铷原子系综自旋噪声谱实验研究

Experimental investigation of spin noise spectroscopy of rubidium atomic ensemble

自旋噪声谱是一种测量自旋涨落的光谱技术,由于无扰动的测量机制,其光谱信号非常微弱.本文基于含有一定压力的缓冲气体的天然丰度铷原子气室,搭建了无外磁干扰的铷原子系综自旋噪声谱测量装置,获得了微弱的铷原子系综自旋噪声谱信号,实现了对铷原子系综自旋特性的测量与表征.研究了探测光光强、频率失谐量、铷原子数密度等参数对自旋噪声谱信号的影响.自旋噪声谱信号的积分与探测光光强的平方成正比,光强会展宽自旋噪声谱的半高全宽.自旋噪声谱信号的积分依赖于探测光的失谐量,共振处呈现凹陷,这是由一定压力的缓冲气体的充入引起均匀展宽所导致.自旋噪声信号的积分与原子数密度的1/2次幂成正比.本研究有助于铷原子自旋噪声谱技术应用于磁场的精密测量等方面,也为高信噪比、小型化铷原子自旋噪声谱测量系统的研制提供了参考.

Spin noise spectroscopy is a very sensitive undisturbed spectroscopic technique for measuring atomic spin fluctuations by using a far-detuned probe laser beam.In this paper,we describe an experimental setup for measuring the spin noise spectroscopy.The spin noise spectra of Rubidium atomic vapor cell filled with 10 Torr of Neon gas and 20 Torr of Helium gas as buffer gas are investigated in a magnetically shielded environment.The dependence of the spin noise power spectral density,separately,on the probe beam’s intensity(I),the probe beam’s frequency detuning(△)and Rubidium atomic number density(n)are measured.The integrated power of Rubidium atomic spin noise spectra is scaled as I^2.Owing to homogeneous broadening,the full width at half maximum of transmission spectrum of the same cell is broadened to△νt=6.9 GHz.Center frequency of transmission spectrum is set to be△=0.The probe beam’s frequency detuning is larger than the half width at half maximum of the transmission spectrum|△|>△νt/2,so the integrated power of Rubidium atomic spin as a result of collisions between the buffer gas√Rubidium atomic spin’s transverse relaxation time becomes shorter while the temperature increases.Only at the condition of non-perturbative probe,including far-off-resonant laser,weak laser intensity and uniform transverse magnetic field,the measured full width at half maximum will be close to the intrinsic linewidth of spin noise spectrum.In this way,we can obtain the Rubidium atomic spin’s transverse relaxation time.This work can be applied to the field of physical constants precision measurement,like Lande g factor and isotopic abundance ratio.In addition,it provides an important reference for developing the high signal-to-noise ratio and compact spin noise spectrometer.