Quantum Properties Of Atom Driven By Bichromatic Field In Photonic Crystals

The phenomenon of spontaneous emission of atom as a quantum property is a hot topic in quantum optics research.Controlling the spontaneous emission of atom can improve the measurement accuracy of optical instruments.Currently,there are two ways to control spontaneous emission: using different driving fields and changing the thermal reservoir environment.For example,bichromatic fields have been used to control the spontaneous emission of atom in a vacuum,and photonic crystals have been used to control the spontaneous emission of atom.However,there has been no report on the use of bichromatic fields in combination with photonic crystals to control the spontaneous emission of atom.Therefore,it is necessary to investigate the properties of spontaneous emission of atom driven by a bichromatic field placed in a photonic crystal.In this thesis,we propose a new computational method,the n-times method,to calculate the spontaneous emission spectra of bichromatic field-driven Λ-type three-level atom and tripod-type four-level atom in anisotropic double-band photonic crystals.We investigate the effect of system parameters on the spontaneous emission spectra of atom and explain the spontaneous emission phenomena of atom using the theory of embellished states.By studying the model of bichromatic field-driven Λ-type three-level atom in anisotropic double-band photonic crystals,a comb-like structure is observed in the spontaneous emission spectrum of the atom.This phenomenon can be explained by the theory of embellished states,where the bichromatic field embellished atom form a series of equally spaced embellished states.The emission peaks are generated by the leap of the atom from the embellished states to the next energy level,and the distance between adjacent emission peaks is equal to the detuning(δ)of the bichromatic field.The odds distribution calculation shows that the emission peaks appear at 2nδ when the initial state of the atom is at a higher energy level and at(2n +1)δ when the initial state of the atom is at a lower energy level,consistent with the observations in the spontaneous emission spectrum.The height of the emission peak depends on the ratio of the Rabi frequency strength of the bichromatic field to the detuning.When the Rabi frequency strength of the bichromatic field is increased,the transfer of particles through the lepton channel causes the emission peak on the outside of the spontaneous emission spectrum to become higher and the emission peak on the inside to decrease.Furthermore,by comparing the spontaneous emission spectra of atom in vacuum and photonic crystals,it is found that the emission peaks located inside the photonic band gap are annihilated,and those at the edges of the photonic band gap are enhanced.By studying the tripod-type four-level atomic model in anisotropic double-band photonic crystals driven by both bichromatic and monochromatic fields,a comb-like spontaneous emission spectrum is observed,but the emission peaks split into double peaks due to the double structure of the embellished states in the upper energy level.When the initial state of the atom is at the upper energy level,only the double peak is present in the spontaneous emission spectrum,appearing at 2nδ.When the initial state of the atom is at the lower energy level,a single peak appears at(2n +1)δ,and a double peak appears at2nδ.By increasing the Rabi frequency intensity of the monochromatic field,the spacing between the embellished energy levels becomes larger,resulting in a larger distance between the double peaks.Under the influence of the photonic band gap and the bichromatic field,increasing the Rabi frequency intensity of the bichromatic field shifts the particles to the embellished energy levels on either side.This causes the height of the inner peak to decrease and the height of the outer peak to increase.Due to the possibility of complete or incomplete quantum phase extinction interference between the leap channels,fluorescence quenching,dark lines,and other phenomena appear in the emission spectrum.All of the above studies have shown that the combination of a bichromatic field and a photonic crystal can be used to cause enhancement,suppression and annihilation of the spontaneous emission of atom.The research in this topic provides some theoretical guidance for the design of optical instruments.