Enhanced Optical Cross Section via Collective Coupling of Atomic Dipoles in a 2D Array

Bettles, Robert J.; Gardiner, S. A.; Adams, Charles S.

doi:10.1103/physrevlett.116.103602

Cited by 234 publications

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“…Their miniaturization is fundamentally limited by the optical wavelength in the case of dielectric mirrors and photonic crystals (1) or by the skin depth for metallic mirrors (2). Recently, resonant scattering has emerged as a method for overcoming these limitations and for controlling light at the atomic scale (3)(4)(5)(6)(7)(8)(9)(10)(11). For instance, highly reflective mirrors based on individual quantum emitters have been demonstrated by coupling them to optical cavities and nanophotonic waveguides (3)(4)(5)(6)(7)(8).…”

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confidence: 99%

“…Such resonant mirrors feature very unusual properties due to their extraordinary nonlinearity down to the single-photon level (3)(4)(5)(6)(7)(8). A two-dimensional (2D) layer of emitters, such as atomic lattices or excitons (9)(10)(11), has also been predicted to act as an efficient mirror when the incident light is resonant with the resonance frequency of the system. Such atomically thin mirrors represent the ultimate miniaturization limit of a reflective surface, and could enable unique applications ranging from quantum nonlinear optics (9-11) to topological photonics (12,13).…”

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Large Excitonic Reflectivity of MonolayerMoSe2Encapsulated in Hexagonal Boron Nitride

et al. 2018

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scattering has emerged as a method for overcoming these limitations and for controlling light at the atomic scale (3-11). For instance, highly reflective mirrors based on individual quantum emitters have been demonstrated by coupling them to optical cavities and nanophotonic waveguides (3-8). Such resonant mirrors feature very unusual properties due to their extraordinary nonlinearity down to the single-photon level (3-8). A two-dimensional (2D) layer of emitters, such as atomic lattices or excitons (9-11), has also been predicted to act as an efficient mirror when the incident light is resonant with the resonance frequency of the system. Such atomically thin mirrors represent the ultimate miniaturization limit of a reflective surface, and could enable unique applications ranging from quantum nonlinear optics (9-11) to topological photonics (12,13).This Report demonstrates that transition metal dichalcogenide (TMD) monolayers can act as atomically thin, electrically switchable, resonant mirrors. These materials are direct-bandgap semiconductors that support tightly bound excitons. Excitonic transitions in TMD monolayers exhibit large oscillator strengths (14-16), resulting in large radiative linewidths compared to excitons in other semiconductor systems. In addition, the excitonic response in monolayers can be controlled electrically via gate-induced doping and by shifting the chemical potential (17)(18)(19).Importantly, these monolayers can be easily integrated with other 2D materials via Van der Waals stacking to improve their quality or add new functionalities. One of the most studied amongst such heterostructures is a TMD monolayer encapsulated by two hexagonal boron nitride 4 (hBN) flakes: this "passivated" monolayer exhibits enhanced carrier mobility (19,20) and reduced photoluminescence linewidth (21,22).Our experiments make use of a device that consists of an hBN-passivated molybdenum diselenide (MoSe 2 ) monolayer placed on an oxide-covered silicon (Si) substrate, and we measure its reflectivity with a normally incident laser beam (Figs. 1A and 1B). The doped Si substrate is used as a gate electrode: by applying a gate voltage (V g ), MoSe 2 monolayers can be made intrinsic or n-doped. When a monochromatic laser beam is tuned to the exciton resonance, we observe substantial reflection from a monolayer device (M1) at V g < 10 V at T = 4 K (Fig. 1C).The reflection contrast between the monolayer region and the substrate disappears at V g > 20 V ( Fig. 1D), indicating that the reflection can be turned off electrically. When we illuminate another monolayer device (M2) with a supercontinuum laser and spectrally resolve the reflection, we find that both the magnitudes and wavelength positions of the reflectance peaks change with V g (Fig. 1E). When the monolayer is intrinsic (V g < 10 V), the reflection is dominated by a peak at the wavelength of the neutral exciton transition. When MoSe 2 is n-doped (V g > 20 V), however, the reflection by the neutral exciton disappears, and a new, weaker, reflectance peak ap...

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Large Excitonic Reflectivity of MonolayerMoSe2Encapsulated in Hexagonal Boron Nitride

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“…These narrow linewidths have a dominant contribution from radiative decay of ∼1.5 meV for MoSe 2 [11,12]. Motivated by these developments, we previously analyzed the optical response of a monolayer TMD theoretically [13] and showed that it realizes an atomically thin mirror [13][14][15].…”

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Realization of an Electrically Tunable Narrow-Bandwidth Atomically Thin Mirror Using MonolayerMoSe2

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Advent of new materials such as van der Waals heterostructures, propels new research directions in condensed matter physics and enables development of novel devices with unique functionalities. Here, we show experimentally that a monolayer of MoSe 2 embedded in a charge controlled heterostructure can be used to realize an electrically tunable atomically-thin mirror, that effects 90% extinction of an incident field that is resonant with its exciton transition. The corresponding maximum reflection coefficient of 45% is only limited by the ratio of the radiative decay rate to the linewidth of exciton transition and is independent of incident light intensity up to 400 Watts/cm 2 . We demonstrate that the reflectivity of the mirror can be drastically modified by applying a gate voltage that modifies the monolayer charge density. Our findings could find applications ranging from fast programmable spatial light modulators to suspended ultra-light mirrors for optomechanical devices.A plethora of ground-breaking experiments have established monolayers of transition metal dichalcogenides (TMD) such as MoSe 2 or WSe 2 as a new class of two dimensional (2D) direct 1

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“…By calculating the scattered electric field across output and input collection lenses, we measure directly the extinction of a single monolayer of atoms, showing that at particular lattice spacings, an incident light beam is almost completely reflected. This work was published in [67].…”

Section: Infinite Limit and Reduction In Complexitymentioning

confidence: 99%

“…We will be following the approaches taken in [101,134]. See as well our paper [67] and the corresponding Supplemental Material.…”

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Cooperative Interactions in Lattices of Atomic Dipoles

Bettles

2017

Springer Theses

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Coherent radiation by an ensemble of scatterers can dramatically modify the ensemble's optical response. This can include, for example, enhanced and suppressed decay rates (superradiance and subradiance respectively), energy level shifts, and highly directional scattering. This behaviour is referred to as cooperative, since the scatterers in the ensemble behave as a collective rather than independently. In this Thesis, we investigate the cooperative behaviour of one-and two-dimensional arrays of interacting atoms.We calculate the extinction cross-section of these arrays, analysing how the cooperative eigenmodes of the ensemble contribute to the overall extinction. Typically, the dominant eigenmode if the atoms are driven by a uniform or Gaussian light beam is the mode in which the atomic dipoles oscillate in phase together and with the same polarisation as the driving field. The eigenvalues of this mode become strongly resonant as the atom number is increased. For a one-dimensional array, the location of these resonances occurs when the atomic spacing is an integer or half integer multiple of the wavelength, thus behaving analogously to a single atom in a cavity. The interference between this mode and additional eigenmodes can result in Fano-like asymmetric lineshapes in the extinction.We find that the kagome lattice in particular exhibits an exceptionally strong interference lineshape, like a cooperative analog of electromagnetically induced transparency.Triangular, square and hexagonal lattices however are typically dominated by one single mode which, for lattice spacings of the order of a wavelength, can be highly subradiant.This can result in near-perfect extinction of a resonant driving field, signifying a significant increase in the atom-light coupling efficiency. We show that this extinction is robust to possible experimental imperfections.

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Enhanced Optical Cross Section via Collective Coupling of Atomic Dipoles in a 2D Array

Cited by 234 publications

References 57 publications

Large Excitonic Reflectivity of MonolayerMoSe2Encapsulated in Hexagonal Boron Nitride

Large Excitonic Reflectivity of MonolayerMoSe2Encapsulated in Hexagonal Boron Nitride

Realization of an Electrically Tunable Narrow-Bandwidth Atomically Thin Mirror Using MonolayerMoSe2

Cooperative Interactions in Lattices of Atomic Dipoles

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