Hasil untuk "Optics. Light"

T. Brabec, F. Krausz

Haifeng Wang, Luping P. Shi, B. Luk’yanchuk et al.

R. Schnabel

Abstract According to quantum theory the energy exchange between physical systems is quantized. As a direct consequence, measurement sensitivities are fundamentally limited by quantization noise, or just ‘quantum noise’ in short. Furthermore, Heisenberg’s Uncertainty Principle demands measurement back-action for some observables of a system if they are measured repeatedly. In both respects, squeezed states are of high interest since they show a ‘squeezed’ uncertainty, which can be used to improve the sensitivity of measurement devices beyond the usual quantum noise limits including those impacted by quantum back-action noise. Squeezed states of light can be produced with nonlinear optics, and a large variety of proof-of-principle experiments were performed in past decades. As an actual application, squeezed light has now been used for several years to improve the measurement sensitivity of GEO  600 – a laser interferometer built for the detection of gravitational waves. Given this success, squeezed light is likely to significantly contribute to the new field of gravitational-wave astronomy. This Review revisits the concept of squeezed states and two-mode squeezed states of light, with a focus on experimental observations. The distinct properties of squeezed states displayed in quadrature phase-space as well as in the photon number representation are described. The role of the light’s quantum noise in laser interferometers is summarized and the actual application of squeezed states in these measurement devices is reviewed.

G. V. Pavan Kumar

C.V. Raman (1888-1970) was one of the pioneering scientists to have emerged from India during the colonial era. His scientific explorations were driven by his curiosity to understand wave phenomena. Naturally, optics and related physical effects were at the heart of such an exploration. Apart from his Nobel prize-winning discovery of the Raman effect, his research included topics such as oblique diffraction, light scattering from liquids and amorphous solids, classical and quantum nature of light, acousto-optics, haloes and coronae (speckles), crystal dynamics and soft modes, optics of minerals, floral colors, physiology of vision and many other aspects related to light in natural settings. In this article, I give a historical overview of some of the work by C.V. Raman and his group that had a direct connection to optics and optical spectroscopy.

S. Longhi

In the past decade, the concept of parity-time symmetry, originally introduced in non-Hermitian extensions of quantum mechanical theories, has come into thinking of photonics, providing a fertile ground for studying, observing, and utilizing some of the peculiar aspects of symmetry in optics. Together with related concepts of non-Hermitian physics of open quantum systems, such as non-Hermitian degeneracies (exceptional points) and spectral singularities, symmetry represents one among the most fruitful ideas introduced in optics in the past few years. Judicious tailoring of optical gain and loss in integrated photonic structures has emerged as a new paradigm in shaping the flow of light in unprecedented ways, with major applications encompassing laser science and technology, optical sensing, and optical material engineering. In this perspective, I review some of the main achievements and emerging areas of -symmetric and non-Hermtian photonics, and provide an outline of challenges and directions for future research in one of the fastest growing research area of photonics.

F. L. Pedrotti, L. Pedrotti, L. Pedrotti

D. Neshev, I. Aharonovich

Optical metasurfaces (OMs) have emerged as promising candidates to solve the bottleneck of bulky optical elements. OMs offer a fundamentally new method of light manipulation based on scattering from resonant nanostructures rather than conventional refraction and propagation, thus offering efficient phase, polarization, and emission control. This perspective highlights state of the art OMs and provides a roadmap for future applications, including active generation, manipulation and detection of light for quantum technologies, holography and sensing. Materials with ‘optical metasurfaces’ (OMs) have surface layers patterned at scales smaller than the wavelength of light, offering fundamentally new ways to manipulate light for many possible applications. Conventional optics generally relies on light being refracted as it passes through materials, or simply reflected from surfaces. Igor Aharonovich at the University of Technology Sydney, and Dragomir Neshev at the Australian National University, Canberra, review the current capabilities and likely future applications of OMs. The authors themselves investigate light capture, scattering and re-emission by OMs to control aspects of light including its phase, polarization and emission characteristics. They foresee new ways to control the properties of light serving to advance technologies including those that exploit the subtle quantum mechanical properties of light. Innovative optical sensors and holography systems are among the many potential uses of OMs.

Biwei Zhang, Martin J. Booth, Qi Hu

Adaptive optics (AO) are reconfigurable devices that compensate for wavefront distortions or aberrations in optical systems such as microscopes, telescopes and ophthalmoscopes. Aberrations have detrimental effects that can reduce imaging quality and compromise scientific information. Sensorless AO methods were introduced to correct aberrations without a separate wavefront sensor, inferring wavefront-related information directly from phase-diverse sample images. Most sensorless AO control systems, although effective and flexible to use, were operated based on empirical experience with suboptimal performance. In this paper, we introduced a Fisher information-based analysis framework to provide information-guided method optimization. Results suggested that our framework can effectively improve the accuracy and efficiency of different sensorless AO methods. The framework is not specific to any AO method or imaging modality and has the potential to benefit a wide range of applications.

V.V. Kotlyar, E.G. Abramochkin, A.A. Kovalev et al.

The optical vortices with the complex amplitude which is presented by the product of the Gaussian function and two Bessel functions with a complex root dependence of the arguments on the cylindrical coordinates and a constant parameter that determines the type of intensity distribution. These beams can be named Bessel-Bessel-Gaussian beams (BBG beams). An explicit expression for the complex amplitude of such beams at any distance from the waist is presented. We have demonstrated that BBG beams have an anomalously high rotation speed: the intensity rotates by almost 45 degrees at a distance much smaller than the Rayleigh length. It is shown that the parameter allow to control the topological charge of the BBG beam. The topological charge increases in jumps by an even number with an increase in the positive value of the parameter.

Wenhan Dong, Zeyu Wan, Yun-Cheng Yang et al.

A comparative study is presented on the dependence of optical and material properties of VCSELs on Ge and GaAs substrate thicknesses as well as epitaxy process conditions. It was found that adjusting the Ge substrate thickness and optimizing the epitaxy process can shift the stopband center and cavity resonance wavelength by several nanometers. Ge-based VCSELs exhibit improved epitaxial uniformity, smaller deviations from design specifications, reduced stoichiometry variations, and strain magnitudes comparable to those of GaAs-based counterparts. In the selected 46.92 μm² sample area, no defects were observed in the quantum well (QW) regions of Ge-based VCSELs, and the threading dislocation density (TDD) was measured to be below 2.13 × 10⁶ cm^−2. These results highlight the potential of Ge substrates as promising candidates for advanced VCSELs.

Zhikai Hu, Manna Gu, Ying Tian et al.

Abstract Metalens is the next generation of optical metasurfaces for compact imaging, sensing, and display applications that allow the phase, polarization, frequency, amplitude, angular momentum, etc. of the incident light to be designed with high degrees of freedom to meet the application requirements, which has attracted broad interest in the field of planar optics. One significant challenge in implementing applications for metalens is the efficient fabrication of large-scale nanostructures with high resolution, robustness and uniform patterning. In this review, we first introduced the manufacturing techniques compatible with metasurfaces fabrication in detail, including masked lithography, maskless lithography, and additive manufacturing, discussed the limitations and provided some insights. Next, we introduced the applications of metalens from the perspective of non-imaging and imaging optics fields. Metalens can enhance the illumination effect, shape beams, and improve the energy conversion efficiency in non-imaging optics. In imaging optics, the role of metalens in replacing traditional optical components in lithography, astronomical observation, microscopic and endoscopic systems is demonstrated. Finally, the challenges that the metalens facing on the road to commercial application are discussed, and the field’s future development is prospected.

Lihong Hong, Haiyao Yang, Jianzhi Zhang et al.

Raman spectroscopy offers a great power to detect, analyze and identify molecules, and monitor their temporal dynamics and evolution when combined with single-molecule surface-enhanced Raman scattering (SM-SERS) substrates. Here we present a SM-SERS scheme that involves simultaneously giant chemical enhancement from WS2 2D materials, giant electromagnetic enhancement from plasmonic nanogap hot spot, and inhibition of molecular fluorescence influence under near-infrared laser illumination. Remarkably we find Coulomb attraction between analyte and gold nanoparticle can trigger spontaneous formation of molecule-hotspot pairing with high precision, stability and robustness. The scheme has enabled realization of universal, robust, fast, and large-scale uniform SM-SERS detection for three Raman molecules of rhodamine B, rhodamine 6G, and crystal violet with a very low detection limit of 10−16 M and at a very fast spectrum acquisition time of 50 ms.

S. Mukamel, M. Freyberger, W. Schleich et al.

Conventional spectroscopy uses classical light to detect matter properties through the variation of its response with frequencies or time delays. Quantum light opens up new avenues for spectroscopy by utilizing parameters of the quantum state of light as novel control knobs and through the variation of photon statistics by coupling to matter. This Roadmap article focuses on using quantum light as a powerful sensing and spectroscopic tool to reveal novel information about complex molecules that is not accessible by classical light. It aims at bridging the quantum optics and spectroscopy communities which normally have opposite goals: manipulating complex light states with simple matter e.g. qubits versus studying complex molecules with simple classical light, respectively. Articles cover advances in the generation and manipulation of state-of-the-art quantum light sources along with applications to sensing, spectroscopy, imaging and interferometry.

M. Bello, G. Platero, J. Cirac et al.

Topological one-dimensional photons induce exotic and tunable quantum emitter dynamics and interactions. The discovery of topological materials has motivated recent developments to export topological concepts into photonics to make light behave in exotic ways. Here, we predict several unconventional quantum optical phenomena that occur when quantum emitters interact with a topological waveguide quantum electrodynamics bath, namely, the photonic analog of the Su-Schrieffer-Heeger model. When the emitters’ frequency lies within the topological bandgap, a chiral bound state emerges, which is located on just one side (right or left) of the emitter. In the presence of several emitters, this bound state mediates topological, tunable interactions between them, which can give rise to exotic many-body phases such as double Néel ordered states. Furthermore, when the emitters’ optical transition is resonant with the bands, we find unconventional scattering properties and different super/subradiant states depending on the band topology. Last, we propose several implementations where these phenomena can be observed with state-of-the-art technology.

W. T. Chen, A. Zhu, Jared Sisler et al.

Existing methods of correcting for chromatic aberrations in optical systems are limited to two approaches: varying the material dispersion in refractive lenses or incorporating grating dispersion via diffractive optical elements. Recently, single-layer broadband achromatic metasurface lenses have been demonstrated but are limited to diameters on the order of 100 μm due to the large required group delays. Here, we circumvent this limitation and design a metacorrector by combining a tunable phase and artificial dispersion to correct spherical and chromatic aberrations in a large spherical plano-convex lens. The tunability results from a variation in light confinement in sub-wavelength waveguides by locally tailoring the effective refractive index. The effectiveness of this approach is further validated by designing a metacorrector, which greatly increases the bandwidth of a state-of-the-art immersion objective (composed of 14 lenses and 7 types of glasses) from violet to near-infrared wavelengths. This concept of hybrid metasurface-refractive optics combines the advantages of both technologies in terms of size, scalability, complexity, and functionality.

K. Krupa, A. Tonello, A. Barthélémy et al.

We provide a perspective overview of the emerging field of nonlinear optics in multimode optical fibers. These fibers enable new methods for the ultrafast light-activated control of temporal, spatial, and spectral degrees of freedom of intense, pulsed beams of light, for a range of different technological applications.

A. Krasnok, D. Baranov, Huanan Li et al.

Scattering of electromagnetic waves lies at the heart of most experimental techniques over nearly the entire electromagnetic spectrum, ranging from radio waves to optics and X-rays. Hence, deep insight into the basics of scattering theory and understanding the peculiar features of electromagnetic scattering is necessary for the correct interpretation of experimental data and an understanding of the underlying physics. Recently, a broad spectrum of exceptional scattering phenomena attainable in suitably engineered structures has been predicted and demonstrated. Examples include bound states in the continuum, exceptional points in PT-symmetrical non-Hermitian systems, coherent perfect absorption, virtual perfect absorption, nontrivial lasing, non-radiating sources, and others. In this paper, we establish a unified description of such exotic scattering phenomena and show that the origin of all these effects can be traced back to the properties of poles and zeros of the underlying scattering matrix. We provide insights on how managing these special points in the complex frequency plane provides a powerful approach to tailor unusual scattering regimes.

Tengfeng Zhu, Yijie Lou, Yihan Zhou et al.

Optics naturally provides us with some powerful mathematical operations. Here we experimentally demonstrate that during reflection or refraction at a single optical planar interface, the optical computing of spatial differentiation can be realized by analyzing specific orthogonal polarization states of light. We show that the spatial differentiation is intrinsically due to the spin Hall effect of light and generally accompanies light reflection and refraction at any planar interface, regardless of material composition or incident angles. The proposed spin-optical method takes advantages of a simple and common structure to enable vectorial-field computation and perform edge detection for ultra-fast and energy-efficient image processing.

K. Vynck, R. Pierrat, R. Carminati et al.

The optics of correlated disordered media is a fascinating research topic emerging at the interface between the physics of waves in complex media and nanophotonics. Inspired by photonic structures in nature and enabled by advances in nanofabrication processes, recent investigations have unveiled how the design of structural correlations down to the subwavelength scale could be exploited to control the scattering, transport and localization of light in matter. From optical transparency to superdiffusive light transport to photonic gaps, the optics of correlated disordered media challenges our physical intuition and offers new perspectives for applications. This article reviews the theoretical foundations, state-of-the-art experimental techniques and major achievements in the study of light interaction with correlated disorder, covering a wide range of systems -- from short-range correlated photonic liquids, to L\'evy glasses containing fractal heterogeneities, to hyperuniform disordered photonic materials. The mechanisms underlying light scattering and transport phenomena are elucidated on the basis of rigorous theoretical arguments. We overview the exciting ongoing research on mesoscopic phenomena, such as transport phase transitions and speckle statistics, and the current development of disorder engineering for applications such as light-energy management and visual appearance design. Special efforts are finally made to identify the main theoretical and experimental challenges to address in the near future.

I. Staude, T. Pertsch, Y. Kivshar

All-dielectric resonant nanophotonics is a rapidly developing research field driven by its exceptional applications for creating low-loss nanoscale metadevices. The tight confinement of the local electromagnetic fields and multiple interferences available in resonant photonic nanostructures can boost many optical effects and offer novel opportunities for the subwavelength control of light–matter interactions. Active, light-emitting nanoscale structures are of high particular interest, as they offer unique opportunities for novel types of light sources and nanolasers. Here, we review the latest advances in this recently emerged and rapidly developing field of light-emitting dielectric resonant nanophotonics enabled by dipolar and multipolar Mie-type resonances. More specifically, we discuss how to employ resonant dielectric nanostructures for the efficient control of emission from quantum dots, two-dimensional transition metal dichalcogenides, and halide perovskites. We also foresee various future research...