A fast-Fourier-transform method of topography and interferometry is proposed. By computer processing of a noncontour type of fringe pattern, automatic discrimination is achieved between elevation and depression of the object or wave-front form, which has not been possible by the fringe-contour-generation techniques. The method has advantages over moire topography and conventional fringe-contour interferometry in both accuracy and sensitivity. Unlike fringe-scanning techniques, the method is easy to apply because it uses no moving components.

Fourier-transform method of fringe-pattern analysis for computer-based topography and interferometry

We have characterized the fundamental photoluminescence (PL) properties of individual, isolated indium phosphide (InP) nanowires to define their potential for optoelectronics. Polarization-sensitive measurements reveal a striking anisotropy in the PL intensity recorded parallel and perpendicular to the long axis of a nanowire. The order-of-magnitude polarization anisotropy was quantitatively explained in terms of the large dielectric contrast between these free-standing nanowires and surrounding environment, as opposed to quantum confinement effects. This intrinsic anisotropy was used to create polarization-sensitive nanoscale photodetectors that may prove useful in integrated photonic circuits, optical switches and interconnects, near-field imaging, and high-resolution detectors.

https://web.stanford.edu/group/cui_group/papers/Yi%20Cui-NW%20light%20emission.pdf

Highly polarized photoluminescence and photodetection from single indium phosphide nanowires.

Stability of n-type doped conducting polymers and consequences for polymeric microelectronic devices

A self-scanned 1024 element photodiode array and minicomputer are used to measure the phase (wavefront) in the interference pattern of an interferometer to lambda/100. The photodiode array samples intensities over a 32 x 32 matrix in the interference pattern as the length of the reference arm is varied piezoelectrically. Using these data the minicomputer synchronously detects the phase at each of the 1024 points by a Fourier series method and displays the wavefront in contour and perspective plot on a storage oscilloscope in less than 1 min (Bruning et al. Paper WE16, OSA Annual Meeting, Oct. 1972). The array of intensities is sampled and averaged many times in a random fashion so that the effects of air turbulence, vibrations, and thermal drifts are minimized. Very significant is the fact that wavefront errors in the interferometer are easily determined and may be automatically subtracted from current or subsequent wavefrots. Various programs supporting the measurement system include software for determining the aperture boundary, sum and difference of wavefronts, removal or insertion of tilt and focus errors, and routines for spatial manipulation of wavefronts. FFT programs transform wavefront data into point spread function and modulus and phase of the optical transfer function of lenses. Display programs plot these functions in contour and perspective. The system has been designed to optimize the collection of data to give higher than usual accuracy in measuring the individual elements and final performance of assembled diffraction limited optical systems, and furthermore, the short loop time of a few minutes makes the system an attractive alternative to constraints imposed by test glasses in the optical shop.

Digital wavefront measuring interferometer for testing optical surfaces and lenses

2.2. Cathodic Electropolymerization 4732 2.2.1. Electropolymerization of PPXs and PPVs 4732 3. Charging-Discharging of Conducting Polymers 4733 3.1. Redox Properties of Oligomers and Polymers 4733 3.2. Specific Phenomena of n-Doping 4739 3.3. Conductivity in Charged Systems 4740 4. Controlling the Electropolymerization Process 4742 4.1. Influence of the Polymerization Technique 4742 4.2. Influence of Experimental Conditions 4743 4.3. Electropolymerization in Novel Electrolytic Media 4745

Electrochemistry of Conducting Polymers—Persistent Models and New Concepts†

We propose a parallel two-step phase-shifting digital holography technique capable of instantaneous measurement of three-dimensional objects, with a view toward measurement of dynamically moving objects. The technique is based on phase-shifting interferometry. The proposed technique carries out the two-step phase-shifting method at one time and can be optically implemented by using a phase-shifting array device located in the reference beam. The array device has a periodic two-step phase distribution, and its configuration is simplified compared with that required for three-step and four-step parallel phase-shifting digital holographies. Therefore the optical system of the proposed technique is more suitable for the realization of a parallel phase-shifting digital holography system. We conduct both a numerical simulation and a preliminary experiment in the proposed technique. The results of the simulation and the experiment agree well with those of sequential phase-shifting digital holography, and results are superior to those obtained by conventional digital holography using the Fresnel transform alone. Thus the effectiveness of the proposed technique is verified.

Parallel two-step phase-shifting digital holography

A monolithic-integrated optical-disk pickup device capable of detecting readout and focus/tracking error signals is proposed, designed, and fabricated. The integrated-optic disk pickup device (IODPU) is constructed by integrating a focusing grating coupler, a grating beam splitter, and photodiodes in a film waveguide on a Si substrate. The function of detecting readout and error signals is demonstrated by butt-coupling a laser diode to the fabricated IODPU.

An integrated-optic disk pickup device

Parallel phase-shifting digital holography can obtain three-dimensional information of a dynamically moving object with high accuracy by using space-division multiplexing of multiple holograms required for phase-shifting interferometry. We demonstrated high-speed parallel phase-shifting digital holography and obtained images of the phase variation of air caused by a compressed gas flow sprayed from a nozzle. In particular, we found the interesting phenomenon of periodic phase distributions. Reconstructed images were obtained at frame rates of 20,000 and 180,000 frames per second.

High-speed phase imaging by parallel phase-shifting digital holography

Electron spin resonance (ESR), electrical conductivity and thermoelectric power are studied in electrochemically prepared and doped polythiophene films. The ESR spin density increases by two orders of magnitude up to dopant concentration of ca. 3 mol%, then decreases, while the conductivity increases drastically by more than ten orders of magnitude until this doping level, followed by a rather mild increase. The ESR linewidth decreases sharply from 9 G to 0.4 G upon slight doping with shape change from Gaussian to Lorenzian. The contribution of Pauli-paramagnetism to the spin succeptibility and the positive thermoelectric power of ca. 20 µV/K which depends linearly on the temperature are observed at heavily doped region. These results are discussed in terms of shallow and deep polarons, and formation of bipolaron up to intermediate doping levels and the hole conduction at the metallic regime.

ESR and Transport Studies in Electrochemically Doped Polythiophene Film

A guided-mode resonance filter integrated in a waveguide cavity resonator constructed by two distributed Bragg reflectors is designed and fabricated for miniaturization of aperture size Reflection efficiency of >90% and wavelength selectivity of 04 nm are predicted in the designed SiO2-based filter with 50-μm aperture by a numerical calculation using the finite-difference time-domain method A maximum reflectance of 67% with 05-nm bandwidth is experimentally demonstrated by the fabricated device at around 850-nm wavelength

Shogo Ura

Papers

Parallel two-step phase-shifting digital holography

An integrated-optic disk pickup device

High-speed phase imaging by parallel phase-shifting digital holography

ESR and Transport Studies in Electrochemically Doped Polythiophene Film

Cavity-resonator-integrated guided-mode resonance filter for aperture miniaturization