bluuebunny/crossref_metadata_2025 huggingface dataset:
The New Systems of Organic Photon-gated Photochemical Hole Burning
Authors: Duoyuan Wang , Lingzhi Hu , Huizhu He , Lizeng Zhao , Xin Mi , Yuxin Ni
Published: February 2023

Recent material research has been devoted to search for two-color or photon-gated photochemical hole burning mechanisms in inorganic as well as organic materials. A mechanism for photon-gated spectral hole burning by donor-acceptor electron transfer in a material composed of meso-tetra-p-tolyl-tetrabenzoporphyrinato)zinc (TZT) (Donor) with halomethanes(acceptor) in poly(methylmethacrylate) (PMMA) thin film at 1.4K was reported by Carter et al.[1]
Marker Mode Structure in the Primary Donor State of Bacterial Reaction Centers
Authors: Lyle P. , Small G.J. , DiMagno T.J. , Norris J.R.
Published: February 2023

Underlying structure for the primary donor absorption profiles of isolated reaction centers Rhodopseudomonas viridis and Rhodobacter sphaeroides (P960 and P870) has recently been uncovered by transient hole burning experiments [1]. A Franck-Condon progression of an intermolecular special pair marker mode (ωsp) was found to originate in the low energy shoulder of the absorption spectra and peak at the one quantum transition. The theory of Hayes and Small [2] for fitting hole burned spectra was extended to include the coupling of the marker mode. Briefly, the theory defines a single site absorption function as being made up of a sum of 0-,1-,… phonon lineshape functions composed of a gaussian distribution for the low energy side and a lorentzian for the high energy side. By constructing a gaussian distribution whose full-width at half maximum is equal to the inhomogeneous broadening and convolving with the single site absorption function, the absorption spectrum is obtained. By further convolving these functions with an exponential decay function of the single sites centered at the bum frequency the absorption spectra after burning a time T is obtained. Important parameters include the Huang-Rhys factor for the phonons and marker mode S,Ssp, the mean phonon frequency ωm, the marker mode frequency ωsp, the width of the one phonon profile Γ, the zero-phonon width γ, and the inhomogeneous broadening Γ1. Most of the parameter values required in the fit can be obtained from experiment. An important test for the theory is how well it can account for the bum wavelength dependence of the hole spectrum.
Elucidation of Photophysics and Photochemistry in Polyacene Photoadducts
Authors: Iannone Mark A. , Scott Gary W.
Published: February 2023

Recently we have reported studies of low-temperature spectroscopy of a series of polyacene photoadducts.1-4 A principal technique has been that of photochemical hole burning at 1.5K. The photochemistry involves the photodecomposition of the adduct back to the constiuent polyacenes. In the present paper we extend this work on the photophysics and photochemistry of AT and also report new results on BrAT.
Fluorine Spin Diffusion Barrier in Pr3+;LaF3 Observed by Cross Relaxation
Authors: Wald L.L. , Hahn E.L. , Lukac M.
Published: February 2023

Photon echo measurements made at 2 °K on the 3H4 - 1D2 transition in Pr3+:LaF3 show that magnetic dipolar couplings between the Pr and F nuclei account for the 56 kHz homogeneous linewidth of this transition.1 The homogeneous broadening arises from the enhanced 141Pr nuclear moment (I=5/2) interacting with the local field fluctuations of the 19F nuclear moments undergoing mutual spin flip transitions. Such resonant fluctuations should, in the absence of a fluorine spin diffusion barrier, produce a homogeneous linewidth of about 200 kHz which is, in fact, roughly what is observed for the inhomogeneous broadening of the Pr3+ hyperfine levels and is considerably broader than that obtained by the photon echo measurements. Shelby et al2 proposed a simple model analogous to the spin diffusion barriers responsible for narrowing the homogeneous lines in certain electron paramagnetic resonance transitions3. In such systems, the field produced by the electron magnetic dipole moment (2-3 orders of magnitude larger than the enhanced nuclear moment associated with the ground state of Pr3+ in LaF3) de-tunes the nearest neighbors from each other, prohibiting mutual spin flips among them. Thus, the fields produced by the neighboring spins are static and their interaction with the paramagnetic ion contributes to the inhomogeneous linewidth and not to homogeneous broadening. The de-tuned neighbors are referred to as the "frozen core." Application of this picture to the case of Pr3+:LaF3 is supported by the calculation of Devoe et al.4 Their Monte Carlo calculation of the Pr3+ optical dephasing times shows that the observed homogeneous linewidth could be explained by deleting the nearest neighbor F spins from the lattice of rapidly fluctuating fluorine moments, in effect, treating them as part of a frozen core.
The irreversible burning of infrared spectral line by laser action on silica contained matters
Authors: Bondaŕ Anatolii M. , Mukhamedgalieva Anel F.
Published: February 2023

The effect of CO2 laser focused radiation (the wave length of 10.6 μm, power density of 103-105 W/cm2) on melted quartz and silica contained minerals - nepheline KNa3 [AlSiO4]4, microcline K[AlSi3O8], kaolinite Al4 [Si4O10](OH)8, etc., has been investigated. The materials mentioned above undergo the laser radiation in the low frequency rang of ungomogeneously broadened infrared absorption line of asymmetric valent Si-O-Si vibrations.
New Developments in Time-and-Space-Domain Holography and Shaping of Light Pulses by Spectral Hole-Burning Filters
Authors: Kaarli Rein , Saari Peeter , Sõnajalg Heiki
Published: February 2023

Photochemically instable dye molecules in low-temperature polymers are distributed not only spatially in the medium but also spectrally along the axis of resonant optical transition frequencies and orientationally with reference to the polarization of the transition. Consequently, such composite organic materials -- spectral hole burning media1-4 -- can be considered as novel optical materials possessing not only three-dimensional photosensitivity but also sensitivity to the wavelength and polarization of the incident light.
Holograms in Time and Space: Imaging Through a Scattering Medium
Authors: Rebane Alexander , Feinberg Jack
Published: February 2023

As an image-bearing wave traverses a scattering medium, the phase of the wave becomes severely distorted. Although most of the light is multiply scattered, a small fraction of the light will be scattered much less than average, and so may still contain information about the original incident wave front. Because this barely-scattered light is extremely weak, it is usually overwhelmed by the multiply-scattered light, so that no image can be observed by eye. Note, however, that the wave that is barely scattered (or not scattered at all) travels a shorter path to the observer's eyes than does the multiply-scattered part of the wave. If the original image-bearing beam is an ultrashort pulse, then in principle, by replacing the eye with a fast, time-resolving detector, one could discriminate between the unscattered, image-containing part of the transmitted light and the multiply-scattered background light. One might use this technique to observe objects embedded in a strongly scattering medium, such as living tissue, if only a fast enough "shutter" could be developed to cut off the strong background of scattered light.
Holographic optical data storage of 2000 images by photochemical hole burning
Authors: Kohler Bern , Bernet Stefan , Renn Alois , Wild Urs P.
Published: February 2023

In addition to its importance for the optical spectroscopy of solids, photochemical spectral hole burning (PSHB) has attracted great interest due to its potential use in high density optical data storage [1]. By encoding information as a function of frequency an enormous increase in storage is possible compared to conventional optical storage materials. The most optimistic estimates predict an increase given by the ratio of the inhomogeneous linewidth to the homogeneous linewidth of the optical transition responsible for hole burning. Until now, however, there have been relatively few investigations of the practical limitations to storing a large number of spectral holes [2,3]. We describe here a recent experiment in which 2000 grayscale images were successfully recorded as holograms in the PSHB material chlorin in polyvinylbutyral. In holographic spectral hole burning the relative phase of the interfering light waves used to prepare the hologram has a strong influence on diffraction properties and, hence, on crosstalk between adjacent holograms [4]. By controlling the phase and frequency during burning in a novel manner, we have minimized crosstalk between the stored images.
Electric-Field Effects on Hole Spectra in Doped Polymers: A Step towards Two-Dimensional Optical Spectroscopy
Authors: Kador L.
Published: February 2023

Optical absorption bands of organic dye molecules or inorganic ions in condensed matter are affected by inhomogeneous broadening [1] and are thus usually much broader than the corresponding homogeneous lines. In disordered systems, the difference can amount to several orders of magnitude at low temperatures. In order to detect the effects of external perturbations such as hydrostatic pressure or electric fields on an inhomogeneous band, the perturbations must therefore have very large magnitudes. The sensitivity can be greatly enhanced by investigating the changes of hole-burning spectra caused by the external fields. In amorphous matrices, an external electric field gives rise to a symmetrical broadening of spectral holes due to the linear Stark effect. This was shown to be true even in the case of centrosymmetric dopant molecules where the first-order Stark effect is ascribed to matrix-induced dipole moments [2] (see Fig. 1). The magnitude of the broadening yields thus information on the electrostatic dye-matrix interaction.
Antihole Formation in Intramolecular Rotational Tunnel Systems
Authors: Gradl G. , Feis A. , Friedrich J.
Published: February 2023

Hole burning in mixed crystals containing methyl groups can be used to determine the difference of the rotational tunnel splitting of the methyl groups in the ground and excited electronic state of the guest probe /1/. Two mechanisms were suggested: If the phototransformation of the probe is photochemical in nature, the difference in tunnel splitting shows up in the side hole pattern which appears upon thermal relaxation of the bleached ground state levels through spin conversion processes. On the other hand, if the phototransformation is purely photophysical in nature, the nuclear spin conversion occurs most probably in the excited triplet state and the tunnel splitting is reflected in the appearance of antiholes.
Subnanosecond Time Resolved Study of Accumulated Photon Echoes in Chlorin Doped Polymer Films at 1.2 K
Authors: Gygax Hansruedi , Görlach Ekkehard , Rebane Alexander , Wild Urs P.
Published: February 2023

Organic impurity systems which exhibit effect of photoburning of persistent spectral holes have several interesting spectroscopic and prospective practical applications [1, 2]. A CW holographic technique for detecting of narrow hole shapes in thin polymer films doped with organic dye molecules can be used in combination with a variable-strength applied electric field to obtain information about the homogeneous line shapes and symmetry properties of the impurity centres [3]. This method serves also as a demonstration of the possibility of parallel optical computing [4].
Hole Burning in the Organic Triplet State: Side Holes in an Amorphous Glass
Authors: Riesen Hans , Krausz Elmars
Published: February 2023

Hole-burning spectroscopy has been widely applied to the S0-S1 transition of organic molecules in amorphous hosts [1-3]. However, only very few reports on the hole-burning spectroscopy of the triplet state have appeared [4,5]. The low oscillator strength of the S0-T1 transition is the obvious handicap in performing such experiments. The oscillator strength of the S0-T1 transition can be dramatically increased by the heavy atom effect [6] making hole-burning experiments in the S0-T1 transition more feasible. A very pronounced heavy atom effect can be expected in ligand-centred singlet -triplet transitions of second and especially third row transition metal complexes leading to lifetimes in the μs range.
Photon-Gated Photochemical Hole Burning in Zinc-Tetrabenzoporphyrin/Aromatic Cyanide System
Authors: Lizeng Zhao , Zhengzhong Lu , Xiulang Zhang , Dongxiang Zhang , Xin Mi , Yuxin Nie , Duoyuan Wang , Lingzhi Hu , Huizhu He , Jie Xie , Junyi Zhang
Published: February 2023

The group of Moerner,et al., first reported two-color hole-burning by donor-acceptor electron transfer for a derivative of zinc-tetrabenzoporphyrin as a donor with halomethane acceptors in a poly (methyl methacrylate) (PMMA) thin film [1]. Their results have opened up a new class of materials for photon-gating.
Hole Multiplexing in Quinone Derivative Photochemical Hole Burning Systems
Authors: Yoshimura Motomu , Nishimura Tetsuya , Yagyu Eiji , Tsukada Noriaki , Takeyama Tetsu
Published: February 2023

We have been interested in PHB mechanism1,2 in the quinone derivatives. The substituent effects of the guest molecules are examined on the hole multiplexing3, hole formation wavelength range and electric field effect4. We especially intend to know how densely multiple holes can be formed by wavelength tuning and Stark tuning.
X-Ray and TEM Analysis of small period W-Si and W-B4C multilayers
Authors: Wood James , Parker Kevin , Scholhamer James , Mansfield John
Published: February 2023

In recent reports of the manufacture and characterization of small period multilayers, researchers have utilized high resolution TEM and an analysis of Cu-Kα X-Ray data to interpret and explain variations of reflectivity from theoretical predictions. These theoretical analyses are based on a dynamical reflectivity calculation which incorporates the Debye-Waller factor to simulate layer/interface roughness. Using the same analysis techniques we have evaluated how layer roughness varies with d-spacing and film thickness for small period (15Å<d<22Å) multilayers.
Analytical Observations and Depth Profile Simulation in regular-d and graded-d Metal/Carbon Multilayers prepared by Laser Pulse Vapour Deposition
Authors: Dietsch R. , Hopfe S. , Mai H. , Oertel G. , Pompe W. , Prokop M. , Schöneich B. , Völlmar S. , Wahner B. , Weiβbrodt P. , Werner P.
Published: February 2023

The metal/carbon multilayers were prepared by Laser Pulse Vapour Deposition (LPVD).
Diffusion Behavior of Metal-Carbon Multilayers
Authors: Akhsakhalyan A.D. , Fraerman A.A. , Platonov Yu. Ya. , Polushkin N.I. , Salashchenko N.N.
Published: February 2023

The effect of annealing on the X-ray optical characteristics of artificial multilayer structures composed of metal (Cr,Fe,Ni,Mo,Rh, W,Pt and others) and carbon is studied. To analyze the changes at annealing a small-angle X-ray diffraction was used. The observed X-ray reflectivity enhancement can be explained by the uphill diffusion of metal atoms.
Atomic Layer Epitaxy of Tungsten and Boron for Multilayer X-ray Optics
Authors: Shurtleff J.K. , Phillips J. , Allred D.D. , Perkins R.T. , Knight L.V. , Thorne J.M.
Published: February 2023

The demand for high quality multilayer x-ray optics (MXOs) has increased as x-ray imaging applications have developed. MXOs must be uniform and smooth with precise periods. The period of the MXO determines the angle and wavelength of the x-ray which can be reflected. Current preparation techniques are limited to a period of approximately 40 Å. To reflect harder x-rays at near normal incidence, smaller periods must be achieved.
Bragg-Fresnel Multilayer Optics for X-ray Microscopy and Spectroscopy
Authors: Vidal B. , Brunel M. , Erko A. , Rochtchoupkine D. , Susini J. , Vincent. P.
Published: February 2023

Application of metallic multilayer mirrors for construction of different components of x-ray optical schemes became more and more frequent. Number of publications gives an examples of objective lenses, monochromators, focusing and imaging devices, based on figured multilayer mirrors. One of the most exited application of such optics in future can be projection X-ray lithography and local analyses of microstructures with submicron resolution for microelectronics technology.

Recently, focusing and imaging by the use of some kinds of "grooved" diffraction optics on flat surfaces instead of the curved substrate had been reported in several papers. This optics is now known as Bragg-Fresnel Multilayer Optics (BFMO) [1,2]. Compared to grazing incidence optics and figured multi-layers optics, BFMO can provide higher spatial and spectral resolutions. That is say, till to spot value up to 0.1μ spatial resolution of BFMO is limited only by the flatness of the plane substrate and accuracy of the lithographic process [3]. In principle BFMO combines the high spatial resolution of Fresnel zone plates and the high radiation stability of multi-layer X-ray mirrors.

This report gives an examples of fabrication, computer simulation and tests for two kind of BFMO: Lamellar Multilayer Gratings (LMG) and Linear Bragg-Fresnel Multilayer Lenses (LBFML). LMG, used here as the first step for the understanding of diffraction property of LBFML, can be very interesting themselves as by spectroscopic instruments with relatively high dispersion and efficiency.
Observation of nuclear diffraction from multilayers containing 57Fe
Authors: Röhlsberger R. , Witthoff E. , Lüken E. , Gerdau E.
Published: February 2023

The small resonance width Г0 of Mößbauer transitions allows monochromatization of synchrotron radiation down to a bandwidth of 10-7 - 10-9 eV by nuclear resonant diffraction. Up to now, the Mößbauer isotopes 57Fe ( E0 = 14.4 keV, Г0 = 4.7 • 10-9 eV) and 169Tm ( E0 = 8.4 keV, Г0 = 1.2•10-7 eV) have been used in this field [ 1-5 ]. In order to observe nuclear resonant diffraction, the competing contribution of electronic scattering with a bandpass of at least a few meV has to be strongly reduced. Precise determinations of hyperfine interactions can be made by observation of quantum beats in the collective decay of the nuclei excited by synchrotron pulses. Most of the experiments have been done with single crystals which have a pure nuclear reflection. In these cases the structure factor for the electronic reflection is zero because of the symmetry of the crystal. The structure factor for the nuclear reflection is nonzero, because subgroups of the Mößbauer nuclei are distinguished by a symmetry breaking hyperfine interaction or by isotopic arrangement [6]. In a layered crystal of 56Fe and 57Fe atoms obviously the electronic and nuclear lattice constant differ by a factor of two, so that a superstructure appears with a pure nuclear reflection. Such a crystal has not been grown up to now, since the preparational requirements are very hard to meet. However, an isotopic superstructure can easily be realized in a multilayer, which need not be a single crystal. Alternating layers containing 56Fe and 57Fe give rise to a multilayer Bragg peak of pure nuclear origin. Such a multilayer will be described here.
Interface Roughness And Void Formation In Si Deposition At Low Temperatures
Authors: Eaglesham D.J. , Windt D.L.
Published: February 2023

X-ray scattering from multilayers (such as Mo-Si) is to a large extent controlled by interface quality, which in turn is frequently controlled by surface morphology. Here we present a study of interface and surface morphology in both crystalline and amorphous Si layers deposited by evaporation in UHV at low substrate temperatures. For simplicity, the interfaces investigated are single monolayers of Ge, so that chemical effects are avoided. Amorphous Si films undergo morphological roughening and void formation, leading to apparent Si-Ge interface widths ≈5nm. In crystalline Si grown at the same temperature and deposition rate the roughness is considerably less marked, although localised void formation still occurs. Both the void density and the apparent interface width of single monolayers of Ge appears under these conditions to be linked to the thickness of crystalline Si deposited.
Studies of multi-layers for short period X-ray mirrors
Authors: Somekh R. E. , Hasan M. M.
Published: February 2023

The production of mirrors to operate at very short X-ray wavelengths (2-5 nm) still provides a challenge for materials scientists. The need for smooth interfaces whilst maintaining a considerable compositional sharpness is inherently problematic, since the former requires layers which are in some way compatible and by implication mutually soluble, whilst the latter is more likely to be achieved when two elements are immiscible.
Observation of Phase Separation in Fe/C Multilayers.
Authors: Akhsaklialyan A. D. , Blyakhman Yu. A. , Gusev S. A. , Polushkin N. I. , Salashchenko N. N.
Published: February 2023

The phenomenon of phase separation in alloys and multilayers is of great fundamental and technological interest [1-4]. There are at least two important aspects in its study. First, uphill interdiffusion currents originate the metastable heterostructures in alloys [3], and they are expected to assist in the formation of atomically abrupt interfaces in artificial multilayer structures. Secondly, this process in nm-scale multilayers may be accompanied by drastic changes in their physical (e.g., mechanical, optical, magnetic, etc.) properties because their layer thicknesses are comparable with spatial interdiffusion scales.
Dependence of optimal deposition temperature of Mo/Si multilayer mirrors on the Mo/Si thickness ratio
Authors: Louis E. , Voorma H.-J. , Koster N.B. , Bijkerk F. , Platonov Yu. Ya. , van Dorssen G.E. , Padmore H.A.
Published: February 2023

The increasing reflectivity of multilayer mirrors has made the use of reflective soft x-ray optical systems, e.g. in soft x-ray microscopy and soft x-ray projection lithography [1,2] possible. However, the use of multi-mirror systems [3] in industrial applications can only be successful if such a system has sufficient throughput. It is therefore necessary to optimize the reflectivity to the highest value possible.
GROWTH AND STRUCTURAL CHARACTERIZATION OF Ni/Ti SUPERMIRRORS FOR NEUTRONS
Authors: Grimmer H. , Böni P. , Elsenhans O. , Friedli H. P. , Leifer K. , Buffat P. , Anderson I. S.
Published: February 2023

The problems of producing and characterizing x-ray mirrors and supermirrors for neutrons are similar. In both cases an abrupt change of the optical properties at the interfaces, low interface roughness and stability of the structure (low diffusion) are required. Unlike for x-rays there are many elements with low neutron absorption. In order to get a large neutron optical contrast at the interfaces, two materials with large coherent scattering length densities of opposite signs have to be combined.
Innovations in the Phasor Diagram That Give Lower Ultimate Quantum Noise
Authors: Mertz Lawrence N.
Published: February 2023

Assembling the phasor diagram recursively in polar rather than cartesian coordinate representation results in lower ultimate quantum noise for interferometric star tracking and speckle imaging.
Imaging System Requirements for Turbulence and Combustion Diagnostics
Authors: Long Marshall B.
Published: February 2023

During the past several years, two-dimensional imaging techniques have become widely used as a diagnostic tool for studying turbulence and combustion. The reason for this increased interest in simultaneous multipoint mapping techniques has been due largely to the realization that the large-scale structures play an important role in these flows and the availability of quantitative data on the spatial characteristics of the structures allows greater understanding of their role. Many different light scattering mechanisms have been used for these studies including Lorenz/Mie,1 Rayleigh,2 fluorescence,3 and Raman4 scattering. The proper selection of the scattering mechanism and the experimental configuration makes it possible to measure the species concentration, temperature, density, or velocity in two dimensions at up to 10,000 different points in a plane intersecting the flow.
Image Classification at Low Light Levels
Authors: Wernick Miles N. , Morris G. Michael
Published: February 2023

At low light levels, a two-dimensional photon-counting detector may be employed to provide an estimate of the cross-correlation between an input image and a set of reference images stored in computer memory. Recent experiments1,2 have demonstrated that in many cases, a small number of detected photoevents is sufficient to yield reliable image recognition. The binary nature of the photon­limited input, coupled with the high rate of operation afforded by commercially available detectors, leads to recognition times on the order of tens of milliseconds.
Exact Variance-Stabilizing Transformations for Image-Signal-Dependent Exponential and Rayleigh Noise
Authors: Prucnal Paul R. , Goldstein Evan L.
Published: February 2023

One problem presented by the processing of optical signals is that the noise encountered tends to be signal-dependent. Coherent sources, for example, generate photon noise characterized by variance that is proportional to the signal value. Sources emitting chaotic or superposed coherent and chaotic radiation exhibit photon noise variance that is quadratic in the signal value. For film-grain noise, the variance is proportional to some power of the signal. Other imaging devices such as optical disks exhibit noise having a similar signal-dependence.
Photon counting and correlation properties of silicon avalanche photodiodes operated in sub-geiger mode
Authors: Brown Robert G W , Daniels Matthew
Published: February 2023

Useful photon-counting and correlation properties of Si APD's in sub-geiger mode are described, with potential of high quantum efficiency and ultralow afterpulsing in an alternative single-photon-counting array detector.
Reconstruction of a Randomly Translating Object from Centroided Photon-Bias-Corrected Data
Authors: de Freitas L.C. , Ayers G.R. , Dainty J.C.
Published: February 2023

In previous work(1-2) a relationship between the centroid image and the object’s image have been derived as well as a 1-D phase reconstruction algorithm for the case of a randomly translating object i.e. when no telescope aberrations or turbulence is present.
High Resolution Imaging at Low Light-Levels Through Weak Turbulence1
Authors: Snyder Donald L. , Schulz Timothy J.
Published: February 2023

The problem we address is that of forming an intensity image of a self-luminous object that emits incoherent quasimonochromatic light which propagates through the atmosphere and is then collected with an ideal, thin-lens telescope and sensed with a photodetector. A clear-air atmosphere having weak turbulence is assumed with resulting random motions of the object’s light falling onto the photodetector. It is assumed that the light level at the photodetector is sufficiently low and the spatiotemporal resolution of the photodetector sufficiently high that the spatial and temporal coordinate of each photoconversion can be measured to become the quantum-limited data available for forming the image. The geometry is indicated in the figure at the right.
High resolution imaging from photon-limited data using pupil segmentation
Authors: Sebag J. , Arnaud J. , Lelievre G. , Nieto J.L.
Published: February 2023

Short-time exposures have a higher resolution than long-time exposures. The resolution gain factor depends on the ratio of the telescope diameter D to the Fried parameter r0which characterizes the atmospheric seeing. This gain first increases with D/ r0 to a maximum value at D/ r0=3.8, after which it decreases as D/ r0 continues to increase. The probability of obtaining a diffraction-limited short-exposure is represented for D/ r0 greater than 3.5 by the expression: Prob ~ 5.6exp [−0.1557 (D/r0)2] ( Fried 1966; Hecquet and Coupinot 1985). For the CFHT, commonly observed value of D/ r0 are quite far from the optimum, typically about 18. So, segmenting the pupil into elements equivalent to smaller diameter telescopes, with more adapted D/ r0, will allow to achieve the highest possible spatial resolution gain.
Detection Tasks and Decision Thoery for Quantum Limited Imagery
Authors: Myers K.J. , Brown D.G. , Wagner R.F. , Barrett H.H. , Rolland J.P.
Published: February 2023

Signal detection theory is an approach to predicting imaging system performance through the calculation of the performance of an ideal or Bayesian observer for some model task.1 By calculating the ideal-observer performance over a range of system design parameters, the effect of those parameters on image quality can be quantified. Implicit in this approach to image assessment is the assumption that ideal performance is relevant to the performance of the human observer, so that a system optimized for the ideal observer will likewise be optimized for the human observer, given an appropriate display strategy. Also implicit is the assumption that the model task is representative of the tasks that are to be performed in the "real world".
Image restoration from low light level degraded data
Authors: Cheng B.T. , Fiddy M.A. , Newman J.D. , Van Vranken R.C. , Clark D.L.
Published: February 2023

We present some preliminary work on the reconstruction of low contrast images for remote sensing type applications. We assume the data to be a set of noise degraded images, and report on the application of reconstruction techniques that both estimate the support of the image use the triple correlation method to obtain the image itself. These reconstruction methods are applied to simulated data in the first instance.
Characterization Studies and Luminescence of Quantum Wires and Dots
Authors: Marzin Jean-Yves
Published: February 2023

Summary not available at time of printing.
Effects of Size Fluctuation on the Optical Properties of Very Narrow InGaAs/InP Quantum Well Wires
Authors: Nojima S. , Notomi M. , Nakao M. , Tamamura T.
Published: February 2023

The authors have succeeded in fabricating very narrow InGaAs/InP quantum well wires (QWWs with cross sections down to 50 Åx100 Å) by combining electron beam lithograhpy, reverse-mesa wet etching, and the subsequent overgrowth onto bare QWW structures.1 Moreover, the authors reported several optical properties of the QWWs thus fabricated which manifested the one dimensional confinement of the electron-hole system.1,2 In order to adequately draw on the potential of QWWs, it is essential, in addition to the fundamental qualities described above, to reduce the QWW size fluctuation.3 This is because great size-fluctuation leads to pronounced fluctuation in quantum levels and the resultant broadening of the otherwise sharp density of state spectrum. Considering this, it is urgent that the relationship between the size fluctuation and the characteristics of QWWs be clarified.
Saturation and carrier sweep-out in electro-absorptive GaAs/GaAIAs MQW diodes
Authors: Goodwill D.J. , Massa J.S. , Buller G.S. , Fancey S.J. , Wachlowski A.
Published: February 2023

While the speed at which a SEED device may be switched is limited fundamentally by carrier vertical transport times and RC effects, in a practical parallel processing system it is likely to be limited by the ratio of incident optical power and device switch energy. Since high speed SEED operation is desirable for a high processing rate, it is important that the device performance is not degraded at high incident power. One of the important mechanisms which result in this degradation is the build-up of a carrier density in the quantum wells (QWs). This carrier density weakens the excitonic absorption feature, resulting in a reduction of the reflectivity contrast ratio. In references [1] and [2] several QW structures were compared and the saturation effects were found to decrease as the sweep-out time [3] was reduced by either lowering or thinning the barrier between wells. An MQW consisting of 100Å GaAs wells and 35Å Ga0.7Al0.3As barriers was therefore developed in [1] and for this structure, at the intensities used in that work, no saturation effects were observed. We have extended the results by examining a similar structure and measuring the saturation of the responsivity and reflectivity at incident intensities up to 40kW/cm2 (1400μW in a spot with 2.1μm 1/e2-1/e2 intensity). Thermal effects were also observed. Using time resolved photoluminescence (TRPL) we have directly measured carrier sweep-out times and so have been able to calculate the carrier densities generated in the saturation experiments.
Femtosecond Dynamics of Room-Temperature Excitons in II-VI Multiple Quantum Wells
Authors: Johnson Anthony M. , Becker Philippe C. , Lee Donghan , de Barros Miriam R. X. , Feldman Robert D. , Prosser Alan G. , Austin Richard F. , Behringer Robert E.
Published: February 2023

In semiconductors, with increasing carrier densities, excitons are screened and eventually lose their oscillator strengths [1]. As a result, the excitonic absorption will be greatly reduced or bleached. One interesting question is: How strongly can excitons, which are electrically neutral but consist of electrons and holes, self-screen the exciton? In bulk GaAs, Fehrenbach et al. [2] observed that the screening of excitons by excitons is very weak, compared to the screening of excitons by free carriers. Recently, Knox et al. [3] found that the bleaching effect of excitons on excitons was stronger than that of the same density of "warm" free carriers in GaAs multiple quantum wells (MQWs). This behavior is qualitatively well explained by the theory of Schmitt-Rink et al. [4], in which only the effects of the Pauli exclusion principle (phase space filling and exchange interaction) are considered for the bleaching of excitons by both excitons and free electron-hole (e-h) pairs, assuming long-range Coulomb screening is very weak in quasi-two-dimensional (2D) QWs. This assumption could be best tested by measuring the bleaching strength of "cold" free e-h pairs which are supposed to screen the exciton most strongly in bulk [1].
Quantum Microcavities and Quantum Well Excitons : An Optimum System For Strong Optical Coupling
Authors: Arakawa Y. , Ishikawa A. , Nishioka M. , Weisbuch C.
Published: February 2023

Several approaches are being attempted to obtain narrow spectral lines and/or controlled spontaneous emission on localized (impurity ions) or delocalized crystal excitations (free electron-hole pairs, excitons). A first way is to quantize electron motion, in an increasing manner in 1, 2 or 3 dimensions, in structures called quantum well,s wires or dots structures. While the approach to quantum wires and dots is being pursued since about 10 years, it did not yield so far any convincing improvement of the optical and optoelectronics properties of solids, in the same way as quantum wells did when compared to “traditional” bulk materials. Another, more recent approach is to remark that broad emission lines and isotropic emission (in the broad sense) are obtained because there is a 3D continuum of photon states available which allow transitions at any direction and energy at which a suitable electronic excitation of the crystal is present. One of the approaches to restrict the available photonic states is that of the photonic bandgap materials, in which the material (more precisely its optical constants) is modulated in all three directions in order to open energy gaps in the propagation of optical waves, identically to the energy gap opening of electron states in solids due to the periodic ion potential. A second way is to bury the light-emitting material in an optical cavity, such that optical modes are separated by more than the emission linewidth. In such a case emission will only occur into one optical mode, with a linewidth detemined by the mode linewidth, and all energy-unmatched crystal excitations will reach this single desexcitation mode through energy and momentum relaxation, as far as non-radiative recombination is negligible.
Quiet Electrons, Noisy photons: Quantum Statistical Effects in Wave Guide Transport
Authors: Büttiker M.
Published: February 2023

Fluctuations of the current at the contacts of a small phase-coherent conductor are compared with fluctuations of the intensity at the contacts of a photon wave guide [1]. The electronic conductor and the photon wave guide are viewed as a target at which carriers incident from the reservoirs (balck body radiators) connected to the contacts are reflected or transmitted into another reservoir. The spatial separation between reservoirs is assumed to be so small that transmission from one contact to another is phase-coherent. We are interested in the fluctuations of the current and the intensity away from their steady state average. Of principal interest are properties of the fluctuations which are directly related to the statistics of indistinguishable quantum particles. Such effects are a consequence of the symmetry of the wave-function under exchange of two carriers. Experiments with photon beams in free space were pionered by Hanburry Brown and Twiss almost forty years ago. In contrast to experiments with beams of light or beams of electrons in free space, experiments in conductors or wave guides have the advantage that a much higher degree of occupation of available states can be achieved. At kT=0 in a conductor, all states below the Fermi energy are occupied. Despite this advantage a clear demonstration of quantum statistical effects in conductors is lacking.
Squeezing With Input State of Large Phase Uncertainty
Authors: Lyubomirsky I. , Shirasaki M. , Haus H. A.
Published: February 2023

Noise suppression in an interferometer, employing a nonlinear Mach-Zehnder squeezer, was proposed[1] and experimentally confirmed[2,3]. The noise characteristics of this squeezer were derived for a coherent state input[4]. It may be advantageous to put the squeezer directly into a modelocked laser resonator where higher power pulses may be utilized. In this case the light acquires a large phase uncertainty. Thus, it is of interest to analyze squeezing with an input state of large phase uncertainty. One approach is to expand the input state in terms of coherent states[5]. Another approach is to use number states, which have total phase uncertainty and also present some interesting quantum features.
Applications of Scanning Force Microscopy for Voltage Measurements with High Spatial and Temporal Resolutions
Authors: Ho Francis , Hou A. Samson , Nechay Bettina A. , Bloom David M. , Ginzton Edward L.
Published: February 2023

To keep pace with device technology as it pushes towards 100-nm line widths and gigahertz operating speeds, new measurement tools are needed for studying mesoscopic device physics and for testing and designing the next generation of ultra-dense integrated circuits. A promising new direction is the use of scanning probe microscopes for such measurements, by utilizing probe tip nonlinearities for heterodyning very high-speed signals.[1-6] We have developed such an ultrafast system, based on the scanning force microscope (SFM), that should theoretically be able to map a voltage profile with subpicosecond temporal resolution and submicron spatial resolution. Furthermore, it is non-invasive, rugged, and does not require vacuum. By using the square-law force interaction between the SFM and sample for mixing and sampling, we have measured voltage transients as fast as 5 picoseconds. We have also used this system to probe VLSI integrated circuits.
Broadly-tunable microcavity light emission
Authors: Larson M. C. , Harris J. S.
Published: February 2023

We report broad tunability (42meV), narrow linewidth (3meV), and enhanced spontaneous emission in quantum well luminescence from a vertical microcavity employing a deformable-membrane top mirror.
Complete Polarization Control of 8x8 Vertical-cavity Surface-emitting Laser Matrix Arrays
Authors: Yoshikawa T. , Kosaka H. , Kurihara K. , Kajita M. , Sugimoto Y. , Kasahara K.
Published: February 2023

Polarization control in vertical-cavity surface-emitting lasers (VCSELs) is important because the devices in which VCSELs are used, such as magneto-optical discs or optical interconections, often use polarization-sensitive elements such as beam spliters. Additionally, a great advantage of VCSELs is that they can readily be used to form arrays; thus, polarization must be controlled for not only single VCSELs but also VCSEL arrays. However, since the VCSEL polarization direction is not determined, the polarization direction of the emitted light is random. In previous works, efforts have been made to control polarization, however, polarization still remains uncontrolled, especially in array form1-3.
Review of photonic bandgaps
Authors: Yablinovitch E.
Published: February 2023

We discuss the status of photonic bandgap structures from a physics and applications viewpoint.
A Vertical Cavity Surface Emitting Laser Operating in a 12 T Magnetic Field at 2K Temperature
Authors: Lyngnes Ove , Gibbs Hyatt M. , Khitrova Galina , Berger Jill D. , Nelson Tom R. , Zapaskii Valerii
Published: February 2023

Recently, concerns have been raised about the presumed improvement in lasing performance in going from a 2D confined system to a OD confined system. Stark et al. (1992, 1993) have studied ≈10 nm GaAs/AlGaAs multiple quantum wells in a perpendicular magnetic field of 12T normal to the quantum wells. Magnetic quantization into equally spaced Landau levels plus the quantum-well quantization along the growth direction result in near-ideal quantum dots. Stark et al. have shown that the 2s magneto-exciton lives ≈ 100 ps, i. e., ≈ 1000 times longer in 12T than 0T, illustrating the phonon bottleneck. Usually hot carriers in a semiconductor excited well above the bandgap relax by a series of optical phonon emissions, thereby transferring energy rapidly (<1ps) and efficiently to the lattice. Schmitt-Rink et al. (1989), Weisbuch et al. (1991), Bockelmann and Bastard (1990), Benisty et al. (1991), and Inoschita et al. (1992) have emphasized that quantum dot quantization in all three dimensions should result in a phonon bottleneck; i.e., only by accident will the distance between energy levels be equal to the phonon energy. This could degrade the performance of a quantum dot laser considerably.
Carrier capture in GaAs quantum wire structures grown on V-groove substrates
Authors: Haacke S. , Deveaud B. , Oberli D.Y. , Kapon E. , Marti U. , Reinhart F.K.
Published: February 2023

Carrier capture in quantum wells (QWs) has been intensively studied in the past years, especially concerning the dependence of the capture time on QW and barrier dimensions [1]. On the other hand, little is known about the carrier transfer and capture times into one-dimensional (ID) quantum wires (QWRs). In particular, in structures such as crescent-shaped QWRs grown on V-groove substrates, in which the carriers are transferred via both 3D barrier and 2D QW regions surrounding the wires, the carrier capture into the QWRs can be quite complex.
Fabrication of GaAs Quantum Dots Grown in Two-dimensional V-Grooves by MOCVD Selective Growth
Authors: Ishida S. , Nishioka M. , Nagamune Y. , Arakawa Y.
Published: February 2023

A reduction of dimensionality of the electron motions in quantum nano-structures allows new device concept as well as new physics[1,2]. For this purpose, various efforts have been devoted to the fabrication of the quantum dot structures. For example, the use of Stranski-Krastanow growth mode is promising to realize uniform and small quantum dot structures[3,4]. However, in this technique, it is difficult to control the position. On the other hand, the GaAs quantum dots on AlGaAs plinths which was grown on SiO2 patterned substrate was realized by MOCVD selective growth technique with a lateral width of 25nm[5]. In this method, the position of the quantum dots is controlled. But, non uniformity of size of the quantum dots due to the size fluctuation of the SiO2 pattern is unavoidable.
Calibrated Noise Measurements in Microcavity Lasers
Authors: Goobar Edgard , Scott Jeff , Robinson Gerry , Akulova Yuliya , Coldren Larry A.
Published: February 2023

During recent years the intensity noise in semiconductor lasers has received considerable attention. This is mainly due to the theoretical predictions [1] and experimental results [2-7] indicating that sub-shot-noise levels, amplitude squeezing, can be obtained if the pump noise is suppressed using a high impedance injection current. Recent results indicate, however, that multimode operation in semiconductor lasers may render increased noise levels in spite of the low pump noise [4-7]. The intensity noise of vertical-cavity surface emitting-lasers VCSELs has been reported in refs. [8] and [9]. In [8] the polarization stability of GaAlAs-GaAs VCSELs was examined and the effect of mode partition between the two polarizations was observed. However, to the best of our knowledge, measurements where the VCSEL noise is directly compared to the fundamental shot-noise level have not yet been reported.
Nonlinear Optical Response of Piezoelectric Multiple Quantum Wells Under Bias
Authors: Huang X. R. , Cartwright A. N. , McCallum D. S. , Harken D. R. , Smirl Arthur L. , Sánchez-Rojas J. L. , Sacedón A. , Calleja E. , Muñoz E.
Published: February 2023

Strained multiple quantum wells (MQWs) that are grown on [111]-oriented substrates have huge intrinsic piezoelectric fields along the growth directions and are attractive for a number of novel nonlinear optical, electronic and electro-optical device applications (e.g. blue shifting SEEDs1). Unfortunately, until recently, very little was known about the nonlinear properties of these piezoelectric MQWs. The existence2 of piezoelectric fields in strained [111]-oriented InGaAs/GaAs QWs and the screening3 of these fields by photoexcited carriers had been demonstrated. In addition, the nonlinear responses of piezoelectric MQW structures to steady-state4 and pulsed5 optical excitations had been reported. However, prior to our recent work, the shot-to-shot accumulation of carriers (which are long-lived because they are spatially separated) had prevented the time resolution of the nonlinear optical and carrier dynamics in piezoelectric MQWs. In the last few months, by placing piezoelectric MQWs in p-i-n structures that were carefully designed to reduce the carrier lifetime, we have finally begun to temporally resolve the nonlinear response. For example, we have been able to definitively demonstrate that the bandstructure of our samples are mechanically clamped, not free; that the nonlinear response is dominated by long range screening of the in-well piezoelectric field by carriers that have escaped the wells and not by in-well screening as originally proposed,6 and that the percarrier nonlinear response is more than an order of magnitude smaller than that in [100]-oriented structures, not an order of magnitude larger as originally purported.4