Light-Driven Nanoscale Vectorial Currents

Controlled charge flows are fundamental to many areas of science and technology, serving as carriers of energy and information, as probes of material properties and dynamics, and as a means of revealing or even inducing broken symmetries. Emerging methods for light-based current control offer promising routes beyond the speed and adaptability limitations of conventional voltage-driven systems. However, optical manipulation of currents at nanometer spatial scales remains a basic challenge and a key step toward scalable optoelectronic systems and local probes. Here, we introduce vectorial optoelectronic metasurfaces as a new class of metamaterial in which ultrafast charge flows are driven by light pulses, with actively-tunable directionality and arbitrary patterning down to sub-diffractive nanometer scales. In the prototypical metasurfaces studied herein, asymmetric plasmonic nanoantennas locally induce directional, linear current responses within underlying graphene. Nanoscale unit cell symmetries are read out via polarization- and wavelength-sensitive currents and emitted terahertz (THz) radiation. Global vectorial current distributions are revealed by spatial mapping of the THz field polarization, also demonstrating the direct generation of elusive broadband THz vector beams. We show that a detailed interplay between electrodynamic, thermodynamic, and hydrodynamic degrees of freedom gives rise to these currents through rapidly-evolving nanoscale forces and charge flows under extreme spatial and temporal localization. These results set the stage for versatile patterning and optical control over nanoscale currents in materials diagnostics, nano-magnetism, microelectronics, and ultrafast information science

The Musicality of Non-Musicians: An Index for Assessing Musical Sophistication in the General Population

Musical skills and expertise vary greatly in Western societies. Individuals can differ in their repertoire of musical behaviours as well as in the level of skill they display for any single musical behaviour. The types of musical behaviours we refer to here are broad, ranging from performance on an instrument and listening expertise, to the ability to employ music in functional settings or to communicate about music. In this paper, we first describe the concept of ‘musical sophistication’ which can be used to describe the multi-faceted nature of musical expertise. Next, we develop a novel measurement instrument, the Goldsmiths Musical Sophistication Index (Gold-MSI) to assess self-reported musical skills and behaviours on multiple dimensions in the general population using a large Internet sample (n = 147,636). Thirdly, we report results from several lab studies, demonstrating that the Gold-MSI possesses good psychometric properties, and that self-reported musical sophistication is associated with performance on two listening tasks. Finally, we identify occupation, occupational status, age, gender, and wealth as the main socio-demographic factors associated with musical sophistication. Results are discussed in terms of theoretical accounts of implicit and statistical music learning and with regard to social conditions of sophisticated musical engagement

All-optical THz pulse shaping in a dynamic waveguide

Controlling light and manipulating its flow is an important capability for the development of new technologies, often relevant to communications, and to fundamental research alike. All optical control using pulsed laser systems allows dynamic photon manipulation on femtosecond timescales and enables ultrafast, reversible switching often unlocking new capabilities beyond passive optical components. In this work, we demonstrate an all-optical platform for THz pulse shaping based on charge carrier photoinjection inside a semiconductor-filled parallel-plate waveguide operating over a broadband frequency range between 0.1 and 1.5 THz. The synthesis of arbitrarily-shaped THz waveforms, tunable in amplitude, linewidth and center frequency, is demonstrated by creating multiple replicas of a single-cycle high-field THz pulse. The physics underlying the platform's inner workings are discussed and we present experimental data collected using pump-probe time domain THz spectroscopy. The platform further demonstrates the ability to tune the phase of the reflected single-cycle pulse and the capability to engineer the instantaneous frequency of a waveform demonstrating positive, negative and compound chirps. We further present preliminary experimental results using such sculpted pulses to perform space to-time imaging as well as time-to-space imaging. We discuss the possibility of dynamic photonic band structure switching and show preliminary demonstrations of coherent control of rotational wave packets in water vapourLa capacité de contrôler la lumière et de manipuler sa propagation est une compétence importante dans le développement de nouvelles technologies souvent essentielle aux communications et à la recherche fondamentale également. Le contrôle entièrement optique employant un laser pulsé permet d'effectuer des manipulations photoniques dynamiques sur l'échelle de la femtoseconde et rend possible des commutations ultrarapides et réversibles souvent débloquant de nouvelles capacités qui vont au-delà des composantes optiques passives.Dans ce manuscrit, nous démontrons une plateforme entièrement optique pour former des impulsions THz basée sur la photo-injection de porteurs de charge à l'intérieur d'un guide d'onde à plaques parallèles empli d'un semiconducteur sur une bande de fréquence allant de 0.1 à 1.5 THz. La synthèse d'impulsions THz de forme arbitraire modulaire en amplitude, largeur de raie, et fréquence centrale est démontrée par la création de multiples répliques d'un pulse THz monocycle à haute intensité. La physique sous-jacente est discutée et nous présentons des données expérimentales collectées utilisant la spectroscopie THz pompe-sonde résolue en temps. La platforme démontre d'ailleurs l'habileté à moduler la phase d'une impulsion monocycle réfléchie ainsi que la capacité de sculpter la fréquence instantanée d'une onde en démontrant un chirp positif, négatif et composés.Nous présentons de plus des résultats expérimentaux supplémentaires employant la méthode de modulation des pulses pour démontrer l'imagerie espace-temps ainsi que temps-espace. Nous discutons de plus de la possibilité de créer des structures de bandes photoniques de façon dynamique et démontrons des résultats préliminaires de manipulation cohérente du paquet d'onde de molécules d'eau à l'état gazeux

Optically-induced mode coupling of terahertz light withing a parallel-plate waveguide

Achieving control over the flow of light opens a great number of research avenues and allows for the development of new optical technology often relevant to the communication industry. All-optical control using ultrafast, short pulsed laser systems further allows dynamic control on time scales as short as a few 10's of femtoseconds which leads to new regimes of interaction where light can be confined or modulated beyond conventional limitations such as the delay-bandwidth limit of a resonator. In this work, we demonstrate all-optical control of mode coupling for THz light propagating in a silicon-filled parallel-plate waveguide. Utilizing terahertz time-domain spectroscopy we probe on femtosecond time scales the light-induced modulation of transmission lines between 0.1 - 4 THz. We observe a spectral interference pattern thus creating an all-optical frequency-selective modulator tunable over 900 GHz in bandwidth. A spatially-defined photoexcitation of charge carriers at the surface of the silicon slab waveguide is injected using a femtosecond near-infrared pulse. The waveguide symmetry is broken and THz light is partially coupled from TM0 to TM1 mode resulting in a strong frequency dependent spectral transmission modulation caused by the coupling of the modes. We demonstrate a widely tunable electric field amplitude transmission by adjusting the relative modal phases by translating the excitation along the propagation direction. The theory of light propagation inside a parallel-plate waveguide is presented along with the techniques employed to generate and detect broadband terahertz pulses. A new time-domain THz spectrometer constructed for these experiments is presented. We further introduce simulation results to picture the physically relevant phenomenon along with coupled-mode theory to depict the scattering mechanism of the TM0 mode into higher-order modes.Accomplir un contrôle arbitraire sur la propagation de la lumière ouvre de nombreuses avenues du point de vue de la recherche fondamentale ainsi que pour le dévelopement de nouvelles technologies applicables à l'industrie de la communication. La modulation purement optique employant la lumière pulsée permet d'effectuer des manipulations dynamiques de la lumière sur des échelles de temps de la dizaine de femtoseconde permettant d'étudier de nouveaux régimes d'intéraction pour lesquels la lumière peut être confinée ou modulée au delà des limites conventionnelles. En employant des pulses terahertz avec un contenu en fréquence allant de 0.1 à 4 THz, nous développons une ligne à transmission employant des semi-conducteurs à faible densité de dopants. Un spectromètre terahertz résolu en temps nous permet d'étudier sur une échelle de la femtoseconde la modulation de cette ligne à transmission effectuée par l'injection de porteurs de charge à l'intérieur d'un guide d'onde à plaques parallèles empli de silicium. Dans ce travail nous démontrons un contrôle purement optique du couplage des modes de lumière terahertz dans un guide d'ondes à plaques parallèles empli de silicium. Nous observons un patron d'interférence démontrant un modulateur en fréquence réglable sur une bande passante de plus de 900 GHz. Un patron d'excitation optique défini spatialement injecte des porteurs de charge près de la surface du silicium en employant un pulse femtoseconde dans l'infrarouge proche. La symétrie interne du guide d'onde est brisée et le pulse THz est partiallement couplé du mode TM0 au mode TM1 résultant en une importante modulation dépendante en fréquence causée par le couplage entre les modes. Nous démontrons un modulateur en amplitude du champ électrique ajustable en fréquence sur une large bande passante en déplaçant le patron d'excitation le long de l'axe de propagation du pulse terahertz. Nous présentons la théorie requise afin d'étudier la propagation de a lumière à l'intérieure d'un guide d'ondes à plaques parallèles ainsi que les techniques employées pour générer et detecter un pulse térahertz. Un nouveau spectromètre THz résolu en temps est construit afin d'accomplir les expériences présentées. Nous présentons des résultats de simulations afin d’imager les phénomènes physiques pertinents et afin de décrire le mécanisme de couplage entre le mode TM0 et les modes d'ordre supérieurs

Perception of musical timbre in congenital amusia: categorization, discrimination and short-term memory

Congenital amusia is a neurodevelopmental disorder that is characterized primarily by difficulties in the pitch domain. The aim of the present study was to investigate the perception of musical timbre in a group of individuals with congenital amusia by probing discrimination and short-term memory for real-world timbral stimuli as well as examining the ability of these individuals to sort instrumental tones according to their timbral similarity. Thirteen amusic individuals were matched with thirteen non-amusic controls on a range of background variables. The discrimination task included stimuli of two different durations and pairings of instrumental tones that reflected varying distances in a perceptual timbre space. Performance in the discrimination task was at ceiling for both groups. In contrast, amusic individuals scored lower than controls on the short-term timbral memory task. Amusic individuals also performed worse than controls on the sorting task, suggesting differences in the higher-order representation of musical timbre. These findings add to the emerging picture of amusia as a disorder that has consequences for the perception and memory of musical timbre, as well as pitch

3107287.pdf

FDTD simulation results for a 32 cycle wavefor

Affective evaluation of simultaneous tone combinations in congenital amusia

AbstractCongenital amusia is a neurodevelopmental disorder characterized by impaired pitch processing. Although pitch simultaneities are among the fundamental building blocks of Western tonal music, affective responses to simultaneities such as isolated dyads varying in consonance/dissonance or chords varying in major/minor quality have rarely been studied in amusic individuals. Thirteen amusics and thirteen matched controls enculturated to Western tonal music provided pleasantness ratings of sine-tone dyads and complex-tone dyads in piano timbre as well as perceived happiness/sadness ratings of sine-tone triads and complex-tone triads in piano timbre. Acoustical analyses of roughness and harmonicity were conducted to determine whether similar acoustic information contributed to these evaluations in amusics and controls. Amusic individuals' pleasantness ratings indicated sensitivity to consonance and dissonance for complex-tone (piano timbre) dyads and, to a lesser degree, sine-tone dyads, whereas controls showed sensitivity when listening to both tone types. Furthermore, amusic individuals showed some sensitivity to the happiness-major association in the complex-tone condition, but not in the sine-tone condition. Controls rated major chords as happier than minor chords in both tone types. Linear regression analyses revealed that affective ratings of dyads and triads by amusic individuals were predicted by roughness but not harmonicity, whereas affective ratings by controls were predicted by both roughness and harmonicity. We discuss affective sensitivity in congenital amusia in view of theories of affective responses to isolated chords in Western listeners