Effects of a laser beam profile on Zeeman electromagnetically induced transparency in the Rb buffer gas cell

• Published in: Journal of physics. B, Atomic, molecular, and optical physics Atomic, molecular, and optical physics, 2013-04, Vol.46 (7), p.75501-1-10
• Main Authors: Nikoli, S N, Radonji, M, Krmpot, A J, Lu i, N M, Zlatkovi, B V, Jelenkovi, B M
• Format: Article
• Language: English
• Subjects: Amplitudes; Applied sciences; Approximation; Beam characteristics: profile, intensity, and power; spatial pattern formation; Buffers; Coherence; Effects of atomic coherence on propagation, absorption and amplification of light; electromagnetically induced transparency; Electronics; Exact sciences and technology; Fundamental areas of phenomenology (including applications); Gaussian; Laser beams; Laser optical systems: design and operation; Lasers; Line shape; Optics; Optoelectronic devices; Physics; Quantum optics; Rb gas cell; Semiconductor electronics. Microelectronics. Optoelectronics. Solid state devices
• ISSN: 0953-4075; 1361-6455
• DOI: 10.1088/0953-4075/46/7/075501

Electromagnetically induced transparency (EIT) due to Zeeman coherences in the Rb buffer gas cell is studied for different laser beam profiles, laser beam radii and intensities from 0.1 to 10 mW cm−2. EIT line shapes can be approximated by the Lorentzian for wide Gaussian laser beam (6.5 mm in diameter) if laser intensity is weak and for a Π laser beam profile of the same diameter. Line shapes of EIT become non-Lorentzian for the Gaussian laser beam if it is narrow (1.3 mm in diameter) or if it has a higher intensity. EIT amplitudes and linewidths, for both laser beam profiles of the same diameter, have very similar behaviour regarding laser intensity and Rb cell temperature. EIT amplitudes are maximal at a certain laser beam intensity and this intensity is higher for narrower laser beams. The EIT linewidth estimated at zero laser intensity is about 50 nT or 0.7 kHz, which refers to 1.5 ms relaxation times of Zeeman coherences in 87Rb atoms in our buffer gas cell. Blocking of the centre of the wide Gaussian laser beam in front of the photo detector yields Lorentzian profiles with a much better contrast to the linewidth ratio for EIT at higher intensities, above ∼2 mW cm−2.