Several years ago, a resonance-shift phenomenon was predicted to exist, termed the stochastic realization shift (SRS), which arises as a consequence of correlated amplitude and frequency variations in a resonant field. An interesting aspect of the phenomenon is that the sign of the SRS in weak and strong fields has been shown to differ. Here, we demonstrate that the SRS may be conveniently studied over a broad range of field strengths via magnetic resonance in an optically pumped alkali-metal vapor. Specifically, we study the SRS in the ground state 0-0 hyperfine transition of
Rb87 for a field undergoing stochastic (yet correlated) amplitude-frequency fluctuations. Under our experimental conditions we find no evidence for a change in sign of the SRS as the field strength undergoes a transition from weak to strong. Further, our results show that in strong fields the magnitude of the SRS may be influenced by the field's spatial variations. \textcopyright{} 1996 The American Physical Society.
Nonlinear magneto-optical resonances occurring for near-zero magnetic field are studied in Rb vapor using light-noise spectroscopy. With a balanced detection polarimeter, we observe high contrast variations of the noise power (at fixed analysis frequency) carried by diode laser light resonant with the $5{\mathrm{S}}_{1∕2}\phantom{\rule{0.2em}{0ex}}(F=2)\ensuremath{\rightarrow}5{\mathrm{P}}_{1∕2}\phantom{\rule{0.2em}{0ex}}(F=1)$ transition
87Rb and transmitted through a rubidium vapor cell as a function of magnetic field
B. A symmetric resonance doublet of anticorrelated noise is observed for orthogonal polarizations around
B=0 as a manifestation of ground-state coherence. We also observe sideband noise resonances when the magnetic field produces an atomic Larmor precession at a frequency corresponding to one-half of the analysis frequency. The resonances on the light fluctuations are the consequence of phase to amplitude noise conversion owing to nonlinear coherence effects in the response of the atomic medium to the fluctuating field. A theoretical model (derived from linearized Bloch equations) is presented that reproduces the main qualitative features of the experimental signals under simple assumptions.