The effect of linewidth in two resonance phenomena

Seyedeh Hamideh Kazemi, Mohammad Mahmoudi

We study the influence of laser profile on the linewidth of the optical spectrum of multi-photon resonance phenomena. First, we investigate the dependence of the absorption spectrum on the laser profile in a two-level system. Thanks to the Laguerre–Gaussian field, the linewidth of the one-photon optical pumping and two-photon absorption peaks are explicitly narrower than that obtained with a Gaussian field. In the next section, it is shown that, compared to the Gaussian fields, the Laguerre–Gaussian ones reduce the linewidth of the optical spectrum in the coherent population trapping. Interestingly, it turns out that the use of a Laguerre–Gaussian beam makes the linewidth of the spectrum narrower as compared with a Gaussian one in Doppler-broadened electromagnetically induced transparency. Moreover, we study the effect of the laser profile on the Autler–Townes doublet structure in the absorption spectrum for a laser-driven four-level atomic system. We also consider the different values of the Laguerre–Gaussian mode beam waist, and, perhaps more remarkably, we find that for the small waist values, the Autler–Townes doublet can be removed and a prominent narrow central peak appears in the absorption spectrum. Finally, we investigate the effect of the laser profile on the linewidth of the sub-natural three-photon absorption peak of double dark resonance. The differences in the linewidth are quite large, offering potential applications in metrology and isotope separation methods. Our results can be used for super ultra-high resolution laser spectroscopy and to improve the resolution of the technology of isotope/isomer separation and photo-biology even at essential overlap of the spectra of the different particles.

Thomas Lindvall, Mikko Merimaa, Ilkka Juhani Tittonen

Lorenzo M. Narducci, Christoph H. Keitel, Gian‐Luca Oppo +1 more

T. A. Fisher, Maurice S. Skolnick, A. M. Afshar +5 more

Tuning of the vacuum Rabi exciton-photon coupling in semiconductor quantum microcavity structures by external electric and magnetic fields is presented. Contrasting effects due to the two external perturbations are found, principally due to the decrease of exciton oscillator strength in electric field and increase of oscillator strength in magnetic field. The strong coupling limit is easily achieved in these high quality structures with line widths on resonance as small as 1 meV. In addition to the tuning phenomena, the effects of exciton Zeeman splitting on the spectra and unexpected linewidth narrowing phenomena on resonance are reported.

Pan-li Qi, Xu‐xing Geng, Guo-Huo Liu +3 more

Abstract We present a theoretical study of the optical-radio-frequency (rf) double resonance on hyperfine ground states of alkali-metal atoms in the geophysical magnetic-field range, in which resonance circularly polarized laser light is used in the optical pumping and detection processes. The analytical expressions of the rf resonance signals corresponding to two ground states are obtained based on atomic multipole moments, where the alignment effect is considered and that is responsible for the resonance shape and linewidth especially when the optical power is relatively strong. In addition, we also obtain the analytical expressions of the linewidths of two separated resonance peaks and one presenting the competition process of the optical pumping, rf field and spin-exchange collision. Two different types of light narrowing phenomena are investigated by comparing the longitudinal relaxation rates of atomic multipole moments for two ground states. Applied to rubidium and cesium atoms, we show a particularly close agreement of our analytical results with more elaborate calculations using density-matrix theory. Our theoretical model is relevant for optimizing the sensitivity of magnetometers.

Carl Kenty