We demonstrate a narrowband optical filter which operates on the 52S1/2 to 52P3/2 transition at 780 nm in rubidium vapor based on optical-pumping-induced dichroism combined with Faraday anomalous dispersion effects. Its peak transmission is 18.4（2）% at the 52S1/2, F = 2 to 5^2P3/2, F＇ = 1, 3 crossover transition, whereas at the 5^2S1/2, F = 2 to 5^2P3/2, F＇ = 2, 3 crossover transition the transmission is 18.6（2）%. Both transitions have a bandwidth （full-width at half-maximum of peak transmission） as narrow as 24.5（8） MHz, which is remarkably improved compared with the narrowest bandwidth as we know. This technique can also be applied to other alkali atoms. OCIS codes： 120.2440, 230.2240, 300.6460. doi： 10.3788/COL201412.101204.
The population ratio between the excited states of rubidium in the electrodeless discharge rubidium vapour lamp is calculated according to the near-infrared spectra in the region of 780-1550 nm. By using a 1529 nm laser, we measure the density of natural rubidium atoms at the 5P3/2 level. The populations of different excited states are then clarified.
We demonstrate experimentally the population inversion between 7S1/2 and 6P3/2 levels of cesium in thermal cesium cell with a 455.5 nm pumping laser.We calculate the relative population probabilities at each level theoretically with the density matrix method.In a steady state,5.8% atoms are at 7S1/2 level and 2.9% at 6P3/2 level,which builds up the population inversion between the two levels.We obtain the fluorescence spectra produced in thermal cesium cell in our experiment.The measured relative intensity of each available fluorescence spectral line in the experiment agrees very well with the theoretical result.The demonstrated population inversion between 7S1/2 and 6P3/2 levels can be used to construct an active optical clock of four-level system with a wavelength of 1469.9 nm.
WANG YanFeiWANG DongYingZHANG TongGangHONG YeLongZHANG ShengNanTAO ZhiMingXIE XiaoPengCHEN JingBiao
