Showing papers in "Journal of Modern Optics in 2010"
TL;DR: In this paper, the authors illustrate the power of the Positive Operator Valued Measures (POVM) concept on examples relevant to applications in quantum cryptography and give a brief introduction to the quantum theory of measurements, including generalized measurements.
Abstract: In quantum information processing and quantum computing protocols the carrier of information is a quantum system and information is encoded in the state of a quantum system. After processing the information it has to be read out what is equivalent to determining the final state of the system. When the possible final states are not orthogonal this is a highly nontrivial task that constitutes the general area of what is known as quantum state discrimination. It consists in finding measurement schemes that, according to some figure of merit, will determine the state of the system. Optimized measurement schemes often lead to generalized measurements (Positive Operator Valued Measures [POVMs]). In this tutorial review we illustrate the power of the POVM concept on examples relevant to applications in quantum cryptography. In order to keep the flow of the presentation we give a brief introduction to the quantum theory of measurements, including generalized measurements (POVMs), in the Appendices.
245 citations
TL;DR: In this article, the concept of colored non-autonomous solitons in nonlinear and dispersive nonautonomous physical systems is introduced. And the fundamental laws of the soliton adaptation to the external potentials are derived.
Abstract: The fundamental concept of colored nonautonomous solitons in nonlinear and dispersive nonautonomous physical systems is introduced. Novel soliton solutions for the nonautonomous nonlinear Schrodinger equation models with linear and harmonic oscillator potentials substantially extend the concept of classical solitons and generalize it to the plethora of nonautonomous solitons that interact elastically and generally move with varying amplitudes, speeds and spectra adapted both to the external potentials and to the dispersion and nonlinearity variations. The parallels between nonlinear guided wave phenomena in optics and nonlinear guided wave phenomena in Bose condensates are clearly demonstrated by considering optical and matter wave soliton dynamics in the framework of nonautonomous evolution equations. The exact analytical solutions and numerical experiments reveal many specific features of nonautonomous solitons. Fundamental laws of the soliton adaptation to the external potentials are derived. Bound sta...
172 citations
TL;DR: The basic theory of TDM is discussed in the framework of electromagnetism and a comparison with conventional widefield microscopes is drawn, highlighting their power of resolution.
Abstract: Tomographic diffractive microscopy (TDM) is an advanced digital imaging technique, which combines the recording of multiple holograms with the use of inversion procedures to retrieve quantitative information on the sample. In this review, we discuss the basic theory of TDM in the framework of electromagnetism and draw a comparison with conventional widefield microscopes. We describe various implementations of TDM, highlighting their power of resolution. Finally, we present some research perspectives for increasing the potential of this promising new imaging modality.
154 citations
TL;DR: A simple analysis of the problems involved in defining spin and orbital angular momenta for electromagnetic fields is presented and some of the remaining challenges are discussed.
Abstract: The association of spin and orbital angular momenta of light with its polarization and helical phase fronts is now well established The problems in linking this with electromagnetic theory, as expressed in Maxwell's equations, are rather less well known We present a simple analysis of the problems involved in defining spin and orbital angular momenta for electromagnetic fields and discuss some of the remaining challenges Crucial to our investigation is the duplex symmetry between the electric and magnetic fields
143 citations
TL;DR: A series of experiments on feature selection and exudates classification using naive Bayes and support vector machine (SVM) classifiers find that the naive Baye and SVM classifiers perform better than the NN classifier.
Abstract: Exudates are among the preliminary signs of diabetic retinopathy, a major cause of vision loss in diabetic patients. Early detection of exudates could improve patients’ chances to avoid blindness. In this paper, we present a series of experiments on feature selection and exudates classification using naive Bayes and support vector machine (SVM) classifiers. We first fit the naive Bayes model to a training set consisting of 15 features extracted from each of 115,867 positive examples of exudate pixels and an equal number of negative examples. We then perform feature selection on the naive Bayes model, repeatedly removing features from the classifier, one by one, until classification performance stops improving. To find the best SVM, we begin with the best feature set from the naive Bayes classifier, and repeatedly add the previously-removed features to the classifier. For each combination of features, we perform a grid search to determine the best combination of hyperparameters ν (tolerance for training er...
114 citations
TL;DR: An overview of the subwavelength confinement of light with plasmonics is presented in this paper, where the authors focus on the surface plasmor-assisted light enhancement via the single metallic aperture.
Abstract: In this review, an overview of the subwavelength confinement of light with plasmonics is presented. Among the varieties of state-of-the-art technologies on this intensively-studied topic, we focus on the surface plasmon-assisted light enhancement via the single metallic aperture. Based on a systematic overview of the physical principles of light enhancement in subwavelength-sized metallic apertures, we investigate various types of apertures and discuss their characteristics.
107 citations
TL;DR: In this paper, the authors present pump probe experiments with femtosecond time resolution using free electron laser (FEL) facilities. And they provide the ideal targets for early experiments by which not only FELs can be characterised and benchmarked but can also be the natural departure point in the hunt for non-linear behaviour of atomistic systems bathed in laser fields of ultrahigh photon energy.
Abstract: The advent of free electron laser (FEL) facilities capable of delivering high intensity pulses in the extreme-UV to X-ray spectral range has opened up a wide vista of opportunities to study and control light matter interactions in hitherto unexplored parameter regimes. In particular, current short wavelength FELs can uniquely drive non-linear processes mediated by inner shell electrons and in fields where the photon energy can be as high as 10 keV and so the corresponding optical period reaches below one attosecond. Combined with ultrafast optical lasers, or simply employing wavefront division, pump probe experiments can be performed with femtosecond time resolution. As single photon ionization of atoms and molecules is by now very well understood, they provide the ideal targets for early experiments by which not only FELs can be characterised and benchmarked but can also be the natural departure point in the hunt for non-linear behaviour of atomistic systems bathed in laser fields of ultrahigh photon ene...
105 citations
TL;DR: In this paper, the magnitudes of the photon momenta in free space, derived by Maxwell and Einstein, and those in homogeneous, dispersionless and lossless dielectrics, associated with Abraham and Minkowski are reviewed.
Abstract: We review the magnitudes of the photon momenta in free space, derived by Maxwell and Einstein, and those in homogeneous, dispersionless and lossless dielectrics, associated with Abraham and Minkowski. These momenta determine the forces exerted by light beams on material objects, as measured in radiation pressure experiments. It is shown that conservation conditions for components of the electromagnetic energy–momentum tensors derived by Abraham and Minkowski, also by Einstein and Laub, are equivalent relations simply derived from Maxwell's equations. The challenge for theory is the reliable interpretation of experimental momentum transfers from light to matter, which requires extensions of the basic theory to include material dispersion and surface effects. The main experiments are reviewed, together with details of a Lorentz-force theory that accounts for them. It is shown that the Abraham kinetic momentum is associated with the overall motion of a dielectric sample, while the Minkowski canonical momentu...
96 citations
TL;DR: In this paper, an outline of paraxial optics is provided in a form that is sufficiently general to incorporate the coherence properties and frequency structure of illumination sources used in diffractive imaging applications.
Abstract: Techniques that recover images from diffraction data obtained using coherent short-wavelength light sources are currently under active development for applications in nanotechnology and structural biology. In this review, an outline of paraxial optics is provided in a form that is sufficiently general to incorporate the coherence properties and frequency structure of illumination sources used in diffractive imaging applications. The Fourier phase problem is formulated in the context of imaging algorithms that are designed to obtain uniquely-determined phase distributions from measurements of diffraction data. The properties of several iterative phase retrieval algorithms for both coherent and partially-coherent diffractive imaging applications are presented in a unified formalism, together with a brief discussion of a non-iterative technique. Approaches to diffractive imaging based on Fraunhofer and Fresnel diffraction configurations are compared. Applications are described utilising quasi-monochromatic t...
84 citations
TL;DR: SLSTR as mentioned in this paper is a high accuracy infrared radiometer which will be embarked in the Earth low-orbit Sentinel 3 operational GMES mission, which should permit global coverage of SST and LST measurements with daily revisit time, useful for climatological and meteorological applications.
Abstract: SLSTR is a high accuracy infrared radiometer which will be embarked in the Earth low-orbit Sentinel 3 operational GMES mission. SLSTR is an improved version of the previous AATSR and ATSR-1/2 instruments which have flown respectively on Envisat and ERS-1/2 ESA missions. SLSTR will provide data continuity with respect to these previous missions but with a substantial improvement due to its higher swaths (750 km in dual view and 1400 km in single view) which should permit global coverage of SST and LST measurements (at 1 km of spatial resolution in IR channels) with daily revisit time, useful for climatological and meteorological applications. Two more SWIR channels and a higher spatial resolution in the VIS/SWIR channels (0.5 km) are also implemented for a better clouds/aerosols screening. Two further additional channels for global scale fire monitoring are present at the same time as the other nominal channels.
84 citations
TL;DR: In this article, a comparison of Mie theory, the T-Matrix null-field method, the discrete-dipole approximation, the finite-element method and the finitedifference time-domain method is presented.
Abstract: A comparison is presented of a number of simulation techniques that are used to compute the scattering of electromagnetic radiation by metallic nanostructures. The simulation techniques considered here are Mie theory, the T-Matrix null-field method, the discrete-dipole approximation, the finite-element method and the finite-difference time-domain method. The suitability of each technique is compared in terms of the accuracy, computation time and the range of geometries to which it can be applied. Using each technique, we perform example calculations by simulating the optical response of an 80 nm diameter Au sphere in vacuum. Our main conclusions are summarised in tabulated form, so that the findings presented in this article may serve as a useful reference guide to those looking for suitable numerical tools to model the optical response of metallic nanostructures.
TL;DR: In this article, the propagation properties of Lorentz and LG-Gauss beams in uniaxial crystals and in free space were investigated numerically and comparatively, and it was found that the propagation behavior of LG beams in the free space behaves very differently from those in free-space.
Abstract: Paraxial propagation of Lorentz and Lorentz–Gauss beams in uniaxial crystals orthogonal to the optical axis is investigated based on the beam propagation equations. Analytical propagation formulae for Lorentz and Lorentz–Gauss beams in uniaxial crystals are derived. The derived propagation formulae reduce to the propagation formulae for Lorentz and Lorentz–Gauss beams in free space under certain conditions. The propagation properties of Lorentz and Lorentz–Gauss beams in uniaxial crystals and in free space are studied numerically and comparatively. It is found that the propagation properties of Lorentz and Lorentz–Gauss beams in uniaxial crystals behave very differently from those in free space, and are closely determined by the parameters of the uniaxial crystals. The uniaxial crystals provide an effective way for generating astigmatic beams.
TL;DR: A new approach to moisture detection in buildings by an optical method that exploits characteristics of the materials and takes into account explicitly the heat and mass exchange between surface and environment.
Abstract: A new approach to moisture detection in buildings by an optical method is presented. Limits of classical and new methods are discussed. The state of the art about the use of IR thermography is illustrated as well. The new technique exploits characteristics of the materials and takes into account explicitly the heat and mass exchange between surface and environment. A set of experiments in controlled laboratory conditions on different materials is used to better understand the physical problem. The testing procedure and the data reduction are illustrated. A case study on a heritage building points up the features of this technique.
TL;DR: In this paper, the authors discuss previous misinterpretations of the binding soliton energy and investigate all possible scenarios of nonlinear soliton tunneling of Schrodinger solitons including soliton splitting on a potential barrier, leading to partial reflection and partial transmission, sub-barrier soliton tunneling and over-barrage soliton reflection.
Abstract: The method of mathematical analogies opens the possibility to study optical and matter-wave solitons in parallel and, due to the evident complexity of experiments with matter wave solitons, offers remarkable possibilities in studies of the BEC systems by performing experiments in the nonlinear optical systems and vice versa. We discuss previous misinterpretations of the binding soliton energy and investigate all possible scenarios of nonlinear soliton tunneling of Schrodinger solitons including soliton splitting on a potential barrier, leading to partial reflection and partial transmission, sub-barrier soliton tunneling and over-barrier soliton reflection. We reveal the most significant modifications of soliton tunneling scenarios due to increasing the binding energy, and show that the self-compressing soliton resembles more the classical particle case than a quantum mechanical behavior. The enhancement of the soliton binding energy is of decisive importance in the testing of a long-standing theoretical r...
TL;DR: The atomic optical bistability (AOB) in multi-level systems has advantages over the two-level system as absorption, dispersion, and nonlinear optical properties of one optical field coupled to one atomic transition can be greatly modified by other optical fields coupled to other connected nearby atomic transitions due to induced atomic coherences.
Abstract: The atomic optical bistability (AOB) in multi-level systems has advantages over the two-level system as absorption, dispersion, and nonlinear optical properties of one optical field coupled to one atomic transition can be greatly modified by other optical fields coupled to other connected nearby atomic transitions in multi-level atomic systems due to induced atomic coherences. By making use of such changes in linear and nonlinear optical properties around resonance, which are related to the electromagnetically induced transparency (EIT), it is easy to manipulate and control nonlinear optical processes in the multi-level atomic systems. We review earlier two-level AOB theory, as well as experiments and some recent studies that made use of multi-level atomic EIT systems in achieving controls of nonlinear optical processes such as instabilities and stochastic resonance associated with the coupled atom–cavity systems.
TL;DR: The 50th anniversary of the first operation of a laser has been widely marked around the globe by researchers, institutions, science and technology commentators and professional societies with an involvement in the laser as discussed by the authors.
Abstract: The 50th anniversary of the first operation of a laser has been widely marked around the globe by researchers, institutions, science and technology commentators and professional societies with an involvement in the laser. The Journal of Modern Optics is no exception to this and we were happy to mark the occasion. So on the 14th of May 2010, just two days short of the anniversary date, the Journal joined in the celebrations taking place at Imperial College London to mark the 50th birthday of the laser. We were delighted that the event was so well attended and are grateful to all of those who came, and especially to those who spoke at the event, which was sponsored jointly by Imperial College and the Journal of Modern Optics. We were treated to some fascinating and entertaining talks covering broad aspects of the laser and its impact, with two fascinating contributions from JMO Board members Miles Padgett and Gerd Leuchs. There was also a special emphasis upon the pivotal role played by Imperial College in the history of the laser in the UK with a series of speakers who covered these contributions. It is not the place to review the whole history of the laser, or indeed even to dig too deeply into the credit for its invention, but it is an opportunity to pass a few comments on the story of the laser and its impact upon science and technology. I am guided here by the fascinating and entertaining account of the early days of the laser and non-linear optics presented by Geoff New who gave the keynote talk of the event at Imperial College. The first recorded operation of a laser took place in Malibu, California in the laboratory of Theodore Maiman at the Hughes Corporation on 16th May 1960. Of course there are many other important contributions to the story, both before and after this date, but it is as well that we can identify a single day when the laser can said to have been born otherwise it would be difficult to celebrate the ‘‘birthday’’. As Geoff pointed out, there was a great deal of basic theoretical and experimental research in the 1950s that underpinned Maiman’s first demonstration of a working ruby laser. After the first experiment it was quite remarkable how quickly the laser was commercialised, and it was the availability of intense laser radiation that caused the daughter field of nonlinear optics to spring to life in 1961 after lying dormant from the late nineteenth century. The rebirth was marked by key experiments on second harmonic generation at the University of Michigan, and later at the Ford Motor Company in Detroit. Most of the fundamental principles of nonlinear optics were established within the next few years, and the technological impact has continued to spread far and wide ever since. Since the invention of the laser, laser technology has burgeoned into a vast field. Following quickly on the heels of the first ruby laser were the first gas lasers and the first semiconductor lasers. Since then the variety of lasers and laser media employed has grown enormously to span solid state materials (e.g. Nd:glass, Nd:YAG and Ti:Sapphire), semiconductors (with a wide array of diode laser types), fibre lasers and gas lasers (e.g. excimers, CO2) suited to all kinds of applications from hand held pointers to lasers capable of generating an energy density exceeding that at the centre of the sun. The techniques for controlling and amplifying the laser emission have also hugely advanced with, for example, mode locking enabling oscillator pulses as short as 3 fs to be produced and frequency stabilisation methods enabling laser linewidths of 5 1 Hz to be achieved. With special amplification architectures such as chirped pulse amplification it is possible to produce, albeit in only a few tens of femtoseconds, laser pulses with a peak power of 10 PW (10 W). The criticism of the early years of the laser that it was ‘‘a discovery waiting for an application’’ has surely been entirely disproven by now. It is instead an invention of remarkably broad impact and pervasiveness. That it has fostered a revolution in science there can be no question. Among countless applications, one could mention the advanced measurement of distance, frequency and time at unprecedented precision, ultrafast measurements now reaching from the femtosecond to the attosecond domain, control of the motion of atoms (leading, for example, to Bose–Einstein condensation), laser driven particle acceleration and the very real prospect of the first laser fusion demonstration within the next 12 months. In the technological sphere the laser has been equally pervasive with enormous
TL;DR: Simulation results show the superiority of the proposed curvelet fusion approach to the traditional fusion techniques like the multiresolution discrete wavelet transform (DWT) technique and the principal component analysis (PCA) technique.
Abstract: There are several medical imaging techniques such as the magnetic resonance (MR) and the computed tomography (CT) techniques. Both techniques give sophisticated characteristics of the region to be imaged. This paper proposes a curvelet based approach for fusing MR and CT images to obtain images with as much detail as possible, for the sake of medical diagnosis. This approach is based on the application of the additive wavelet transform (AWT) on both images and the segmentation of their detail planes into small overlapping tiles. The ridgelet transform is then applied on each of these tiles, and the fusion process is performed on the ridgelet transforms of the tiles. Simulation results show the superiority of the proposed curvelet fusion approach to the traditional fusion techniques like the multiresolution discrete wavelet transform (DWT) technique and the principal component analysis (PCA) technique. The fusion of MR and CT images in the presence of noise is also studied and the results reveal that unlik...
Abstract: We consider collective spontaneous emission from an ensemble of N identical two-level atoms prepared by absorption of a single photon–a.k.a. single photon Dicke superradiance. We discuss dynamical properties of superradiance for small (R ≪ λ) and large (R ≫ λ) atomic cloud. Moreover, we address the effects of virtual processes on collective decay rate and Lamb shift. It turns out that virtual processes lead to relatively small yet interesting effects on the time evolution of a rapidly decaying state. However, such processes substantially modify the dynamics of trapped states by bringing in new channels of decay.
TL;DR: In this article, the impact of different partially coherent light sources on the formation and the reconstruction of digital off-axis holograms was analyzed and the achieved lateral resolution and the accuracy for the detection of optical path length changes were compared to results obtained with laser light.
Abstract: The main drawbacks of laser-based digital holographic microscopy (DHM) are coherent noise and disturbances due to parasitic reflections in the experimental setup. To overcome some of these problems, investigations on the performance of partially coherent light in DHM-based live cell imaging were carried out. First, the impact of different partially coherent light sources on the formation and the reconstruction of digital off-axis holograms was analyzed. Therefore, the achieved lateral resolution and the accuracy for the detection of optical path length changes were compared to results obtained with laser light. In additional experiments, we investigated if partial coherent light can be utilized in DHM for quantitative phase contrast imaging of living cells in incident light configuration by using light from specifically selected reflective sample interfaces. The obtained results show the applicability of partially coherent light in off-axis DHM and its use to for the reduction of disturbances due to coher...
TL;DR: The development of IR sensors, initially linked to astronomical observations, since World War II and for many years has been fostered essentially by defence applications, particularly thermo-vision and, later on, smart vision and detection, for surveillance and warning as discussed by the authors.
Abstract: Infrared (IR) technologies (materials, devices and systems) represent an area of excellence in science and technology and, even if they have been generally confined to a selected scientific community, they have achieved technological and scientific highlights constituting ‘innovation drivers’ for neighbouring disciplines, especially in the sensors field. The development of IR sensors, initially linked to astronomical observations, since World War II and for many years has been fostered essentially by defence applications, particularly thermo-vision and, later on, smart vision and detection, for surveillance and warning. Only in the last few decades, the impact of silicon technology has changed the development of IR detectors dramatically, with the advent of integrated signal read-outs and the opening of civilian markets (EO communications, biomedical, environmental, transport and energy applications). The history of infrared sensors contains examples of real breakthroughs, particularly true in the case of...
TL;DR: In this article, a temperature and emissivity measurement methodology for IR thermography using two IR cameras in a stereo arrangement with detectors working in different wavelength bands is described, where the two radiation distributions measured by the IR cameras are rebuilt on the object surface mesh by means of the pinhole camera model and are used to write a system of equations in which emissivities and temperatures are unknown quantities.
Abstract: This work describes a temperature and emissivity measurement methodology that applies the multi-wavelength pyrometry principle to IR thermography using two IR cameras in a stereo arrangement with detectors working in different wavelength bands. The two radiation distributions measured by the IR cameras are rebuilt on the object surface mesh by means of the pinhole camera model and are used to write a system of equations in which emissivities and temperatures are unknown quantities. By solving the system, the temperature and directional emissivity of the material under test can be measured for each wavelength band. The influence on the proposed methodology of the IR camera noise and of the temperature bias between the two cameras is numerically analysed in the case of gray and non-gray bodies. To validate the proposed methodology, an experimental test was performed on an object with known emissivity (measured in a conventional way).
TL;DR: It was found that the thermal load of ablations onto flat PMMA plates declines steadily when the allowed local frequency decreases or when the diameter of the blocked area increases, which seems to be optimal for avoiding corneal collagen denaturation with minimum compromise on treatment duration.
Abstract: The purpose of this work was to evaluate the extent that minimisation of the thermal load of the ablation in high-speed laser corneal refractive surgery is possible. To do this, thermal load from ablations onto flat PMMA plates was recorded with an infrared thermal camera and analysed for different flying-spot sorting algorithms (from pure randomised to 36 Hz local frequency) using a 500 Hz laser system with a fluence of 500 mJ/cm2, and aspheric ablation profiles. Each ablation configuration was repeated three times. Thermal load valid for corneal ablations was modelled based upon the results from ablations onto flat PMMA plates. It was found that the thermal load of ablations onto flat PMMA plates declines steadily when the allowed local frequency decreases or when the diameter of the blocked area increases. With this laser system, a local frequency of 39 Hz dynamically controlled over a diameter of 3.865 mm seems to be optimal for avoiding corneal collagen denaturation with minimum compromise on treatme...
TL;DR: In this article, a method for the design of a refractive optical surface intended for the generation of a prescribed irradiance distribution is proposed, which is based on the gradient optimization of the refractive surface represented as a bicubic spline in spherical coordinates.
Abstract: A method is suggested for the design of a refractive optical surface intended for the generation of a prescribed irradiance distribution. The method is based on the gradient optimization of the refractive surface represented as a bicubic spline in spherical coordinates. The optical elements that produce the uniform irradiance distribution in the elliptic and rectangular regions for point and extended light sources are computed. The energy efficiency of the optical elements is more than 73%; the nonuniformity of the generated irradiance distribution is less than 7.5%. The ratio of the illuminated region size to the thickness of the optical system is about 6.5. This value is twice as large as that for optical elements presented in other available publications.
TL;DR: In this paper, a comprehensive derivation for the equation of geodesics in curved optical spaces is provided, and the resolution of the image of a line source radiating in the Maxwell fisheye and the Veselago-Pendry slab lens is analyzed.
Abstract: This paper reviews some properties of lenses in curved and folded optical spaces. The point of the paper is to show some limitations of geometrical optics in the analysis of subwavelength focusing. We first provide a comprehensive derivation for the equation of geodesics in curved optical spaces, which is a tool of choice to design metamaterials in transformation optics. We then analyse the resolution of the image of a line source radiating in the Maxwell fisheye and the Veselago–Pendry slab lens. The former optical medium is deduced from the stereographic projection of a virtual sphere and displays a heterogeneous refractive index n(r) which is proportional to the inverse of 1 + r 2. The latter is described by a homogeneous, but negative, refractive index. It has been suggested that the fisheye makes a perfect lens without negative refraction [Leonhardt, Philbin arxiv:0805.4778v2]. However, we point out that the definition of super-resolution in such a heterogeneous medium should be computed with respect...
TL;DR: In this paper, an organic material, namely 4-[(E)-(2-phenylhydrazinylidene)methyl]tetrazolo[1,5-a]quinoline abbreviated as TeQu, with different donor substituents was synthesized.
Abstract: An organic material, namely 4-[(E)-(2-phenylhydrazinylidene)methyl]tetrazolo[1,5-a]quinoline abbreviated as TeQu, with different donor substituents were synthesized. The TeQu-doped poly methylmethacrylate (PMMA) thin films were prepared with a doping concentration of 0.5% by weight. The third-order nonlinear optical properties of the composite films were investigated using the single-beam Z-scan technique with 7 ns laser pulses at 532 nm wavelengths. The Z-scan studies reveal that the compounds exhibit a self-defocusing effect at 532 nm. The nonlinear optical susceptibility, χ(3) and nonlinear refractive index, n 2 of the TeQu/PMMA composite films are of the order of and respectively. The compounds exhibit good optical limiting properties at the wavelength used.
TL;DR: In this article, the authors studied the nonclassicality of photon-added squeezed vacuum (PASV) and its decoherence in thermal environment in terms of the sub-Poissonian statistics and the negativity of the Wigner function.
Abstract: We studied the nonclassicality of photon-added squeezed vacuum (PASV) and its decoherence in thermal environment in terms of the sub-Poissonian statistics and the negativity of the Wigner function (WF). By converting the PASV to a squeezed Hermite polynomial excitation state, we derive a compact expression for the normalization factor of m-PASV, which is an m-order Legendre polynomial of squeezing parameter r. We also derive the explicit expression of WF of m-PASV and find the negative region of WF in phase space. We show that there is an upper bound value of r for this state to exhibit sub-Poissonian statistics increasing as m increases. Then we derive the explicit analytical expression of time evolution of WF of m-PASV in the thermal channel and discuss the loss of nonclassicality using the negativity of WF. The threshold value of decay time is presented for the single PASV.
TL;DR: In this paper, optical diffraction tomography is considered as a non-linear inverse scattering problem and tackled within the Bayesian estimation framework and preliminary results, obtained by applying the inversion algorithm to laboratory controlled data, are presented.
Abstract: In this paper, optical diffraction tomography is considered as a non-linear inverse scattering problem and tackled within the Bayesian estimation framework. The object under test is a man-made object known to be composed of compact regions made of a finite number of different homogeneous materials. This a priori knowledge is appropriately translated by a Gauss–Markov–Potts prior. Hence, a Gauss–Markov random field is used to model the contrast distribution whereas a hidden Potts–Markov field accounts for the compactness of the regions. First, we express the a posteriori distributions of all the unknowns and then a Gibbs sampling algorithm is used to generate samples and estimate the posterior mean of the unknowns. Some preliminary results, obtained by applying the inversion algorithm to laboratory controlled data, are presented.
TL;DR: In this article, a tapered fiber is fabricated by heating and stretching a piece of optical fiber after the polymer protective cladding has been removed, and applied in a ring erbium-doped fiber laser (EDFL) to generate dual-wavelength lasing oscillations.
Abstract: A tapered fiber is fabricated by heating and stretching a piece of optical fiber after the polymer protective cladding has been removed. An equidistant comb-like transmission spectrum, with a spacing of 1.6 nm and an extinction ratio of more than 5 dB, was obtained by the tapered fiber due to the multibeam interferences of the cladding modes. The tapered fiber was applied in a ring erbium-doped fiber laser (EDFL) to generate dual-wavelength lasing oscillations. The EDFL operates at wavelengths of 1557.0 nm and 1558.6 nm with a stable peak power and a signal-to-noise ratio of more than 40 dB.
TL;DR: In this paper, the authors presented infrared imaging and thermomechanical behavior of stress-induced martensite transformation occurring in shape memory alloys and compared the obtained stress-strain curves and the elaborated temperature characteristics.
Abstract: Infrared imaging and thermomechanical behavior of stress-induced martensite transformation occurring in shape memory alloys is presented. TiNi shape memory alloy specimens have been subjected to a modified program of a stress-controlled tension test, i.e. at various stages of the martensite transformation the loading was kept constant for 3 min. After that the specimen was reloaded to the martensite transformation limit, followed by unloading, when the reverse transformation occurred. During the loading and unloading processes the specimen mechanical parameters and the infrared radiation from the specimen surface were continuously recorded. By comparison of the obtained stress–strain curves and the elaborated temperature characteristics, the current state and the progress of the martensite transformation developing in the shape memory alloy under these conditions has been studied.
TL;DR: In this article, the authors analyzed the effect of atmospheric effects on the performance of free space optical (FSO) communication links and showed that for multiple detectors with the same surface area as a single detector there is a critical link range less than which the SNR decreases for larger values of M.
Abstract: In free space optical (FSO) communication links, atmospheric effects including absorption, scattering and turbulence have significant impacts on the quality of the laser beam propagating through the free space channel. Absorption and/or scattering due to the atmospheric particles result in optical losses, whereas turbulence contributes to the intensity scintillation which can severely impair the operation of FSO links. In this paper, using a modified model we analyze the atmospheric effects on the signal-to-noise ratio (SNR) and the bit error rate (BER) performance of an FSO system. We show that for multiple detectors with the same surface area as a single detector there is a critical link range less than which the SNR decreases for larger values of M.