We present two new designs of optoacoustic waveguides supporting nonlinear Brillouin scattering (SBS). The first design, optimized for forward SBS, comprises a rectangular core supporting a low-loss optical mode, suspended in air by a series of transverse ribs. The ribs are engineered to exhibit a complete acoustic stopband and suppress the transverse leakage of acoustic waves. The second design we discuss here is a realization of an Anti-Resonant Reflecting Acoustic Waveguide, which are analogues of optical ARROWs. These waveguides, capable of co-localization and guiding of both the optical and GHz acoustic waves in simple, translationally invariant waveguides, are shown to support backwards SBS.
Stimulated Brillouin scattering (SBS) is a strong nonlinear interaction between optical and mechanical modes of nanophotonic waveguides, whereby the optical field can generate and maintain extremely strong acoustic waves. Until recently, it was believed that the high losses associated with metals would render SBS unmeasureable in plasmonic systems. However recent work has shown that the confinement of acoustic modes in metallic structures, together with strong field gradients that occur on metal-dielectric surfaces, can result in SBS gain orders-of-magnitude greater than that in dielectric waveguides. This gain scales such that it is able to overcome the intrinsic loss of some surface plasmon polariton (SPP) configurations, depending on the waveguide geometry.
Here we examine the interaction of light and sound in plasmonic systems, including the forces and scattering processes in the presence of highly-lossy optical and acoustic modes. We examine the thermal effects arising from the optical loss and show how the measured gain is determined by the CW power-handling capabilities of the plasmonic mode. We examine a range of possible waveguide geometries and establish relevant Figures of Merit for evaluating a range of realistic plasmonic waveguides, and examine how geometrical scaling affects the SBS gain in both forward (co-propagating) and backward (counter-propagating) SBS configurations. We find that SPP-driven SBS will be measureable within a broad range of waveguides, and present general design rules for measuring SBS in different material systems. Finally, we discuss the challenges and opportunities for harnessing this effect in the first experiments.
It is well known that effective medium description of metamaterials requires much caution, even for strongly subwavelength systems. Boundary effects play a dramatic role in finite samples with discrete structure, making their observable properties quite different from the predictions of effective medium theory. We report some new findings regarding the distinction between a homogenised response and actual properties of discrete structures, looking into canonical shape of metamaterial objects. Even for large size (up to 20000 “meta-atoms”), we observe a difference between large discretised spheres and a continuous one, which is important for practical design and future development of metamaterials. Finally, we also provide the results for non-resonant discrete finite systems
Butt-coupling of light into a surface plasmon is a simple and compact coupling method with a range of potential uses in photonic circuitry. Although butt-coupling has been successfully implemented in many coupling configurations, the coupling effectiveness is not fully understood. Here, we present a semi-analytical study which models the coupling efficiency of an incident beam into a surface plasmon on silver in the presence of loss using an projection method in one dimension. We find that the coupling efficiencies for silver between the wavelengths of 0:38 - 1:6 μm reach 77 - 88% with optimum incident beam parameters.
We review recent demonstration of stimulated Brillouin scattering in a chalcogenide photonic chip and its application to
optical and microwave signal processing tasks. The interaction between light and sound via stimulated Brillouin scattering
(SBS) was exploited in chalcogenide photonic circuits to achieve on-chip SBS slow and fast light, microwave photonic
filters, and dynamic gratings using travelling-wave geometry. Using a ring-resonator geometry, photonic-chip based
Brillouin laser was demonstrated.
The ability to control the speed of light on an optical chip is fundamental to the development of nanophotonic components for alloptical
signal processing and sensing [1-7]. However this is a significant challenge, because chip-scale waveguides require very large
changes in group index (Δng) to achieve appreciable pulse delays. Here, we use Stimulated Brillouin Scattering (SBS) to report the
demonstration of on-chip slow, fast and negative group velocities with Δng ranging from −44 to +130, and delays of up to 23ns at a
pump power of ~300mW and propagation length of 7cm. These results are obtained using a highly-nonlinear chalocogenide (As2S3)
rib waveguide, in which the confinement of both photons and phonons results in strong interaction. SBS can be used to achieve
controllable pulse delays at room temperature over a large wavelength and signal-bandwidth . These results open up a new set of
photonic applications ranging from microwave photonics  to spectrometry .
We report the first demonstration of on-chip stimulated Brillouin scattering (SBS). SBS is characterized in a
chalcogenide (As2S3) photonic chip where the measured Brillouin shift and full-width at half-maximum (FWHM)
linewidth are 7.7 GHz and 34 MHz respectively. The measured Brillouin gain coefficient (gB) is 0.715 x 10-9 m/W, consistent with the theoretical estimate.