Saturable nonlinear refraction in hot atomic vapor

Atomic vapors make flexible and useful nonlinear optical media when light is detuned far from resonances. However, few direct measurements of their nonlinear coefficients have been performed to date. We present a measurement of the Kerr coefficient for various detunings to both the red and blue of the $D2\mathrm{}$ line in hot atomic rubidium vapor. Saturation effects complicate the interpretation of the standard z-scan method, but a simple saturation model agrees well with our data. We find values of $n_2\approx \pm {10}^{-7}{\mathrm{cm}}^2/\mathrm{W}$ for 1 GHz detunings from the $D2\mathrm{}$ line.