Laser-noise-induced correlations and anti-correlations in electromagnetically induced transparency

Abstract

High degrees of intensity correlation between two independent lasers were observed after propagation through a rubidium vapor cell in which they generate Electromagnetically Induced Transparency (EIT). As the optical field intensities are increased, the correlation changes sign (becoming anti-correlation).The experiment was performed in a room temperature rubidium cell, using two diode lasers tuned to the 85 Rb D2 line (λ = 780nm). The cross-correlation spectral function for the pump and probe fields is numerically obtained by modeling the temporal dynamics of both field phases as diffusing processes. We explored the dependence of the atomic response on the atom-field Rabi frequencies, optical detuning and Doppler width. The results show that resonant phase-noise to amplitude-noise conversion is at the origin of the observed signal and the change in sign for the correlation coefficient can be explained as a consequence of the competition between EIT and Raman resonance processes.PACS. 32.80.Qk Coherent control of atomic interactions with photons -42.50.Gy Effects of atomic coherence on propagation, absorption, and amplification of light; electromagnetically induced transparency and absorption

Power spectra and correlations of intensity fluctuations in electromagnetically induced transparency

“…The correlations of intensity fluctuations reduce with increasing optical power (Rabi frequency). Similar power behaviour of correlations between two independent optical beams in the EIT experiment is observed in [7]. Variation in the correlation coefficient is explained in [7] as a consequence of the competition between EIT and Raman processes.…”

“…Similar power behaviour of correlations between two independent optical beams in the EIT experiment is observed in [7]. Variation in the correlation coefficient is explained in [7] as a consequence of the competition between EIT and Raman processes. The result is that in EIT the best reduction of excess atomic noise can be reached at low optical intensity (Rabi frequency).…”

“…The result is that in EIT the best reduction of excess atomic noise can be reached at low optical intensity (Rabi frequency). Theoretical consideration of the intensity correlations in EIT is done in [7,17]. …”

“…Sub-Poissonian statistics of photons is observed in EIT [4]. A high degree of quantum correlations of coupled optical fields have been observed recently [5][6][7]. Several schemes have been proposed to produce squeezing in coupled optical fields in a coherently prepared atomic medium [8][9][10][11][12].…”

Electromagnetically induced transparency with noisy lasers

“…For Electromagnetically Induced Transparency (EIT) in atomic and other systems [2], such deleterious noise conversion is of great interest because of the wide application of EIT in atomic clocks [3,4], magnetometers [5], quantum optics [6,7] and quantum communications [8][9][10]. Laser phase-noise-to-intensitynoise conversion in the absence of atomic ground state coherence and its role in atomic-clock instability [1,[11][12][13] and the effect of laser phase-noise on photon-photon correlations in atomic vapor cells [6,7] have been studied previously. However, the role of EIT coherence in noise processes remains to be understood.…”