Investigations Of The Quantum Interference In Multi-Level Atomic Systems And Interference Filter

The interaction of atoms with light is one of the most important fields in physics. Since the 1970, using the semiconductor diode lasers and people begin to study the interaction of multi-level atoms with coherent light.Recently, Electromagnetically induced transparency (EIT) induced by the atomic coherence has been found various applications and attracted extensively attention, since the EIT medium have low linear absorption, steep dispersion and large nonlinear effects at low light and the EIT medium can also be used for quantum state transfer between matter and light. EIT effect provided a tool to manipulate the linear or nonlinear absorption and dispersion of atom medium. Using the effect, the group velocity of optical pulse can be reduced to thousands to decades meter per second. While the group velocity of optical pulse was being reduced, the pulse signal of light was also compressed into the atom medium, which provided an important method for overcoming the problem that photons can't be local easily due to it's fast propagation. The dissertation introduce the EIT effects in the interaction of multi-level atoms with light. The work are divided into two parts: (1) introduce experimental observation of Two EIT and it's interaction, experimental observation of CPT in multi-level atomic system. (2) design a narrowband F-P interference filter whose resonant frequency can be tuned by changing it's temperature. The main accomplished works are as follows:1) A four-level tripod system is formed in the D1 line in ⁸⁷Rb atoms by choosing proper circularly-polarized probe, coupling and trigger beams. We introduce experimental observations and theoretical calculations of Two EIT windows and enhanced EIT signal in the four-level tripod system. The Two EIT dips produced by a strong coupling beam and a weak trigger beam were observed in the absorption spectrum of probe field when the frequency detuning of trigger beam was different from that of the coupling beam. When the frequency detuning of trigger beam was near or equal to that of the coupling beam, the EIT dip created by coupling beam clearly became larger.2) By choosing two circularly-polarized beams (coupling and trigger beams) with degenerate frequency to couple to transition from 5S_1/2, F=2 to 5P_1/2, F'=1, the CPT effect occurred and the absorption of the other beam(probe beam) interaction with another transition from 5S_1/2, F=1 to 5P_1/2, F'=2 was reduced.3) We study the filter in order to suppress the control lights. By controlling the temperature of the filter, the distance between two ends of F-P interference filter can be changed, so the frequency of laser which is resonance with the F-P interference filter can be continuously tuned. The free spectral range of the filter is 13.6 GHz, the full width at half maximum (FWHM) is 541MHz. The transmittance will achieve up to 82%, while the laser whose frequency is 2-10GHz away from the resonance frequency will be reflected ( reflectance is about 99.3%-99.7%). When the controlled temperature fluctuate is less than±0.005℃, the fluctuate of transmitted light power is less than 2.5%.