Matthew van Niekerk, Saman Jahani, Justin Bickford, Pak Cho, Stephen Anderson, Gerald Leake, Daniel Coleman, Michael L. Fanto, Christopher C. Tison, Gregory A. Howland, Zubin Jacob, and Stefan F. Preble. 4/2021.

Two-dimensional extreme skin depth engineering for CMOS photonics

. J. Opt. Soc. Am. B, 38, 4, Pp. 1307-1316.

Extreme skin depth engineering (e-skid) can be applied to integratedphotonics to manipulate the evanescent field of a waveguide. Here wedemonstrate that e-skid can be implemented in two directions in order todeterministically engineer the evanescent wave allowing for denseintegration with enhanced functionalities. In particular, by increasingthe skin depth, we enable the creation of two-dimensional (2D) e-skiddirectional couplers with large gaps and operational bandwidth. Here weexperimentally validate 2D e-skid for integrated photonics in acomplementary metal--oxide semiconductor (CMOS) photonics foundry anddemonstrate strong coupling with a gap of 1.44 {\textmu}m.

See also: Photonics
Xingyu Gao, Chinmay Khandekar, Zubin Jacob, and Tongcang Li. 3/24/2021.

Thermal equilibrium spin torque: Near-field radiative angular momentum transfer in magneto-optical media

. Physical Review B, 103, 12.

Spin and orbital angular momentum of light plays a central role in quantum nanophotonics as well as topological electrodynamics. Here, we show that the thermal radiation from finite-size bodies comprising nonreciprocal magneto-optical materials can exert a spin torque even in global thermal equilibrium. Moving beyond the paradigm of near-field heat transfer, we calculate near-field radiative angular momentum transfer between finite-size nonreciprocal objects by combining Rytov's fluctuational electrodynamics with the theory of optical angular momentum. We prove that a single magneto-optical cubic particle in nonequilibrium with its surroundings experiences a torque in the presence of an applied magnetic field (T-symmetry breaking). Furthermore, even in global thermal equilibrium, two particles with misaligned gyrotropy axes experience equal-magnitude torques with opposite signs which tend to align their gyrotropy axes parallel to each other. Our results are universally applicable to semiconductors like InSb (magnetoplasmas) as well as Weyl semimetals which exhibit the anomalous Hall effect (gyrotropic) at infrared frequencies. Our work paves the way towards near-field angular momentum transfer mediated by thermal fluctuations for nanoscale devices.

See also: Thermal, Photonics
Reza Baghdadi, Ekkehart Schmidt, Saman Jahani, Ilya Charaev, Michael G W Müller, Marco Colangelo, Di Zhu, Konstantin Ilin, Alexej D Semenov, Zubin Jacob, Michael Siegel, and Karl K Berggren. 2/2/2021.

Enhancing the performance of superconducting nanowire-based detectors with high-filling factor by using variable thickness

. Superconductor Science and Technology, 34.

Current crowding at bends of superconducting nanowire single-photon detector (SNSPD) is one of the main factors limiting the performance of meander-style detectors with large filling factors. In this paper, we propose a new concept to reduce the influence of the current crowding effect, a so-called variable thickness SNSPD, which is composed of two regions with different thicknesses. A larger thickness of bends in comparison to the thickness of straight nanowire sections locally reduces the current density and reduces the suppression of the critical current caused by current crowding. This allows variable thickness SNSPD to have a higher critical current, an improved detection efficiency, and decreased dark count rate in comparison with a standard uniform thickness SNSPD with an identical geometry and film quality.

See also: Photonics
Shaimaa I. Azzam, Krishnakali Chaudhuri, Alexei Lagutchev, Zubin Jacob, Young L., Vladimir M. Shalaev, Alexandra Boltasseva, and Alexander V. Kildishev. 1/27/2021.

Single and Multi-Mode Directional Lasing from Arrays of Dielectric Nanoresonators

. Laser \& Photonics Reviews, 15.

Abstract The strong electric and magnetic resonances in dielectric subwavelength structures have enabled unique opportunities for efficient manipulation of light–matter interactions. Besides, the dramatic enhancement of nonlinear light–matter interactions near so-called bound states in the continuum (BICs) has recently attracted enormous attention due to potential advancements. However, the experimental realizations and the applications of high-Q factor resonances in dielectric resonances in the visible have thus far been considerably limited. In this work, the interplay of electric and magnetic dipoles in arrays of dielectric nanoresonators is explored. The experimental realization of high-Q factor resonances in the visible through the collective diffractive coupling of electric and magnetic dipoles is reported. It is also shown that coupling the Rayleigh anomaly of the array with the dipoles of the individual nanoresonators can result in the formation of different types of BICs. The resonances in the visible regime is utilized to achieve lasing action at room temperature with high spatial directionality and low threshold. Finally, multi-mode, directional lasing is experimentally demonstrated and the BIC-assisted lasing mode engineering in arrays of dielectric nanoresonators is studied. It is believed that the results enable a new range of applications in flat photonics through realizing on-chip controllable single and multi-wavelength micro-lasers.

See also: Photonics


Chinmay Khandekar, Farhad Khosravi, Zhou Li, and Zubin Jacob. 12/2020.

New spin-resolved thermal radiation laws for nonreciprocal bianisotropic media

. New Journal of Physics, 22.

A chiral absorber of light can emit spin-polarized (circularly polarized) thermal radiation based on Kirchhoff’s law which equates spin-resolved emissivity with spin-resolved absorptivity for reciprocal media at thermal equilibrium. No such law is known for nonreciprocal media. In this work, we discover three spin-resolved Kirchhoff’s laws of thermal radiation applicable for both reciprocal and nonreciprocal planar media. In particular, these laws are applicable to multi-layered or composite slabs of generic bianisotropic material classes which include (uniaxial or biaxial) birefringent crystals, (gyrotropic) Weyl semimetals, magnetized semiconductors, plasmas, ferromagnets and ferrites, (magnetoelectric) topological insulators, metamaterials and multiferroic media. We also propose an experiment to verify these laws using a single system of doped indium antimonide (InSb) thin film in an external magnetic field. Furthermore, we reveal a surprising result that the planar slabs of all these material classes can emit partially circularly polarized thermal light without requiring any surface patterning, and identify planar configurations which can experience nontrivial thermal optomechanical forces and torques upon thermal emission into the external environment at lower temperature (nonequilibrium). Our work also provides a new fundamental insight of detailed balance of angular momentum (in addition to energy) of equilibrium thermal radiation, and paves the way for practical functionalities based on thermal radiation using nonreciprocal bianisotropic materials.

See also: Thermal, Photonics
TODD VAN MECHELEN and Zubin Jacob. 10/26/2020.

Viscous Maxwell-Chern-Simons theory for topological electromagnetic phases of matter

. Physical Review B, 102, 15.

Chern-Simons theories have been very successful in explaining integer and fractional quantum Hall phases of matter, topological insulators, and Weyl semimetals. However, it remains an open question as to whether Chern-Simons theories can be adapted to topological photonics. We develop a viscous Maxwell-Chern-Simons theory to capture the fundamental physics of a topological electromagnetic phase of matter. We show the existence of a unique spin-1 skyrmion in the viscous Hall fluid arising from a photonic Zeeman interaction in momentum space. Our work bridges the gap between electromagnetic and condensed matter topological physics while also demonstrating the central role of photon spin-1 quantization in identifying new phases of matter.

See also: Topological, Photonics
Zhujing Xu, Zubin Jacob, and Tongcang Li. 9/18/2020. Enhancement of rotational vacuum friction by surface photon tunneling. Nanophotonics, 10, 1, Pp. 537-543.

When a neutral sphere is rotating near a surface in vacuum, it will experience a frictional torque due to quantum and thermal electromagnetic fluctuations. Such vacuum friction has attracted many interests but has been too weak to be observed. Here we investigate the vacuum frictional torque on a barium strontium titanate (BST) nanosphere near a BST surface. BST is a perovskite ferroelectric ceramic that can have large dielectric responses at GHz frequencies. At resonant rotating frequencies, the mechanical energy of motion can be converted to electromagnetic energy through resonant photon tunneling, leading to a large enhancement of the vacuum friction. The calculated vacuum frictional torques at resonances at subGHz and GHz frequencies are several orders larger than the minimum torque measured by an optically levitated nanorotor recently, and are thus promising to be observed experimentally. Moreover, we calculate the vacuum friction on a rotating sphere near a layered surface for the first time. By optimizing the thickness of the thin-film coating, the frictional torque can be further enhanced by several times.

See also: Quantum, Photonics
Li-Ping Yang and Zubin Jacob. 9/3/2020.

Single-photon pulse induced giant response in N > 100 qubit system

. npj Quantum Information, 6.

The temporal dynamics of large quantum systems perturbed weakly by a single excitation can give rise to unique phenomena at the quantum phase boundaries. Here, we develop a time-dependent model to study the temporal dynamics of a single photon interacting with a defect within a large system of interacting spin qubits (N > 100). Our model predicts a quantum resource, giant susceptibility, when the system of qubits is engineered to simulate a first-order quantum phase transition (QPT). We show that the absorption of a single-photon pulse by an engineered defect in the large qubit system can nucleate a single shot quantum measurement through spin noise read-out. This concept of a single-shot detection event (“click”) is different from parameter estimation, which requires repeated measurements. The crucial step of amplifying the weak quantum signal occurs by coupling the defect to a system of interacting qubits biased close to a QPT point. The macroscopic change in long-range order during the QPT generates amplified magnetic noise, which can be read out by a classical device. Our work paves the way for studying the temporal dynamics of large quantum systems interacting with a single-photon pulse.

Minkyung Kim, Zubin Jacob, and Junsuk Rho. 7/20/2020.

Recent advances in 2D, 3D and higher-order topological photonics

. Light: Science & Applications, 9, 1.

Over the past decade, topology has emerged as a major branch in broad areas of physics, from atomic lattices to condensed matter. In particular, topology has received significant attention in photonics because light waves can serve as a platform to investigate nontrivial bulk and edge physics with the aid of carefully engineered photonic crystals and metamaterials. Simultaneously, photonics provides enriched physics that arises from spin-1 vectorial electromagnetic fields. Here, we review recent progress in the growing field of topological photonics in three parts. The first part is dedicated to the basics of topological band theory and introduces various two-dimensional topological phases. The second part reviews three-dimensional topological phases and numerous approaches to achieve them in photonics. Last, we present recently emerging fields in topological photonics that have not yet been reviewed. This part includes topological degeneracies in nonzero dimensions, unidirectional Maxwellian spin waves, higher-order photonic topological phases, and stacking of photonic crystals to attain layer pseudospin. In addition to the various approaches for realizing photonic topological phases, we also discuss the interaction between light and topological matter and the efforts towards practical applications of topological photonics.

See also: Topological, Photonics
Saman Jahani, Li-Ping Yang, Adrián Buganza Tepole, Joseph C. Bardin, Hong X. Tang, and Zubin Jacob. 4/9/2020.

Probabilistic vortex crossing criterion for superconducting nanowire single-photon detectors

. Journal of Applied Physics, 127, 14, Pp. 143101.

Superconducting nanowire single-photon detectors have emerged as a promising technology for quantum metrology from the mid-infrared to ultraviolet frequencies. Despite recent experimental successes, a predictive model to describe the detection event in these detectors is needed to optimize the detection metrics. Here, we propose a probabilistic criterion for single-photon detection based on single-vortex (flux quanta) crossing the width of the nanowire. Our model makes a connection between the dark counts and photon counts near the detection threshold. The finite-difference calculations demonstrate that a change in the bias current distribution as a result of the photon absorption significantly increases the probability of single-vortex crossing even if the vortex potential barrier has not vanished completely. We estimate the instrument response function and show that the timing uncertainty of this vortex tunneling process corresponds to a fundamental limit in timing jitter of the click event. We demonstrate a trade-space between this intrinsic (quantum) timing jitter, quantum efficiency, and dark count rate in TaN, WSi, and NbN superconducting nanowires at different experimental conditions. Our detection model can also explain the experimental observation of exponential decrease in the quantum efficiency of SNSPDs at lower energies. This leads to a pulse-width dependency in the quantum efficiency, and it can be further used as an experimental test to compare across different detection models.

See also: Quantum, Photonics