Hedenapier9293

A broadband and low-dispersion high refractive index (HRI) metamaterial formed by symmetrically etching two identical metasurfaces on both sides of a dielectric slab has been numerically and experimentally demonstrated in the terahertz region. The unit cell of the metasurface is a Jerusalem cross surrounded by a square metal ring, in which there are two magnetic resonances and one electric resonance. The proposed metamaterial simultaneously possesses high effective permittivity and permeability in broadband frequencies, since the multiple resonances result in a significant bandwidth expansion of a HRI. The simulation results reveal that the refractive index of the proposed metamaterial reaches up to 27 in the frequency range of 0.39-0.65 THz, and the relative bandwidth is about 44%. Furthermore, the fluctuation of the refractive index in this frequency band is less than 6%, showing a good low-dispersion characteristic. We also fabricated a sample to verify this HRI property. Experimental results are in good agreement with numerical simulations. This broadband HRI metamaterial is desirable in many fields, such as in high-resolution imaging and optical communications.We provide a novel approach for estimating the modal and chromatic dispersions of the LP01 and LP11 modes traversing a two-mode fiber (TMF). read more A modal interferometer is used to measure the differential group delay (DGD) and chromatic dispersion for the two modes in the 1260-1360 nm telecommunication band. The measurement principle is based on an investigation of a transmitted spectrum through temporal decomposition by means of a Fourier transform. The diagnosis of the DGD and chromatic dispersion for the two modes is discussed theoretically and experimentally. The experimental results obtained here exactly match those obtained previously. The salient feature of the present method is that the modal interferometer configuration makes it possible to measure both the DGD and chromatic dispersion and also estimate the shape of optical pulses traversing a TMF.A highly sensitive surface plasmon resonance fiber sensor for a vector magnetic field is proposed. The sensor is composed of a half-side gold-coated multimode-single-mode-multimode hetero-core fiber structure encapsulated with ferrofluids. The half-side gold film on the fiber not only produces the surface plasmon resonance, but also breaks the centrosymmetry of the light field in the fiber. Moreover, the magnetic-field-dependent anisotropy of the surrounding ferrofluids makes the sensor sensitive to both the intensity and direction of the magnetic field. Owing to the unique half-side coating configuration and the resulting enhancement of the evanescent field, the sensor can achieve a sensitivity as high as 1008 pm/Oe to the magnetic field intensity. The proposed sensor, possessing advantages such as high sensitivity, ease of fabrication, and low cost, has potential in the detection of a weak vector magnetic field.A general eigen equation has been deduced that can handle ideal and non-ideal quarter-wavelength cases of Bragg-reflection waveguide structure for nonlinear interaction with matching layers on each side of the active region. In particular, this equation allows for solving the cases when the Bragg reflectors are non-ideal quarter-wavelength thick. With this equation, we propose a Bragg-reflection waveguide structure based on the AlxGa1-xAs/GaAs material system with high figure-of-merit |ξd e f f | total nonlinearity and checked the influence if the thickness of the quarter-wavelength Bragg reflectors is off by 10%.The full width at half maximum (FWHM) of lossy mode resonances (LMRs) in the optical spectrum depends on the homogeneity of the thin film deposited. In this Letter, a method for improving the FWHM is applied for an LMR generated by a D-shaped optical fiber in reflection configuration. For this purpose, three samples with different attenuation were deposited with DC sputtering thin films of SnO2-x, and a further controlled immersion of the samples in water was performed. A laser-cleaner method was used to improve the FWHM characteristics of one of the samples from 106 to 53 nm. This improvement can be applied to thin-film-based sensors where there is a problem with the inhomogeneity of the coating thickness. Moreover, with this technique, it was proved that a coated length of just 3-4 mm permits the generation of an LMR, with implications for the miniaturization of the final device.Real-time 3-D tracking of a fast-moving object has found important applications in industry, traffic control, sports, biomedicine, defense, etc. However, it is difficult to adopt typical image-based object tracking systems in a fast-moving object tracking in real time and for a long duration, because reliable and robust image processing and analysis algorithms are often computationally exhausted, and limited storage and bandwidth can hardly fulfill the great demand of high-speed photography. Here we report an image-free 3-D tracking approach. The approach uses only two single-pixel detectors and a high-speed spatial light modulator for data acquisition. link2 By illuminating the target moving object with six single-period Fourier basis patterns, the approach is able to analytically calculate the position of the object with the corresponding single-pixel measurements. The approach is low-cost, and data- and computation-efficient. We experimentally demonstrate that the proposed approach can detect and track a fast-moving object at a frame rate of 1666 frames per second by using a 10,000 Hz digital micromirror device. Benefiting from the wide working spectrum of single-pixel detectors, the reported approach might be applicable for hidden fast-moving object tracking.The wave nature and diffraction of light pose a significant bottleneck to the continued performance and efficiency scaling of a wide variety of integrated photonic devices, often necessitating solutions based on resonance, slow-light, or plasmonics to derive enhanced light-matter interaction. Here, we introduce all-dielectric waveguides that exploit the vectorial nature of light to achieve strong subdiffraction confinement in high index dielectrics, enabling characteristic mode dimensions below λ02/1000 without metals or plasmonics. We further show how these ultra-small mode areas may coincide or diverge from the nonlinear effective mode area. The work opens the door to new types of waveguide-based devices featuring strong near-field confinement, Purcell factors, and nonlinear effects, with broad applications spanning classical and quantum optics.For coupled linear cavity-random fiber Raman lasers, for the first time, to the best of our knowledge, we demonstrate a new mechanism of emergence of the random pulses, with the anomalous statistics satisfying optical rogue waves' criteria experimentally. The rogue waves appear as a result of the coupling of two Raman cascades, namely, a linear cavity laser with a wavelength of 1.55 µm and a random laser with a wavelength nearly 1.67 µm, along with coupling of the orthogonal states of polarization (SOPs). link3 The coherent coupling of SOPs causes localization of the trajectories in the vicinity of these states, whereas polarization instability drives escape taking the form of chaotic oscillations. Antiphase dynamics in two cascades result in the suppression of low amplitude chaotic oscillations and enable the anomalous spikes, satisfying rogue waves criteria.We report on narrowband terahertz (THz) radiation generation via optical rectification from a BaGa4Se7 crystal. The dense phonon mode distribution of the BaGa4Se7 crystal causes narrow transmission bands in the THz frequency range with enhanced nonlinear susceptibility magnitudes, thus permitting strong narrowband THz radiation generation at the frequencies of 1.97 and 2.34 THz. In comparison to THz radiation generated from a ZnTe crystal, the narrowband THz radiation produced by the BaGa4Se7 crystal is 4.5 times higher at 1.97 THz and 63% higher at 2.34 THz, thus making BaGa4Se7 a viable crystal for use in such areas as security and medicine.Probabilistic shaping (PS) allows tunable spectral efficiency that is suitable for realizing high throughput intra-data center transceivers. In this Letter, we integrate the cost-minimizing distribution matching (CMDM) in the probability amplitude shaping scheme to generate PS-PAM signals with ultra-short symbol block lengths for reduced serial processing delay. We detail the principle of CMDM and present two different methods of implementation. We demonstrate that CMDM enables the transmission of single wavelength net 200 Gbit/s PS-PAM-8 over 2 km of single-mode fiber (SMF). We show that similar performance is achievable using a constant composition distribution matcher, yet requiring 10 times longer symbol block lengths. We also report, to the best of our knowledge, the first demonstration of net 800 Gbit/s transmission over 2 km of SMF using a packaged 4-λ electro-absorption modulated laser transmitter optical sub-assembly (TOSA).The nonlinear transformation of fluctuations by frequency broadening is found to produce strong anti-correlations in the spectral output. This effect is investigated by dispersive Fourier transform measurements. We exploit the anti-correlations in order to cancel the intensity noise in a subsequent sum-frequency mixing step. This principle allows for the generation of tunable visible pulses by cascaded nonlinear mixing whilst maintaining the same intensity noise performance as the input pulses. In addition, we demonstrate that the power fluctuations occurring in the process of passive stabilization of the carrier-envelope phase locking via difference frequency generation may be cancelled by an analogous strategy.We address the resonant response and bistability of the exciton-polariton corner states in a higher-order nonlinear topological insulator realized with a kagome arrangement of microcavity pillars. Such states are resonantly excited and exist due to the balance between pump and losses, on one hand, and between nonlinearity and dispersion in inhomogeneous potential landscape, on the other hand, for pump energy around eigen-energies of corresponding linear localized modes. Localization of the nonlinear corner states in a higher-order topological insulator can be efficiently controlled by tuning pump energy. We link the mechanism of corner state formation with symmetry of the truncated kagome array. Corner states coexist with densely packed edge states but are well isolated from them in energy. Nonlinear corner states persist even in the presence of perturbations in a corner microcavity pillar.Polarization-encoded free-space quantum communication requires a quantum state source featuring fast modulation, long-term stability, and a low intrinsic error rate. Here we present a polarization encoder that, contrary to previous solutions, generates predetermined polarization states with a fixed reference frame in free-space. The proposed device does not require calibration either at the transmitter or at the receiver and achieves long-term stability. A proof-of-concept experiment is also reported, demonstrating a quantum bit error rate lower than 0.2% for several hours without any active recalibration.