Search results for "terahertz"
showing 10 items of 152 documents
Spin-resolved terahertz spectroscopy
2016
As such, terahertz spectroscopy cannot resolve the spin structure of conducting particles. Here we introduce the spin sensitivity to terahertz spectroscopy by using the spin-valve configuration of the sample. As a result, the number density and momentum scattering time of conduction electrons in a ferromagnetic metal can be resolved according to their spin.
Generation of broadband THz transients via metallic spintronic emitters driven by 20-fs pulses at 1030 nm
2020
We explore power and bandwidth scaling for the generation of highly-temporally-confined THz transients from spintronic emitters, driven by the 250-fs and 20-fs pulses of a high-power 28-MHz Yb-based laser, spectrally centered at 1030 nm.
Effect of DC Electric Field on the Emitted THz Signal of Antenna-Coupled Spintronic Emitters
2019
We study the impact of an external electric DC field on antenna-coupled spintronic THz emitters driven by a 90 fs, 1550 nm laser oscillator. Simultaneous application of external electric and magnetic field shows a quadratic decrease in peak-peak THz pulse with increase in the bias voltage. We ascribe this decrease to Joule heating caused by the DC current flowing through the spintronic material.
Femtosecond exciton dynamics in WSe2 optical waveguides
2020
Van-der Waals (vdW) atomically layered crystals can act as optical waveguides over a broad range of the electromagnetic spectrum ranging from Terahertz to visible. Unlike common Si-based waveguides, vdW semiconductors host strong excitonic resonances that may be controlled using non-thermal stimuli including electrostatic gating and photoexcitation. Here, we utilize waveguide modes to examine photo-induced changes of excitons in the prototypical vdW semiconductor, WSe2, prompted by femtosecond light pulses. Using time-resolved scanning near-field optical microscopy we visualize the electric field profiles of waveguide modes in real space and time and extract the temporal evolution of the op…
Impact of pump wavelength on terahertz emission of a cavity-enhanced spintronic trilayer
2018
We systematically study the pump-wavelength dependence of terahertz pulse generation in thin-film spintronic THz emitters composed of a ferromagnetic Fe layer between adjacent nonmagnetic W and Pt layers. We find that the efficiency of THz generation is essentially at for excitation by 150 fs pulses with center wavelengths ranging from 900 to 1500 nm, demonstrating that the spin current does not depend strongly on the pump photon energy. We show that the inclusion of dielectric overlayers of TiO2 and SiO2, designed for a particular excitation wavelength, can enhance the terahertz emission by a factor of of up to two in field.
Tuning the Ultrafast Response of Fano Resonances in Halide Perovskite Nanoparticles
2020
International audience; The full control of the fundamental photophysics of nanosystems at frequencies as high as few THz is key for tunable and ultrafast nanophotonic devices and metamaterials. Here we combine geometrical and ultrafast control of the optical properties of halide perovskite nanoparticles, which constitute a prominent platform for nanophotonics. The pulsed photoinjection of free carriers across the semiconducting gap leads to a subpicosecond modification of the far-field electromagnetic properties that is fully controlled by the geometry of the system. When the nanoparticle size is tuned so as to achieve the overlap between the narrowband excitons and the geometry-controlled…
Octave-spanning coherent supercontinuum generation in a step-index tellurite fiber and towards few-cycle pulse compression at 2 μ m
2021
Abstract We experimentally demonstrate 140-THz bandwidth (at −20 dB) supercontinuum generation in a 10 cm-long all-normal dispersion step-index tellurite fiber pumped by a turn-key femtosecond fiber laser emitting at 2 . 11 μ m at a repetition rate of 19 MHz. The soliton self-frequency shifted thulium-doped fiber mode-locked laser emits initial transform-limited pulses, with 85-fs pulse duration, that are subsequently quasi-linearly chirped (over more than 50 THz) during the above nJ-level nonlinear propagation. Moreover, we numerically demonstrate the possible pulse compression down to 12 fs by means of additional linear propagation in a standard step-index fluoride fiber with anomalous di…
Antenna Tapering Strategy for Near-Field Enhancement Optimization in Terahertz Gold Nanocavities
2019
Plasmonic nanoantennas (NAs) have received a growing attention in recent years due to their ability to confine light on sub-wavelength dimensions [1]. More recently, this property has been exploited in the terahertz (THz) frequency range (0.1–10 THz) for enhanced sensing and spectroscopy [2], as well as for more fundamental investigations [3]. These applications typically require high local electric fields that can be achieved by concentrating THz radiation into deeply sub-wavelength volumes located at the NAs extremities. However, the achievable near-field enhancement values are severely limited by the poor resonance quality factor of traditional rod-shaped THz NAs. Unlike what is commonly…
Nano-holes vs nano-cracks in thin gold films: What causes anomalous THz transmission?
2015
Nano-structuring materials can change their properties extraordinarily, but so can defects caused by manufacturing. We study the effect of capacitive defects on terahertz transmission in golden nanomeshes, and find their influence crucial.
Space-time features of THz emission from optical rectification in sub-wavelength areas
2011
We present our investigation on the THz space-time emission characteristic induced by the non-paraxial generation regime in highly localized THz generation via optical rectification on sub-wavelength areas.