Terms Of Optics Research Articles

Ultrabroadband high-resolution silicon RF-photonic beamformer

Microwave photonics aims to overcome the limitations of radiofrequency devices and systems by leveraging the unique properties of optics in terms of low loss and power consumption, broadband operation, immunity to interference and tunability. This enables versatile functions like beam steering, crucial in emerging applications such as the Internet of Things (IoT) and 5/6G networks. The main problem with current photonic beamforming architectures is that there is a tradeoff between resolution and bandwidth, which has not yet been solved. Here we propose and experimentally demonstrate a novel switched optical delay line beamformer architecture that is capable of achieving the desired maximum resolution (i.e., 2M pointing angles for M-bit coding) and provides broadband operation simultaneously. The concept is demonstrated by means of a compact (8 × 3 mm2) 8 (5-bit) delay line Silicon Photonic chip implementation capable of addressing 32 pointing angles and offering 20 GHz bandwidth operation.

Unveiling Impact of Electron Beam Optics on Weld Attributes in EN30B Steel

The influence of electron optics in terms of beam oscillation (BO) has been studied on weld quality of several steels and reported to develop cosmetic weld with smooth surface and enhanced weld properties. However, effect of electron beam oscillation on the weld quality of medium carbon low alloy steel, especially EN30B, have not reported well and investigated in this study. By manipulating magnetic lens in-line with electron beam, the diameter of oscillating beam (OD) and its effect on weld quality has been studied. The OD was changed between 0.5 mm and 2 mm. Numerous tests, including XRD, SEM, EBSD, hardness, wear, and tensile, were used to characterize the weld quality. Welds with BO significantly lowered the heat input rate than welds without oscillation. In presence of beam oscillation, retained austenite (RA) in the weld increased and it became least in welds made without BO. Tensile residual stress was found in the fusion zone (FZ) and it was higher with beam oscillation, especially with higher OD. In contrast to columnar grains predominantly found in welds made without BO, significant equiaxed grains were identified in welds made with BO. Nonmetallic inclusions (NMIs) in the weld became finer and less by use of BO. Introducing BO enhanced the hardness and reduced wear rate of weld, particularly at greater beam OD. Although Weld strength was diminished in comparison to the base metal (BM), beam oscillation increased the weld's ductility and strength.

Neuromorphic Computing Based on Wavelength-Division Multiplexing

Optical neural networks (ONNs), or optical neuromorphic hardware accelerators, have the potential to dramatically enhance the computing power and energy efficiency of mainstream electronic processors, due to their ultra-large bandwidths of up to 10’s of terahertz together with their analog architecture that avoids the need for reading and writing data back-and-forth. Different multiplexing techniques have been employed to demonstrate ONNs, amongst which wavelength-division multiplexing (WDM) techniques make sufficient use of the unique advantages of optics in terms of broad bandwidths. Here, we review recent advances in WDM-based ONNs, focusing on methods that use integrated microcombs to implement ONNs. We present results for human image processing using an optical convolution accelerator operating at 11 Tera operations per second. The open challenges and limitations of ONNs that need to be addressed for future applications are also discussed.

Comparison of light capturing approaches in Laser-Induced Breakdown Spectroscopy (LIBS) for multichannel spectrometers

LIBS technique requires the spectroscopic analysis of the light emitted by a laser-induced plasma plume. One challenge of the different approaches to capture the plasma light emission is the significant shot-to-shot variations of the plume inhomogeneities, position, and morphology. This is even more challenging when multichannel CCD spectrometers are used, because the light should be homogeneously divided among multiple capturing optical fibers (typically up to 8 fibers) with stable spectral efficiency for all channels. Otherwise, any further analysis of the atomic emission spectra involving multiple channels, such as line intensity ratios, Boltzmann plots, or calibration-free LIBS, could be compromised by the morphology-dependent spectral artifacts induced by the collection optics. In this work, we assess the performance of several collection optics in terms of overall capturing efficiency and channel-to-channel variations due to changes in plasma morphology. Results clearly show that this could be an issue even with the approaches with the best spatial homogenization, including optical fibers and Köhler optics.

An Engineer's Brief Introduction to Microwave Quantum Optics and a Single-Port State-Space Representation

Classical microwave circuit theory is incapable of representing some phenomena at the quantum level. To include quantum statistical effects, various theoretical treatments can be employed. Quantum input-output network (QION) theory is one such treatment. Another formalism, called SLH theory, incorporates scattering matrices ( S ), coupling vectors ( L ), and system Hamiltonians ( H ). These theoretical treatments require a reformulation of classical microwave theory. To make these topics comprehensible to an electrical engineer, we demonstrate some underpinnings of microwave quantum optics in terms of microwave engineering. For instance, we equate traveling-wave phasors in a transmission line ( $V_0^+$ ) directly to bosonic field operators. Furthermore, we extend QION to include a state-space representation and a transfer function for a single port quantum network. This serves as a case study to highlight how microwave methodologies can be applied in open quantum systems. Although the same conclusion could be found from a full SLH theory treatment, our method was derived directly from first principles of QION.

Manufacturing Signatures of Injection Molding and Injection Compression Molding for Micro-Structured Polymer Fresnel Lens Production.

Injection compression molding (ICM) provides enhanced optical performances of molded polymer optics in terms of birefringence and transmission of light compared to Injection molding (IM). Nevertheless, ICM requires case-dedicated process optimization to ensure that the required high accuracy geometrical replication is achieved, particularly especially in the case of surface micro-features. In this study, two factorial designs of experiments (DOE) were carried out to investigate the replication capability of IM and ICM on a micro structured Fresnel lens. A laser scanning confocal microscope was employed for the quality control of the optical components. Thus, a detailed uncertainty budget was established for the dimensional measurements of the replicated Fresnel lenses, considering specifically peak-to-valley (PV) step height and the pitch of the grooves. Additional monitoring of injection pressure allowed for the definition of a manufacturing signature, namely, the process fingerprint for the evaluation of the replication fidelity under different process conditions. Moreover, considerations on the warpage of parts were related to a manufacturing signature of the molding processes. At last, the global part mass average and standard deviation were measured to correlate local geometrical replication performances with global part quality trends.

Workbench in the Teaching of Optics to Junior High School

Over the last 20 years, not much research has been carried out on improving teaching and learning process of Optics. The new technology in Optics teaching has a lot of advantages, which is impossible to be offered by any book. The study determined the status of textbooks in Physics of Optics in terms of availability, relevance of content, scope of subject-matter, and suitability; the degree of need for workbench in Optics; the validity of the proposed developed workbench in Optics as rated by Physics experts in terms of introduction, learning competencies, presentation of concepts, and exercises. The descriptive-developmental research design was used in the development of the workbench patterned from the ADDIE model. The content of the workbench was based on the competencies present in the K-12 science curriculum guide. The validity of the developed workbench was determined with the use of questionnaires. Results revealed that there is a limited number of textbooks for the subject Physics of Optics and there is an urgent need for a workbench in Optics. The content of the developed workbench is highly valid in terms of introduction, objectives, presentation of concepts and exercises. The developed workbench is strongly acceptable as instructional materials for students of Optics.

Experimental validation of the Achromatic Telescopic Squeezing (ATS) scheme at the LHC

The Achromatic Telescopic Squeezing scheme offers new techniques to deliver unprecedentedly small beam spot size at the interaction points of the ATLAS and CMS experiments of the LHC, while perfectly controlling the chromatic properties of the corresponding optics (linear and non-linear chromaticities, off-momentum beta-beating, spurious dispersion induced by the crossing bumps). The first series of beam tests with ATS optics were achieved during the LHC Run I (2011/2012) for a first validation of the basics of the scheme at small intensity. In 2016, a new generation of more performing ATS optics was developed and more extensively tested in the machine, still with probe beams for optics measurement and correction at β* = 10 cm, but also with a few nominal bunches to establish first collisions at nominal β* (40 cm) and beyond (33 cm), and to analysis the robustness of these optics in terms of collimation and machine protection. The paper will highlight the most relevant and conclusive results which were obtained during this second series of ATS tests.

Constitutive relations in classical optics in terms of geometric algebra

To have a closed system, the Maxwell electromagnetic equations should be supplemented by constitutive relations which describe medium properties and connect primary fields (E, B) with secondary ones (D, H). J.W. Gibbs and O. Heaviside introduced the basis vectors {i, j, k} to represent the fields and constitutive relations in the three-dimensional vectorial space. In this paper the constitutive relations are presented in a form of Cl3,0 algebra which describes the vector space by three basis vectors {σ1, σ2, σ3} that satisfy Pauli commutation relations. It is shown that the classification of electromagnetic wave propagation phenomena with the help of constitutive relations in this case comes from the structure of Cl3,0 itself. Concrete expressions for classical constitutive relations are presented including electromagnetic wave propagation in a moving dielectric.

Reflectivity of the Outer Retina on Spectral-Domain Optical Coherence Tomography as a Predictor of Photoreceptor Cone Density

To investigate the relationship between outer retinal reflectivity on spectral-domain optical coherence tomography and cone density in the corresponding area. Prospective cross-sectional observational study. In this institutional-based study, 20 eyes of 10 patients presenting maculopathies with various degrees of impairment of the photoreceptor layer (central serous chorioretinopathy, chronic central serous chorioretinopathy, maculopathy associated with hydroxychloroquine, and healthy eyes) were studied. Selection criteria were intended to ensure good image quality. Inner segment ellipsoid band reflectivity, global retinal reflectivity, and relative inner segment ellipsoid reflectivity (defined as the ratio of inner segment ellipsoid band reflectivity on overall retinal reflectivity) were measured on a longitudinal reflectance profile extracted from the spectral-domain optical coherence tomography B-scan. The cone metrics were measured in the same region of interest, located in the perifoveal area, using an adaptive optics retinal camera. Inner segment ellipsoid and relative ellipsoid reflectivity were closely correlated with cone density (Pearson r: 0.72 and 0.70, respectively, P < .01). Outer retinal reflectivity on the transversal optical coherence tomography scan can be correlated to adaptive optics in terms of photoreceptor density. This quantitative approach using optical coherence tomography images could have important implications in the management of maculopathies.

Constitutive relations in optics in terms of geometric algebra

To analyze the electromagnetic wave propagation in a medium the Maxwell equations should be supplemented by constitutive relations. At present the classification of linear constitutive relations is well established in tensorial-matrix and exterior p-form calculus. Here the constitutive relations are found in the context of Clifford geometric algebra. For this purpose Cl1,3 algebra that conforms with relativistic 4D Minkowskian spacetime is used. It is shown that the classification of linear optical phenomena with the help of constitutive relations in this case comes from the structure of Cl1,3 algebra itself. Concrete expressions for constitutive relations which follow from this algebra are presented. They can be applied in calculating the propagation properties of electromagnetic waves in any anisotropic, linear and nondissipative medium.

Competitiveness of stationary planar low concentration photovoltaic modules using silicon cells: A focus on concentrating optics

The economical competitiveness of stationary Low Concentration Photovoltaic (LCPV) modules is evaluated, starting from detailed expressions of the Levelized Cost of Energy (LCoE). For trackless LCPV to be competitive with standard modules, the key approach is to maximize the performance of concentrating optics in terms of yearly averaged effective optical power ratio. To express this a novel parameter named Pro,eff is introduced and its contribution to the expression of LCoE for LCPV modules is discussed. By comparing the LCoEs of standard and LCPV modules, threshold conditions for Pro,eff and for the relative unitary cost of concentrating optics Cr are found, in dependence on the geometrical concentration gain G and as a function of other sensitive design parameters.Aiming at the maximization of Pro,eff, the novel design of a modified prism-coupled compound parabolic stationary concentrator is introduced, as a trackless LCPV solution compatible with standard flat panel size, weight and installation infrastructures. It provides geometrical concentration gain G=5, an acceptance angle of 24° and Pro,eff=81%, using a reflective primary concentrator and high refractive index dielectric for the secondary optics. A first experimental validation of the approach is given by a proof-of-concept prototype, implemented in commercially available polymethylmethacrylate, suitable for quasi-stationary installations requiring seasonal adjustment.

Quantum noise, scaling, and domain formation in a spinor Bose-Einstein condensate

In this paper we discuss Bose-Einstein spinor condensates for $F=1$ atoms in the context of $^{87}\text{R}\text{b}$, as studied experimentally by the Stamper-Kurn group [L. E. Sadler et al., Nature (London) 443, 312 (2006)]. The dynamical quantum fluctuations of a sample that starts as a condensate of $N$ atoms in a pure $F=1$, ${m}_{F}=0$ state are described in analogy to the two-mode squeezing of quantum optics in terms of an $\mathfrak{s}\mathfrak{u}(1,1)$ algebra. In this system the initial ${m}_{F}=0$ condensate acts as a source (pump) for the creation pairs of ${m}_{F}=1,\ensuremath{-}1$ atoms. We show that even though the system as a whole is described by a pure state with zero entropy, the reduced density matrix for the ${m}_{F}=+1$ degree of freedom, obtained by tracing out the ${m}_{F}=\ensuremath{-}1,0$ degrees of freedom, corresponds to a thermal state. Furthermore, these quantum fluctuations of the initial dynamics of the system provide the seeds for the formation of domains of ferromagnetically aligned spins.

Quantization of contact manifolds and thermodynamics

The physical variables of classical thermodynamics occur in conjugate pairs such as pressure/volume, entropy/temperature, chemical potential/particle number. Nevertheless, and unlike in classical mechanics, there are an odd number of such thermodynamic co-ordinates. We review the formulation of thermodynamics and geometrical optics in terms of contact geometry. The Lagrange bracket provides a generalization of canonical commutation relations. Then we explore the quantization of this algebra by analogy to the quantization of mechanics. The quantum contact algebra is associative, but the constant functions are not represented by multiples of the identity: a reflection of the classical fact that Lagrange brackets satisfy the Jacobi identity but not the Leibnitz identity for derivations. We verify that this ‘quantization’ describes correctly the passage from geometrical to wave optics as well. As an example, we work out the quantum contact geometry of odd-dimensional spheres.

Fermionic Linear Optics Revisited

We provide an alternative view of the efficient classical simulatibility of fermionic linear optics in terms of Slater determinants. We investigate the generic effects of two-mode measurements on the Slater number of fermionic states. We argue that most such measurements are not capable (in conjunction with fermion linear optics) of an efficient exact implementation of universal quantum computation. Our arguments do not apply to the two-mode parity measurement, for which exact quantum computation becomes possible, see quant-ph/0401066.

Beam optics applications: quantumlike versus classical-like domains

A review of the charged-particle beam optics in terms of recently developed approaches within both classical-like and quantumlike frameworks is presented. On the basis of the mutual connection of optics and mechanics, a brief overview of the quantumlike approach to electron optics is presented. In particular, the main results of the optical applications of the thermal wave model in phase space are given within the Wigner-Weyl picture. Furthermore, the tomographic approach in both classical-like and quantumlike domains in terms of the marginal-probability distribution is also presented. In particular, possible applications of the tomographic approach to optical problems with aberrations for accelerators are put forward. Some aspects of using quantumlike systems in quantum computing projects are discussed.

Charged-particle-beam propagator in wave-electron optics: phase-space and tomographic pictures.

Within the framework of the thermal-wave model, the quantumlike description of electron optics in terms of the propagator is given. First we briefly review the standard description in configuration space by analogy to quantum mechanics and in connection with recent investigations of charged-particle-beam transport that have used the concept of propagator. Then new insights are given by extension of the analysis of the particle-beam propagator to the phase-space context for which our system is described by the Wigner quasi-distribution function, as well as to the tomography context for which our system is described by the marginal distribution. Furthermore, the integrals of motion of a charged-particle beam and their relation to the propagator concept are discussed. Finally, the perturbation theory for a charged-particle-beam propagator is developed in the above-described two contexts and is applied to some simple optical devices.

Application of the generalized curvilinear variable axis lens to electron projection

The concept of the curvilinear variable axis lens (CVAL) has been introduced for the optics of projection reduction exposure with variable axis immersion lenses, an approach to electron projection lithography reported elsewhere. In the proof-of-concept system the special case of a planar CVAL following the fundamental imaging ray of the lens system was implemented and next generation lithography-commensurate performance was demonstrated. The present work addresses the question of whether general types of CVAL with different configurations of the optical elements are practical and acceptable in performance. Specifically, an analysis is presented of the performance trends of such optics in terms of blur and distortion depending on configuration, number and position of the optical elements in the system, as well as their relative drive requirements.

Performance of the advanced photon source 1-BM beamline optics

Bending magnet beamlines at third-generation synchrotron sources combined with well-designed optics offer unique capabilities for providing high x-ray fluxes into relatively small focal spots. This article provides a description of the x-ray optics used in the Advanced Photon Source 1-BM beamline. The performance of these optics in terms of the delivered flux ( 9×1011 ph/s/100 mA at 10 keV), energy resolution [ΔE/E≈1.5×10−4 with Si(111)], and focusing properties (spot size ≈0.25×0.60 mm) is compared with that expected from ideally reflecting and shaped optics.

Image Simulation of Extreme Ultraviolet Lithography Optics: Effect of Multilayer Coatings

Multilayer deposition technology is indispensable to the production of extreme ultraviolet (EUV) optics. However, the criteria of the multilayer d-spacing control techniques that are needed from the viewpoint of ULSI lithography has not yet been made clear. We have numerically evaluated EUV lithography optics in terms of the imaging performance and pattern placement accuracy. The tolerance of d-spacing distribution error for a two-mirror imaging optics was derived from a simulation method that takes multilayer reflectance and phase shift into consideration. Also, an image-contrast enhancement technique based on the d-spacing distribution is proposed for a three-mirror imaging optics.