1. Direct sampling of electric-field vacuum fluctuations
by C. Riek, D. V. Seletskiy, A. S. Moskalenko, J. F. Schmidt, P. Krauspe, S. Eckart, S. Eggert, G. Burkard, and A. Leitenstorfer
Science
Volume ():aac9788
October 1, 2015
Copyright © 2015, American Association for the Advancement of Science

2. Fig. 1 Experimental principle with demonstration of ultrahigh bandwidth and sensitivity.
Experimental principle with demonstration of ultrahigh bandwidth and sensitivity. (A) Scheme of electro-optic sampling of an electric-field waveform (red) by an ultrafast probe pulse (green), consisting of an electro-optic crystal (EOX), a quarter-wave plate (λ/4), Wollaston polarizer (WP) and differential photocurrent detector (DD). (B) Classical electro-optic signal ΔI/I and corresponding electric-field amplitude versus delay time td (red line). The intensity envelope of the 5.8-fs probe pulse is shown in arbitrary units for comparison (green line). (C) Spectral multi-THz amplitude (red) and phase (blue) obtained by Fourier transform.
C. Riek et al. Science 2015;science.aac9788
Copyright © 2015, American Association for the Advancement of Science

3. Fig. 2 Studying vacuum fluctuations via statistic readout and longitudinal modification of the probed space-time volume.
Studying vacuum fluctuations via statistic readout and longitudinal modification of the probed space-time volume. (A) A diagram shows longitudinal expansion of the probe volume: stretching the sampling pulse from 5.8 fs (green) to 100 fs (black) causes temporal averaging over the vacuum field (red), leading to reduction of the detected noise amplitude. (B) Green histogram: normalized counting probability as a function of electro-optic readout by the short pulse. Black histogram: probe pulse stretched to 100 fs. Red graph: de-convoluted wave function |Ψ0|2 of the electric field ground state.
C. Riek et al. Science 2015;science.aac9788
Copyright © 2015, American Association for the Advancement of Science

4. Fig. 3 Detection by transverse expansion of the space-time segment.
Detection by transverse expansion of the space-time segment. (A) Sketch featuring lateral increase of sampling cross section which leads to averaging over noise patterns within circled areas. (B) Differential histograms obtained by subtracting the result for confocal detector position with w0 = 4.25 μm from a set of histograms at positions with beam diameter expanding from 4.25 μm (black) to 17 μm (purple), 25 μm (cyan), 50 μm (orange) and 85 μm (red).
C. Riek et al. Science 2015;science.aac9788
Copyright © 2015, American Association for the Advancement of Science

5. Fig. 4 Dependence of vacuum amplitude on transverse extension of probed space-time volume.
Dependence of vacuum amplitude on transverse extension of probed space-time volume. Relative excess noise of electro-optic signal ΔI/I (right vertical axis) and rms vacuum amplitude ΔEvac (left vertical axis) versus probe radius w0 (blue squares). Red lines: theoretical assessment based on Eq. 5.
C. Riek et al. Science 2015;science.aac9788
Copyright © 2015, American Association for the Advancement of Science