Observation of two-photon absorption at low power levels using tapered optical fibers in rubidium vapor

TL;DR

This paper demonstrates two-photon absorption in rubidium vapor using tapered optical fibers at extremely low power levels, revealing unique spectral features caused by transit-time broadening.

Contribution

It reports the first observation of two-photon absorption at nanowatt power levels in tapered fibers with distinctive spectral characteristics.

Findings

Two-photon absorption observed at <150 nW power levels

Spectra show sharp peaks due to transit-time broadening

Enhanced nonlinear effects in tapered fibers

Abstract

Nonlinear optical effects can be enhanced in tapered optical fibers with diameters less than the wavelength of the propagating light. Here we report on the observation of two-photon absorption using tapered fibers in rubidium vapor at power levels of less than 150 nW. Transit-time broadening produces two-photon absorption spectra with sharp peaks that are very different from conventional line shapes.