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Journal of Modern Optics

Timo Paschen, Michael Förster, Michael Krüger, Christoph Lemell, Georg Wachter, Florian Libisch, Thomas Madlener, Joachim Burgdörfer, Peter Hommelhoff
In this article, we present coherent control of above-threshold photoemission from a tungsten nanotip achieving nearly perfect modulation. Depending on the pulse delay between fundamental ([Formula: see text]) and second harmonic ([Formula: see text]) pulses of a femtosecond fiber laser at the nanotip, electron emission is significantly enhanced or depressed during temporal overlap. Electron emission is studied as a function of pulse delay, optical near-field intensities, DC bias field and final photoelectron energy...
June 17, 2017: Journal of Modern Optics
Devrim Toslak, Damber Thapa, Muhammet Kazim Erol, Yanjun Chen, Xincheng Yao
This aim of this study was to test the feasibility of smartphone-based specular microscopy of the corneal endothelium at a sub-cellular resolution. Quantitative examination of endothelial cells is essential for evaluating corneal disease such as determining a diagnosis, monitoring progression and assessing treatment. Smartphone-based technology promises a new opportunity to develop affordable devices to foster quantitative examination of endothelial cells in rural and underserved areas. In our study, we incorporated an iPhone 6 and a slit lamp to demonstrate the feasibility of smartphone-based microscopy of the corneal endothelium at a sub-cellular resolution...
2017: Journal of Modern Optics
Damber Thapa, Benquan Wang, Yiming Lu, Taeyoon Son, Xincheng Yao
Functional optical coherence tomography (OCT) of stimulus-evoked intrinsic optical signal (IOS) promises to be a new methodology for high-resolution mapping of retinal neural dysfunctions. However, its practical applications for non-invasive examination of retinal function have been hindered by the low signal-to-noise ratio (SNR) and small magnitude of IOSs. Split spectrum amplitude-decorrelation has been demonstrated to improve the image quality of OCT angiography. In this study, we exploited split spectrum strategy to improve the sensitivity of IOS recording...
2017: Journal of Modern Optics
Yasuo Tomita, Eiji Hata, Keisuke Momose, Shingo Takayama, Xiangming Liu, Katsumi Chikama, Jürgen Klepp, Christian Pruner, Martin Fally
We present an overview of recent investigations of photopolymerizable nanocomposite photonic materials in which, thanks to their high degree of material selectivity, recorded volume gratings possess high refractive index modulation amplitude and high mechanical/thermal stability at the same time, providing versatile applications in light and neutron optics. We discuss the mechanism of grating formation in holographically exposed nanocomposite materials, based on a model of the photopolymerization-driven mutual diffusion of monomer and nanoparticles...
December 15, 2016: Journal of Modern Optics
Aleksandra Klimek, Michał Jachura, Wojciech Wasilewski, Konrad Banaszek
We propose a simple architecture based on multimode quantum memories for collective readout of classical information keyed using a pair coherent states, exemplified by the well-known binary phase shift keying format. Such a configuration enables demonstration of the superadditivity effect in classical communication over quantum channels, where the transmission rate becomes enhanced through joint detection applied to multiple channel uses. The proposed scheme relies on the recently introduced idea to prepare Hadamard sequences of input symbols that are mapped by a linear optical transformation onto the pulse position modulation format [Guha, S...
November 12, 2016: Journal of Modern Optics
M Dąbrowski, R Chrapkiewicz, W Wasilewski
Warm atomic vapor quantum memories are simple and robust, yet suffer from a number of parasitic processes which produce excess noise. For operating in a single-photon regime precise filtering of the output light is essential. Here, we report a combination of magnetically tuned absorption and Faraday filters, both light-direction insensitive, which stop the driving lasers and attenuate spurious fluorescence and four-wave mixing while transmitting narrowband Stokes and anti-Stokes photons generated in write-in and readout processes...
November 12, 2016: Journal of Modern Optics
Khabat Heshami, Duncan G England, Peter C Humphreys, Philip J Bustard, Victor M Acosta, Joshua Nunn, Benjamin J Sussman
Quantum light-matter interfaces are at the heart of photonic quantum technologies. Quantum memories for photons, where non-classical states of photons are mapped onto stationary matter states and preserved for subsequent retrieval, are technical realizations enabled by exquisite control over interactions between light and matter. The ability of quantum memories to synchronize probabilistic events makes them a key component in quantum repeaters and quantum computation based on linear optics. This critical feature has motivated many groups to dedicate theoretical and experimental research to develop quantum memory devices...
November 12, 2016: Journal of Modern Optics
Mark Keil, Omer Amit, Shuyu Zhou, David Groswasser, Yonathan Japha, Ron Folman
Here we review the field of atom chips in the context of Bose-Einstein Condensates (BEC) as well as cold matter in general. Twenty years after the first realization of the BEC and 15 years after the realization of the atom chip, the latter has been found to enable extraordinary feats: from producing BECs at a rate of several per second, through the realization of matter-wave interferometry, and all the way to novel probing of surfaces and new forces. In addition, technological applications are also being intensively pursued...
October 10, 2016: Journal of Modern Optics
J V Thompson, B H Hokr, V V Yakovlev
The ability to control the propagation of light through scattering media is essential for atmospheric optics, astronomy, biomedical imaging and remote sensing. The optimization of focusing light through a scattering medium is of particular interest for the case of highly scattering materials. Optical wavefront beam-shaping plays a critical role in optimizing such a propagation; however, an enormous field of adjustable parameters makes the overall task complicated. Here, we propose and experimentally evaluate several variations on the standard continuous sequential algorithm that hold a promise of revealing new, faster and more efficient optimization algorithms for selecting an optical wavefront to focus light through a scattering medium...
2016: Journal of Modern Optics
Anthony Corcoran, Gonzalo Muyo, Jano van Hemert, Alistair Gorman, Andrew R Harvey
Optical coherence tomography (OCT) and reflectance imaging are used in clinical practice to measure the thickness and transverse dimensions of retinal features. The recent trend towards increasing the field of view (FOV) of these devices has led to an increasing significance of the optical aberrations of both the human eye and the device. We report the design, manufacture and application of the first phantom eye that reproduces the off-axis optical characteristics of the human eye, and allows the performance assessment of wide-field ophthalmic devices...
December 15, 2015: Journal of Modern Optics
Marco López, Helmuth Hofer, Stefan Kück
A highly accurate method for the determination of the detection efficiency of a silicon single-photon avalanche diode (Si-SPAD) is presented. This method is based on the comparison of the detected count rate of the Si-SPAD compared to the photon rate determined from a calibrated silicon diode using a modified attenuator technique, in which the total attenuation is measured in two attenuation steps. Furthermore, a validation of this two-step method is performed using attenuators of higher transmittance. The setup is a tabletop one, laser-based, and fully automated...
December 8, 2015: Journal of Modern Optics
Thomas M Barlow, Robert Bennett, Almut Beige
Quantum optical systems, like trapped ions, are routinely described by master equations. The purpose of this paper is to introduce a master equation for two-sided optical cavities with spontaneous photon emission. To do so, we use the same notion of photons as in linear optics scattering theory and consider a continuum of travelling-wave cavity photon modes. Our model predicts the same stationary state photon emission rates for the different sides of a laser-driven optical cavity as classical theories. Moreover, it predicts the same time evolution of the total cavity photon number as the standard standing-wave description in experiments with resonant and near-resonant laser driving...
December 8, 2015: Journal of Modern Optics
Bernhard Baumann, Stefan Zotter, Michael Pircher, Erich Götzinger, Sabine Rauscher, Martin Glösmann, Jan Lammer, Ursula Schmidt-Erfurth, Marion Gröger, Christoph K Hitzenberger
Depolarization of light can be measured by polarization-sensitive optical coherence tomography (PS-OCT) and has been used to improve tissue discrimination as well as segmentation of pigmented structures. Most approaches to depolarization assessment for PS-OCT - such as the degree of polarization uniformity (DOPU) - rely on measuring the uniformity of polarization states using spatial evaluation kernels. In this article, we present a different approach which exploits the spectral dimension. We introduce the spectral DOPU for the pixelwise analysis of polarization state variations between sub-bands of the broadband light source spectrum...
2015: Journal of Modern Optics
R Haindl, W Trasischker, B Baumann, M Pircher, C K Hitzenberger
An improved three-beam Doppler optical coherence tomography system was developed. It utilizes a custom-made three-facet prism telescope to improve the transversal resolution at the sample. Furthermore, a two-axis gimbal-less MEMS mirror is used to minimize off-pivot beam movement at the pupil of the eye, enabling circular scanning for in vivo retinal measurements. We demonstrate the system's abilities for in vitro circular scanning to measure absolute flow and to reconstruct the full velocity vector on a bifurcation flow phantom...
2015: Journal of Modern Optics
Samarendra K Mohanty, Vasudevan Lakshminarayananan
Optogenetics is an innovative technique for optical control of cells. This field has exploded over the past decade or so and has given rise to great advances in neuroscience. A variety of applications both from the basic and applied research have emerged, turning the early ideas into a powerful paradigm for cell biology, neuroscience and medical research. This review aims at highlighting the basic concepts that are essential for a comprehensive understanding of optogenetics and some important biological/biomedical applications...
2015: Journal of Modern Optics
Fernando E Camino, Chang-Yong Nam, Yutong T Pang, Jessica Hoy, Matthew D Eisaman, Charles T Black, Matthew Y Sfeir
We present a methodology for probing light-matter interactions in prototype photovoltaic devices consisting of an organic semiconductor active layer with a semitransparent metal electrical contact exhibiting surface plasmon-based enhanced optical transmission. We achieve high-spectral irradiance in a spot size of less than 100 μm using a high-brightness laser-driven light source and appropriate coupling optics. Spatially resolved Fourier transform photocurrent spectroscopy in the visible and near-infrared spectral regions allows us to measure external quantum efficiency with high sensitivity in small-area devices (<1 mm(2))...
December 15, 2014: Journal of Modern Optics
Wenlong Lu, Ming Chang, Po-Cheng Chen, Wun-Mao Luo
Diffraction limit is usually a thorny problem in an optical inspection system. In this investigation, a model-based deconvolution technique was developed to recover diffraction-limited images, where images with sizes smaller than the diffraction limit could be recognized. Experiments were carried out with a traditional microscope at 200× magnification coupled with a halogen light source for a series of line width samples. The point spread function of the imaging optics was first obtained from an estimated model and then combined with a nonlinear deconvolution algorithm to calculate the full width at half maximum and reconstruct the line widths...
December 12, 2014: Journal of Modern Optics
Weston Thomas, Christopher Middlebrook
Personal electronic devices such as cell phones and tablets continue to decrease in size while the number of features and add-ons keep increasing. One particular feature of great interest is an integrated projector system. Laser pico-projectors have been considered, but the technology has not been developed enough to warrant integration. With new advancements in diode technology and MEMS devices, laser-based projection is currently being advanced for pico-projectors. A primary problem encountered when using a pico-projector is coherent interference known as speckle...
December 12, 2014: Journal of Modern Optics
A Balbuena Ortega, M L Arroyo Carrasco, M M Méndez Otero, V L Gayou, R Delgado Macuil, H Martínez Gutiérrez, M D Iturbe Castillo
In this paper, the nonlinear refractive index of colloidal gold nanoparticles under continuous wave illumination is investigated with the z-scan technique. Gold nanoparticles were synthesized using ascorbic acid as reductant, phosphates as stabilizer and cetyltrimethylammonium chloride (CTAC) as surfactant agent. The nanoparticle size was controlled with the CTAC concentration. Experiments changing incident power and sample concentration were done. The experimental z-scan results were fitted with three models: thermal lens, aberrant thermal lens and the nonlocal model...
December 12, 2014: Journal of Modern Optics
Yang Wu, Damien P Kelly
The distribution of the complex field in the focal region of a lens is a classical optical diffraction problem. Today, it remains of significant theoretical importance for understanding the properties of imaging systems. In the paraxial regime, it is possible to find analytical solutions in the neighborhood of the focus, when a plane wave is incident on a focusing lens whose finite extent is limited by a circular aperture. For example, in Born and Wolf's treatment of this problem, two different, but mathematically equivalent analytical solutions, are presented that describe the 3D field distribution using infinite sums of [Formula: see text] and [Formula: see text] type Lommel functions...
December 12, 2014: Journal of Modern Optics
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