Resonance Broadening of Homogeneous Caesium Vapor in Absorption.

A. E. Korolev, Vladimir N. Nazarov, Dmitry I. Staselko

Felix T. Ullrich

Chris Gregory

The resonance broadening of homogeneous Cs vapor in absorption was studied by means of the contour method. The intensities were obtained via the method of "astigmatic photometry" by utilizing the astigmatism of the Rowland grating. The pressure of the homogeneous absorbing vapor ranged from ${10}^{\ensuremath{-}2}$ to 17.5 mm Hg. The half breadth $\ensuremath{\gamma}$ varied rather linearly with the number of atoms per unit volume, with $(\frac{{\ensuremath{\gamma}}_{1}}{N})\ifmmode\times\else\texttimes\fi{}{10}^{7}=1.45$, $(\frac{{\ensuremath{\gamma}}_{2}}{N})\ifmmode\times\else\texttimes\fi{}{10}^{7}$ for the $^{2}P_{\frac{3}{2}}$ and $^{2}P_{\frac{1}{2}}$ eomponents of the resonance lines, respectively. The average value of the ratio of half breadths $\frac{{\ensuremath{\gamma}}_{1}}{{\ensuremath{\gamma}}_{2}}$ was found to be 1.8. The experimental half-width $\ensuremath{\gamma}$ is found to be about 1\textonehalf{} times larger than that predicted by W. V. Houston. Below pressures of 10 mm Hg the lines exhibited symmetrical broadening according to the "dispersion" formula. At higher pressures indications of a violet and red asymmetry are present for the $^{2}P_{\frac{3}{2}}$ and $^{2}P_{\frac{1}{2}}$ components, respectively. A definite band on the red side of the $^{2}P_{\frac{3}{2}}$ and one on the violet side of the $^{2}P_{\frac{1}{2}}$ was observed.

Sebastián Brandt, A. Nagel, Oliver G. Schmidt +2 more

Summary form only given, as follows.The 30 kHz linewidth and extremely steep dispersion of a coherent dark resonance in a caesium vapor cell allows measurements of magnetic fields to about 10 nT in 0.1 s integration time, limited by stray fields. The narrow resonance should make possible a compact frequency standard. In a preliminary experiment the authors used a coherent dark resonance in a 2 cm long caesium vapor cell to measure magnetic fields with about 10-5 uncertainty. Two diode lasers (852 nm wavelength) were phase-locked onto each other with a 9.2 GHz frequency offset, corresponding to the frequency ground state separation of the two caesium levels. The difference frequency is derived from a stable tunable rf source. Absorption spectrum of the caesium coherent population trapping resonance for linear laser polarizations is illustrated; it is split into seven components by a magnetic field parallel to the laser polarization direction. The width of the individual lines is only 130 kHz due to power broadening. The steep slope of the resonance could be used to lock the frequency of the 9.2 GHz rf source. This would provide a compact frequency reference.

Mark W. Zemansky

John Francis Ward, A. V. Smith

We report observations of saturation of two-photon-resonant third-harmonic generation and of fluorescence following two-photon absorption in cesium vapor. Weakening dependence of these processes on fundamental power and broadening of the resonance line with increased fundamental power are both seen. It is shown that hole burning is important in a certain power range with the resonance becoming predominantly homogeneously broadened at higher power levels.