the EOX measurements and validates our oximetry equations. Retinal vessel oxygen saturation was measured in a human subject and found to be 65%O<SUB>2</SUB>Sat and 101 - 102%O<SUB>2</SUB>Sat in the veins and arteries on the optic disk. Irregularities in the background measured away from the optic disk resulted in a large variance in the calculated saturation when compared to measurements made on the disk.
An optical testing instrument, the Eyeglass Image Quality Mapper, has been developed that maps the power, astigmatism, and modulation transfer function over the surface of a progressive addition eyeglass lens. This instrument models the manner in which the eye views different regions of the lens and is automated so that testing can be performed without supervision and in a reasonable amount of time.In this paper, we describe the concept development, final design, and use of the instrument.