Figure 2

(a) Measured response bandwidths versus the probe laser Rabi frequencies (\(\Omega _{p}\)) for five different sets of probe beam waists. The coupling laser beam waists were adjusted during the experiments to maintain their slightly larger than the probe, and its Rabi frequency is fixed to \(\Omega _{c} = 2\pi \times \) 4.55 MHz. The response bandwidth decreases with the probe laser Rabi frequency for each probe beam waist. (b) The dependence of response bandwidths on the probe beam waists with fixing probe laser Rabi frequency and coupling laser Rabi frequency \(\Omega _{p} = 2\pi \times \) 5.22 MHz, \(\Omega _{c} = 2\pi \times \) 4.55 MHz. The atomic response bandwidth decreases with the probe beam waist. The solid line shows the fitting result. Inset: The output power as a function of \(\delta _{f}\) obtained with a spectrum analyzer at the probe beam waist \(\omega _{p} = 65~\mu \text{m}\). The 3 dB bandwidth is about 1.5 MHz. The error bars are standard deviations of 10 measurements for all data sets