Demonstration of an exposed-core fiber platform for two photon rubidium spectroscopy

Abstract

We demonstrate a promising fiber architecture for generating strong photon-photon interactions. Exposed-core silica optical fibers possess low-loss guidance between 400 and 1700 nm crucial for quantum-logic applications. The potential of this fiber is demonstrated by exciting a two-photon transition within a rubidium vapor using an exposed-core silica optical fiber. Transit-time broadened spectral features enable measurement of the evanescent-field scale length of (120 ± 20) nm which shows excellent agreement with the characteristics of the modeled fiber mode (118 ± 2) nm. We observe a two-photon absorption coefficient of 8.3 cm-1 for one optical mode in response to a transmitted power of 1.3 mW in the second mode. A clear pathway to an exposed-core fiber exhibiting substantial absorption mediated by a single photon is identified.