Separation of enantiomers by their enantiospecific interaction with achiral magnetic substrates.

It is commonly assumed that recognition and discrimination of chirality, both in nature and in artificial systems, depend solely on spatial effects. However, recent studies have suggested that charge redistribution in chiral molecules manifests an enantiospecific preference in electron spin orientation. We therefore reasoned that the induced spin polarization may affect enantiorecognition through exchange interactions.

Ensemble-averaged Rabi oscillations in a ferromagnetic CoFeB film.

Rabi oscillations describe the process whereby electromagnetic radiation interacts coherently with spin states in a non-equilibrium interaction. To date, Rabi oscillations have not been studied in one of the most common spin ensembles in nature: spins in ferromagnets. Here, using a combination of femtosecond laser pulses and microwave excitations, we report the classical analogue of Rabi oscillations in ensemble-averaged spins of a ferromagnet.

Magnetization switching in ferromagnets by adsorbed chiral molecules without current or external magnetic field.

Ferromagnets are commonly magnetized by either external magnetic fields or spin polarized currents. The manipulation of magnetization by spin-current occurs through the spin-transfer-torque effect, which is applied, for example, in modern magnetoresistive random access memory. However, the current density required for the spin-transfer torque is of the order of 1 × 10 A·cm, or about 1 × 10 electrons s cm.

Parametric Harmonic Generation as a Probe of Unconstrained Spin Magnetization Precession in the Shallow Barrier Limit.

We study the parametric excitation of high orders of magnetization precession in ultrathin films having perpendicular magnetic anisotropy. We observe that for a given driving field amplitude the harmonic generation can be increased by lowering the barrier with the application of an in-plane magnetic field in the manner of the Smit-Beljers effect. In this effect, the magnetic stiffness is reduced not by lowering the magnitude of the magnetic field upon which the spins precess, but rather by effectively releasing the field's "anchoring" point.

Rabi oscillations and self-induced transparency in InAs/InP quantum dot semiconductor optical amplifier operating at room temperature.

We report direct observations of Rabi oscillations and self-induced transparency in a quantum dot optical amplifier operating at room temperature. The experiments make use of pulses whose durations are shorter than the coherence time which are characterized using Cross-Frequency-Resolved Optical Gating. A numerical model which solves the Maxwell and Schrödinger equations and accounts for the inhomogeneously broadened nature of the quantum dot gain medium confirms the experimental results.

Extreme nonlinearities in InAs/InP nanowire gain media: the two-photon induced laser.

We demonstrate a novel laser oscillation scheme in an InAs / InP wire-like quantum dash gain medium. A short optical pulse excites carriers by two photon absorption which relax to the energy levels providing gain thereby enabling laser oscillations. The nonlinear dynamic interaction is analyzed and quantified using multi-color pump-probe measurements and shows a highly efficient nonlinear two photon excitation process which is larger by more than an order of magnitude compared to common quantum well and bulk gain media.

Complex characterization of short-pulse propagation through InAs/InP quantum-dash optical amplifiers: from the quasi-linear to the two-photon-dominated regime.

We describe direct measurements at a high temporal resolution of the changes experienced by the phase and amplitude of an ultra-short pulse upon propagation through an inhomogenously broadened semiconductor nanostructured optical gain medium. Using a cross frequency-resolved optical gating technique, we analyze 150 fs-wide pulses propagating along an InP based quantum dash optical amplifier in both the quasi-linear and saturated regimes. For very large electrical and optical excitations, a second, trailing peak is generated and enhanced by a unique two-photon-induced amplification process.