Robert W Boyd

Robert W Boyd
University of Ottawa · Department of Physics

PhD

About

1,104
Publications
132,837
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36,155
Citations

Publications

Publications (1,104)
Article
A nonlinear self-focusing material can amplify random small-amplitude phase modulations present in an optical beam, leading to the formation of amplitude singularities commonly referred to as optical caustics. By imposing polarization structuring on the beam, we demonstrate the suppression of amplitude singularities caused by nonlinear self-phase m...
Article
Light can carry both spin and orbital angular momentum. While it is known that a nonparaxial circularly polarized beam couples the spin angular momentum to orbital angular momentum, this phenomenon does not hold upon collimation of the field. With the rising interest in epsilon-near-zero photonics, integral ingredients to this field are the beam-sh...
Preprint
We present octave-wide bandpass filters in the terahertz (THz) region based on bilayer-metamaterial (BLMM) structures. The passband region has a super-Gaussian shape with a maximum transmittance approaching 70% and a typical stopband rejection of 20 dB. The design is based on a metasurface consisting of a metallic square-hole array deposited on a t...
Article
In general, there are different, relatively independent forms of orbital angular momenta at a given propagation distance, which might exhibit different dynamic spatial characteristics. One type involves a beam with a helical phasefront that rotates around its own beam center, such as a Laguerre–Gaussian (LG) beam with an azimuthal index not equal t...
Article
Spaceplates are novel flat-optic devices that implement the optical response of a free-space volume over a smaller length, effectively “compressing space” for light propagation. Together with flat lenses such as metalenses or diffractive lenses, spaceplates have the potential to enable the miniaturization of any free-space optical system. While the...
Article
The utility of all parametric nonlinear optical processes is hampered by phase-matching requirements. Quasi-phase-matching, birefringent phase matching, and higher-order-mode phase matching have all been developed to address this constraint, but the methods demonstrated to date suffer from the inconvenience of only being phase matched for a single,...
Preprint
Full-text available
A nonlinear self-focusing material can amplify random small-amplitude phase modulations present in an optical beam, leading to the formation of amplitude singularities commonly referred to as optical caustics. By imposing polarization structuring on the beam, we demonstrate the suppression of amplitude singularities caused by nonlinear self-phase m...
Article
Multiresonant metasurfaces could enable many applications in filtering, sensing, and nonlinear optics. However, developing a metasurface with more than one high-quality-factor or high-Q resonance at designated resonant wavelengths is challenging. Here, we experimentally demonstrate a plasmonic metasurface exhibiting different, narrow surface lattic...
Article
Optical metasurfaces consist of 2D arrangements of scatterers, and they control the amplitude, phase, and polarization of an incidence field on demand. Optical metasurfaces are the cornerstone for a future generation of flat optical devices in a wide range of applications. The rapid advances in nanofabrication have made the versatile design and ana...
Preprint
Full-text available
We model spontaneous parametric down-conversion (SPDC) as classical difference frequency generation (DFG) of the pump field and a hypothetical stochastic "vacuum" seed field. We analytically show that the second-order spatiotemporal correlations of the field generated from the DFG process replicate those of the signal field from SPDC. Specifically,...
Article
Asymmetric transmission - direction-selective electromagnetic transmission between two ports - is a phenomenon exhibited by two-dimensional chiral systems. The possibility of exploiting this phenomenon in chiral metasurfaces opens exciting possibilities for applications such as optical isolation and routing without external magnetic fields. This wo...
Conference Paper
We demonstrate excitation of guided lattice resonances inside a semiconductor thin-film in a inhomogeneous metasurface enabled by a lossy plasmonic lattice reso-nanances with a record Q -factor value over 10,000.
Conference Paper
We experimentally demonstrate a 2.25-Gbit/s DPSK free-space optical link that resilience to turbulence-induced modal coupling loss. The measured average mixing loss is ~14.6-dB less than a single-mode-fiber-coupled system based on 200 random turbulence realizations.
Conference Paper
We experimentally demonstrate a 6-Gbit/s 16-QAM pilot-assisted self-coherent free-space optical link with enhanced misalignment tolerance. BER performance below the 7% FEC threshold can be achieved for up to 0.13° angular- or 9-mm lateral misalignments.
Conference Paper
We measure the orbital angular momentum (OAM) spectrum of the field generated from spontaneous parametric down-conversion (SPDC) in the high-gain regime. The experimentally measured spectra and the angular Schmidt number are consistent with theoretical predictions.
Article
The development of metasurfaces has enabled unprecedented portability and functionality in flat optical devices. Spaceplates have recently been introduced as a complementary element to reduce the space between individual metalenses, which will further miniaturize entire imaging devices. However, spaceplates necessitate an optical response which dep...
Preprint
Resonances in optical systems are useful for many applications, such as frequency comb generation, optical filtering, and biosensing. However, many of these applications are difficult to implement in optical metasurfaces because traditional approaches for designing multi-resonant nanostructures require significant computational and fabrication effo...
Article
Full-text available
The dependence of the efficiency of various nonlinear-optical processes on the background linear relative electric permittivity ϵ and magnetic permeability μ of the material is analytically and numerically investigated. The conversion efficiency of low-order harmonic-generation processes, as well as the increase rate of Kerr-effect nonlinear phase...
Preprint
Multiresonant metasurfaces could enable many applications in filtering, sensing and nonlinear optics. However, developing a metasurface with more than one high-quality-factor or high-Q resonance at designated resonant wavelengths is challenging. Here, we experimentally demonstrate a plasmonic metasurface exhibiting different, narrow surface lattice...
Article
The authors include references that appeared on arXiv during the preparation of their paper [Opt. Express29, 22034 (2021)10.1364/OE.427734].
Article
Full-text available
In free-space optical communications that use both amplitude and phase data modulation (for example, in quadrature amplitude modulation (QAM)), the data are typically recovered by mixing a Gaussian local oscillator with a received Gaussian data beam. However, atmospheric turbulence can induce power coupling from the transmitted Gaussian mode to hig...
Article
Full-text available
In contrast to imaging using position-resolving cameras, single-pixel imaging uses a bucket detector along with spatially structured illumination to compressively recover images. This emerging imaging technique is a promising candidate for a broad range of applications due to the high signal-to-noise ratio (SNR) and sensitivity, and applicability i...
Preprint
Full-text available
A moving dielectric medium can displace the optical path of light passing through it, a phenomenon known as the Fresnel-Fizeau optical drag effect. The resulting displacement is proportional to the medium's velocity. In this article, we report on an anomalous optical drag effect, where the displacement is still proportional to the medium's speed bu...
Article
Natural materials show a very weak magnetic response. During the past decades, many attempts have been made to enhance magnetism. Suitably structured metallic particles and high-permittivity dielectric particles have been primarily used for this purpose. In this special issue of JOSAB on "Collective Effects and Coupling Phenomena," we have propose...
Preprint
Full-text available
Optical metasurfaces consist of a 2D arrangement of scatterers, and they control the amplitude, phase, and polarization of an incidence field on demand. Optical metasurfaces are the cornerstone for a future generation of flat optical devices in a wide range of applications. The rapidly growing advances in nanofabrication have made the versatile des...
Preprint
Full-text available
Asymmetric transmission - direction-selective control of electromagnetic transmission between two ports - is an important phenomenon typically exhibited by two-dimensional chiral systems. Here, we study this phenomenon in chiral plasmonic metasurfaces supporting lattice plasmons modes. We show, both numerically and experimentally, that asymmetric t...
Article
A single multi-plane light convertor (MPLC) is applied to simultaneously mitigate turbulence-induced crosstalk and demultiplex two orbital angular momentum (OAM) multiplexed channels for a free-space optical link. Comprised of six programmable phase planes, the MPLC is placed at the receiver side for turbulence mitigation and channel demultiplexing...
Article
Quantum-state tomography is the conventional method used to characterize density matrices for general quantum states. However, the data acquisition time generally scales linearly with the dimension of the Hilbert space, hindering the possibility of dynamic monitoring of a high-dimensional quantum system. Here, we demonstrate a direct tomography pro...
Preprint
Full-text available
Bianisotropy is a powerful concept enabling asymmetric optical response, including asymmetric reflection, absorption, optical forces, light trapping, and lasing. The physical origin of these asymmetric effects can be understood from magnetoelectric coupling and asymmetrical field enhancement. Here, we theoretically propose highly asymmetric second-...
Preprint
The development of metasurfaces has enabled unprecedented portability and functionality in flat optical devices. Spaceplates have recently been introduced as a complementary element to reduce the space between individual metalenses. This will further miniaturize entire imaging devices. However, a spaceplate necessitates a non-local optical response...
Article
Full-text available
A dense cloud of atoms with randomly changing positions exhibits coherent and incoherent scattering. We show that an atomic cloud of subwavelength dimensions can be modeled as a single scatterer where both coherent and incoherent components of the scattered photons can be fully explained based on effective multipole moments. This model allows us to...
Article
The resonance properties of a plasmonic dipole antenna array depend on its geometry and the properties of its surrounding medium. The linear optical properties of an array of plasmonic dipole antennas can be modified with the inclusion of an epsilon-near-zero (ENZ) thin film. In this work, we numerically investigate the roles of the antenna dimensi...
Article
Full-text available
Centuries of effort to improve imaging has focused on perfecting and combining lenses to obtain better optical performance and new functionalities. The arrival of nanotechnology has brought to this effort engineered surfaces called metalenses, which promise to make imaging devices more compact. However, unaddressed by this promise is the space betw...
Article
The nonlinear response of liquids in the terahertz regime has recently attracted significant interest, even though very few measurements have been reported. Here, we report on our measurements based on a z-scan technique of the nonlinear refractive-index coefficient n2 at terahertz frequencies for several liquids with noncentrosymmetric molecules,...
Article
Full-text available
The large number of spatial modes supported by standard multimode fibers is a promising platform for boosting the channel capacity of quantum and classical communications by orders of magnitude. However, the practical use of long multimode fibers is severely hampered by modal crosstalk and polarization mixing. To overcome these challenges, we devel...
Article
Full-text available
Free-space optical communication is a promising means to establish versatile, secure and high-bandwidth communication between mobile nodes for many critical applications. While the spatial modes of light offer a degree of freedom to increase the information capacity of an optical link, atmospheric turbulence can introduce severe distortion to the s...
Article
The orbital angular momentum (OAM) of photons presents a degree of freedom for enhancing the secure key rate of free-space quantum key distribution (QKD) through mode-division multiplexing (MDM). However, atmospheric turbulence can lead to substantial modal crosstalk, which is a long-standing challenge to MDM for free-space QKD. Here, we show that...
Article
Full-text available
Geometrical chirality is a property of objects that describes a three-dimensional mirror-symmetry violation and therefore it requires a nonvanishing spatial extent. In contrary, optical chirality describes only the local handedness of electromagnetic fields and neglects the spatial geometrical structure of optical beams. In this Letter we put forwa...
Article
Beams carrying orbital-angular-momentum (OAM) have gained much interest due to their unique amplitude and phase structures. In terms of communication systems, each of the multiple independent data-carrying beams can have a different OAM value and be orthogonal to all other beams. This paper will describe the use of multiplexing and the simultaneous...
Preprint
Full-text available
The nonlinear optical response of materials is the foundation upon which applications such as frequency conversion, all-optical signal processing, molecular spectroscopy, and nonlinear microscopy are built. However, the utility of all such parametric nonlinear optical processes is hampered by phase-matching requirements. Quasi-phase-matching, biref...
Preprint
A dense cloud of atoms with randomly changing positions exhibits coherent and incoherent scattering. We show that an atomic cloud of subwavelength dimensions can be modeled as a single scatterer where both coherent and incoherent components of the scattered photons can be fully explained based on effective multipole moments. This model allows us to...
Article
Full-text available
Plasmonic nanostructures hold promise for the realization of ultra-thin sub-wavelength devices, reducing power operating thresholds and enabling nonlinear optical functionality in metasurfaces. However, this promise is substantially undercut by absorption introduced by resistive losses, causing the metasurface community to turn away from plasmonics...
Preprint
Full-text available
Analyses based on quantum metrology have shown that the ability to localize two incoherent point sources can be significantly enhanced through the use of mode sorting. Here we experimentally investigate the effect of partial coherence on the sub-diffraction limit localization of two sources based on parity sorting. When the sources are fully cohere...
Preprint
Full-text available
Quantum state tomography is the conventional method used to characterize density matrices for general quantum states. However, the data acquisition time generally scales linearly with the dimension of the Hilbert space, hindering the possibility of dynamic monitoring of a high-dimensional quantum system. Here, we demonstrate a direct tomography pro...
Preprint
Full-text available
Atmospheric turbulence generally limits free-space optical (FSO) communications, and this problem is severely exacerbated when implementing highly sensitive and spectrally efficient coherent detection. Specifically, turbulence induces power coupling from the transmitted Gaussian mode to higher-order Laguerre-Gaussian (LG) modes, resulting in a sign...
Preprint
Full-text available
Spatial resolution is one of the most important specifications of an imaging system. Recent results in quantum parameter estimation theory reveal that an arbitrarily small distance between two incoherent point sources can always be efficiently determined through the use of a spatial mode sorter. However, extending this procedure to a general object...
Conference Paper
We demonstrate that digital multi-probe time reversal can effectively suppress crosstalk for mode-division multiplexing. The performance of multi-probe time reversal is experimentally characterized over a 340-m free-space link and a 1-km standard multimode fiber.
Conference Paper
We demonstrate that ultra-strongly coupled SPP and ENZ modes in gold and indium tin oxide bi-films are strongly confined, can propagate for several microns, and offer a useful platform for nanophotonics at NIR frequencies.
Conference Paper
We experimentally demonstrate wavelength conversion by four-wave mixing in an epsilon-near-zero based metasurface. We observed conversion efficiency of 0.16% using a 127-nm thick metasurface near the 1550-nm C band with 4-GW/cm ² pump peak intensity.
Conference Paper
We propose and demonstrate a single-pixel temporal imaging system with high resolution, efficiency and sensitivity. A terahertz pulse with pulse energy as low as 5 fJ is compressively imaged with a resolution down to 16 fs.
Conference Paper
We experimentally demonstrate the generation of dynamic spatiotemporal structured beams that exhibit two orbital-angular-momenta simultaneously using a Kerr frequency comb. The mode purity of the revolving and rotating LG 30 beam is obtained to be ~89%.
Conference Paper
Full-text available
We experimentally demonstrate an ultra-high Q -factor ( ≈ 2400) surface lattice resonance in a plasmonic metasurface, that can be a great platform for highly-efficient flat optical applications e . g . biosensors, nanolasers, and metalenses.
Conference Paper
We present progress in designing high-performance spaceplates, devices that can mimic free propagation to replace space in an imaging system, where we attain a compression factor of R = 11 . 5 with a NA = 0 . 26.