Laser Physics

The strong coupling treatment of the Fröhlich-type polaronic system, based on a canonical transformation and a standard Landau-Pekar type variational wave function, is applied to the polaronic system consisting of an impurity in a condensate. Within this approach the Relaxed Excited States are retrieved as a typical polaronic feature in the energy spectrum. For these states we calculate the corresponding effective mass and the minimal coupling constant required for them to occur. The present approach allows to derive approximate expressions for the transition energies between different Relaxed Excited States in a much simpler way than with the full Mori-Zwanzig approach, and with a good accuracy, which improves with increasing coupling. The transition energies obtained here can be used as the spectroscopic fingerprint for the experimental observation of Relaxed Excited States of impurities in a condensate.

The possibility of creating an integrated-optical chemical sensor that makes it possible to control the content of ammonia and other pollutants in air is demonstrated. A sensor of this type is experimentally studied. The limiting sensitivity of the integrated-optical ammonium sensor is estimated. The possibility of applying integrated-optical sensors in ecological monitoring is discussed.