Experimental solid mechanics relies heavily on surface displacement and deformation gradient measurements. Digital image/ speckle correlation (DISC) uses digital image processing to resolve displacement and deformation gradient fields. The practical implementation of DISC involves important challenges such as computation complexity and the discrepancy of the sensitivities and accuracies claimed in previous studies. We develop an iterative, spatial-gradient based algorithm, which uses only first-order spatial derivatives of the images before and after deformation. Simulated images are then used to verify this algorithm, as well as to study the impact of speckle size on the accuracy. Based on these simulations, the sensitivity of DISC to displacement and deformation gradient, as well as an optimal speckle size for optimal accuracy, is recommended. The algorithm is then calibrated using rigid body translation and rotation, and an application of DISC to thermomechanical diagnostics of electronic packaging is also presented. © 2001 Society of Photo-Optical Instrumentation Engineers.

Currently, cellular action potentials are detected using either electrical recordings or exogenous fluorescent probes that sense the calcium concentration or transmembrane voltage. Ca imaging has a low temporal resolution, while voltage indicators are vulnerable to phototoxicity, photobleaching, and heating. Here, we report full-field interferometric imaging of individual action potentials by detecting movement across the entire cell membrane. Using spike-triggered averaging of movies synchronized with electrical recordings, we demonstrate deformations up to 3 nm (0.9 mrad) during the action potential in spiking HEK-293 cells, with a rise time of 4 ms. The time course of the optically recorded spikes matches the electrical waveforms. Since the shot noise limit of the camera (~2 mrad/pix) precludes detection of the action potential in a single frame, for all-optical spike detection, images are acquired at 50 kHz, and 50 frames are binned into 1 ms steps to achieve a sensitivity of 0.3 mrad in a single pixel. Using a self-reinforcing sensitivity enhancement algorithm based on iteratively expanding the region of interest for spatial averaging, individual spikes can be detected by matching the previously extracted template of the action potential with the optical recording. This allows all-optical full-field imaging of the propagating action potentials without exogeneous labels or electrodes.

We experimentally demonstrate a spatially non-blocking five-port optical router, which is based on microring resonators tuned through the thermo-optic effect. The characteristics of the microring-resonator-based switching element are investigated to achieve balanced performances in its two output ports. The optical router is fabricated on the SOI platform using standard CMOS processing. The effective footprint of the device is about 440×660 μm2. The microring resonators have 3-dB bandwidths of larger than 0.31 nm (38 GHz), and extinction ratios of better than 21 dB for through ports and 16 dB for drop ports. Finally, 12.5 Gbps high-speed signal transmission experiments verify the routing functionality of the optical router.

One of the possible noise sources for the space-based gravitational wave detector LISA (the Laser Interferometer Space Antenna), associated with its test masses, is that due to spatial variations in surface potential (or patch effect) across the surfaces of the test mass and its housing. Such variations will lead to force gradients which may result in a significant acceleration noise term. Another noise source is that due to temporal variations in the surface potential, which in conjunction with any ambient dc voltage or net free charge on the test mass may also produce a significant acceleration noise term. The ST-7 demonstrator mission is designed to test technologies for LISA, including the gravitational reference sensor, which contains a gold-coated gold/platinum (Au/Pt) alloy test mass, surrounded by a housing that carries the electrodes for sensing and control. We have used a Kelvin probe at the Goddard Space Flight Center to make spatial and temporal measurements of contact potential differences for a selection of materials (Au/Pt, beryllia, alumina, titanium) and coatings (gold, diamond-like carbon, indium tin oxide, titanium carbide). Our investigations indicate that subject to certain assumptions all of these coatings appear to satisfy the ST-7 requirement that patch effect spatial variations should be less than 100 mV. The data also revealed evidence of behavioural trends with pressure and possible contamination effects. Regarding temporal variations, the current accuracy of the instrument is limiting the measurements at a level above the likely LISA requirements. We discuss our results and draw some conclusions of relevance to LISA.

We have designed and fabricated a directed logic architecture consisting of two silicon microring resonators that can perform XOR and XNOR operations. The microring resonators are modulated through thermo-optic effect. Two electrical modulating signals applied to the microring resonators represent the two operands of the logical operation. The logical function is evaluated through the directed propagation of light in the device, and the result is represented by the output optical signal. Both XOR and XNOR operations at 20 kbits are demonstrated.

We demonstrate a 26 Gbit/s Mach-Zehnder silicon optical modulator. The doping concentration and profile are optimized, and a modulation efficiency with the figure of merit (VπL) of 1.28 V·cm is achieved. We design an 80-nm-wide intrinsic silicon gap between the p-type and n-type doped regions to reduce the capacitance of the diode and prevent the diode from working in a slow diffusion mode. Therefore, the modulator can be driven with a small differential voltage of 0.5 V with no bias. Without the elimination of the dissipated power of the series resistors and the reflected power of the electrical signal, the maximum power consumption is 3.8 mW.

The optical system and end-station of bending-magnet beamline BL16B1, dedicated to small-angle X-ray scattering (SAXS) at the Shanghai Synchrotron Radiation Facility, is described. Constructed in 2009 and upgraded in 2013, this beamline has been open to users since May 2009 and supports methodologies including SAXS, wide-angle X-ray scattering (WAXS), simultaneous SAXS/WAXS, grazing-incidence small-angle X-ray scattering (GISAXS) and anomalous small-angle X-ray scattering (ASAXS). Considering that an increasing necessity for absolute calibration of SAXS intensity has been recognized in in-depth investigations, SAXS intensity is re-stated according to the extent of data processing, and the absolute intensity is suggested to be a unified presentation of SAXS data in this article. Theory with a practical procedure for absolute intensity calibration is established based on BL16B1, using glass carbon and water as primary and secondary standards, respectively. The calibration procedure can be completed in minutes and shows good reliability under different conditions. An empirical line of scale factor estimation is also established for any specific SAXS setup at the beamline. Beamline performance on molecular weight (MW) determination is provided as a straightforward application and verification of the absolute intensity calibration. Results show good accuracy with a deviation of less than 10% compared with the known value, which is also the best attainable accuracy in recent studies using SAXS to measure protein MW. Fast MW measurement following the demonstrated method also enables an instant check or pre-diagnosis of the SAXS performance to improve the data acquisition.

We design and fabricate a four-port optical router, which is composed of eight microring-resonator-based switching elements, four optical waveguides and six waveguide crossings. The extinction ratio is about 13 dB for the through port and larger than 30 dB for the drop port. The crosstalk of the measured optical links is less than -13 dB. The average tuning power consumption is about 10.37 mW and the tuning efficiency is 5.398 mW/nm. The routing functionality and optical signal integrity are verified by transmitting a 12.5 Gb/s PRBS optical signal.