薄原子蒸气的双光子Dicke窄化选择反射光谱

Two-Photon Dicke-Narrowing Selective Reflection Spectroscopy in Thin Atomic Vapor

研究了囚禁于两电介质面间的Λ型三能级原子的双光子Dicke窄化选择反射(TDNSR)光谱。通过对不同膜厚及不同抽运光强度的TDNSR线型的分析,发现由于蒸气中的原子与电介质表面碰撞的消激发效应和薄蒸气膜中的慢原子效应,以及双光子光谱的消多普勒配置,TDNSR线型在很多情形下表现为亚多普勒结构,且线型随蒸气膜层的厚度与探测光波长的比值呈周期性变化。当L=2mλ/4(m为正整数)时,TDNSR消失。而当2mλ/4<L<(2m+2)λ/4时,线型为典型的色散曲线,且L趋近(2m+1)λ/4时对称性增强.精确调谐强抽运光于能级2〉-3〉的跃迁时,在探测光的共振区域Δd=0附近,TDNSR极高的变化率表明探测光具有显著的群速变慢效应。

Two-photon Dicke-narrowing selective reflection （TDNSR） spectroscopy is studied in a system of A-type three-level atoms confined between two dielectric walls. TDNSR lines are investigated for the cases of different thicknesses of the vapor film and different strengths of the pump field. Because of de-excited behavior induced by atom-wall collision, effect of slow atoms in a thin atomic vapor film and Doppler-free configuration, sub-Doppler lines can be obtained in many cases. It is also found that TDNSR lines change periodically with the ratio of L/λ （L is the thickness of the atomic film and λ is the wavelength of the probe field）. TDNSR disappears for L =2mλ/4 （m is an integer） and revives a typical dispersion shape for 2mλ/4〈L〈（2m＋2）λ/4 with an enhanced symmetry when L approaches to （2m＋1）λ/4. As the pump field is exactly tuned to the transition ｜ 2〉 - ｜ 3〉, the fast variation of TDNSR near △d = 0 （△d is the detuning of the probe field） indicates a dramatically group-velocity reduction of the probe field.