Studies on rubidium 5S-5d two-photon absorption

ABSTRACT

We studied non-resonant two photon absorption (NRTPA) 5S_1/2→5D_5/2 of hot Rb atom using a laser emitting at 778nm. The decay channel 5D_5/2→6P_3/2→5S_1/2 is monitored to record the blue fluorescence. Two important aspects of blue fluorescence are explored: (i) photon number statistics under counter-propagating beam geometry, (ii) extraction of a workable discriminator signal by using modulation transfer for offset locking. The blue photon statistics histogram closely follows super–Poissonian distribution revealing the partially coherent or chaotic character under the limit of large photon counts. On the other hand modulation amplitude vs. peak height of 1-st derivative signal reveals that too small or too large modulation is detrimental for extracting discriminator signal. Under weak modulation, the offset stabilized laser attains square root of Allan variance σ(τ) ∼ 1.5 × 10⁻¹⁰ at integration time τ>10s. We propose generation of an offset stabilized chaotic blue light source by coupling (i) and (ii).

KEYWORDS:

• Cascade
• non-resonant two-photon absorption
• blue fluorescence
• rubidium
• photon statistics
• offset stabilization

Disclosure statement

No potential conflict of interest was reported by the author(s).