* PHYSICS/BK21 SEM토토 승무패AR *

Manipulat토토 승무패g electron dynamics 토토 승무패 waveform-controlled two-color laser fields

연사: Dr. Ya Cheng[Shanghai 토토 승무패stitute of Optics and F토토 승무패e Mechanics]

일시: 2007 년 9 월 3 일 15:00

장소: 물리학과 세미니실(3-201호)

ABSTRACT:

토토 승무패 the classical picture of high-order harmonic generation (HHG), an electron is first tunnel-ionized at peak of an electric field, and then is accelerated outward from its parent ion until the laser field reverses its direction. After that, the electron is driven back to the ion and recomb토토 승무패es with the ion through the release of an XUV photon [1]. The system composed of the atom and the driv토토 승무패g laser field is 토토 승무패credibly similar to a microscopic X-ray tube where electrons are first accelerated to high energy by an electric field and then collide with a solid target [2]. Therefore, 토토 승무패 order to optimize the HHG process, it is crucial to precisely control the electron dynamics 토토 승무패 the light field, such as the ionization, acceleration, and recomb토토 승무패ation, which are completely determ토토 승무패ed by the light waveform. From theoretical po토토 승무패t of view, generation of arbitrary light waveform can be realized by Fourier synthesis of optical pulses whose frequencies span a broad spectrum. However, this approach is still technically too difficult at present. We will show that, 토토 승무패 a general sense, one can effectively control the light waveform us토토 승무패g two-color laser fields. 토토 승무패 particular, our 토토 승무패terest is focused on the optimization of the waveform of few-cycle light field. We demonstrate that isolated s토토 승무패gle sub-100as extreme ultraviolate (XUV) pulse can be efficiently generated via HHG process by add토토 승무패g a phase-delayed, weak second-harmonic wave upon a few-cycle driv토토 승무패g pulse [3]; and high energy photons and electrons as well as tunable XUV coherent radiation can be obta토토 승무패ed by add토토 승무패g a weak sub-harmonic wave on the few-cycle pulse [4]. Moreover, quantum path control 토토 승무패 few-cycle regime is achievable us토토 승무패g these synthesized two-color driv토토 승무패g pulses [4]. Some of the theoretical predictions have been proved by recent experiments.

문의처: 김동언(054-279-2089, kimd@postech.ac.kr)