Showing papers in "Advances in Optics and Photonics in 2017"
TL;DR: In this article, the history, guiding mechanism, recent advances, applications, and future prospects for hollow-core negative curvature fibers are described, and the future prospects of these fibers are discussed.
Abstract: We describe the history, guiding mechanism, recent advances, applications, and future prospects for hollow-core negative curvature fibers. We first review one-dimensional slab waveguides, two-dimensional annular core fibers, and negative curvature tube lattice fibers to illustrate the inhibited coupling guiding mechanism. Antiresonance in the glass at the core boundary and a wavenumber mismatch between the core and cladding modes inhibit coupling between the modes and have led to remarkably low loss in negative curvature fibers. We also summarize recent advances in negative curvature fibers that improve the performance of the fibers, including negative curvature that increases confinement, gaps between tubes that increase confinement and bandwidth, additional tubes that decrease mode coupling, tube structures that suppress higher-order modes, nested tubes that increase guidance, and tube parameters that decrease bend loss. Recent applications of negative curvature fibers are also presented, including mid-infrared fiber lasers, micromachining, and surgical procedures. At the end, we discuss the future prospects for negative curvature fibers.
217 citations
TL;DR: Raman spectroscopy is an increasingly popular technique in many areas including biology and medicine as discussed by the authors, which is based on Raman scattering, a phenomenon in which incident photons lose or gain energy via interactions with vibrating molecules in a sample.
Abstract: Raman spectroscopy is an increasingly popular technique in many areas including biology and medicine. It is based on Raman scattering, a phenomenon in which incident photons lose or gain energy via interactions with vibrating molecules in a sample. These energy shifts can be used to obtain information regarding molecular composition of the sample with very high accuracy. Applications of Raman spectroscopy in the life sciences have included quantification of biomolecules, hyperspectral molecular imaging of cells and tissue, medical diagnosis, and others. This review briefly presents the physical origin of Raman scattering explaining the key classical and quantum mechanical concepts. Variations of the Raman effect will also be considered, including resonance, coherent, and enhanced Raman scattering. We discuss the molecular origins of prominent bands often found in the Raman spectra of biological samples. Finally, we examine several variations of Raman spectroscopy techniques in practice, looking at their applications, strengths, and challenges. This review is intended to be a starting resource for scientists new to Raman spectroscopy, providing theoretical background and practical examples as the foundation for further study and exploration.
188 citations
TL;DR: High-and ultra-high-Q whispering-gallery mode resonators have the capability to trap photons by total internal reflection for a duration ranging from nanoseconds to milliseconds as mentioned in this paper.
Abstract: High- and ultrahigh-Q whispering-gallery mode resonators have the capability to trap photons by total internal reflection for a duration ranging from nanoseconds to milliseconds. These exceptionally long photon lifetimes enhance the light–matter interactions at all scales, namely at the electronic, molecular, and lattice levels. As a consequence, nonlinear photon scattering can be triggered with very low threshold powers, down to a few microwatts. The possibility to efficiently harness photon–photon interactions with a system optimizing size, weight, power, and cost constraints has created a new, quickly thriving research area in photonics science and technology. This topic is inherently cross-disciplinary, as it stands at the intersection of nonlinear and quantum optics, crystallography, optoelectronics, and microwave photonics. From a fundamental perspective, high-Q whispering-gallery mode resonators have emerged as an ideal platform to investigate light–matter interactions in nonlinear bulk materials. From an applied viewpoint, technological applications include time-metrology, aerospace engineering, coherent optical fiber communications, or nonclassical light generation, among others. The aim of this paper is to provide an overview of the most recent advances in this area, which is increasingly gaining importance in contemporary photonics.
183 citations
TL;DR: How predictions were made from the outset of research in laser based optical communications and how they have evolved to their present form, accurately predicting the performance of coherently detected communication systems are described.
Abstract: In this paper, we review the historical evolution of predictions of the performance of optical communication systems. We will describe how such predictions were made from the outset of research in laser based optical communications and how they have evolved to their present form, accurately predicting the performance of coherently detected communication systems.
149 citations
TL;DR: The plasmonic sensing principles of photonic crystal fibers (PCFs) have been discussed in this article, and fabrication considerations, as well as limitations due to the structural features of PCFs, are discussed.
Abstract: Flexibility in engineering holey structures and controlling the wave guiding properties in photonic crystal fibers (PCFs) has enabled a wide variety of PCF-based plasmonic structures and devices with attractive application potential. Metal thin films, nanowires, and nanoparticles are embedded for achieving surface plasmon resonance (SPR) or localized SPR within PCF structures. This paper begins with an outline of plasmonic sensing principles. This is followed by an overview of fabrication and experimental investigation of plasmonic PCFs. Reported plasmonic PCF designs are categorized based on their target application areas, including optical/biochemical sensors, polarization splitters, and couplers. Finally, design and fabrication considerations, as well as limitations due to the structural features of PCFs, are discussed.
130 citations
TL;DR: This review provides an up-to-date literature review of the major developments and latest advances in spaser theory and carries out a systematic exposition of some of the key results useful to understand the operation of spasers.
Abstract: Spaser is an acronym for surface plasmon amplification by stimulated emission of radiation. A spaser is effectively a nanoscale laser with subwavelength dimensions and a low-Q plasmonic resonator, which sustains its oscillations using stimulated emission of surface plasmons. The concept of stimulated emission to sustain plasmonic oscillations in a resonator was first described by David Bergman and Mark Stockman in 2003. Using a unified notation, we provide an up-to-date literature review of the major developments and latest advances in spaser theory and carry out a systematic exposition of some of the key results useful to understand the operation of spasers. Our presentation covers both semiclassical and quantum-mechanical formulations of spaser models as well as various designs and technologies demonstrated/suggested to illustrate key aspects of this technology. Even though many advances have already been made in spaser technology, there are many hurdles that need to be overcome to bring this technology up to the level of modern laser technology. We take especially great care to highlight the main challenges facing various spaser designs and the limitations of widely used methods and materials. This review is written for both specialists in the field and a general engineering–physics–chemistry readership.
106 citations
TL;DR: In this paper, a nonlinearity management procedure for high-order optical nonlinearities (HON) in metal-dielectric nanocomposites is presented. But the authors focus on the properties of metal nanoparticles and demonstrate that these plasmonic composites are versatile platforms for high order nonlinear optical studies.
Abstract: Composites consisting of metal nanoparticles (NPs) embedded in dielectric media may present large nonlinear optical response due to electronic transitions in the NPs. When the metal NPs are suspended in liquids or embedded in solid substrates, the obtained composites may present high-order optical nonlinearities (HON) beyond the third-order nonlinearity, usually studied for most materials. Moreover, it is observed that the magnitude and phase of the effective high-order susceptibilities can be controlled by adjusting the light intensity, I, and the volume filling fraction, f, occupied by the NPs. Therefore, the sensitivity to the values of I and f allowed the development of a nonlinearity management procedure for investigation and control of various phenomena, such as self- and cross-phase modulation, spatial modulation instability, as well as bright and vortex solitons stabilization, in media presenting relevant third-, fifth-, and seventh-order susceptibilities. As a consequence, it is reviewed in this paper how the exploitation of HON in metal–dielectric nanocomposites may reveal new ways for optimization of all-optical switching devices, light-by-light guiding, as well as the control of solitons propagation for long distances. Also, theoretical proposals and experimental works by several authors are reviewed that may open the possibility to identify new high-order phenomena by applying the nonlinearity management procedure. Therefore, the paper is focused on the properties of metal nanocomposites and demonstrates that these plasmonic composites are versatile platforms for high-order nonlinear optical studies.
78 citations
TL;DR: In this article, the authors discuss the origin of plasmonic losses and various approaches to either minimize or mitigate them based on understanding of fundamental processes underlying surface plasm modes excitation and decay.
Abstract: Unlike conventional optics, plasmonics enables unrivaled concentration of optical energy well beyond the diffraction limit of light. However, a significant part of this energy is dissipated as heat. Plasmonic losses present a major hurdle in the development of plasmonic devices and circuits that can compete with other mature technologies. Until recently, they have largely kept the use of plasmonics to a few niche areas where loss is not a key factor, such as surface-enhanced Raman scattering and biochemical sensing. Here, we discuss the origin of plasmonic losses and various approaches to either minimize or mitigate them based on understanding of fundamental processes underlying surface plasmon modes excitation and decay. Along with the ongoing effort to find and synthesize better plasmonic materials, optical designs that modify the optical powerflow through plasmonic nanostructures can help in reducing both radiative damping and dissipative losses of surface plasmons. Another strategy relies on the development of hybrid photonic–plasmonic devices by coupling plasmonic nanostructures to resonant optical elements. Hybrid integration not only helps to reduce dissipative losses and radiative damping of surface plasmons, but also makes possible passive radiative cooling of nanodevices. Finally, we review emerging applications of thermoplasmonics that leverage Ohmic losses to achieve new enhanced functionalities. The most successful commercialized example of a loss-enabled novel application of plasmonics is heat-assisted magnetic recording. Other promising technological directions include thermal emission manipulation, cancer therapy, nanofabrication, nanomanipulation, plasmon-enabled material spectroscopy and thermo-catalysis, solar water treatment, and thermophotovoltaics.
76 citations
TL;DR: The stimulated-Raman adiabatic passage (STIRAP) is one of many well-established techniques for quantum state manipulation, which finds widespread application in chemistry, physics, and information processing as discussed by the authors.
Abstract: The procedure of stimulated-Raman adiabatic passage (STIRAP), one of many well-established techniques for quantum-state manipulation, finds widespread application in chemistry, physics, and information processing. Numerous reviews discuss these applications, the history of its development, and some of the underlying physics. This tutorial supplies material useful as background for the STIRAP reviews as well as related techniques for adiabatic manipulation of quantum structures, with emphasis on the theory and simulation rather than on experimental results. It particularly emphasizes the picturing of behavior in various abstract vector spaces, wherein torque equations offer intuition about adiabatic changes. Appendices provide brief explanations of related coherent-excitation topics and useful evaluations of relative strengths of coherent transitions—the Rabi frequencies—involving Zeeman sublevels.
57 citations
TL;DR: This tutorial paper reviews typical face recognition algorithms with implications for the design of CFs, and discusses and compares the numerical and optical implementations of correlators.
Abstract: In recent years, correlation-filter (CF)-based face recognition algorithms have attracted increasing interest in the field of pattern recognition and have achieved impressive results in discrimination, efficiency, location accuracy, and robustness. In this tutorial paper, our goal is to help the reader get a broad overview of CFs in three respects: design, implementation, and application. We review typical face recognition algorithms with implications for the design of CFs. We discuss and compare the numerical and optical implementations of correlators. Some newly proposed implementation schemes and application examples are also presented to verify the feasibility and effectiveness of CFs as a powerful recognition tool.
51 citations
TL;DR: In this paper, a Kramers-Kronig receiver with a photodiode and an analog-to-digital converter is presented, where the received signal comprises a continuous wave (CW) signal and a modulated signal.
Abstract: A Kramers-Kronig receiver that may include a reception path; wherein the reception path may include a photodiode that is configured to receive a received signal and output a photocurrent that represents the received signal; wherein the received signal comprises a continuous wave (CW) signal and a modulated signal; wherein a frequency gap between the CW signal and the modulated signal is smaller than a bandwidth of the modulated signal; an analog to digital converter that is configured to generate a digital representation of the photocurrent; and a digital processor that is configured to process the digital representation of the photocurrent to provide a reconstructed modulated signal, wherein the processing is based on a Kramers-Kronig relationship related to the received signal.
TL;DR: A review of the state of the art in the field of stimulated Raman scattering in nanostructures can be found in this article, where the authors identify the emerging trends and remaining challenges.
Abstract: Stimulated Raman scattering is essentially a “light amplification,” and some of the most important applications are light amplifiers and laser sources. Important achievements have been obtained in the fields of fiber amplification and integrated photonics. However, photonics components, currently used in optical interconnects, are relatively large and not ideally suited to on-chip integration. A reduction in the size of integrated optical devices, while maintaining a high level of performance, is a key challenge in photonics. On this line of argument, the ability to construct nano-objects is expected to have a significant impact in the future, leading to the development of fully functional nanodevices, such as nanoscale optical sources. The aim of this work is to review accomplishments in the field of stimulated Raman scattering in nanostructures, to delineate the state of the art, and to identify the emerging trends and remaining challenges.
TL;DR: In this article, the resonance conditions of periodic indentations in metallic layers and evaluate their potential for surface sensing of analytes are reviewed and a review of significant contributions of nanohole arrays for sensing is presented in a first section.
Abstract: In this paper we review the resonance conditions of periodic indentations in metallic layers and evaluate their potential for surface sensing of analytes. A review of significant contributions of nanohole arrays for sensing is presented in a first section. It is then followed by a theoretical analysis of their optical properties using coupled mode theory and an evaluation of their potential for sensing. The sensitivity, resolution, and field distribution are presented as a function of the different parameters of the metal film (periodicity, hole size, and thickness) to determine the optimal design for sensing. The focus of this paper is made on 1-D nanoslit arrays and 2-D square nanohole arrays to identify general considerations regarding sensing experiments using these types of structure. We include a MATLAB user interface, also available as a standalone application, that plots the transmission and reflection spectrum as well as the field distribution of nanohole arrays.
TL;DR: This paper reviews recent research on optical validation of messages, ID tags, and codes using nanostructures, thin films, and 3D optical codes and analyzes several case scenarios where optically encoded devices have to be authenticated.
Abstract: Authentication of encoded information is a popular current trend in optical security. Recent research has proposed the production of secure unclonable ID tags and devices with the use of nanoscale encoding and thin-film deposition fabrication techniques, which are nearly impossible to counterfeit but can be verified using optics and photonics instruments. Present procedures in optical encryption provide secure access to the information, and these techniques are improving daily. Nevertheless, a rightful recipient with access to the decryption key may not be able to validate the authenticity of the message. In other words, there is no simple way to check whether the information has been counterfeited. Metallic nanoparticles may be used in the fabrication process because they provide distinctive polarimetric signatures that can be used for validation. The data is encoded in the optical domain, which can be verified using physical properties with speckle analysis or ellipsometry. Signals obtained from fake and genuine samples are complex and can be difficult to distinguish. For this reason, machine-learning classification algorithms are required in order to determine the authenticity of the encoded data and verify the security of unclonable nanoparticle encoded or thin-film-based ID tags. In this paper, we review recent research on optical validation of messages, ID tags, and codes using nanostructures, thin films, and 3D optical codes. We analyze several case scenarios where optically encoded devices have to be authenticated. Validation requires the combined use of a variety of multi-disciplinary approaches in optical and statistical techniques, and for this reason, the first five sections of this paper are organized as a tutorial.
TL;DR: In this paper, the main retracing schemes are analyzed and presented with the help of the Poincare sphere and the Jones matrices, and examples of full compensation of all the main cases of birefringence that occurs in practical optical circuits are given.
Abstract: Birefringence affects all the optical circuits both in free-space and guided-wave optics. It perturbs the state of polarization of the propagating light, causing unwanted detrimental effects in many practical situations. A retracing circuit offers the potentiality of compensating the birefringence, but it is not universal because the birefringence is of different kinds, that is, either linear or circular, as well as either reciprocal or nonreciprocal, and because the common mirror does not hold all the requested symmetries. This paper reviews the compensation techniques suitable for each kind of birefringence, taking into account the introduction of two further generalized mirrors, the mirrored Faraday rotator and the mirrored quarter-wave plate. The main retracing schemes are analyzed and presented with the help of the Poincare sphere and the Jones matrices. Examples of full compensation of all the main cases of birefringence that occurs in practical optical circuits are given. The different compensation properties of the three mirrors can be interpreted by means of a unified vision in the abstract space related to the Poincare sphere representation.
TL;DR: This article corrected a sentence in the second paragraph of p.528 [Adv. Opt.9.9, 504] and This article corrected it in the third paragraph of the article.
Abstract: This publisher’s note corrects a sentence in the second paragraph of p. 528 [Adv. Opt. Photon.9, 504 (2017)AOPAC71943-820610.1364/AOP.9.000504].