Ion-trap laser

Laser operation with a single trapped $\rm Ca^+$ ion in a high-finesse optical cavity is predicted at a wavelength of $866\,{\rm nm}$. Different from a conventional laser, the formation of two thresholds can be observed. For both small and large pump strengths the field is quasi-thermal, in an intermediate region laser light with Poissonian and even sub-Poissonian statistics is produced. Atomic coherence effects play an important role. The multi-level system is treated by generalizing the pump-operator approach (Europhys. Lett. , 33 (1996) 515).