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Optically induced magnetization, whose relaxation time is of the order of a hundred picoseconds, and coherent oscillations of magnons in terahertz region were observed in an antiferromagnet NiO by polarization spectroscopy with the pump-probe technique.
We inspect inner surfaces of valve body spool bores down to 5 mm diameter for porosity defects, using an optical probe with ∼50 µm lateral resolution. The probe can also distinguish porosity from bump-type defects.
We demonstrate detection and sizing of single nanoparticles down to 30 nm by monitoring the mode splitting induced by a nanoparticle in an ultra-high quality factor (UHQ) microtoroid. Theory and methods are discussed.
We reconstruct the magnetic near-field and source current distribution of a linear coupled-dipole IR optical antenna from the complete 3D electric vector near-field as probed using scattering-type scanning near-field optical microscopy. Fine details associated with antenna coupling are observed.
A quantum key distribution scheme using macroscopic coherent light with phases of ±δand optically pre-amplified direct differential detection is described. The scheme is favorable for practical implementation and wavelength multiplex with conventional optical signals.
We lithographically fabricate arrays of optical antennas with ~6nm gaps. The enhancement factor from surface-enhanced Raman scattering measurement is ~5 times larger than the same structure with ~18nm gaps.
Laser and optical engineering challenges and recent progress in the area of high pulse-energy direct-detection atmospheric lidar near 1.5 microns wavelength are described.
Frequency doubling of high-energy Nd-doped laser emission yields harmonically converted laser energy (532-nm) of 1.2-J with 60 % conversion efficiency using a high optical quality top-seeded solution growth CsB3O5 crystal.
Employing high-yield production of graphene by liquid-phase exfoliation, a series of dispersions with large populations of graphene single and few layers was prepared. Nonlinear optical properties of these graphene dispersions were studied using the open aperture Z-scan technique at 532 nm and 1064 nm. The graphene dispersions exhibit broadband nonlinear scattering induced optical limiting.
The bandwidth of quantum-dash lasers under optical injection modulation is sharply enhanced when the injection photons are ~33 meV more energetic than the laser emission. This new bandwidth-enhancement mechanism is attributable to stimulated Raman scattering.
The maximum operating temperature of previously reported terahertz quantum-cascade lasers (QCLs) has empirically been limited to a value of ~ ħω/kB. Here, we report a new design scheme for terahertz QCLs and achieve 163-K operation for a 1.8-THz QCL, which is a factor of 1.9 larger than ħω/kB.
Using a new technique for single-domain shear-ordering of elastomeric photonic crystals we demonstrate novel opto-elastic properties. Tensile stress experiments demonstrate coupled mechanical and optical anisotropy, producing striking colour tuning depending on the stretch direction.
We describe a scheme for far-field subwavelength fingerprinting in the mid-IR and THz bands. The approach relies on evanescent wave retrieval, mediated by scattering on a subwavelength nanostructure.
We present results from measurements of ultrafast thermal transport in Graphene. We find that on picosecond time scales and 5-20 micron length scales hot carriers, instead of the phonons, are the dominant carriers of thermal energy. The thermal transport is found to be diffusive with a diffusivity of ~500 cm2/s.
The intrinsic spin Hall effect is observed in undoped GaAs quantum-well samples by temporally resolving the current generation process in the ballistic regime, where the extrinsic spin Hall effect is absent.
We report high-speed electronic control of ultrafast polariton amplification in a semiconductor microcavity. A >90% reduction of the parametric scattering gain is obtained by tuning the intracavity electric field to turn on inter-well resonant tunneling.
We investigated a coherent anti-Stokes Raman scattering microscopy with a single-pass picoseconds supercontinuum-seeded optical parametric amplifier (SCOPA). Our SCOPA system is substantially simpler because the pump and Stokes lasers are automatically overlapped.
We describe the different optical responses of geometrically related metamaterials with an analytical method based on multipoles. Metamaterials affecting the polarization eigenstates or mimicking EIT-like phenomena can be understood and explained on simple analytical grounds.
We investigate Second Harmonic Generation at the surface of nanoparticles both by modeling and experiment. We present an ab initio simulation method, which allows deducing surface properties as well as the nature of adsorbed molecules.
An arbitrary body or aggregate can be made perfectly absorbing at discrete frequencies, if a precise amount of dissipation is added under specific conditions of coherent monochromatic illumination. This effect arises from the interaction of optical absorption and wave interference, and corresponds to moving a zero of the S-matrix onto the real wavevector axis. It is thus the time-reversed process...
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