Theoretical Study Of Coherent Control Of Optical Properties In A Ladder-Type System

The study of coherent control of optical properties and optical courses is one of the most important and active research front fields in international optics nowadays. The study of coherent control has not only an important theoretical value, but also wide application prospects in many fields, such as quantum optics, nonlinear optics, quantum information and photo-communication, etc. In addition, Atomic coherence effects have multiple potential applications in many aspects. Among numerous phenomena of atom coherence, lasing without inversion (LWI) has received tremendous attention. As a new method of producing laser, LWI can obtain laser light in spectral domains, e.g. the x-ray evenγ-ray range, where conventional methods based on population inversion are not available or are difficult to implement, so LWI has wide application prospects.Based on the work of the former people, we studied the lasing without inversion and coherent control of optical properties in an open Ladder-type system in this paper. This paper consists of four chapters.In Chapter 1, we explained the significance for studying coherent control and LWI, showed the basic principle of producing LWI, and introduced simply the current research state of coherent control and LWI.In Chapter 2, we analyzed the effects of the spontaneously generated coherence (SGC) and parameters of system on the gain, dispersion and population differences. The result shows that, SGC can leads to lasing without inversion (LWI), electromagnetically induced transparency (EIT) and high dispersion (index of refraction) without absorption, the switching between LWI and lasing with inversion also can be realized by adjusting the strength of SGC. The manipulation roles of atomic exit and injection rates, the incoherent pump rate and the Rabi frequency of the driving field on effect of the probe gain are also analyzed for the open ladder type system under two cases that the incoherent pumping is present and not.In Chapter 3, the control role of the relative phase between the probe and driving fields on the gain, dispersion and populations in an open ladder system with spontaneously generated coherence (SGC) is investigated. It is shown that by adjusting the value of the relative phase, the conversion from lasing with inversion to lasing without inversion can be realized; high index of the refraction with zero absorption and the electromagnetically induced transparency can be achieved; in the open system with SGC and phase control, LWI gain that when the incoherent pumping is absent is much larger than that when incoherent pumping presents. Moreover, the LWI gain that in the open system is obviously larger than that in the closed system. In addition, the manipulation roles of incoherent pumping rate, atomic exit and ratio injection rates on phase control have been analyzed.In Chapter 4, we investigated the population transfer by ultrashort pulse in closed ladder-type three-level atom system. It shows that the population transfer closely depends on Rabi frequency and chirp rate; at suitable Rabi frequency and chirp rate, almost complete population transfer can be produced; in addition, the ratio of the dipole moments and the pulse width have important effects on the population transfer.