Hui-Yuan Daniel Chen
Fields of expertise
Ultrafast spectroscopy, Spectroscopy, Laser physics, Solid-state physics, Transition metal oxides, liquid-sheet transient absorption spectroscopy
Biography
My research interests involve the ultrafast response timescales in semiconductors pushed by the high operational speed in sub-nanoseconds, the nonlinear interaction between high-density carrier injection in power electronics, and the exploration of light-control phase transition in quantum materials.Current work
Scientific research projects:Ultrafast carrier injection dynamics of wide-bandgap perovskite oxides
Non-equilibrium electron physics in 5d honeycomb Mott insulator
Broadband IR-to-VIS transient spectroscopy on photoexcited Kitaev material α-Li2IrO3
Ultrafast dynamics of solvated iron tris-bipyridine using liquid-sheet transient absorption spectroscopy
Laboratory practice:
Optimized the rotational chip holder for generating ultrathin liquid sheets down to 200 nm under vacuum.
Diagnostic and maintenance for chirp-pulse amplification (CPA) laser cavity at LACUS.
Commissioning of time-resolved Resonant Inelastic X-ray Scattering (trRIXS) setup at SwissFEL.
Professional course
LabVIEW CLAD
Education
M.Sc.
Graduate Institution of Photonics and Optoelectronics
National Taiwan University
B.S.
Department of Electrophysics
National Chiao Tung University
Research
Ultrabroadband impulsive stimulated Raman scatter
In a scientific mission collaborated with CEA (Paris, France) and CFEL (Hamburg, Germany), I designed a high-speed deep-UV spectrometer necessary for high-sensitivity measurements. The high-speed referenced spectrometer is equipped with two identical 2048-pixel high-sensitivity (1300 V/(lx･s)) CMOS linear detectors with a spectral response down to 200 nm and a maximum line rate of 4,500 lines/s (10MHz video rate digitizer with 16-bit resolution inside). The noise level of for a single scan is below 280 μOD, which is essential to this mission. As discussed above, the dynamics are probed in the liquid phase with a path length of only a few microns limiting the amount of signal from the experiment. To see the consecutive internal conversion steps, it is key to obtain a high signal-to-noise ratio with the high-sensitivity deep-UV time spectrometer.We established state-of-the-art time-resolved transient absorption spectroscopy for liquid nanosheets. The OH stretching mode of liquid water in real-time was revealed for the first time thanks to the sub-5 fs resolution. The mission was achieved by joint expertise from groups in CFEL(Hamburg), EPFL (Lausanne), and CEA(France). Previous literature only reports this mode via vibrational spectroscopy; however, it’s never been temporally resolved due to the lack of short pulses in the deep ultraviolet (DUV) region to probe the OH bond. Moreover, the characteristic lifetime of the OH-stretching mode, around 50 fs, is interestingly on the same scale as the formation lifetime of the OH radical in ionized water.