Unique structural and optical properties of atomically thin two-dimensional semiconducting transition metal dichalcogenides enable in principle their efficient coupling to photonic cavities having ...the optical mode volume close to or below the diffraction limit. Recently, it has become possible to make all-dielectric nano-cavities with reduced mode volumes and negligible non-radiative losses. Here, we realise low-loss high-refractive-index dielectric gallium phosphide (GaP) nano-antennas with small mode volumes coupled to atomic mono- and bilayers of WSeFormula: see text. We observe a photoluminescence enhancement exceeding 10Formula: see text compared with WSeFormula: see text placed on planar GaP, and trace its origin to a combination of enhancement of the spontaneous emission rate, favourable modification of the photoluminescence directionality and enhanced optical excitation efficiency. A further effect of the coupling is observed in the photoluminescence polarisation dependence and in the Raman scattering signal enhancement exceeding 10Formula: see text. Our findings reveal dielectric nano-antennas as a promising platform for engineering light-matter coupling in two-dimensional semiconductors.
Time-varying metasurfaces are emerging as a powerful instrument for the dynamical control of the electromagnetic properties of a propagating wave. Here we demonstrate an efficient time-varying ...metasurface based on plasmonic nano-antennas strongly coupled to an epsilon-near-zero (ENZ) deeply subwavelength film. The plasmonic resonance of the metal resonators strongly interacts with the optical ENZ modes, providing a Rabi level spitting of ∼30%. Optical pumping at frequency ω induces a nonlinear polarization oscillating at 2ω responsible for an efficient generation of a phase conjugate and a negative refracted beam with a conversion efficiency that is more than 4 orders of magnitude greater compared to the bare ENZ film. The introduction of a strongly coupled plasmonic system therefore provides a simple and effective route towards the implementation of ENZ physics at the nanoscale.
The integration of optoelectronic devices, such as transistors and photodetectors (PDs), into wearables and textiles is of great interest for applications such as healthcare and physiological ...monitoring. These require flexible/wearable systems adaptable to body motions, thus materials conformable to non-planar surfaces, and able to maintain performance under mechanical distortions. Here, we prepare fibre PDs combining rolled graphene layers and photoactive perovskites. Conductive fibres (∼500 Ω/cm) are made by rolling single-layer graphene (SLG) around silica fibres, followed by deposition of a dielectric layer (Al
O
and parylene C), another rolled SLG as a channel, and perovskite as photoactive component. The resulting gate-tunable PD has a response time∼9ms, with an external responsivity∼22kA/W at 488nm for a 1V bias. The external responsivity is two orders of magnitude higher, and the response time one order of magnitude faster, than state-of-the-art wearable fibre-based PDs. Under bending at 4mm radius, up to∼80% photocurrent is maintained. Washability tests show∼72% of initial photocurrent after 30 cycles, promising for wearable applications. This article is protected by copyright. All rights reserved.
Abstract
Layered materials (LMs) produced by liquid phase exfoliation (LPE) can be used as building blocks for optoelectronic applications. However, when compared with mechanically exfoliated flakes, ...or films prepared by chemical vapor deposition (CVD), LPE-based printed optoelectronic devices are limited by mobility, defects and trap states. Here, we present a scalable fabrication technique combining CVD with LPE LMs to overcome such limitations. We use black phosphorus inks, inkjet-printed on graphene on Si/SiO
2
, patterned by inkjet printing based lithography, and source and drain electrodes printed with an Ag ink, to prepare photodetectors (PDs). These have an external responsivity (
R
ext
)∼337 A W
−1
at 488 nm, and operate from visible (∼488 nm) to short-wave infrared (∼2.7
µ
m,
R
ext
∼
48 mA W
−1
). We also use this approach to fabricate flexible PDs on polyester fabric, one of the most common used in textiles, achieving
R
ext
∼
6 mA W
−1
at 488 nm for an operating voltage of 1 V. Thus, our combination of scalable CVD and LPE techniques via inkjet printing is promising for wearable and flexible applications.
Abstract Layered material heterostructures (LMHs) can be used to fabricate electroluminescent devices operating in the visible spectral region. A major advantage of LMH-based light emitting diodes ...(LEDs) is that electroluminescence (EL) emission can be tuned across that of different exciton complexes (e.g. biexcitons, trions, quintons) by controlling the charge density. However, these devices have an EL quantum efficiency as low as ∼10 −4 %. Here, we show that the superacid bis-(triuoromethane)sulfonimide (TFSI) treatment of monolayer WS 2 -LEDs boosts EL quantum efficiency by over one order of magnitude at room temperature. Non-treated devices emit light mainly from negatively charged excitons, while the emission in treated ones predominantly involves radiative recombination of neutral excitons. This paves the way to tunable and efficient LMH-based LEDs.
Next-generation data networks need to support Tb/s rates. In-phase and quadrature (IQ) modulation combine phase and intensity information to increase the density of encoded data, reduce overall power ...consumption by minimising the number of channels, and increase noise tolerance. To reduce errors when decoding the received signal, intersymbol interference must be minimised. This is achieved with pure phase modulation, where the phase of the optical signal is controlled without changing its intensity. Phase modulators are characterised by the voltage required to achieve a \(\pi\) phase shift V\(_{\pi}\), the device length L, and their product V\(_{\pi}\)L. To reduce power consumption, IQ modulators are needed with\(<\)1V drive voltages and compact (sub-cm) dimensions, which translate in V\(_\pi\)L\(<\)1Vcm. Si and LiNbO\(_3\) (LN) IQ modulators do not currently meet these requirements, because V\(_{\pi}\)L\(>\)1Vcm. Here, we report a double single-layer graphene (SLG) Mach-Zehnder modulator (MZM) with pure phase modulation in the transparent regime, where optical losses are minimised and remain constant with increasing voltage. Our device has \(V_{\pi}L\sim\)0.3Vcm, matching state-of-the-art SLG-based MZMs and plasmonic LN MZMs, but with pure phase modulation and low insertion loss (\(\sim\)5dB), essential for IQ modulation. Our \(V_\pi L\) is\(\sim\)5 times lower than the lowest thin-film LN MZMs, and\(\sim\)3 times lower than the lowest Si MZMs. This enables devices with complementary metal-oxide semiconductor compatible V\(_\pi\)L (\(<\)1Vcm) and smaller footprint than LN or Si MZMs, improving circuit density and reducing power consumption by one order of magnitude.
The integration of optoelectronic devices, such as transistors and photodetectors (PDs), into wearables and textiles is of great interest for applications such as healthcare and physiological ...monitoring. These require flexible/wearable systems adaptable to body motions, thus materials conformable to non-planar surfaces, and able to maintain performance under mechanical distortions. Here, we prepare fibre PDs combining rolled graphene layers and photoactive perovskites. Conductive fibres (\(\sim\)500\(\Omega\)/cm) are made by rolling single layer graphene (SLG) around silica fibres, followed by deposition of a dielectric layer (Al\(_{2}\)O\(_{3}\) and parylene C), another rolled SLG as channel, and perovskite as photoactive component. The resulting gate-tunable PDs have response time\(\sim\)5ms, with an external responsivity\(\sim\)22kA/W at 488nm for 1V bias. The external responsivity is two orders of magnitude higher and the response time one order of magnitude faster than state-of-the-art wearable fibre based PDs. Under bending at 4mm radius, up to\(\sim\)80\% photocurrent is maintained. Washability tests show\(\sim\)72\% of initial photocurrent after 30 cycles, promising for wearable applications.
Layered material heterostructures (LMHs) can be used to fabricate
electroluminescent devices operating in the visible spectral region. A major
advantage of LMH-light emitting diodes (LEDs) is that ...electroluminescence (EL)
emission can be tuned across that of different exciton complexes (e.g.
biexcitons, trions, quintons) by controlling the charge density. However, these
devices have an EL quantum efficiency as low as$\sim$10$^{-4}$\%. Here, we show
that the superacid bis-(triuoromethane)sulfonimide (TFSI) treatment of
monolayer WS$_2$-LEDs boosts EL quantum efficiency by over one order of
magnitude at room temperature. Non-treated devices emit light mainly from
negatively charged excitons, while the emission in treated ones predominantly
involves radiative recombination of neutral excitons. This paves the way to
tunable and efficient LMH-LEDs
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