Spinning polariton vortices with magnetic field

This is an accepted manuscript of an article published by American Physical Society in Physical Review B on 12/03/2020, available online: https://doi.org/10.1103/PhysRevB.101.104308 The accepted version of the publication may differ from the final published version.We study the formation dynamics of spinor polariton condensates trapped in ring-shaped confining potentials created by excitonic reservoirs. We consider in detail the interplay of the effective spin-orbit interaction provided by transverse electric and transverse magnetic photonic modes splitting (TE-TM splitting) and exciton Zeeman splitting provided by an external magnetic field. We demonstrate that tuning of the trap size obtained by shaping of the external nonresonant and depolarized pumping allows formation of pairs of half-vortices of topological charges ±1/2 in both spin components. Further, we show that the probabilities of the realizations of four possible vortex configurations strongly depend on the value of the magnetic field. For certain values of the field, the probability of the formation of a vortex with desired topological charge reaches 90%, which opens the possibility of on-demand control of angular momentum of quantum fluids of light with a magnetic field.Published versio

Optical analogue of Dresselhaus spin–orbit interaction in photonic graphene

This is an accepted manuscript of an article published by Springer in Nature Photonics on 30/11/2020, available online: https://doi.org/10.1038/s41566-020-00729-z The accepted version of the publication may differ from the final published version.The concept of gauge fields plays a significant role in many areas of physics, from particle physics and cosmology to condensed-matter systems, where gauge potentials are a natural consequence of electromagnetic fields acting on charged particles and are of central importance in topological states of matter1. Here, we report on the experimental realization of a synthetic non-Abelian gauge field for photons2 in a honeycomb microcavity lattice3. We show that the effective magnetic field associated with transverse electric–transverse magnetic splitting has the symmetry of the Dresselhaus spin–orbit interaction around Dirac points in the dispersion, and can be regarded as an SU(2) gauge field4. The symmetry of the field is revealed in the optical spin Hall effect, where, under resonant excitation of the Dirac points, precession of the photon pseudospin around the field direction leads to the formation of two spin domains. Furthermore, we observe that the Dresselhaus-type field changes its sign in the same Dirac valley on switching from s to p bands, in good agreement with the tight-binding modelling. Our work demonstrating a non-Abelian gauge field for light on the microscale paves the way towards manipulation of photons via spin on a chip.Published versio

Novel Use of Matched Filtering for Synaptic Event Detection and Extraction

Efficient and dependable methods for detection and measurement of synaptic events are important for studies of synaptic physiology and neuronal circuit connectivity. As the published methods with detection algorithms based upon amplitude thresholding and fixed or scaled template comparisons are of limited utility for detection of signals with variable amplitudes and superimposed events that have complex waveforms, previous techniques are not applicable for detection of evoked synaptic events in photostimulation and other similar experimental situations. Here we report on a novel technique that combines the design of a bank of approximate matched filters with the detection and estimation theory to automatically detect and extract photostimluation-evoked excitatory postsynaptic currents (EPSCs) from individually recorded neurons in cortical circuit mapping experiments. The sensitivity and specificity of the method were evaluated on both simulated and experimental data, with its performance comparable to that of visual event detection performed by human operators. This new technique was applied to quantify and compare the EPSCs obtained from excitatory pyramidal cells and fast-spiking interneurons. In addition, our technique has been further applied to the detection and analysis of inhibitory postsynaptic current (IPSC) responses. Given the general purpose of our matched filtering and signal recognition algorithms, we expect that our technique can be appropriately modified and applied to detect and extract other types of electrophysiological and optical imaging signals

Design and fabrication of Cherenkov flux-flow oscillator

The Josephson Flux-Flow Oscillator (FFO) has been used as an on chip local oscillator at frequencies up to 650 GHz. The FFO linewidth of about 1 MHz was measured in the resonant regime at V <915 mu V for niobium - aluminum oxide - niobium tunnel junctions, while considerably larger values were reported at higher voltages. To overcome this fundamental linewidth broadening we propose a novel on chip Cherenkov radiation flux-flow oscillator (CRFFO). It consists of a long Josephson junction and a superconducting slow wave transmission line that modifies essentially the junction dispersion relation. Two SIS detectors are connected both to the long Josephson junction and the transmission line to evaluate available microwave power. The output power coming both from the long junction and the transmission line is estimated at different bias conditions

Forward and backward waves in Cherenkov flux-flow oscillators

Josephson flux-flow oscillators (FFOs) have been used as an on-chip local oscillator at frequencies up to 650 GHz. An autonomous FFO linewidth of about 1 MHz was measured in the resonant regime at V-b <950 mu V for niobium-aluminium oxide-niobium tunnel junctions, while considerably larger values were reported at higher voltages. To overcome this fundamental linewidth broadening we propose an on-chip Cherenkov radiation Aux-flow oscillator (CRFFO). It consists of a long Josephson junction and a superconducting slow-wave transmission line that modifies significantly the junction dispersion relation. Two superconductor-insulator-superconductor junction detectors are connected to both the long Josephson junction and the slow-wave line to determine the available microwave power. The power is measured at different CRFFO biasing conditions. Both a forward wave and a backward wave oscillation regime are observed. An FFO and a CRFFO with the same junction parameters are compared

van der Waals metal-organic framework as an excitonic material for advanced photonics

\u3cp\u3evan der Waals metal-organic framework (MOF) is used as an excitonic material for advanced photonics. van der Waals supports different types of excitons and provides a dimensional confinement effect, which is especially pronounced for 2D structures and strongly changes the exciton parameters. The restrictions can also be overcome by creating microcavities with Bragg mirrors made of atomically thin organic semiconductors inside. Such a device is an elegant solution for manipulation of exciton states by light, but its construction remains highly sophisticated.\u3c/p\u3

Rogue events in the group velocity horizon

The concept of rogue waves arises from a mysterious and potentially calamitous phenomenon of oceanic surfaces. There is mounting evidence that they are actually commonplace in a variety of different physical settings. A set of defining criteria has been advanced; this set is of great generality and therefore applicable to a wide class of systems. The question arises naturally whether there are generic mechanisms responsible for extreme events in different systems. Here we argue that under suitable circumstances nonlinear interaction between weak and strong waves results in intermittent giant waves with all the signatures of rogue waves. To obtain these circumstances only a few basic conditions must be met. Then reflection of waves at the so-called group-velocity horizon occurs. The connection between rogue waves and event horizons, seemingly unrelated physical phenomena, is identified as a feature common in many different physical systems