Extreme light for studying ultrafast electron dynamics in matters, attosecond pulses
일 시 : 2023년 11월 29일 수요일 17:00
연 사 : 김 경 택 교수 (광주과학기술원)
장 소 : 자연과학관 B117호
HOST : 윤 재 웅 교수님
초 록
The 2023 Nobel Prize in Physics was awarded to three scientists, Pierre Agostini (USA, Ohio State Univ.), Ferenc Krausz (Germany, Max Planck Institute), and Anne L'Huillier (Sweden, Lund Univ.), for their significant contributions to the generation, measurement, and application of attosecond pulses that are useful for studying ultrafast electron dynamics in matters.
The characteristic time scale of the electron motion in matter is attosecond (1 as = 10^-18 s) second. For example, it takes only 150 as for an electron to orbit a hydrogen atom. To investigate the electron dynamics, attosecond light pulses are essential. Prof. Anne L'Huillier and her colleagues discovered in 1987 that intense laser pulses incident on atoms could generate high-order harmonics in extreme ultraviolet, or X-ray wavelengths. These high-order harmonic radiations were expected to be valuable light sources for applications, especially in generating extremely short attosecond pulses. However, at that time, there were no suitable methods for measuring attosecond pulses. Prof. Pierre Agostini's research team found clues in the photoelectron phenomenon. In 2001, they introduced a method to characterize attosecond pulses. They produced photoelectrons using attosecond pulses in the presence of a laser pulse which provides the phase information of attosecond pulses. They were able to measure attosecond pulses with a duration of only 250 as. Franck Krausz's research team advanced laser technology, and succeeded in generating a single isolated attosecond pulse in the same year, 2001. The emergence of attosecond pulses allowed the observation of physical phenomena that were previously unobservable. In particular, it has become possible to study ultrafast phenomena, such as photoionization, which were believed to occur instantaneously. In this colloquium, we aim to discuss the historical background leading to the discovery of high-order harmonic phenomena that laid the foundation for the generation of attosecond pulses, the development of attosecond pulse measurement techniques, advances in attosecond time-resolved spectroscopy research, and future research in this field.