Generation and Direct Detection of Broadband Mesoscopic Polarization-Squeezed Vacuum

Using a traveling-wave optical parametric amplifier with two orthogonally oriented type-I BBO crystals pumped by picosecond pulses, we generate vertically and horizontally polarized squeezed vacuum states within a broad frequency-angular range. Depending on the phase between these states, fluctuations in one or another Stokes parameter are suppressed below the shot-noise limit. Because of the large number of photon pairs produced, no local oscillator is required, and 3 dB squeezing is observed by means of direct detection.

Figure 1

Experimental setup. UVF, UV filter; QP, quartz plates; PBS, polarizing beam splitter; D1 and D2, detectors.

Figure 2

Dependence of the OPA output on the pump power for the beam waist $70\mu \mathrm{m}$ (a) and $500\mu \mathrm{m}$ (b). Solid lines show a fit with Eq. (2), $m=34$ (a) and $m=1400$ (b).

Figure 3

NRF in $S_2$ (squares, solid line) and $S_3$ (circles, dashed line) depending on the quartz plates tilt.

Figure 4

NRF in $S_2$ versus quartz plates tilt for degenerate (squares) and nondegenerate (circles) phase matching.