نتایج جستجو برای: optical coherent transient
تعداد نتایج: 441505 فیلتر نتایج به سال:
We have studied the ultrafast optical response of native-oxide terminated Si~001! with pump-probe reflectivity using 800 nm, 28 fs pulses at an excitation density of (5.560.3)310 cm. Time-dependent reflectivity changes comprise third-order-response coherent-transient variations arising from anisotropic state filling and linear-response variations arising from excited free carriers, state fillin...
Charge separation mediated by linearly-polarized light in transparent insulators is analyzed numerically by integrating the equations of motion of a bound charge. It is shown that large static and transient dipole moments can be induced by the magnetic component of light at nonrelativistic intensities regardless of whether the pumplight is coherent or incoherent. Quantitative estimates show tha...
Subtle atomic motion in a Bi crystal excited by a 35 fs-laser pulse has been recovered from the transient reflectivity of an optical probe measured with an accuracy of 10(-5). Analysis shows that a novel effect reported here-an initial negative drop in reflectivity-relates to a delicate coherent displacement of atoms by the polarization force during the pulse. We also show that reflectivity osc...
Generation and tomography of arbitrary optical qubits using transient collective atomic excitations.
We demonstrate the preparation of heralded Fock-basis qubits (a|0〉+b|1〉) from transient collective spin excitations in a hot atomic vapor. The preparation event is heralded by Raman-scattered photons in a four-wave mixing process seeded by a weak coherent optical excitation. The amplitude and phase of the seed field allow arbitrary control over the qubit coefficients. The qubit state is charact...
Using femtosecond transient absorption spectroscopy on excited-state helium atoms in a plasma created through optical field ionization, we measured the decay of 2(3)S-2(3)P excitation with sub-ps temporal resolution. The population evolution shows that initial decay is significantly faster than the electron-atom collisions and three orders of magnitude faster than the single atom spontaneous de...
Ultrashort pulses of intense, coherent, and tunable far-infrared (FIR) and mid-infrared (MIR) radiation, achievable with freeelectron lasers (FELs) and optical parametric amplifiers (OPAs), provide unique opportunities to investigate low energy dynamics in solids. This paper reviews our recent experiments on bulk and quantum-confined semiconductors using such radiation. These experiments includ...
The study of photoexcited strongly correlated materials is attracting growing interest since their rich phase diagram often translates into an equally rich out-of-equilibrium behaviour. With femtosecond optical pulses, electronic and lattice degrees of freedom can be transiently decoupled, giving the opportunity of stabilizing new states inaccessible by quasi-adiabatic pathways. Here we show th...
Coherent phonon excitation via femtosecond laser pulses can be used to control physical properties of matter, and enhancing coherent is highly relevant. Here, we report the strong enhancement in ${\mathrm{Fe}}_{3}{\mathrm{GeTe}}_{2}$ (FGT) resonance Raman effect. On basis transient optical spectroscopy measurements, ${A}_{1\mathrm{g}}$ FGT obtained as a function pump photon energy. Its maximize...
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