Studies of a High-Gain Pulsed 87Rb Microwave Maser

Bouwe Bolger, B.J. Robinson, J. Ubbink

Pierre Tremblay, Jean Beaubien, A. Michaud +1 more

The laser-pumped 87Rb maser showed many new experimental features.1 A precise understanding of the maser behavior is obtained by considering a simple three-level atom, located inside a microwave cavity, interacting with a frequency-modulated laser. This simple model is based on the density operator formalism within a semi-classical approach. We show that moderately rapid modulation of the laser frequency results in sustained large hyperfine coherence, thus high gain, due to reduced light broadening, even for a high intensity pump. This is optimally achieved with a given modulation depth which is proportional to the light intensity. This last result has also been obtained when considering only the maximization of the population inversion.2 On the other hand the modulation greatly decreases the dependence of the maser frequency upon the laser frequency (through the variation of the light shift), therefore reducing the requirements for the mid- and the long-term frequency stability of the pumping laser. Finally the maser frequency suffers a small modulation, relatively insensitive to the modulation depth, which becomes negligible for sufficiently high modulation frequencies.

Aldo Godone, Filippo Levi, Salvatore Micalizio

The propagation of a band-limited light pulse through an atomic medium under a Λ excitation scheme is theoretically analyzed in this paper. We consider in particular the case where the light pulse is detected through the coherent microwave emission of the atomic ensemble (coherent population trapping maser). Significant differences are predicted with respect to the more usual optical detection (electromagnetically induced transparency signal) and found in agreement with the experimental results. Higher signal delays were observed in the microwave emission than in the optical signal with an equivalent group velocity of 6 m/s as well as highly superluminal propagation under a proper modulation scheme. The experiments were performed with a thermal 87Rb vapor in buffer gas.

N. BLOEMBERGEN

Ning Lu, Claus Benkert

David Ziemkiewicz, Sylwia Zielińska‐Raczyńska

O could be used as a gain medium in a solid-state maser. By taking advantage of radiative microwave transitions between highly excited Rydberg states, one can achieve population inversion and masing in a wide range of wavelengths. In the pulsed emission regime, the considered excitonic system is characterized by intricate and rich dynamics, which are investigated numerically, taking into account several key features of the medium, such as strong Stark shift of energy levels and the presence of the Rydberg blockade effect.