Experimental demonstration of stimulated Raman scattering in the evanescent field of a tapered nanofiber immersed in a liquid

Summary form only given. Tapered nanofibers are fibers that are stretched until their diameter becomes comparable to the optical wavelength. As the length of such nanofibers can reach tens of centimeters, the guided mode that presents a strong evanescent field can be used to efficiently excite “evanescent nonlinearities” in the medium surrounding the nanofiber. This evanescent field was already used in many applications, for instance to probe the atomic fluorescence of gases, and also for spectroscopic measurements. However, to our knowledge, this field has never been used to perform optical nonlinearities, the so-called “evanescent nonlinearities”, except in two very recent communications . In this work, we present the demonstration of stimulated Raman scattering in the evanescent field of a nanofiber immersed in ethanol. The nanofiber was drawn from a telecom fiber with a home-made pulling platform. The targeted diameter and length are respectively 440 nm and 6 cm. The pump source was a frequency doubled Nd:YAG laser emitting pulses at 532 nm whose full width at half maximum is 510 ps. We observed the first Stokes of ethanol at 630 nm (see fig. below). The conversion efficiency is about 40 % for an input pump energy of 0.24 μJ. This first experimental demonstration of stimulated Raman scattering in the evanescent field of a nanofiber immersed in a liquid opens the way to the study of a new kind of experiments and components, thanks to the various materials that can form or surround the nanofiber and the feasibility of nanosystems such as nanoloops or nanoresonators.