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Single-cycle THz fields electro-optical sampling with single-photon detectors


Figure 1 (A) THz time-domain spectroscopy using electro-optic sampling to characterize the THz field trace and spectrum using a classical balanced detection scheme. (B) Power spectrum corresponding to the measurement in A (red curve) and in an un-purged setup (blue curve).

Figure 2. Calibration setup with EOM and experimental lock-in balanced detection scheme using two single photon detectors. (A) Experimental scheme for calibration of detection using electro-optic modulation. (B) Measured variance of the detection method using EOM with single photon counts indicating the measurement is shot-noise limited. (C) Using ps-time tagging resolution of the photon counting software, a difference measurement was performed between counts of detectors D1 (red) and D2 (blue) using markers M inserted every 20 kHz to synchronize timing with the antenna modulation.

Figure 3. Terahertz detection using single photons. (A) Experimental scheme for measuring THz field using squeezed vacuum. The THz field generated from a photoconductive antenna (PCA) is overlapped to the squeezed vacuum pulse into a GaAs electro-optical crystal. The phase shift introduced by the THz pulse on the squeezed vacuum probe is measured by a balanced detection using single photon detectors. (B) Measured phase shift (∆Φ) induced by THz field (blue squares) overlapped with the phase shift from standard electro-optic sampling (EOS) scaled to the measured value (red line). The integration time for each data point was 105 mins. (C) Measured variance of the detection method indicating the final measurement is shot-noise limited so THz field is not adding noise.