Large evanescently-induced Brillouin scattering at the surrounding of a nanofibre

Abstract

Brillouin scattering has been widely exploited for advanced photonics functionalities such as microwave photonics, signal processing, sensing, lasing, and more recently in micro- and nano-photonic waveguides. Most of the works have focused on the opto-acoustic interaction driven from the core region of micro- and nano-waveguides. Here we observe, for the first time, an efficient Brillouin scattering generated by an evanescent field nearby a single-pass sub-wavelength waveguide embedded in a pressurised gas cell, with a maximum gain coefficient of 18.90 ± 0.17 m−1W−1. This gain is 11 times larger than the highest Brillouin gain obtained in a hollow-core fibre and 79 times larger than in a standard single-mode fibre. The realisation of strong free-space Brillouin scattering from a waveguide benefits from the flexibility of confined light while providing a direct access to the opto-acoustic interaction, as required in free-space optoacoustics such as Brillouin spectroscopy and microscopy. Therefore, our work creates an important bridge between Brillouin scattering in waveguides, Brillouin spectroscopy and microscopy, and opens new avenues in light-sound interactions, optomechanics, sensing, lasing and imaging.

Optical microfiber or nanofiber: a miniature fiber-optic platform for nanophotonics

“…13(c). Apart from an airtight box, other sealed chambers have also been applied to satisfy various experimental requirements, for example, capillary [256–258] and stainless steel tube [92,259] .Vacuum treatingFor atom optics, silica MNFs are usually installed in a vacuum chamber. During the installation procedure, a flux of argon gas is maintained to protect the MNF surface from pollution [260] .…”

“…13(c). Apart from an airtight box, other sealed chambers have also been applied to satisfy various experimental requirements, for example, capillary [256–258] and stainless steel tube [92,259] .…”

“…has been adopted for studying optoacoustic interactions [73,74,92,93] and optomechanical technology [94] . So far, optical MNFs have been attracting broad interest from near-field optics, nonlinear optics, atom optics, and optomechanics to optical nanowaveguides, micro-couplers, resonators, sensors, and lasers.…”

“…Fifthly, by selecting an appropriate diameter-to-wavelength ratio (Dfalse/λ), a large field gradient in the evanescent field can be generated in the vicinity of the MNF surface, which has been exploited for manipulating micro/nanoparticles [85] and cold atoms [86–88] . Finally, owing to their small mass, optical MNFs can exhibit a sensitive optomechanical response (typically manifested as mechanical vibrations) to the momentum change of the waveguided light fields [89–91] , which has been adopted for studying optoacoustic interactions [73,74,92,93] and optomechanical technology [94] . So far, optical MNFs have been attracting broad interest from near-field optics, nonlinear optics, atom optics, and optomechanics to optical nanowaveguides, micro-couplers, resonators, sensors, and lasers.…”

Photothermally Induced Birefringence in an Optical Nanofiber for All‐Optical Polarization Manipulation

“…Optical nanofiber (NF), with the advantages of open evanescent field, tightly confined optical mode and diffraction‐free propagation, has been a versatile platform for light‐gas interaction. For NF coupled with warm gas, there has been reported highly efficient electromagnetically induced transparency, [ 1,2 ] two‐photon absorption, [ 3 ] saturated absorption, [ 4 ] stimulated Brillouin, [ 5 ] and stimulated Raman scattering. [ 6 ] The strongly guiding property of NF combined with the subwavelength diameter also results in additional intriguing phenomena, such as the intrinsic spin‐momentum locking associated with the fast‐decaying evanescent field and the azimuthal asymmetry in intensity distribution for the quasi‐linearly polarized (QLP) fundamental mode, [ 7–9 ] i.e., the $$H{E_{11}}$$ mode.…”