Ultrashort Coherent Light Sources:
From Femtosecond to Attosecond
Professor Chang Hee Nam
Dept. of Physics and Coherent X-ray Research Center, KAIST, Korea
11:30 am Friday, 26 August 2011, EN313 Lecture Theatre (EN Building), Hawthorn.
Recent advances in femtosecond laser technology have revolutionized ultrafast science. At CXRC we have developed high-power femtosecond laser technology for the investigation of ultrafast phenomena. Using a CPA (chirped pulse amplification) technique, we developed a high power femtosecond laser operating at 1 kHz and obtained 25 fs, 0.15 TW laser pulses. By further compressing the output, we recently succeeded in generating 3.7 fs, 0.3 TW laser pulses. In addition the direct CEP locking method, developed at CXRC to stabilize CEP of a femtosecond laser, has been utilized to stabilize the CEP of few-cycle pulses, realizing the CEP stabilization of a femtosecond oscillator for 24 hours without realignment of any optical components.
Based on the femtosecond laser technology developed here, we have investigated attosecond pulse generation based on high harmonic processes. High harmonics emitted from gaseous atoms driven by intense femtosecond laser pulse possess unique capability of attosecond pulse generation. The high harmonic pulse can form an attosecond pulse train with equally spaced harmonic spectrum or an isolated single attosecond pulse with broad continuum spectrum. Using high harmonic attosecond pulses, we are pursuing attosecond science to reveal ultrafast atomic and molecular dynamics with unprecedented temporal resolution.
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