Hasil untuk "Optics. Light"

M. Bouchard, Venkatakaushik Voleti, César S. Mendes et al.

We report a three-dimensional microscopy technique—swept, confocally-aligned planar excitation (SCAPE) microscopy—that allows volumetric imaging of living samples at ultrahigh speeds. Although confocal and two-photon microscopy have revolutionized biomedical research, current implementations are costly, complex and limited in their ability to image three-dimensional volumes at high speeds. Light-sheet microscopy techniques using two-objective, orthogonal illumination and detection require a highly constrained sample geometry and either physical sample translation or complex synchronization of illumination and detection planes. In contrast, SCAPE microscopy acquires images using an angled, swept light sheet in a single-objective, en face geometry. Unique confocal descanning and image rotation optics map this moving plane onto a stationary high-speed camera, permitting completely translationless three-dimensional imaging of intact samples at rates exceeding 20 volumes per second. We demonstrate SCAPE microscopy by imaging spontaneous neuronal firing in the intact brain of awake behaving mice, as well as freely moving transgenic Drosophila larvae. A swept light-sheet microscopy scheme allows volumetric imaging of living samples at high speed.

N. Kundtz, David R. Smith

K. Heshami, D. England, P. Humphreys et al.

Quantum light–matter interfaces are at the heart of photonic quantum technologies. Quantum memories for photons, where non-classical states of photons are mapped onto stationary matter states and preserved for subsequent retrieval, are technical realizations enabled by exquisite control over interactions between light and matter. The ability of quantum memories to synchronize probabilistic events makes them a key component in quantum repeaters and quantum computation based on linear optics. This critical feature has motivated many groups to dedicate theoretical and experimental research to develop quantum memory devices. In recent years, exciting new applications, and more advanced developments of quantum memories, have proliferated. In this review, we outline some of the emerging applications of quantum memories in optical signal processing, quantum computation and non-linear optics. We review recent experimental and theoretical developments, and their impacts on more advanced photonic quantum technologies based on quantum memories.

R. Ulrich, A. Simon

O. Hess, J. Pendry, S. Maier et al.

Zabih Ghassemlooy, S. Arnon, M. Uysal et al.

Haitao Liu, P. Lalanne

Peng Peng, Wanxia Cao, Ce Shen et al.

The recently developed notion of parity–time (PT) symmetry in optical systems has spawned intriguing prospects. So far, most experimental implementations have been reported in solid-state systems. Here, we report the first experimental demonstration of optical anti-PT symmetry—the counterpart of conventional PT symmetry—in a warm atomic-vapour cell. Rapid coherence transport via flying atoms leads to a dissipative coupling between two long-lived atomic spin waves, allowing for the observation of the essential features of anti-PT symmetry with unprecedented precision on the phase-transition threshold, as well as refractionless light propagation. Moreover, we show that a linear or nonlinear interaction between the two spatially separated beams can be achieved. Our results advance non-Hermitian physics by bridging to the field of atomic, molecular and optical physics, where new phenomena and applications in quantum and nonlinear optics aided by (anti-)PT symmetry could be anticipated. Parity–time symmetry in optics is studied in a warm atomic vapour, where its counterpart, anti-parity–time symmetry, as well as refractionless propagation, can also be observed.

T. Philbin, C. Kuklewicz, S. Robertson et al.

The physics at the event horizon resembles the behavior of waves in moving media. Horizons are formed where the local speed of the medium exceeds the wave velocity. We used ultrashort pulses in microstructured optical fibers to demonstrate the formation of an artificial event horizon in optics. We observed a classical optical effect: the blue-shifting of light at a white-hole horizon. We also showed by theoretical calculations that such a system is capable of probing the quantum effects of horizons, in particular Hawking radiation.

Skyler P. Selvin, XuanHao Wang, Handi Deng et al.

Photoacoustic tomography (PAT) and thermoacoustic tomography (TAT) both leverage acoustic signals generated by electromagnetic absorption to noninvasively image deep tissues. PAT operates by detecting optical absorption, whereas TAT targets radiofrequency (RF) absorption, providing complementary information on tissue composition and structure. Combining these modalities into a single system promises richer contrast but remains difficult due to the expense and complexity of the RF source. Here, we show that PAT can be integrated with a low-cost RF heater and used to image both optical and RF absorption in tissue phantoms. RF Heating-Enhanced Photoacoustic Tomography (HEPAT) maps RF absorption via temperature-dependent changes in thermomechanical properties, which enables the use of slow, inexpensive RF subsystems and provides an additional layer of contrast. HEPAT therefore provides distinct, complementary contrast relative to existing photoacoustic imaging systems, expanding specificity and diagnostic power while opening new avenues for studying temperature-related tissue phenomena.

L. Caspani, R. Kaipurath, M. Clerici et al.

New propagation regimes for light arise from the ability to tune the dielectric permittivity to extremely low values. Here, we demonstrate a universal approach based on the low linear permittivity values attained in the ε-near-zero (ENZ) regime for enhancing the nonlinear refractive index, which enables remarkable light-induced changes of the material properties. Experiments performed on Al-doped ZnO (AZO) thin films show a sixfold increase of the Kerr nonlinear refractive index (n_{2}) at the ENZ wavelength, located in the 1300 nm region. This in turn leads to ultrafast light-induced refractive index changes of the order of unity, thus representing a new paradigm for nonlinear optics.

Nouri Mohammad, Olivero Paolo, Kroker Stefanie et al.

In this paper, we discuss several enhancement approaches to increase the resolution and sensitivity of optical microscopy as a tool for dimensional nanometrology. Firstly, we discuss a newly developed through-focus microscopy technique providing additional phase information from the afocal images to increase the nanoscale sensitivity of classical microscopy. We also explore different routes to label-free or semiconductor compatible labelling super-resolution microscopy suitable for a broad range of technical applications. We present initial results from, a new wide-field super-resolution imaging technique enabled by Raman scattering. In addition, we discuss super-resolution imaging using NV centres in nano-diamonds as labels and their application in future reference standards.

Zhuoyi Wang, Xingyuan Lu, Zhigang Chen et al.

Abstract Links and knots are exotic topological structures that have garnered significant interest across multiple branches of natural sciences. Coherent links and knots, such as those constructed by phase or polarization singularities of coherent light, have been observed in various three-dimensional optical settings. However, incoherent links and knots—knotted or connected lines of coherence singularities—arise from a fundamentally different concept. They are “hidden” in the statistic properties of a randomly fluctuating field, making their presence often elusive or undetectable. Here, we theoretically construct and experimentally demonstrate such topological entities of incoherent light. By leveraging a state-of-the-art incoherent modal-decomposition scheme, we unveil incoherent topological structures from fluctuating light speckles, including Hopf links and Trefoil knots of coherence singularities that are robust against coherence and intensity fluctuations. Our work is applicable to diverse wave systems where incoherence or practical coherence is prevalent, and may pave the way for design and implementation of statistically-shaped topological structures for various applications such as high-dimensional optical information encoding and optical communications.

Anton Mukhamedshin, Wan Aizuddin W Razali, Xiaohong Yang et al.

In this paper, we have investigated the optical properties of a newly synthesized material consisting of a few-nm-thin flakes of ruby ( $\mathrm{Al}_2\mathrm{O}_3\mathrm{:Cr}^{3+}$ ), referred to as rubyene . Both theoretical and experimental approaches focus on the photoluminescence of $\mathrm{Cr}^{3+}$ , particularly exploring the effects of the refractive index of the surrounding medium on the radiative and nonradiative lifetimes of the photoexcited chromium ions, and the consequences of the diverse shapes of the thin rubyene flakes. Notably, we demonstrate how such susceptibility of the radiative rates to the refractive index allows for insight into the orientation of the crystallographic axes relative to the surface of the flakes. Although the effect of the environment on the nonradiative relaxation rates is an order of magnitude smaller than its effect on the radiative rates, the achieved sensitivity of our measurements was sufficient to observe both. The presented theoretical analysis of nonradiative transitions has broader implications for Förster-type energy transfer, especially in scenarios where the refractive index of the medium is non-uniform. Our results demonstrate good agreement between the theory and the experiment and establish the potential of rubyene in optical nanosensing applications, highlighting its sensitivity to environmental refractive index changes.

Mamta Kapoor

Higher-order nonlinear Schrödinger equations are frequently analyzed as a result of research into nonlinear wave mechanics in intricate physical systems. In this work, the 4th-order Schrödinger equation with cubic-quintic nonlinearity is solved using semi-analytical method named Shehu HPM. Higher-order dispersive effects are considered by 4th-order components, and equilibrium between self-focusing and saturation events in nonlinear media is modeled by the cubic–quintic nonlinearity. The intricate interaction of higher-order components with nonlinearity is frequently too complex for traditional numerical methods to handle, requiring reliable and precise semi-analytical techniques. The fetched results demonstrate exceptional agreement between exact and approximated solutions, validated through rigorous graphical compatibility analysis. The success of this approach underscores its effectiveness in handling higher-order dispersive and nonlinear terms, offering a reliable alternative to purely numerical techniques.

Khalil Sabour, Yaroslav V. Kartashov

We introduce higher order polariton topological insulator (HOTI) realized with fractal array of microcavity pillars arranged into Sierpinski gasket-like geometry. This system exhibiting self similarity in different generations, can support localized modes either in the external or multiple internal corners depending on the controllable distortion introduced into first generation structure. Nonlinear corner modes can be selectively excited in this dissipative system using resonant optical pumping. Strong polariton-polariton interactions lead to tilt of the resonance curves and bistability as the pump amplitude increases, allowing control over corner state profiles. Linear stability analysis illustrates dynamical stability of such states. Our results show how nontrivial topology manifests itself in self similar, aperiodic structures and indicate that fractal geometry may bring qualitatively new localization scenarios in polariton HOTIs.

Yida Song, Zhengshu Zhang, Yi Shen et al.

Optical tweezers have been widely used for optical manipulation of various particles. At present, there are different type of optical tweezers. Among them, holographic optical tweezers have attracted growing attention as a powerful tools for optical trapping, optical transportation and optical sorting in many fields, due to its excellent properties including great flexibility and high convenience. Experimentally, however, the structured light has been easily distorted, which would lead to serious degradation of optical manipulation performance. In this work, the distortion of structured light is theoretically analyzed. In the following, the distortion of structured light are numerically simulated and experimentally measured. It shows that the simulated results are in consistent with the experimental ones. Then, an approach for decreasing its optical distortion is proposed, and the results reveal that the distortion of structured light can be effectively corrected. Accordingly, our study provides a way for improving the distorted structured light, which is useful for optically manipulating various particles in optical tweezers.

Ruediger Grunwald, Martin Bock

The recognition, decoding and tracking of vortex patterns is of increasing importance in many fields, ranging from the astronomical observations of distant galaxies to turbulence phenomena in liquids or gases. Currently, coherent light beams with orbital angular momentum (OAM) are of particular interest for optical communication, metrology, micro-machining or particle manipulation. One common task is to identify characteristic spiral patterns in pixelated intensity maps at real-world signal-to-noise ratios. A recently introduced combination of polar mapping and Fast Fourier Transform (FFT) was extended to novel sampling configurations and applied to the quantitative analysis of the spiral interference patterns of OAM beams. It is demonstrated that specific information on topological parameters in non-uniform arrays of OAM beams can be obtained from significantly distorted and noisy intensity maps by extracting one- or two-dimensional angular frequency spectra from single or concatenated circular cuts in either spatially fixed or scanning mode. The method also enables the evaluation of the quality of beam shaping and optical transmission. Results of proof-of-principle experiments are presented, resolution limits are discussed, and the potential for applications is addressed.

Yi-Han Luo, Baoqi Shi, Wei Sun et al.

Abstract The analysis of optical spectra—emission or absorption—has been arguably the most powerful approach for discovering and understanding matter. The invention and development of many kinds of spectrometers have equipped us with versatile yet ultra-sensitive diagnostic tools for trace gas detection, isotope analysis, and resolving hyperfine structures of atoms and molecules. With proliferating data and information, urgent and demanding requirements have been placed today on spectrum analysis with ever-increasing spectral bandwidth and frequency resolution. These requirements are especially stringent for broadband laser sources that carry massive information and for dispersive devices used in information processing systems. In addition, spectrum analyzers are expected to probe the device’s phase response where extra information is encoded. Here we demonstrate a novel vector spectrum analyzer (VSA) that is capable of characterizing passive devices and active laser sources in one setup. Such a dual-mode VSA can measure loss, phase response, and dispersion properties of passive devices. It also can coherently map a broadband laser spectrum into the RF domain. The VSA features a bandwidth of 55.1 THz (1260–1640 nm), a frequency resolution of 471 kHz, and a dynamic range of 56 dB. Meanwhile, our fiber-based VSA is compact and robust. It requires neither high-speed modulators and photodetectors nor any active feedback control. Finally, we employ our VSA for applications including characterization of integrated dispersive waveguides, mapping frequency comb spectra, and coherent light detection and ranging (LiDAR). Our VSA presents an innovative approach for device analysis and laser spectroscopy, and can play a critical role in future photonic systems and applications for sensing, communication, imaging, and quantum information processing.

Jinyong Ma, Jihua Zhang, Jake Horder et al.

Quantum light sources are essential building blocks for many quantum technologies, enabling secure communication, powerful computing, precise sensing and imaging. Recent advancements have witnessed a significant shift towards the utilization of ``flat" optics with thickness at subwavelength scales for the development of quantum light sources. This approach offers notable advantages over conventional bulky counterparts, including compactness, scalability, and improved efficiency, along with added functionalities. This review focuses on the recent advances in leveraging flat optics to generate quantum light sources. Specifically, we explore the generation of entangled photon pairs through spontaneous parametric down-conversion in nonlinear metasurfaces, as well as single photon emission from quantum emitters including quantum dots and color centers in 3D and 2D materials. The review covers theoretical principles, fabrication techniques, and properties of these sources, with particular emphasis on the enhanced generation and engineering of quantum light sources using optical resonances supported by nanostructures. We discuss the diverse application range of these sources and highlight the current challenges and perspectives in the field.