Single- and few-layer crystals of exfoliated MoTe2 have been characterized spectroscopically by photoluminescence, Raman scattering, optical absorption measurements. We find that in the monolayer limit displays strong photoluminescence. On basis complementary results, we conclude is a direct-gap semiconductor with an band gap 1.10 eV. This new material extends spectral range atomically thin materials from visible to near-infrared.

We employ ultrafast pump-probe spectroscopy to directly monitor electron tunneling between discrete orbital states in a pair of spatially separated quantum dots. Immediately after excitation, several peaks are observed the spectrum due Coulomb interactions photogenerated charge carriers. By tuning relative energy two dots and monitoring temporal evolution spectra hole times separately measured resonant is shown be mediated both by elastic inelastic processes. Ultrafast ($<5\text{ }\text{...

The increasing role of two-dimensional (2D) devices requires the development new techniques for ultrafast control physical properties in 2D van der Waals (vdW) nanolayers. A special feature heterobilayers assembled from vdW monolayers is femtosecond separation photoexcited electrons and holes between neighboring layers, resulting formation Coulomb force. Using laser pulses, we generate a 0.8 THz coherent breathing mode MoSe2/WSe2 heterobilayers, which modulates thickness heterobilayer should...

Acoustic nanocavities (ANCs) with resonance frequencies much above 1 GHz are prospective to be exploited in sensors and quantum operating devices. Nowadays, acoustic fabricated from van der Waals (vdW) nanolayers allow them exhibit of the breathing mode up f ∼ THz quality factors Q 103. For such high frequencies, electrical methods fail, optical techniques used for generation detection coherent phonons. Here, we study experimentally WSe2 layers thicknesses 8 130 nm deposited onto silica...

We employ ultrafast pump-probe spectroscopy with photocurrent readout to directly probe the dynamics of a single hole spin in single, electrically tunable self-assembled quantum dot molecule formed by vertically stacking InGaAs dots. Excitons defined configurations are initialized one two dots using circularly polarized picosecond pulses. The time-dependent configuration is probed selective optical absorption resulting few Fermion complex. Taking advantage sub-5 ps electron tunneling an...

We propose and demonstrate a surface acoustic wave-driven converter of light into plasmon polaritons. An otherwise unstructured thin metal film is deformed by traveling waves on piezoelectric substrate underneath. This spatially periodic corrugation enables to bridge the momentum gap between free-space radiation surface-bound modes. principle realized with plain gold films ${\text{LiNbO}}_{3}$ wafer where induce ripples in metal. For near-infrared we observe efficiencies order...

We propose and implement a new concept for thermochromic plasmonic elements. It is based on vanadium dioxide (VO2) nanocrystals located in the near field of surface plasmon polaritons supported by an otherwise unstructured gold thin film. When VO2 undergoes metal-insulator phase transition, coupling conditions conversion light into propagating change markedly. In particular, we realize grating couplers with substantial switching contrast as well tunable Kretschmann configuration. The use...

The nonlinear process of second harmonic generation (SHG) in monolayer (1L) transition metal dichalcogenides (TMD), like WS2, strongly depends on the polarization state excitation light. By combination plasmonic nanostructures with 1L-WS2 by transferring it onto a nanoantenna array, hybrid metasurface is realized impacting dependency its SHG. Here, we investigate how dipole resonances affect SHG plasmonic-TMD metasurfaces spectroscopy. We show that affected lattice structure arrays as well...

We report a comprehensive study of the ultrafast optoelectronic response single self-assembled InGaAs/GaAs quantum dot embedded in $n\text{\ensuremath{-}}i$-Schottky photodiode device. While manipulation artificial atom relies on two independently tunable picosecond pulse trains, sensitive all electrical readout is achieved via photocurrent. apply our methods to probe temporal evolution absorption spectrum following coherent optical generation $s$-shell exciton. Our measurements reveal...

A phase-stable superposition of femtosecond pulses from a compact erbium-doped fiber source and their second harmonic is shown to induce ultrashort ∼μA current bursts in single unbiased GaAs nanowires. Current injection relies on quantum interference one- two-photon absorption pathways. The vector direction the solely dictated by polarization relative phase harmonically related light components while its power dependence consistent with third order optical nonlinearity.

Electron spin transport and dynamics are investigated in a single, high-mobility, modulation-doped, GaAs quantum well using ultrafast two-color Kerr-rotation micro-spectroscopy, supported by qualitative kinetic theory simulations of diffusion transport. Evolution the spins is governed Dresselhaus bulk Rashba structural inversion asymmetries, which manifest as an effective magnetic field that can be extracted directly from experimental coherent precession. A precession length L-SOI defined...

Ultrafast pump‐probe spectroscopy is employed to directly monitor the tunneling of charge carriers from single and vertically coupled quantum dots probe intra‐molecular dynamics. Immediately after resonant optical excitation, several peaks are observed in spectrum arising Coulomb interactions between photogenerated carriers. The influence few‐Fermion photoexcited system temporal evolution response probed time domain. In addition, times for electrons holes QD nanostructure independently...

We present a comprehensive experimental and theoretical study of the power dependence coherently controlled currents in bulk GaAs. Currents are optically induced by phase-stable femtosecond $\ensuremath{\omega}/2\ensuremath{\omega}$ pulse pairs. For moderate irradiances, these linked to third-order optical nonlinearity ${\ensuremath{\chi}}^{(3)}(0;\ensuremath{\omega},\ensuremath{\omega},\ensuremath{-}2\ensuremath{\omega})$. Here we focus on elevated irradiances where absorption saturation...

We explore the impact of ∼500 MHz surface acoustic waves traveling across a commensurable plasmonic grating coupler. A stroboscopic technique involving synchronized to modelocked optical source allows time-resolve dynamical electromechanically induced perturbation. The wave periodically enhances or decreases ripple static grating. Most remarkably, dynamic deformation deliberately modulates coupler's efficiency by ±2% during ∼2 ns cycle.

A single InGaAs∕GaAs quantum dot is addressed in a two-color femtosecond transmission experiment the optical near-field of nanometer-scale shadow mask. After resonant excitation wetting layer beneath nanoisland, we detect changes with narrow band femtojoule probe pulses. We find bleaching signals order 10−5 that arise from individual interband transitions. Moreover, nonlinear response reveals picosecond dynamics associated carrier relaxation dot. As result, have developed an ultrafast tool...

A 58 MHz femtosecond Ti:sapphire oscillator is optimized for long wavelength operation beyond 900 nm. Sub 30 fs, approximately 3 nJ pulses with a bandwidth exceeding 20 THz are realized central wavelengths nm < or = lambda 960 This laser opens up new perspectives the sensitive time-resolved spectroscopy of various semiconductor nanostructures. Moreover, its second harmonic serves as source visible multi-milliwatt tunable around 475

The drift of electron spin helices in an external in-plane electric field GaAs quantum wells is studied by means time-resolved magneto-optical Kerr microscopy. evolution the distribution measured for different excitation powers reveals that, short delay times and higher powers, helix slows down while its envelope becomes anisotropic. effect understood as a local decrease gas mobility due to collisions with nonequilibrium holes within spot reproduced well kinetic theory framework. For larger...

We implement a versatile concept to time-resolve optical nonlinearities of semiconductors in amplitude and phase. A probe pulse transmitted through the optically pumped sample is superimposed with first subharmonic spectral components derived from same laser source. This effective ω/2ω pair induces coherently controlled current time-integrating semiconductor detector. Current interferograms obtained by scanning time delay then reveal electric field 2ω part as well its pump-induced...

We propose and demonstrate an ultrabroadband concept to characterize amplitude phase changes of femtosecond pulses. The radiation is superimposed with the first subharmonic spectral components from same laser source. This effective ω/2ω pulse pair induces a coherently controlled charge current in time-integrating semiconductor detector. An interferometric variation time delay between harmonically related then reveals electric field 2ω part. method realized second harmonic compact Er:fiber...

Understanding and controlling the spin degree of freedom in two-dimensional transition metal dichalcogenides offers potential for designing functional quantum materials. This work investigates dynamics photo- resident carrier spins an encapsulated MoSe2 monolayer using non-degenerate time-resolved Kerr-rotation microscopy. The lightly doped exhibits clear exciton trion resonances with spin-polarizations that are characterized by a fast (~20 ps) decay attributed to photocarrier relaxation...

Nonlinear optical processes often suffer from rather weak efficiencies. Here, the authors investigate two-photon absorption in ZnSe and demonstrate a tremendous enhancement of coefficient $\ensuremath{\beta}({\ensuremath{\omega}}_{1},{\ensuremath{\omega}}_{2})$ nondegenerate regime. Considering constant frequency sum ${\ensuremath{\omega}}_{1}+{\ensuremath{\omega}}_{2}$, they measure an about tenfold increase $\ensuremath{\beta}$ at ratio...