Range selective phase-shifting frequency-modulated digital holography with temporal-heterodyning.

We demonstrate that a time of flight (TOF) camera can be used to perform range selective temporal-heterodyne frequency-modulated continuous wave digital holography (TH FMCW DH). The modulated arrayed detection of a TOF camera allows efficient integration of holograms at a selected range with range resolutions significantly less than the optical system's depth of field. TH FMCW DH also allows for on-axis geometries to be achieved, where background light not at the internal modulation frequency of the camera is filtered out. Range selective TH FMCW DH imaging was achieved for both image holograms and Fresnel holograms using on-axis DH geometries. A 2.39 GHz FMCW chirp bandwidth resulted in a DH range resolution of 6.3 cm.

Range selective digital holographic imaging using FMCW lidar.

The integration of chirped frequency modulated continuous wave (FMCW) lidar techniques into digital holography enables range selective holographic imaging well beyond the depth of field of the system. The technique uses FMCW transmit and reference beams. By frequency shifting the reference beam to compensate for the typical FMCW beat frequency associated with a particular range, temporally stable holograms are formed for objects at the selected range. The holograms associated with objects at all other ranges oscillate and integrate towards zero. Experimental demonstrations of the technique are presented, showing enhanced imaging of objects at different ranges and cancellation of obscuring objects. The technique is expandable to range-Doppler selective digital holographic imaging.

Digital holographic polarimeter using dual reference beam interferometry.

An off-axis digital holographic imaging polarimeter was developed to estimate the Jones matrices of an object. The Jones vector image of the electric field returned from the object is determined from a single holographic recording using the interference between the dual, nearly orthogonal, reference beams. The technique compensates for phase variations in the optical beam paths between the recorded holograms and relaxes the need to generate orthogonal illumination polarization states. A minimization algorithm was developed to compute an estimation of the Jones matrix image of an object based on a set of measured Jones vector images. A proof-of-concept demonstration was performed to compute an estimated Jones matrix image of a polarimetrically complex object using digital holograms recorded with 6 different illumination polarizations.

Demonstration of stimulated photon echo isolation using interferometric cancellation.

An alternative to phase-matched angled beam spatial-spectral holographic grating geometries for separating stimulated photon echoes (SPEs) from the probing pulse is proposed and demonstrated. By use of a Mach-Zehnder geometry with inhomogeneously broadened medium in both paths, the SPE can be interferometrically isolated from the generating probe pulse. This interferometric-based technique is well suited to waveguide geometries, which have benefits for future quantum and classical optical signal processing applications such as quantum memories, correlation, and efficient cryogenic microwave-to-optical conversion. Experimental demonstrations showing interferometric-based isolation in Tm3+-doped LiNbO3 at 3.2 K are performed and analyzed.

Comparison of computed tomographic angiography and noncontrast magnetic resonance angiography in preoperative evaluation of living renal donors.

INTRODUCTION: The computed tomographic angiography (CTA) renal donor protocol is an established method of preoperative renal vascular pedicle evaluation in prospective renal donors. However, CTA is associated with significant radiation exposure and intravenous contrast administration. The newer noncontrast-enhanced magnetic resonance angiography (NCE-MRA) techniques, especially arterial spin labeling (ASL) with steady-state free precession (SSFP) hold promise as an effective alternative. We prospectively compared CTA with NCE MRA for accuracy in the evaluation of renal arterial anatomy in prospective renal donors. METHODS: A total of 43 subjects underwent CTA followed by NCE MRA in a prospective comparative study. The number of renal arteries and early branching of renal arteries were noted in both kidneys in all subjects. Intermodality agreement was calculated using "K" (Kappa) statistics and 95% confidence interval for both modalities. RESULTS: A total of 63 single, 21 double, and 2 triple arteries were detected in 43 subjects on CTA. CTA showed an early branch in 17 kidneys. NCE MRAshowed 64 single arteries, 20 double arteries, and 2 triple arteries. A total of 14 kidneys showed an early branch. Unweighted Kappa statistic of agreement between CTA and NCE MRA for number of renal arteries and for frequency of early branching was 0.9707 and 0.8822, respectively. CONCLUSIONS: The newer NCE MRA techniques such as ASL with SSFP among others are potential alternatives for CTA, in the evaluation of prospective renal donors.

Spectral engineering of slow light, cavity line narrowing, and pulse compression.

More than 4 orders of magnitude of cavity-linewidth narrowing in a rare-earth-ion-doped crystal cavity, emanating from strong intracavity dispersion caused by off-resonant interaction with dopant ions, is demonstrated. The dispersion profiles are engineered using optical pumping techniques creating significant semipermanent but reprogrammable changes of the rare-earth absorption profiles. Several cavity modes are shown within the spectral transmission window. Several possible applications of this phenomenon are discussed.

Standardisation of a two-site PTH immunoradiometric assay using various solid phase formats.

BACKGROUND & OBJECTIVES: Estimation of parathyroid hormone (PTH) levels is important in the management of metabolic bone disorders. Here we describe a simple, sensitive and specific second generation immunoradiometric assay (IRMA) to detect intact PTH levels using different solid phase matrices. Different methods for immobilization of antibodies have also been evaluated. METHODS: Experiments were carried out with physical adsorption of antibodies, covalent coupling using 2 per cent glutaraldehyde and N,N`carbonyldiimidazole. In all cases, antibodies raised against C-terminal were used as solid phase agent. Detector antibodies were N terminal antibodies that were radio-iodinated with [125] I followed by gel purification. Several of the antibodies coupled to various solid phase matrices were incubated with PTH standards and the detector antibody as well as the commercially available tracer from DiaSorin kit to identify a suitable match pair. RESULTS: The best pair was polyclonal C-terminal PTH antibody along with the kit tracer from DiaSorin with regards to antibody coated to magnetic cellulose particles. Among the various antibodies and the solid phases evaluated, the best assay was obtained with the matched pair of antibodies (70×G67 and 70×G68) from Fitzgerald immobilized on polystyrene tubes. The polyclonal antibody against C-terminal PTH was chosen as the capture antibody and [125] I labelled polyclonal antibody against N-terminal PTH as the tracer. The sample values obtained in the antibody coated tubes were comparable to those obtained using a commercial kit. INTERPRETATION & CONCLUSIONS: The results indicated the feasibility of adopting this system for further development into a PTH IRMA for regular production as there is no indigenous kit available for intact PTH.

Demonstrations of analog-to-digital conversion using a frequency domain stretched processor.

The first proof-of-concept demonstrations are presented for a broadband photonic-assisted analog-to-digital converter (ADC) based on spatial spectral holography (SSH). The SSH-ADC acts as a frequency-domain stretch processor converting high bandwidth input signals to low bandwidth output signals, allowing the system to take advantage of high performance, low bandwidth electronic ADCs. Demonstrations with 50 MHz effective bandwidth are shown to highlight basic performance with approximately 5 effective bits of vertical resolution. Signal capture with 1600 MHz effective bandwidth is also shown. Because some SSH materials span over 100 GHz and have large time apertures (approximately 10 micros), this technique holds promise as a candidate for the next generation of ADCs.

Multigigahertz range-Doppler correlative signal processing in optical memory crystals.

Analog optical signal processing of complex radio-frequency signals for range-Doppler radar information is theoretically described and experimentally demonstrated using crystalline optical memory materials and off-the-shelf photonic components. A model of the range-Doppler processing capability of the memory material for the case of single-target detection is presented. Radarlike signals were emulated and processed by the memory material; they consisted of broadband (> 1 GHz), spread-spectrum, pseudorandom noise sequences of 512 bits in length, which were binary phase-shift keyed on a 1.9 GHz carrier and repeated at 100 kHz over 7.5 ms. Delay (range) resolution of 8 ns and Doppler resolution of 130 Hz over 100 kHz were demonstrated.

Recovery of spectral features readout with frequency-chirped laser fields.

A data-processing technique is proposed for use with conventional frequency-chirped absorption spectroscopy to ensure accurate mapping of spectral features into time-domain signatures with arbitrarily fast readout chirp rates. This technique recovers the spectrum from a signal that is distorted owing to the fast chirp rate and therefore facilitates fast measurement of the spectral features over a broad spectral range with high resolution. Both numerical simulations and experimental results are presented.

Long-time-storage mechanism for Tm:YAG in a magnetic field.

We obtained a long-time-storage mechanism for spectral features in thulium ions doped into YAG by applying a magnetic field that splits the electronic ground state. We show experimentally that the storage time can be more than 30 s, which is 3 orders of magnitude longer than that of the metastable state that normally is used for information storage in this material. Level splitting and storage lifetimes for various magnetic field strengths of as much as 5 T were investigated. This storage mechanism will be relevant in the many coherent transient-based signal-processing schemes in which Tm:YAG is being used, and we demonstrate long-time storage in a basic data storage application.