The Theoretical Study Of Lasing Without Inversion In An Open Three Level Ladder-Type System

The study of lasing without inversion (LWI)is an important and active research frontfield in international lasing physics nowadays. The study of LWI has not only an importanttheoretical value, but also wide application prospects. As a new mechanism of producing laser,LWI have received considerable attention for their potential to obtain laser light in spectraldomains, e.g. the x-ray or even γ-ray range, where conventional methods based on populationinversion are not available or are difficult to implement.Based on the work of the former people, we presented at first the theoretical model of theopen three level Ladder-Type LWI system. In this paper, we mainly studied the effect ofGaussian transverse profile of the driving and laser file, and the effect of propagation on theopen three level Ladder-Type LWI system. This paper consists of three chapters.In Chapter 1, we explained the significance for studying LWI and the basic principle ofproducing LWI, introduced simply the current research state and the main contents for theimportant study subject at present.In Chapter2, we studied the effect of Gaussian transverse profile for the driving and laserfiles on lasing without population inversion (LWI) in an open three level Ladder-Type System.Moreover, we discussed also the effect of the unsaturated gain coefficient, the cavity-dampingrate, the ratio of the atomic injection rates and atomic exit rate on the corresponding system.In Chapter3, under regarding the Doppler effects due to atomic motion and regardless ofthe Doppler effects, we studied the propagation effects on lasing without inversion in theopen four-level system, respectively. When ignoring the Doppler effects, we discussed theeffects of the propagation length on the probe gain, the Rabi frequency of the driving andprobe fields, and discussed the effect of the driving field Rabi frequency at the entrance ofthe active medium on the probe gain for a propagation length of 5.2 cm. When consideringthe Doppler effects and the probe and driving fields and the atomic motion co-propagating,we analyzed the probe gain, the Rabi frequency of the driving and probe fields and thepopulations as the functions of the propagation length and studied respectively the probe gainfor a propagation length of 5.2 cm as the function of the driving field Rabi frequency at theentrance of the active medium and as the function of the Doppler broadening. We contrastedthe numerical simulation results in the four transmission cases among the probe field, thedriving field and the atomic motion.