Hasil untuk "Optics. Light"

C. Genet, T. Ebbesen

N. Long

R. Sutherland

M. Pu, Xiong Li, Xiaoliang Ma et al.

The nanoscale structures inspired by the natural catenaries can achromatically spin light wave. The catenary is the curve that a free-hanging chain assumes under its own weight, and thought to be a “true mathematical and mechanical form” in architecture by Robert Hooke in the 1670s, with nevertheless no significant phenomena observed in optics. We show that the optical catenary can serve as a unique building block of metasurfaces to produce continuous and linear phase shift covering [0, 2π], a mission that is extremely difficult if not impossible for state-of-the-art technology. Via catenary arrays, planar optical devices are designed and experimentally characterized to generate various kinds of beams carrying orbital angular momentum (OAM). These devices can operate in an ultra-broadband spectrum because the anisotropic modes associated with the spin-orbit interaction are almost independent of the incident light frequency. By combining the optical and topological characteristics, our approach would allow the complete control of photons within a single nanometric layer.

Janpeter Hirsch, Simon Kubitza, Max Schiemangk et al.

We present a robust and compact micro-integrated, frequency-tunable, optical frequency reference module developed to improve the long-term frequency stability of lasers in quantum technology and satellite laser communication applications. The module is based on a volume holographic Bragg grating (VHBG) and features a multi-level temperature stabilization concept, packaged into a sealed housing with dimensions of <inline-formula><tex-math notation="LaTeX">$96\,\times \,96\,\times \,35\,\text{mm}^{3}$</tex-math></inline-formula>. The module has a frequency tuning range of more than <inline-formula><tex-math notation="LaTeX">$\text{65}\,\text{GHz}$</tex-math></inline-formula> with a near-linear behavior. We demonstrate short-term frequency stabilities between <inline-formula><tex-math notation="LaTeX">$2 \times 10^{5}\,\text{Hz}^{2}/\text{Hz}$</tex-math></inline-formula> and <inline-formula><tex-math notation="LaTeX">$4 \times 10^{7}\,\text{Hz}^{2}/\text{Hz}$</tex-math></inline-formula> in the Fourier frequency range from <inline-formula><tex-math notation="LaTeX">$\text{20}\,\text{Hz}$</tex-math></inline-formula> to <inline-formula><tex-math notation="LaTeX">$\text{200}\,\text{kHz}$</tex-math></inline-formula>, and a minimum overlapping Allan deviation of <inline-formula><tex-math notation="LaTeX">$\sigma (\tau =1000\,s) = 1.7 \times 10^{-10}$</tex-math></inline-formula>, and <inline-formula><tex-math notation="LaTeX">$1.5 \times 10^{-9}$</tex-math></inline-formula> over 24<inline-formula><tex-math notation="LaTeX">$\,$</tex-math></inline-formula>h. The module can also be operated as a wavemeter and spectrometer, yielding residuals below <inline-formula><tex-math notation="LaTeX">$\text{0.33}\,\text{GHz}$</tex-math></inline-formula> with second-order polynomial regression calibration, and reliably measuring frequency noise PSDs of lasers whose noise exceeds that of the reference module.

J. Kobashi, H. Yoshida, M. Ozaki

Bo Wu, Wenkai Zhang, Hailong Zhou et al.

Public-key encryption is essential for secure communications, eliminating the need for pre-shared keys. However, traditional schemes such as RSA (Rivest-Shamir-Adleman) and elliptic curve cryptography rely on computational complexity, making them increasingly susceptible to advances in computing power and algorithms. Physical-layer encryption, which leverages the intrinsic properties of physical systems, offers a promising alternative with security rooted in physics. Despite progress in this field, public-key encryption at the optical layer remains largely unexplored. Here, we propose a novel optical public-key encryption scheme based on partially coherent light sources. The cryptographic keys are encoded in the incoherent optical transmission matrix of an on-chip Mach-Zehnder interferometer mesh, providing high complexity and resilience to computational attacks. We experimentally demonstrate encrypted image transmission over 40 km of optical fiber with high decryption fidelity and achieve a 10 Gbit/s optical encryption rate using a lithium niobate photonic chip. This represents the first implementation of public-key encryption at the physical optical layer. The approach offers key advantages in security, cost, energy efficiency, and compatibility with commercial optical communication systems. By integrating public-key encryption into photonic hardware, this work opens a new direction for secure and high-speed optical communications in next-generation networks.

Omar E. Olarte, J. Andilla, E. Gualda et al.

This paper is intended to give a comprehensive review of light-sheet (LS) microscopy from an optics perspective. As such, emphasis is placed on the advantages that LS microscope configurations present, given the degree of freedom gained by uncoupling the excitation and detection arms. The new imaging properties are first highlighted in terms of optical parameters and how these have enabled several biomedical applications. Then, the basics are presented for understanding how a LS microscope works. This is followed by a presentation of a tutorial for LS microscope designs, each working at different resolutions and for different applications. Then, based on a numerical Fourier analysis and given the multiple possibilities for generating the LS in the microscope (using Gaussian, Bessel, and Airy beams in the linear and nonlinear regimes), a systematic comparison of their optical performance is presented. Finally, based on advances in optics and photonics, the novel optical implementations possible in a LS microscope are highlighted.

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.

G.I. Greisukh, I.A. Levin, O.A. Zakharov

Using the example of the development of two simple dual-band monofocal IR objectives, approaches to the layout and design of their optical schemes are demonstrated, depending on whether compensation for the effects of temperature changes on the optical characteristics of these lenses is required or not. It is shown that in the case when thermal compensation is not required, superior optical characteristics can be achieved in a simple triplet, in which the flat surface of the frontal fractional lens carries a diffractive microstructure. In the case of passive athermalization, the optical scheme of the objective becomes more complicated and consists of refractive two-line power and correction components, in the latter of which the flat surface of one of the lenses carries a diffractive microstructure. Due to highly efficient diffractive microstructures, the longitudinal chromaticism of both objectives is reduced almost to the diffraction limit and, in combination with a low level of residual monochromatic aberrations at high light intensity, the maximum resolution is provided for uncooled microbolometers used as matrix receivers.

C. Rosales-Guzmán, A. Forbes

Xiangang Luo

In the past centuries, the scale of engineering optics has evolved toward two opposite directions: one is represented by giant telescopes with apertures larger than tens of meters and the other is the rapidly developing micro/nano‐optics and nanophotonics. At the nanoscale, subwavelength light–matter interaction is blended with classic and quantum effects in various functional materials such as noble metals, semiconductors, phase‐change materials, and 2D materials, which provides unprecedented opportunities to upgrade the performance of classic optical devices and overcome the fundamental and engineering difficulties faced by traditional optical engineers. Here, the research motivations and recent advances in subwavelength artificial structures are summarized, with a particular emphasis on their practical applications in super‐resolution and large‐aperture imaging systems, as well as highly efficient and spectrally selective absorbers and emitters. The role of dispersion engineering and near‐field coupling in the form of catenary optical fields is highlighted, which reveals a methodology to engineer the electromagnetic response of complex subwavelength structures. Challenges and tentative solutions are presented regarding multiscale design, optimization, fabrication, and system integration, with the hope of providing recipes to transform the theoretical and technological breakthroughs on subwavelength hierarchical structures to the next generation of engineering optics, namely Engineering Optics 2.0.

A. Ryabchun, A. Bobrovsky

Modern optics and photonics constantly require break‐through materials and designs in order to achieve miniature, lightweight, highly tunable, and effective optical devices. One of the basic optical components is the diffraction grating (DG), widely used for the dispersion of light, beam steering, etc. This review gathers research efforts on diffractive optical elements based on cholesteric liquid crystal (CLC) materials with a supramolecular helical architecture. All main types and fabrication approaches of periodic diffractive structures from CLCs are classified and described. Key optical properties of DGs, their advantages and drawbacks are considered. Special attention is paid on the tunability of DGs including design principles and prospective chiral materials. The review consists of three parts divided according to the formation mechanism of diffractive structures: i) the spontaneously formed periodic structures from CLCs confined in cells with hybrid or homeotropic boundary conditions; ii) DGs generated by external electric field applied to CLCs layers; iii) light‐generated DGs (e.g., obtained by holography, mask exposure, photoalignment). The review also aims to initiate and gain collaborations between physicists, engineers and organic chemists to combine novel chiral photoswitches and molecular motors with sophisticated optical design paving the way towards novel smart optical materials.

Yuancheng Fan, Nian‐Hai Shen, Fuli Zhang et al.

2D optics is gradually emerging as a frontier in modern optics. Plasmons in graphene provide a prominent platform for 2D optics in which the light is squeezed into atomic scale. This report highlights some recent progresses in graphene plasmons toward the 2D optics. The launch, observation, and advanced manipulation of propagating graphene plasmons for 2D optical circuits are described. Representative achievements associated with graphene metasurfaces, challenges, recent progresses like photoexcited graphene metasurfaces, and the transformation optics linking 2D to bulk optics with singularity are investigated.

Rahul Kumar Gangwar, Sneha Kumari, Akhilesh Kumar Pathak et al.

The current generation is witnessing a huge interest in optical waveguides due to their salient features: they are of low cost, immune to electromagnetic interference, easy to multiplex, have a compact size, etc. These features of optical fibers make them a useful tool for various sensing applications including in medicine, automotives, biotechnology, food quality control, aerospace, physical and chemical monitoring. Among all the reported applications, optical waveguides have been widely exploited to measure the physical and chemical variations in the surrounding environment. Optical fiber-based temperature sensors have played a crucial role in this decade to detect high fever and tackle COVID-19-like pandemics. Recognizing the major developments in the field of optical fibers, this article provides recent progress in temperature sensors utilizing several sensing configurations including conventional fiber, photonic crystal fiber, and Bragg grating fibers. Additionally, this article also highlights the advantages, limitations, and future possibilities in this area.

Zhihua Ding, Zhiyi Liu

Martin Montagnac, Yoann Brûlé, Aurélien Cuche et al.

Abstract Light emission of europium (Eu3+) ions placed in the vicinity of optically resonant nanoantennas is usually controlled by tailoring the local density of photon states (LDOS). We show that the polarization and shape of the excitation beam can also be used to manipulate light emission, as azimuthally or radially polarized cylindrical vector beam offers to spatially shape the electric and magnetic fields, in addition to the effect of silicon nanorings (Si-NRs) used as nanoantennas. The photoluminescence (PL) mappings of the Eu3+ transitions and the Si phonon mappings are strongly dependent of both the excitation beam and the Si-NR dimensions. The experimental results of Raman scattering and photoluminescence are confirmed by numerical simulations of the near-field intensity in the Si nanoantenna and in the Eu3+-doped film, respectively. The branching ratios obtained from the experimental PL maps also reveal a redistribution of the electric and magnetic emission channels. Our results show that it could be possible to spatially control both electric and magnetic dipolar emission of Eu3+ ions by switching the laser beam polarization, hence the near field at the excitation wavelength, and the electric and magnetic LDOS at the emission wavelength. This paves the way for optimized geometries taking advantage of both excitation and emission processes.

Panqiu Jiang, Jiale Mu, Yuxing Liu et al.

In this work, a new structure is used to enhance the nonlinear effect in the cavity, which improves the performance of the 1.3[Formula: see text][Formula: see text]m broadband swept source. The swept source adopts a semiconductor optical amplifier (SOA), a circulator, a coupler, and a tunable filter. In the structure, the light passes through the nonlinear medium (SOA) twice in two opposite directions, which excites the nonlinear effect and increases the performance of the swept source. The tunable filter is based on a polygon rotating mirror and gratings. Traditionally, multiple SOAs are adopted to improve the sweep range and the optical power, which increases the cost and complexity of the swept source. The method proposed in this paper can improve the spectral range and optical power of the swept sources without additional accessories. For the short-cavity swept source, the power increases from 6[Formula: see text]mW to 7.7[Formula: see text]mW, and the sweep range increases from 98[Formula: see text]nm to 120[Formula: see text]nm. The broadband swept sources could have wide applications in biomedical imaging, sensor system, measurement and so on.

M.G. Tokmachev

The paper proposes an algorithm for processing a photo of a granule in order to determine its volume. Factors that influence the result of automatic data processing in the optical micrometry method are investigated. It is shown that by estimating the outline of an ellipse-shaped granule, the algorithm determines its volume with a relative error of 0.4 %, which corresponds to an error in determining the granule diameter of 1 pixel.

S. Zafar Ali, M.K. Islam, D.A. Mazhar

This milestone work overcomes the lower bandwidth limitation of Erbium Doped Fiber Laser (EDFRL) by inserting a Moiré Grating in the laser loop, with closely spaced wavelengths so that beating of wavelengths produces a very high bandwidth pulsed chaos. The chaos bandwidth variation is studied with respect to three parameters i.e., wavelength spacing, fiber Bragg grating bandwidth and fiber nonlinearity. The high bandwidth chaos can be produced with rich and flatter spectral content by controlling the said parameters in a narrow range studied in this work. The chaotic pulses become narrow in pulse width, closely spaced in time and more dynamic in amplitude. The Lyapunov Exponent increases as the chaos becomes more unpredictable. The EDRFL, known for more control parameters can be deployed in higher bandwidth chaos generation applications besides semiconductor laser.