Highly efficient and reproducible evanescent Raman converters based on a silica nanofiber immersed in a liquid

Abstract

We present highly efficient and reproducible Raman converters built with a silica nanofiber immersed in ethanol. The converters are pumped at 532 nm in the sub-nanosecond regime and the first Stokes order photons are generated in the evanescent field probing the liquid at 630 nm. Two standard fibers (SMF28, 460HP) are tested and compared. The Raman conversion operating range limited by the damage threshold is optimized, leading to an external Raman conversion efficiency up to 60% with a nanofiber radius of 300 nm and a length of 8 cm. The extracted Stokes energy is 0.29 µJ, which is three times higher than the previous result. We give guidelines for the design of other efficient evanescent Raman converters, opening the way for a new family of all-fibered compact Raman sources.

Laser-induced breakdown measurements of silica nanofibers in air and immersed in water, ethanol and isopropanol

“…For each medium we have drawn 10 nanofibers of each radius. The length of each nanofiber was 2 cm in order to avoid non linear effects such as Raman effect in the liquid and hence to study the LIB alone [6,7].…”

“…Nanofibers can also exhibit an intense evanescent field which has been exploited for optical sensing [3] or optical traps for quantum applications [4,5]. The excitation of optical non linearities such as stimulated Raman effect [6,7] or Kerr effect in the evanescent field of nanofibers immersed in liquids has also been demonstrated [8]. In all the above-mentioned applications the optical mode is guided by total internal reflection at the interface between the silica nanofiber and the surrounding medium that can be vacuum, a gas or a liquid.…”

Long-time optical transmittance measurements of silica nanofibers

“…Thanks to its small diameter, this component has a strong confinement of light inside the silica enabling the generation of nonlinear effects such as the generation of supercontinuum [1]. It has also an intense evanescent field exploited for optical sensing [2], optical traps for quantum applications [3] and the excitation of non linearities when immersed in liquids [4,5,6]. Despite all these attractive applications, the nanofiber performances are limited by the degradation of its transmittance during time and by its short lifetime.…”

Laser-Induced Damage in Silica Nanofibers in Air and Immersed in Different Liquids in the Nanosecond Regime

“…This property has been exploited for optical sensing [2] or optical traps for quantum applications [3]. The excitation of optical nonlinearities such as Stimulated Raman Scattering (SRS) [4] or Kerr effect in the evanescent field of nanofibers immersed in liquids has also been demonstrated [5].…”

“…Then, before being pulled the fiber was removed from its polymer cladding with a mechanical stripper and cleaned with an optical paper wet by a drop of ethanol. The nanofibers were drawn with a pulling rig using a simple butane flame [4]. The butane flame softens the fiber central part while two computer-controlled translation stages elongate it following the "pull and brush" technique to create the nanofiber and the tapers.…”