Showing papers in "Journal of The Optical Society of America B-optical Physics in 2017"

Review of recent progress on single-frequency fiber lasers [Invited]

Abstract: Single-frequency fiber lasers have drawn intense attention for their extensive applications from high-resolution spectroscopy and gravitational wave detection to materials processing due to the outstanding properties of low noise, narrow linewidth, and the resulting long coherence length. In this paper, the recent advances of single-frequency fiber oscillators and amplifiers are briefly reviewed in the broad wavelength region of 1–3 μm. Performance improvements in laser noise and linewidth are addressed with the newly developed physical mechanisms. The solution to achieving higher power/energy is also discussed, accompanied by the start-of-the-art results achieved to date.

Lattice modes and plasmonic linewidth engineering in gold and aluminum nanoparticle arrays

Abstract: Metallic nanoparticles arranged in arrays have been shown to support both localized surface plasmons (LSPs) and diffractive grating behavior, related to the inter-particle period. By selecting both the period and particle size, it is possible to generate lattice modes that are caused by interference of the LSP and the grating Rayleigh anomaly. These hybrid modes show a Fano-like lineshape with reduced linewidth relative to the LSP mode. In this paper, we study the lattice modes supported by gold and aluminum nanoparticle arrays in the visible and UV, both experimentally and theoretically. The measured and simulated dispersion curves allow us to comprehensively analyze the details of the LSP coupling in the array. We show that when the spectral position of the Rayleigh anomaly, dependent on the period of the array, is slightly blue-shifted with respect to the LSP resonance, the quality factor of the lattice mode is significantly increased. We also provide evidence that the formation of the lattice modes critically depends on the incident light polarization, with maximum coupling efficiency between LSPs and the in-plane scattered light when the polarization direction is perpendicular to the propagation direction of the grazing wave. The results obtained provide design rules for high quality factor resonances throughout the visible and ultraviolet spectral ranges.

Tomographic phase microscopy: principles and applications in bioimaging [Invited].

Abstract: Tomographic phase microscopy (TPM) is an emerging optical microscopic technique for bioimaging. TPM uses digital holographic measurements of complex scattered fields to reconstruct three-dimensional refractive index (RI) maps of cells with diffraction-limited resolution by solving inverse scattering problems. In this paper, we review the developments of TPM from the fundamental physics to its applications in bioimaging. We first provide a comprehensive description of the tomographic reconstruction physical models used in TPM. The RI map reconstruction algorithms and various regularization methods are discussed. Selected TPM applications for cellular imaging, particularly in hematology, are reviewed. Finally, we examine the limitations of current TPM systems, propose future solutions, and envision promising directions in biomedical research.

Generalized 4 × 4 matrix formalism for light propagation in anisotropic stratified media: study of surface phonon polaritons in polar dielectric heterostructures

Abstract: We present a generalized 4×4 matrix formalism for the description of light propagation in birefringent stratified media. In contrast to previous work, our algorithm is capable of treating arbitrarily anisotropic or isotropic, absorbing or non-absorbing materials and is free of discontinuous solutions. We calculate the reflection and transmission coefficients and derive equations for the electric field distribution for any number of layers. The algorithm is easily comprehensible and can be straightforwardly implemented in a computer program. To demonstrate the capabilities of the approach, we calculate the reflectivities, electric field distributions, and dispersion curves for surface phonon polaritons excited in the Otto geometry for selected model systems, where we observe several distinct phenomena ranging from critical coupling to mode splitting, and surface phonon polaritons in hyperbolic media.

Parametric feedback cooling of levitated optomechanics in a parabolic mirror trap

Abstract: Levitated optomechanics, a new experimental physics platform, holds promise for fundamental science and quantum technological sensing applications. We demonstrate a simple and robust geometry for optical trapping in vacuum of a single nanoparticle based on a parabolic mirror and the optical gradient force. We demonstrate parametric feedback cooling of all three motional degrees of freedom from room temperature to a few millikelvin. A single laser at 1550 nm and a single photodiode are used for trapping, position detection, and cooling for all three dimensions. Particles with diameters from 26 to 160 nm are trapped without feedback to 10−5 mbar, and with feedback-engaged, the pressure is reduced to 10−6 mbar. Modifications to the harmonic motion in the presence of noise and feedback are studied, and an experimental mechanical quality factor in excess of 4×107 is evaluated. This particle manipulation is key to building a nanoparticle matter-wave interferometer in order to test the quantum superposition principle in the macroscopic domain.

Gas-phase broadband spectroscopy using active sources: progress, status, and applications.

Abstract: Broadband spectroscopy is an invaluable tool for measuring multiple gas-phase species simultaneously. In this work we review basic techniques, implementations, and current applications for broadband spectroscopy. We discuss components of broadband spectroscopy including light sources, absorption cells, and detection methods and then discuss specific combinations of these components in commonly used techniques. We finish this review by discussing potential future advances in techniques and applications of broadband spectroscopy.

Tunable resonant Goos–Hänchen and Imbert–Fedorov shifts in total reflection of terahertz beams from graphene plasmonic metasurfaces

Abstract: Highly tunable enhanced lateral displacements in the center of gravity of a totally reflected light beam from a graphene plasmonic metasurface are investigated. Multiple reflections of the incident beam, and the resonance coupling between the incident beam and the surface modes of the graphene metasurface in each reflection, are employed to enhance the Goos–Hanchen and Imbert–Fedorov shifts in the proposed structure. It is shown that spatial Goos–Hanchen and Imbert–Fedorov shifts as high as 1089λ0 and −44.66λ0 (λ0: incident wavelength) are achievable in the proposed structure. The effects of different parameters, including the incident beam waist, temperature, the scattering time, and the chemical potential of the graphene, on the shift values are then studied. Because of the strong light confinement in the surface modes of the graphene metasurface, the dispersion properties of these modes, and, therefore, the coupling strength between the incident beam and these modes, are highly sensitive to the parameters of the reflecting structure and the incident beam itself. The high sensitivity of the coupling strength between the incident beam and the surface modes is then exploited to tune the shift values. It is shown that by introducing a small change of ΔμC=0.02 eV in the chemical potential of the graphene, the spatial Goos–Hanchen and Imbert–Fedorov shift variations of 855λ0 and −31λ0 can be achieved, respectively. The wide range of lateral shift variations along with the relatively small required actuation power support the application of the proposed structure in the realization of optical devices, such as temperature sensors and switches.

Limits of coherent supercontinuum generation in normal dispersion fibers

Abstract: We study the largely unexplored transition between coherent and noise-seeded incoherent continuum generation in all-normal dispersion (ANDi) fibers and show that highly coherent supercontinua with spectral bandwidths of one octave can be generated with long pump pulses of up to 1.5 ps duration, corresponding to soliton orders of up to N=600. In terms of N, this corresponds to an approximately 50 times increase of the coherent regime compared to anomalous dispersion pumping. In the transition region between coherent and incoherent spectral broadening, we observe the manifestation of nonlinear phenomena that we term incoherent cloud formation and incoherent optical wave breaking, which lead to a gradual or instantaneous coherence collapse of supercontimuum (SC) spectral components, respectively. The role played by stimulated Raman scattering and parametric four-wave mixing during SC generation in ANDi fibers is shown to be more extensive than previously recognized: their nonlinear coupling contributes to the suppression of incoherent dynamics at short pump pulse durations, while it is responsible for non-phase-matched parametric amplification of noise observed in the long pulse regime. We further discuss the dependence of SC coherence on fiber design, and present basic experimental verifications for our findings using single-shot detection of SC spectra generated by picosecond pulses. This work outlines both the further potential as well as the limitations of broadband coherent light source development for applications such as metrology, nonlinear imaging, and ultrafast photonics, among others.

Pulsed fluoride fiber lasers at 3 μm [Invited]

Abstract: Enormous performance gains have been made in fluoride-based fiber lasers operating around 3 μm due to advances in fiber fabrication and improvements in high-power pump diode technologies during the last decade. Pulsed fluoride fiber lasers capable of producing high-energy/high-peak power mid-infrared pulses are of significant interest for a variety of applications. Q-switched and mode-locked fiber lasers have been demonstrated with various techniques in recent years. In this paper, pulsed Er3+- and Ho3+-doped ZBLAN (ZrF4-BaF2-LaF3-AlF3-NaF) fiber lasers are reviewed, and our achievement of pulsed fiber laser sources at 3 μm is presented. Power/energy scaling of pulsed ZBLAN fiber lasers and their potential applications are discussed.

High-power coherent beam polarization combination of fiber lasers: progress and prospect [Invited]

Abstract: Coherent polarization beam combining (CPBC) of fiber lasers has the potential to scale the output total power while simultaneously maintaining good beam quality. In this paper, we will present the very recent technical advance in a single-channel coherently combinable linearly polarized narrow-linewidth fiber amplifier and high-power CPBC system. The noise property of a recently developed near 2 kW fiber amplifier and its feasibility in a CPBC system, CPBC of four 500-W-level fiber amplifiers and two kilowatt fiber amplifiers are demonstrated for the first time, which is also the first result for a 2 kW CPBC system. We have also performed numerical analysis on the performance scaling of CPBC, and deduced handy design guidelines for CPBC of a 64-element high-power system.

High-power fiber lasers based on tandem pumping

Abstract: Power scaling of fiber lasers is challenged by several factors, such as the brightness of the pump source, the nonlinear effect, modal instability, and so on. Pumping active fibers with high-brightness fiber lasers instead of laser diodes is a promising solution for the brightness limitation and modal instability. In this paper, for the first time to our knowledge, we present a general review on the achievements of various kinds of high-power fiber lasers based on the tandem pumping scheme in the past few years. The requirements for tandem pumping ytterbium (Yb), erbium (Er), thulium (Tm), and holmium (Ho)-doped fibers are analyzed, and corresponding achievements are summarized. Hundreds of watts of fiber lasers at ∼1020, ∼1500, and 1900 nm and hundred-watt-level fiber lasers at ∼1150 and ∼1180 nm have been successfully achieved. Then, these powerful fiber lasers with high brightness can be employed as pump sources for Yb-, Er-, Tm- and Ho-doped fibers. Moreover, a recent experimental result of a 3.5 kW Yb-doped fiber amplifier in an all-fiber format is reported in addition to previous typical achievements. The underlying challenges for further power scaling, including the nonlinear effect suppression and special fiber design, are briefly discussed. Exploring the tandem pumping scheme in novel application fields is discussed as well.

Nonlinear temporal compression in multipass cells: theory

Abstract: The use of multipass cells as a way to spatially homogenize self-phase modulation and distribute its accumulation over the propagation distance is analyzed in detail, with the aim to perform nonlinear temporal compression In addition to the insertion of nonlinear media at specific locations in the cell, as already demonstrated, we also propose to fill the cell with a noble gas, as is done in hollow capillary-based setups This makes the accumulation of B-integral continuous rather than discrete In this case, analytical estimates for the B-integral per round trip and scaling rules are provided as a function of cavity geometry and gas parameters Then, three-dimensional numerical simulations are performed to assess the spatiotemporal couplings in the output beam in various conditions This model is checked against experimental data presented in the literature, and used to predict our proposed scheme performance We believe that these techniques constitute a promising way to allow temporal compression at energy levels beyond 10 mJ, where capillary-based setups are difficult to implement

High-order dispersion in Kerr comb oscillators

Abstract: We numerically investigate the effect of high-order dispersion on Kerr frequency comb generation in optical microresonators characterized with anomalous group velocity dispersion (GVD) using realistic slot-waveguide-based silicon nitride microring and spheroidal crystalline magnesium fluoride resonators. Our numerical simulations indicate that all orders of GVD should be taken into account to obtain the correct envelope shape of the generated Kerr frequency comb. High-order GVD affects the 3 dB comb bandwidth, nonlinear conversion efficiency, and frequency recoil of the comb spectrum (i.e., spectral shift effect), as well as pulse peak power and the power dependence of the pulse timing. Additionally, high-order dispersion terms affect the spectral position of a dispersive wave generated in a microresonator. Our results emphasize the influence of the pump power on the dispersive wave radiation frequency as well as the repetition rate of the generated frequency comb. The latter has significant practical ramifications, for instance, for the use of resonator-based frequency combs in optical clocks. We also observe competition in the generation of two different pulses corresponding to nearly the same spectral envelope. These mode-locked combs appear in the presence of a strong negative fourth-order GVD; one of them takes a hyperbolic-secant soliton shape, while the other resembles a Gaussian pulse superimposed on a modulated pedestal. The appearance and stability of the latter pulse depend on the numerical integration technique utilized.

Reflection compensation mediated by electric and magnetic resonances of all-dielectric metasurfaces [Invited]

Abstract: All-dielectric nanostructures have recently emerged as a promising alternative to plasmonic devices, as they also possess pronounced electric and magnetic resonances and allow effective light manipulation. In this work, we study optical properties of a composite structure that consists of a silicon nanoparticle array (metasurface) and high-index substrate aiming at clarifying the role of substrate on reflective properties of the nanoparticles. We develop a simple semi-analytical model that describes interference of separate contributions from the nanoparticle array and the bare substrate to the total reflection. Applying this model, we show that matching the magnitudes and setting the π-phase difference of the electric and magnetic dipole moments induced in nanoparticles, one can obtain a suppression of reflection from the substrate coated with metasurface. We perform numerical simulations of sphere and disk nanoparticle arrays for different permittivities of the substrate. We find full agreement with the semi-analytical results, which means that the uncoupled-element model adequately describes nanostructure reflective properties, despite the effects of induced bi-anisotropy. The model explains the features of the reflectance spectrum, such as a number of dips and their spectral positions, and shows why it may not coincide with the spectral positions of Mie resonances of the single nanoparticles forming the system. We also address practical aspects of the antireflective device engineering: we show that the uncoupled-element model is applicable to the structures on top of silicon substrates, including lithographically defined nanopillars. The reflectance suppression from the nanoparticle array on top of the silicon substrate can be achieved in a broad spectral range with a disordered nanoparticle array and for a wide range of incidence angles.

Single-frequency microwave imaging with dynamic metasurface apertures

Abstract: Conventional microwave imaging schemes, enabled by the ubiquity of coherent sources and detectors, have traditionally relied on frequency bandwidth to retrieve range information, while using mechanical or electronic beamsteering to obtain cross-range information This approach has resulted in complex and expensive hardware when extended to large-scale systems with ultrawide bandwidth Relying on bandwidth can create difficulties in calibration, alignment, and imaging of dispersive objects We present an alternative approach using electrically large, dynamically reconfigurable, metasurface antennas that generate spatially distinct radiation patterns as a function of tuning state The metasurface antenna consists of a waveguide feeding an array of metamaterial radiators, each with properties that can be modified by applying a voltage to diodes integrated into the element By deploying two of these apertures, one as the transmitter and one as the receiver, we realize sufficient spatial diversity to alleviate the dependence on frequency bandwidth and obtain range and cross-range information using measurements at a single frequency We experimentally demonstrate this proposal by using two 1D dynamic metasurface apertures and reconstructing various 2D scenes (range and cross-range) Furthermore, we modify a conventional reconstruction method—the range migration algorithm—to be compatible with such configurations, resulting in an imaging system that is efficient in software and hardware The imaging scheme presented in this paper has broad application to radio frequency imaging, including security screening, through-wall imaging, biomedical diagnostics, and synthetic aperture radar

Observation of Lévy statistics in one-dimensional erbium-based random fiber laser

Abstract: We report on measurements of the statistical fluctuations of the output intensity in a continuous-wave-pumped erbium-doped one-dimensional random fiber laser (RFL), with specially designed Bragg grating scatterers. Transitions from Gaussian to Levy-like and back to the Gaussian regime, similar to those observed in three-dimensional random lasers, are described as the input excitation power increases from below to above the RFL threshold. Our results are consistent with theoretical predictions for the sequence of statistical regimes of output intensity in random laser systems. We also discuss experimental and theoretical connections with the photonic spin-glass behavior of the erbium-doped RFL, which displays a replica-symmetry-breaking phase above the threshold.

Entanglement-enhanced Neyman–Pearson target detection using quantum illumination

Abstract: Quantum illumination (QI) provides entanglement-based target detection—in an entanglement-breaking environment—whose performance is significantly better than that of optimum classical-illumination target detection. QI’s performance advantage was established in a Bayesian setting with the target presumed equally likely to be absent or present and error probability employed as the performance metric. Radar theory, however, eschews that Bayesian approach, preferring the Neyman–Pearson performance criterion to avoid the difficulties of accurately assigning prior probabilities to target absence and presence and appropriate costs to false-alarm and miss errors. We have recently reported an architecture—based on sum-frequency generation (SFG) and feedforward (FF) processing—for minimum error-probability QI target detection with arbitrary prior probabilities for target absence and presence. In this paper, we use our results for FF-SFG reception to determine the receiver operating characteristic—detection probability versus false-alarm probability—for optimum QI target detection under the Neyman–Pearson criterion.

Graphene-based mid-infrared biosensor

Abstract: We propose a new graphene-based metamaterial biosensor to achieve tunable plasmon-induced transparency in the mid-infrared (mid-IR) regime. The structure consists of a graphene sheet with three cut-out strips that has been located on a substrate. It is shown that the plasmonically induced transparency (PIT) can be realized by breaking the symmetry of the structure in the normal incidence and also changing the polarization of the incident light in the symmetric case. By optimizing the physical parameters of the antennas, an extremely strong optical sensing coefficient (about 99%) is observed in the mid-IR frequency range based on the PIT effect, which is much larger than that of related previous studies. More importantly, we observed a blueshift in the transparency window through the increase of the gate voltage of the graphene’s chemical potential. The transparency window strongly depends on the physical parameters of the substrate and filling material. Furthermore, it is found that the biosensing application of the proposed structure is highly dependent on inserting an ultra-thin buffer layer between the graphene and substrate layer, leading to a tunable PIT in the mid-IR regime.

Diffractive waveplate arrays [Invited]

Abstract: Diffractive waveplate technology presents an opportunity for designing arrays of all types of optical components. We present here different architectures of arrays of waveplate lenses and vector vortex waveplates. Due to the continuous nature of diffractive waveplate coatings and the high spatial resolution of the technology, the sizes of array elements can span from micrometers to tens of millimeters. Both fixed and electrically switchable arrays are discussed. Arrays of diffractive waveplates present new challenges and opportunities for digital light polarization holography for applications in polarizer-free displays, smart windows, optical communications, beam shaping, and other photonics technologies.

High repetition rate mid-infrared supercontinuum generation from 13 to 53 μm in robust step-index tellurite fibers

Abstract: We demonstrate broadband supercontinuum generation over two infrared octaves, spanning from 1.3 to 5.3 μm, with an output power of 150 mW in robust step-index tellurite fibers with core diameters between 3.5 and 4.3 μm. As a pump source, we use femtosecond mid-IR pulses from a home-built post-amplified optical parametric oscillator tunable between 1.5 and 4.0 μm at a 43 MHz repetition rate. We study the influence of core size, pump wavelength, and fiber length to optimize the spectral bandwidth. A key requirement for efficient spectral broadening is a low and rather flat average anomalous dispersion over a wide spectral range that can be tailored accordingly by changing the fiber core diameter. Numerical simulations based on the generalized nonlinear Schrodinger equation are in good agreement with experimental results.

Decoupling of hyperfine structure of Cs D_1 line in strong magnetic field studied by selective reflection from a nanocell

Abstract: Decoupling of total electronic and nuclear spin moments of Cs atoms in an external magnetic field for the case of atomic D1 line, leading to onset of the hyperfine Paschen–Back (HPB) regime, is studied theoretically and experimentally. Selective reflection (SR) of laser radiation from an interface of dielectric window and atomic vapor confined in a nanocell with 300 nm gap thickness is implemented for the experimental studies. The real-time derivative of SR signal with a frequency position coinciding with atomic transitions is used in the measurements, providing ∼40 MHz spectral resolution and linearity of the signal response with respect to the transition probability. The behavior of 28 individual Zeeman transitions in a wide range of longitudinal magnetic field (0–6 kG) is tracked under the excitation of Cs vapor by a low-intensity σ+-polarized cw laser radiation. For B≥6 kG, only eight transitions with nearly equal probabilities and the same frequency slope remain in the spectrum, which is a manifestation of the HPB regime. The obtained experimental results are in very good agreement with the numerical modeling. A small divergence of the SR signal as well as subwavelength thickness and sub-Doppler spectral linewidth inherent to nanocell make it possible for the employed technique to be used for distant remote sensing of a magnetic field with high spatial and B-field resolution.

Dynamics of finite energy Airy beams modeled by the fractional Schrödinger equation with a linear potential

Abstract: The dynamics of finite energy Airy beams modeled by the fractional Schrodinger equation (FSE) with a linear potential are numerically investigated. Different from the propagation properties of Airy beams described by the standard Schrodinger equation, the splitting phenomenon, which is presented under the FSE without potential, is influenced by the quadratic chirp and the Levy index. As the linear potential is considered, the periodic evolution of Airy beams is shown, and the period is inversely proportional to the linear potential coefficient. The beam width can undergo an abrupt decrease or increase depending on the sign of potential coefficient. The beam deviation distance increases with the beam width greatly changed if the Levy index increases. Moreover, the quadratic chirp does not influence the evolution period but the intensity distribution. In addition, the intriguing properties are analytically clarified. All these features confirm the promising applications of Airy beams in optical manipulation and optical switch.

Radiation pressure on a diffractive sailcraft

Abstract: Advanced diffractive metamaterial films may afford advantages over passive reflective surfaces for a variety space missions that use solar or laser in-space propulsion. Three cases are compared: sun-facing diffractive sails, Littrow diffraction configurations, and conventional reflective sails. A simple Earth-to-Mars orbit transfer at a constant attitude with respect to the sunline finds no penalty for transparent diffractive sails. Advantages of the latter approach include actively controlled metasails, reuse of photons, and mission-specific optimization schemes.

Hyperspectral holography: an alternative application of the Fourier transform spectrometer

Abstract: An alternative application of the Fourier transform spectroscopy (FTS) principles and techniques is proposed. Registration of hyperspectral holograms in incoherent light by using FTS is suggested. This work generalizes and develops our previous results on registration of hyperspectral Fresnel’s and image plane holograms. Theoretical and experimental results are provided and discussed. The proposed method is applied to the problems of digital holographic microscopy, including speckle noise reduction, hyperspectral imaging, and coloring and optical profiling. A major advantage of the proposed method is that it allows simultaneous recovery of the amplitude, the phase, and the spectral frequency σ of the wave field in a single registration process.

Analytical solutions to the finite-pulse Bloch model for multidimensional coherent spectroscopy

Abstract: We present perturbative analytical solutions to the optical Bloch equations at third order, with finite duration Gaussian pulse envelopes. We find that a given double-sided Feynman diagram in this approximation can be conveniently described in the frequency domain as a product of the expression in the impulsive limit and a finite-pulse factor. Finite-pulse effects are Feynman-diagram-dependent, however, and include nontrivial phase corrections that can occur even in the case of transform-limited pulses. The results constitute a practical framework for modeling phenomena in multidimensional coherent spectroscopy that cannot easily be captured in the impulsive limit, including the roles of bandwidth, resonance, and pulse chirp.

Mid-infrared emission in Tb^3+-doped selenide glass fiber

Abstract: The mid-infrared (MIR) emission behavior of Tb3+-doped Ge–As–Ga–Se bulk glasses (500, 1000, and 1500 ppmw Tb3+) and unstructured fiber (500 ppmw Tb3+) is investigated when pumping at 2.013 μm. A broad emission band is observed at 4.3–6.0 μm corresponding to F57→F67, with an observed emission lifetime of 12.9 ms at 4.7 μm. The F47 level is depopulated nonradiatively and so it is proposed that Tb3+-doped Ge–As–Ga–Se fiber may operate as a quasi-three-level MIR fiber laser. Underlying glass-impurity vibrational absorption bands are numerically removed to give the true Tb3+ absorption cross section, as required for Judd–Ofelt (J–O) analysis. Radiative transition rates calculated from J–O theory are compared with measured lifetimes. A numerical model of the three-level Tb3+-doped fiber laser is developed for Tb3+ doping of 8.25×1024 ions m−3 (i.e., 500 ppmw) and dependence of laser performance on fiber length, output coupler reflectivity, pump wavelength, signal wavelength, and fiber background loss is calculated. Results indicate the feasibility of an efficient three-level MIR fiber laser operating within 4.5–5.3 μm, pumped at either 2.013 or 2.95 μm.

Integration in analog optical computing using metasurfaces revisited: toward ideal optical integration

Abstract: In this paper, we introduce a modified optical integrator based on suitably designed metamaterial blocks. The integration is performed on an impinging wave pattern as it propagates through these blocks. So far, various metamaterial-based optical integrators have been implemented with appropriate performance in the case of zero-DC input signals. However, these integrators suffer from low accuracy when fed by signals rich in low-frequency contents. The latter property arises from truncation of low-frequency contents of the input wave in the Fourier domain. To solve this shortcoming, we propose a new metasurface-based structure which reflects low-frequency parts of the input signal in the Fourier domain. This subtracted part is then measured in the input and compensated in the detected output signal. The numerically simulated output responses verify superior performance of the proposed structure compared to conventional metamaterial-based optical integrator in the case of input signals with considerable low-frequency contents. These findings may lead to remarkable achievements in light-based plasmonic signal processors at nanoscale, which can replace their bulky conventional dielectric lens-based counterparts.

Hybrid plasmon–phonon polariton bands in graphene–hexagonal boron nitride metamaterials [Invited]

Abstract: We theoretically investigate mid-infrared electromagnetic wave propagation in multilayered graphene–hexagonal boron nitride (hBN) metamaterials. Hexagonal boron nitride is a natural hyperbolic material that supports highly dispersive phonon polariton modes in two Reststrahlen bands with different types of hyperbolicity. Due to the hybridization of surface plasmon polaritons of graphene and hyperbolic phonon polaritons of hBN, each isolated unit cell of the graphene–hBN metamaterial supports hybrid plasmon–phonon polaritons (HPPs). Through the investigation of band structure of the metamaterial we find that, due to the coupling between the HPPs supported by each unit cell, the graphene–hBN metamaterial can support HPP bands. The dispersion of these bands can be noticeably modified for different thicknesses of hBN layers, leading to the appearance of bands with considerably flat dispersions. Moreover, analysis of light transmission through the metamaterial reveals that this system is capable of supporting high-k propagating HPPs. This characteristic makes graphene–hBN metamaterials very promising candidates for the modification of the spontaneous emission of a quantum emitter, hyperlensing, negative refraction, and waveguiding.

Magnetic field concentration with coaxial silicon nanocylinders in the optical spectral range

Abstract: Resonant magnetic energy accumulation is theoretically investigated in the optical and near-infrared regions. It is demonstrated that the silicon nanocylinders with and without coaxial through holes can be used for the control and manipulation of optical magnetic fields, providing up to 26-fold enhancement of these fields for the considered system. Magnetic field distributions and dependence on the parameters of nanocylinders are revealed at the wavelengths of magnetic dipole and quadrupole resonances responsible for the enhancement. The obtained results can be applied, for example, to designing nanoantennas for the detection of atoms with magnetic optical transitions.

Collapse-induced orientational localization of rigid rotors [Invited]

Abstract: We show how the ro-translational motion of anisotropic particles is affected by the model of continuous spontaneous localization (CSL), the most prominent hypothetical modification of the Schrodinger equation restoring realism on the macroscale. We derive the master equation describing collapse-induced spatio-orientational decoherence and demonstrate how it leads to linear- and angular-momentum diffusion. Since the associated heating rates scale differently with the CSL parameters, the latter can be determined individually by measuring the random motion of a single levitated nanorotor.