Strengths and Linewidths of Two Photon 5s -- 6s Hyperfine Transitions of Rb

Using a single frequency tapered amplifier diode laser scanning around 993 nm in a Rb cell, we have measured the four $\Delta $F$=$0 hyperfine lines of the Doppler free two photon 5s -- 6s transition in $^{\mathrm{85}}$Rb and $^{\mathrm{87}}$Rb. We have confirmed a two photon transition by measuring the signal strength vs laser power squared and observing a linear relationship. We are currently measuring the transition linewidth dependence on laser power. We will also measure the transition linewidth dependence on an external DC electric field.