(a) Sketch of high-speed ASOPS system. Optical paths are represented by solid lines, electrical signals by dashed lines. (b) Setup for optical pump-probe measurements. (c) High-speed ASOPS THz spectrometer setup.
(a) Frequency shifter output measured with a radio-frequency spectrum analyzer. The main peak at is used as reference for the save oscillator feedback loop. Modulations at harmonics of 30 kHz are residual carrier and mirror frequency signals and contributions due to nonlinearities in the frequency shifter.
(a) Circles: Deviation of the true time delay from the calibrated time delay vs calibrated time delay. Squares: Same data as circle symbols with linear contribution due to residual stepper motor misalignment subtracted. (b) FWHM of second cross-correlation peak vs calibrated time delay.
(a) Reflectivity changes of superlattice after impulsive optical excitation. (b) Extracted oscillatory contributions due to coherent acoustic phonons (inset shows zoom into early time delays revealing details of contributions due to zone-folded acoustic phonons). (c) Fourier-transform of data shown. (b) Data are scaled by a factor 10 above 700 GHz. (d) Signal resolution of pump-probe setup vs total measurement time (square symbols) and shot-noise limit (solid line).
Extracted modulations of raw data (shown in top inset) due to multiple reflections of an acoustic pulse within the top Si layer of a silicon-on-metal-on-insulator structure (bottom inset).
(a) THz transient acquired within 1 s acquisition time in a nitrogen purged setup. (b) Fourier-transform spectrum of data shown in panel (a) (top curve) and of data acquired within 110 s acquisition time with water vapor present in the setup (bottom curve). Curves are offset one order of magnitude for better visibility. (c) Top panel: water vapor transmission spectrum for our experimental conditions compiled from the HITRAN database. Bottom panel: measured water vapor transmission spectrum (solid line) together with the frequency dependent dynamic range limit of the setup (dashed line, data are partly outside plotted range). The inset shows a zoom into the line at approximately 1.4 THz.
Article metrics loading...
Full text loading...