Showing papers by "Jianying Zhou published in 2001"

Ultrafast population transfer in three-level Λ systems driven by few-cycle laser pulses

Abstract: The maximal population transfer in three-level $\ensuremath{\Lambda}$ system driven by linear polarized few-cycle laser pulses is investigated numerically. A time-dependent Schr\"odinger equation without the rotating wave approximation is solved. The maximal population transfer depends critically on the chirp rate and the intensity of the pulses. Almost complete population transfer can be achieved if the difference between the transition dipole moments is not very large.

Generation of high-quality 10-femtosecond laser pulses with intracavity spatial and spectral control

Abstract: Spatial and spectral control, using an intracavity capillary and a slit, is applied to improve the output pulse quality of a Ti:sapphire laser. Satellite-free 10-fs optical pulses with a smooth spectral and spatial profile have been generated. Employing a root-mean-square formalism for pulse characterization, spatial, spectral and temporal intensity distributions are analyzed for laser pulses with a duration as short as three to four optical cycles.

A novel approach for infrared optical activation of neodymium-doped porous silicon using microwave radiation

Abstract: A novel approach for infrared optical activation of neodymium-doped porous silicon (PS:Nd), using microwave radiation, is reported. PS:Nd was prepared using constant-potential electrochemical doping; the effects of microwave heating time, microwave power and the dosage of heat-conducting medium used on the room-temperature photoluminescence (PL) in the infrared region for PS:Nd were investigated. The treated samples emitted intense room-temperature luminescence around 1.06 and 0.90 µm. In addition to thermal activation, the non-thermal interaction of microwave radiation with PS:Nd, mainly resulting in the spread of rare earth and the trapping of oxygen by neodymium ions in the porous layer, is considered to play an important role in the optical activation of neodymium.

Generation of high-quality sub-10 femtosecond laser pulses with intracavity spatial and spectral control

Abstract: Summary form only given. Generation of sub-10 fs optical pulses requires a spectral bandwidth of more than 100 nm. Literature data for such pulses very often show pronounced satellite structures in both the frequency and time domain, however. In this situation, the usual pulse characterization by the FWHM of the intensity profile often yields a poor description of the real waveforms. Here we propose new pulse parameters for the characterization of pulses with significant temporal and spectral substructure. We apply this method to improve the laser pulse quality using the parameters for resonator design guidelines which allow generation of nearly single transverse mode smooth sub-10 fs optical pulses from a Ti:sapphire laser.