基于相干粒子数囚禁的电磁诱导光栅研究

Electromagnetically induced grating based on the coherent population trapping

基于相干布居囚禁,提出了一种新的电磁诱导光栅物理模型,得到了该模型下介质极化率的解析表达式.由于相干布居囚禁引入的原子相干性,介质极化率会形成增益、无吸收高折射率点以及暗态三个区域.根据该理论模型,基于87Rb的原子能级,提出了一种新型衍射光栅实现方案,并进行了分析与计算.结果表明,在无吸收高折射率点处,这种光栅是一种纯相位光栅,一级衍射强度可达到0.4;在增益区域中,发现这种光栅是相位光栅和幅度光栅组合而成的混合型光栅,在其最大增益点,一级衍射效率最大可达1.26,二级衍射效率也可增加到0.31.

Based on the coherent population trapping theory, a new physical model of the electromagnetically induced grating （EIG） is proposed. Analytical expression of the dielectric susceptibility is derived using this model. Owing to the atomic coherence, introduced by the coherent population trapping, three regions of dielectric susceptibility, i.e. , a gain region, a region with no absorption and high-refraction index, and a dark region, are formed. Based on this model and the energy level of 87 Rb, a novel scheme to implement the diffraction grating is proposed. Moreover, theoretical analysis and calculation of this grating are carried out. The results show that in the region with no absorption and high refractive index, the grating presents a pure phase grating and the first-order diffraction intensity can reach 0.4. In the gain region, however, the grating is a combination of phase grating and amplitude grating, and at its largest-gain point, the maximum of the first-order diffraction efficiency arrives at 1.26, and the second-order diffraction efficiency can also increase to 0.31.