Browsing by Author "Tang, W. T."

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Controllable subwavelength-ripple and -dot structures on YBa2Cu3O7 induced by ultrashort laser pulses
(2012-11-01)
Luo, C. W.
;
Tang, W. T.
;
Wang, H. I.
;
Liao, L. W.
;
Lo, H. P.
The evolution of periodic ripples and dots on an YBa2Cu3O7 surface irradiated by single-beam and dual-beam femtosecond laser pulses is investigated. The density and size of the dots can be controlled by the number of pulses. The spatial period of these ripples does not show a close relation to the pulse number. However, the orientation and geometrical period of the ripples are strongly dependent on the polarization and incident angle of the laser pulses, respectively. The formation processes are also discussed based on the dependence.
Ultrafast Dynamics in Optimally Doped YBa(2)Cu(3)O(7-delta) Observed with White Light Pump-probe Spectroscopy
(2011-01-01)
Wang, Y. T.
;
Lee, Y. H.
;
Chen, Y. -J.
;
Tang, W. T.
;
Luo, C. W.
The quasiparticle relaxation dynamics in optimally doped (001) YBa(2)Cu(3)O(7-delta) thin films were measured at various temperatures by white light pump-probe technique. The 2D ultrafast spectroscopy with broadband (similar to 200 nm) and high time-resolution (similar to 9 fs) was performed by the non-collinear optical parametric amplifier (NOPA). The relaxation time and the amplitude of the transient transmissivity changes (Delta T/T) are wavelength-dependent. The maximum Delta T/T appears at around 625 nm (similar to 1.98 eV) which corresponds to the transition between the Fermi level and the UHB (upper Hubbard band). Furthermore, the oscillations with similar to 150, similar to 320, similar to 500 cm(-1) have been clearly observed in the Fourier transformed graph of the 2D ultrafast spectroscopy, which are consistent with the phonon modes in Raman-scattering spectra.
Ultrafast Dynamics in Optimally Doped YBa2Cu3O7-delta Observed with White Light Pump-probe Spectroscopy
(2011-01-01)
Wang, Y. T.
;
Lee, Y. H.
;
Chen, Y. -J.
;
Tang, W. T.
;
Luo, C. W.
The quasiparticle relaxation dynamics in optimally doped (001) YBa2Cu3O7-delta thin films were measured at various temperatures by white light pump-probe technique. The 2D ultrafast spectroscopy with broadband (similar to 200 nm) and high time-resolution (similar to 9 fs) was performed by the non-collinear optical parametric amplifier (NOPA). The relaxation time and the amplitude of the transient transmissivity changes (Delta T/T) are wavelength-dependent. The maximum Delta T/T appears at around 625 nm (similar to 1.98 eV) which corresponds to the transition between the Fermi level and the UHB (upper Hubbard band). Furthermore, the oscillations with similar to 150, similar to 320, similar to 500 cm(-1) have been clearly observed in the Fourier transformed graph of the 2D ultrafast spectroscopy, which are consistent with the phonon modes in Raman-scattering spectra.