Abstract

The 7³S₁ → 6³P₂ (λ = 546.1-nm) transition of atomic mercury has received considerable spectroscopic attention. In this paper we examine phase conjugation reflectivities and line shapes for various pump powers on this line. The geometry is that of backward D4WM: counterpropagating pump beams and a weak probe intersect at an angle of 0.750° in a quartz mercury discharge cell. The inductively coupled rf discharge provides a density difference of 10⁹–10¹¹ atoms/cm³ between the levels of interest, which yields a small signal absorption α in the 0.3–3-cm⁻¹ range. The best fit to the measured α(l) on line center is obtained using α(l) = α₀/[1 + (l/l_s)] with l_s = 30 mW/cm². This form of α(l) is different from what one would expect for a low pressure gas with Doppler broadening. Phase conjugation has been observed with pump powers as low as 3 mW. Spectra obtained by observing the conjugate beam as the laser frequency is scanned through resonance exhibit line broadening of 64–490 MHz depending on pump power. Additionally, line splitting is observed with increasing pump power. These splittings were 72 MHz at 134 mW of pump power. With an estimated Rabi frequency (Ω) of ~60 MHz, the predicted splitting is 3/2 Ω = 90 MHz.

© 1985 Optical Society of America