Table 1 Differences in crystal and waveplates orientations between classic spectrally decoded EO sampling (Fig. 1) and the new phase diversity (DEOS) system (Fig. 2).

From: Phase Diversity Electro-optic Sampling: A new approach to single-shot terahertz waveform recording

 

Classic spectrally decoded EO sampling

DEOS

Pockels crystal

[-110] axis parallel to THz field

[-110] perpendicular to THz field

Input laser polarization

at 0 or 90 degrees wrt THz field

at 45 degrees wrt THz field

QWP (*)

one axis at 45 degrees wrt [-110]

one axis along [-110]

HWP (*)

optional

at 22.5 degrees wrt [-110]

Transfer functions H1 and H2

  1. For the classical system, we indicate the most commonly used crystal orientation, which corresponds to maximal Pockels effect. (*): For classic spectrally decoded EO sampling, several quarter wave plates (QWP) and half wave plates (HWP) configurations are possible and we indicate here the angles for the so-called balanced detection. Note that for DEOS, the orientations are chosen in order to obtain information phase diversity at the two outputs, i.e., transfer functions with interleaved zeros (see also Fig. 2c). Ω is the input THz signal angular frequency, and C is the laser chirp rate (see text and Eq. 2).
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