Eur. Phys. J. D 55, 9-15 (2009)
https://doi.org/10.1140/epjd/e2009-00195-4

Visible superfluorescence from optically pumped europium atoms

Spectroscopy Division, Bhabha Atomic Research Centre, 400 085 Mumbai, India

Corresponding author: ^a nakhate@barc.gov.in

Received: 15 April 2009
Revised: 20 May 2009
Published online: 30 June 2009

Abstract

We have observed superfluorescence (SF) on five atomic transitions at visible wavelengths 633.58, 635.00, 640.09, 640.61 and 736.22 nm in Doppler broadened gas of europium (Eu) atom. The nanosecond SF pulses were observed by longitudinally pumping Eu vapor column with a pulsed dye laser to upper states 4f⁶5d6s², ⁸D_7/2 at 346.79 nm and 4f⁷5d6p, ¹⁰F_5/2 at 348.73 nm from the ground state 4f⁷6s², ⁸S_7/2. High optical conversion efficiency ≈10% was measured for these SF transitions. Our experiment deals with the large sample multilevel SF in the regime where the length of the excited column L is greater than the maximum value of the Arecchi-Courtens length (L_c). The observed variation of SF peak intensity (I_fl) and time delay for SF evolution (τ_D) with number of atoms in the excited state (N) resemble theoretically predicted SF scaling laws for transverse excitation, namely I_fl ∝N and although the experimental condition is similar to the swept excitation. This could be due to the Rabi frequency associated with the pump transition which is comparable to the SF delay time precluding the initiation of SF at different times along the sample and results in transverse (instantaneous) excitation. The experimental τ_D values were found to be in agreement with the quantum mechanical calculations describing SF.