Stimulated emission and lasing

V. P. Klochkov, E. B. Verkhovskiĭ

The stimulated emission threshold of a dye laser was found to depend on the method of formation of a longitudinal pulsed laser beam used as the pump. Excitation with a focused pump beam reduced the lasing threshold. The effect was strongest when the Q factor of the resonator cavity was low. This reduction in the lasing threshold by focusing the pump laser beam was attributed to an increase in the rate of spontaneous emission resulting from lasing of desqueezed states (enhancement of 'zero-field' fluctuations responsible for the appearance of spontaneous emission). An increase in the spontaneous emission rate reduced the buildup time of stimulated emission during the early stages and thus reduced the lasing threshold.

H.-G. Unger

Jan Jeske, Desmond W. M. Lau, Xavier Vidal +12 more

Stimulated emission is the process fundamental to laser operation, thereby producing coherent photon output. Despite negatively charged nitrogen-vacancy (NV−) centres being discussed as a potential laser medium since the 1980s, there have been no definitive observations of stimulated emission from ensembles of NV− to date. Here we show both theoretical and experimental evidence for stimulated emission from NV− using light in the phonon sidebands around 700 nm. Furthermore, we show the transition from stimulated emission to photoionization as the stimulating laser wavelength is reduced from 700 to 620 nm. While lasing at the zero-phonon line is suppressed by ionization, our results open the possibility of diamond lasers based on NV− centres, tuneable over the phonon sideband. This broadens the applications of NV− magnetometers from single centre nanoscale sensors to a new generation of ultra-precise ensemble laser sensors, which exploit the contrast and signal amplification of a lasing system. Here Jeskeet al. show both theoretical and experimental evidence for stimulated emission from negatively charged nitrogen vacancy centres using light in the phonon sidebands around 700 nm, demonstrating its suitability as a laser medium.

Mathieu Hautefeuille, Juan A. Hernández-Cordero

Michal Hausner, Vít Procházka, Vlastimil Vrba

Creating a coherent source of gamma radiation remains one of the biggest motivations in gamma-ray optics. Such a source would utilize the stimulated emission of gamma photons. However, to achieve lasing in the high-energy regime other physical principles such as the lasing without inversion are needed to be explored. One of the currently developed approaches uses coherent control of gamma radiation waveforms to induce transparency in a medium by applying ultra-acoustic vibrations. In this paper a theoretical description of the stimulated emission and coherent control of gamma rays is developed on the basis of a one-dimensional quantum mechanical formalism. The model of the gamma radiation coherent control shows a good agreement with the conventional semiclassical description of the phenomenon. The model of the stimulated emission was developed with the assumptions which enable to propose a specific experimental arrangement for simultaneous detections of pairs of gamma photons. This proposal is further discussed in the context of the experimental observation of the stimulated emission of gamma photons.

Galina A. Nemova