AC Stark shift and temperature shift in laser pumped rubidium frequency standards

Full text: We report our study on the light-shift (AC-Stark effect) and buffer-gas induced effects (e.g. temperature effect) on the ground-state ('clock') transition of rubidium atoms contained in cm-scale glass cells. Rb atoms are optically pumped by radiation from a DFB laser diode (at 780 nm). Microwave radiation resonant with the clock transition frequency is applied via a resonator cavity, and the clock transition is detected in the light transmission. Narrow double resonance linewidths are obtained by adding buffer gases (Dicke narrowing). Control of the buffer-gas mixture allows reducing the temperature coefficient. By adjusting the total buffer-gas pressure, we are able to adjust the pump optical frequency to the point of the zero lightshift. We have successfully produced cells that simultaneously show a low intensity light-shift (δf/f ∼ 1 x 10-12 cm /uW) as well as a small temperature coefficient (δf/f < 9 x 10-12 /K), and pave the way for improved Rb atomic frequency standards. (author)