This internally developed setup allows the measurement of the optical properties of flat samples (refractive index and extinction coefficient) both in static and in time-resolved manner. As the optical properties are determined by the electron distribution of the material under study, processes involving changes in the electron distribution can be investigated.
The ultrafast ellipsometer endstation allows the study of processes occurring during the interaction of light with solid surfaces that involve changes in the electron distribution of the sample. The setup will measure the relative change in the phase and amplitude of light reflected from the surface in a static or in a time-resolved (80 fs) manner. Since these quantities are directly related to the structural and optical properties of the sample, the real and imaginary part of the frequency-dependent dielectric function and its change upon laser excitation (at ~800 nm) will be accessible. A complementary setup operating in the 350-750 nm range is available at the ELIps end-station of ELI Beamlines.
Figure 1: Design of ultrafast ellipsometer setup
|Wavelengths of pump beam||810 nm central wavelength|
|Spectral range of probe||700-900 nm|
|Probe spot size at the sample||<400 um (later to be improved)|
|Time range||0-0.5 ns|
|Time resolution||~80 fs (later to be improved)|
|Dynamic range of spectrometer||85000:1|
|Pulse characteristic of the laser||>8 fs, 80 MHz rep. rate|
|Angle of incidence||
65° (planned to be variable later)
Flat solid samples larger than 5mm x 5 mm can be handled, surface roughness should not exceed 50nm.
The ellipsometric data of the sample is collected by conventional spectrometer, of which optical resolution is approx. 7nm (grating based spectrometer).