Light Amplification by Centers having a Stokes Shift in Absorption and Luminescence

D. Mergerian, Jordan J. Markham

V. L. Bogdanov, V. P. Klochkov

Yoshiaki Kato, Kunioki Mima, S. V. Bulanov

Peter J. Warter

Small differences between the emission and absorption spectra of three-level maser centers can have a pronounced effect on maser operation. This paper considers the effects of a Stokes shift, the simplest and most probable difference. If there is a Stokes shift which is large compared to the linewidth, the operation of the maser will be essentially four level. If there is a small Stokes shift (some fraction of the linewidth) the operation will still be three level, but the Stokes shift will significantly affect the operation of the maser. The principal effects will be a shift of the maser line from the peak in the fluorescent emission line (away from the absorption peak) and a reduction in the upper level population required to reach the threshold of oscillation. The evidence is not conclusive as to whether there is a Stokes shift in the ruby R1 line, but if there is a shift it is at most a small fraction of the fluorescent linewidth at room temperature. Shifts of the ruby maser line to the red have been observed by D'Haenens and Asawa and have been attributed to large temperature changes. It is likely that the temperature shift, while important, will not explain the shift which has been observed. Gires and Mayer have found the lower state population of an operating ruby maser to be approximately 75% of the unexcited population rather than approximately 50% and have suggested a Stokes shift as a possible cause of the reduction in the upper state population at threshold. This paper considers the effect of such a small Stokes shift on the operation of an otherwise ideal three-level maser.

S. G. Voloshenyuk, L. V. Vovk, E I Zabello +1 more

An asymmetry effect in the amplification and efficiency of an optically dense amplifier is predicted theoretically and confirmed experimentally for opposite and concurrent collinear signal and pump paths. The effect is due to a difference in the losses as a result of the two-stage absorption of pump radiation in a system of luminescing centers described by a model of three energy levels. Calculations are made of various characteristics of this type of amplifier using the quasisteady-state approximation.

Evgueni F. Martynovich, V. P. Dresvyanskiy, С. А. Зилов +3 more

A spatially periodic distribution of the luminescence intensity of F2 and F 3 + color centers is observed in LiF crystals with induced anisotropy. The period of spatially periodic modulation of the luminescence intensity generally coincides with the period of the change in the polarization state of excitation light. For F2 centers, the experimental axial spatially periodic dependence of the luminescence intensity is close to the calculated dependence obtained in the description of the absorption and radiative transitions in the centers by linear oscillators oriented along six C 2 axes of the cubic crystal. However, for F 3 + centers, the same experiment shows a spatially periodic distribution of luminescence intensity with a modulation period shorter by a factor of 2. It is shown that this effect of modulation frequency doubling in the spatially periodic pattern of the luminescence of color centers arises due to the nonlinear dependence of the luminescence intensity on the excitation light intensity. For F 3 + centers, upon luminescence excitation in the absorption band with λmax = 452 nm, the modulation frequency doubling is due to the saturation of the metastable triplet state of such a center.