Non-Faraday rotation of photon-echo polarization in ytterbium vapor

Abstract

Non-Faraday rotation of photon-echo polarization was investigated at the $J=1\ensuremath{\leftrightarrow}J=0$ transition in a wide range of longitudinal magnetic field strength. The echo was generated at the intercombination transition $(6s6p)^{3}P_{1}\ensuremath{\rightarrow}(6{s}^{2})^{1}S_{0}$ of $^{174}\mathrm{Yb}$ by two resonant laser pulses of linear (parallel or mutually orthogonal) polarization. A detailed analysis of the echo polarization performed by an angled echo technique has shown quite different behavior in the weak and strong magnetic field limits. The photon echo has polarization close to linear at a magnetic field strength $\mathcal{B}\ensuremath{\leqslant}5\phantom{\rule{0.3em}{0ex}}\mathrm{G}$; its polarization plane rotates around the magnetic field vector clockwise or counterclockwise depending on the magnetic field orientation relative to the wave vector. The photon-echo polarization components and echo power oscillate as functions of $\mathcal{B}$. As the magnetic field increases, the oscillations become smaller and almost disappear at a magnetic field $\mathcal{B}\ensuremath{\approx}40\phantom{\rule{0.3em}{0ex}}\mathrm{G}$; the photon echo does not disappear at this magnetic field, but its polarization vector no longer has a preferred orientation. Numerical calculations of the photon echo generated at a spectral wide line agree with the experimental behavior of the photon-echo polarization for an arbitrary magnetic field.