Spin noise spectroscopy is a very sensitive undisturbed spectroscopic technique for measuring atomic spin fluctuations by using a far-detuned probe laser beam. In this paper, we describe an experimental setup for measuring the spin noise spectroscopy. The spin noise spectra of Rubidium atomic vapor cell filled with 10 Torr of Neon gas and 20 Torr of Helium gas as buffer gas are investigated in a magnetically shielded environment. The dependence of the spin noise power spectral density, separately, on the probe beam’s intensity (
I), the probe beam’s frequency detuning (
Δ) and Rubidium atomic number density (
n) are measured. The integrated power of Rubidium atomic spin noise spectra is scaled as
$ {I^2}$
. Owing to homogeneous broadening, the full width at half maximum of transmission spectrum of the same cell is broadened to
$\Delta {\nu _t} = {\rm{6}}.{\rm{9}}\;{\rm{GH}}{\rm{z}}$
. Center frequency of transmission spectrum is set to be
$\varDelta = {\rm{0}}$
. The probe beam’s frequency detuning is larger than the half width at half maximum of the transmission spectrum
$\left| \varDelta \right| > {{\Delta {\nu _t}}}/{{\rm{2}}}$
, so the integrated power of Rubidium atomic spin noise spectra is scaled as
$\varDelta^{-1}$
. And there is a dip for
$|\varDelta| < {{\Delta {\nu _t}}}/{{\rm{2}}}$
as a result of collisions between the buffer gas and Rubidium atoms. The integrated power of Rubidium atomic spin noise spectra is scaled as
$ \sqrt n $
. The Rubidium atomic spin's transverse relaxation time becomes shorter while the temperature increases. Only at the condition of non-perturbative probe, including far-off-resonant laser, weak laser intensity and uniform transverse magnetic field, the measured full width at half maximum will be close to the intrinsic linewidth of spin noise spectrum. In this way, we can obtain the Rubidium atomic spin's transverse relaxation time. This work can be applied to the field of physical constants precision measurement, like Lande
gfactor and isotopic abundance ratio. In addition, it provides an important reference for developing the high signal-to-noise ratio and compact spin noise spectrometer.
下载:
