Investigation Of Property For Lasing Without Inversion In Complex System

Recently, many people have been devoted to the study of laser because it plays an importantrole in people’s daily life and scientific and technological domain. The theory of lasing withoutinversion enable people to find a new road for the high frequency and ultra high frequency laser.In the first part, we review some fundamental points involved about the condition of thegenerating of laser theoretically, the basic structure of laser, and the problem for populationinversion which is difficult or impossible to achieve in the high frequency and ultra high frequencyrange. The second chapter describes the basic theoretical knowledge about lasing without inversion,including the cause and method of no population inversion in the process of inversionless lasing,and the different origins in bare state base and dressed state base.In the third chapter, utilizing the master equation we obtain the approximate steady-stateanalytical solution of populations and system gain within the dressed-state regime, and discuss thecondition of the generating of laser without inversion, the dependence of population distributionand system gain on Rabi frequency of the probe and coherence field in three-level Δ-configurationsystem.. The results show that in the condition of resonant, the system can produce lasing withoutinversion if we select the appropriate spontaneous emission rate such as bc acandab5ac.Laserwithoutinversionisoccurredwhenoneofthetwofieldsisstrong.In the fourth chapter, we deduce the steady-state analytical solution of population distributionand system gain, and discuss the conditions of the generating of laser without inversion, as well asthe dependence of population distribution and system gain on Rabi frequency of the auxiliary fieldand probe detuning in four-level diamond configuration. The results show that the probe Rabifrequency could not be much smaller than spontaneous emission rates, the auxiliary field isindispensable and must be a strong one in order to present gain. By adjusting the Rabi frequency ofthe auxiliary field, we can obtain the conversion from lasing without inversion to lasing withinversion. Our results will be helpful for the choice of medium in the experiment.