Reducing the light-shift in the diode laser pumped rubidium atomic clock

One impediment to achieving the promise of enhanced laser-pumped gas cell clock performance resides with the light-shift effect, a phenomenon whereby diode laser optical frequency fluctuations are mapped onto the atomic clock´s output frequency. The alternative to tightly stabilizing the diode laser in order to overcome this problem is to develop means of reducing the actual magnitude of the light-shift. Here, we briefly review two strategies for accomplishing this, and introduce a new one based on optical pumping with laser-induced-fluorescence (LIF). The advantage of LIF optical pumping is that the clock´s output frequency is insensitive to laser frequency fluctuations. Though LIF optical pumping creates a dependence of clock frequency on laser intensity variations, it is to be noted that diode lasers have very low intensity noise. Consequently, with regards to the light-shift effect the LIF strategy takes advantage of an inherent diode laser strength