Abstract
We quantify the strength of stimulated forward Brillouin scattering in hollow-core photonic bandgap fiber through a combination of experiments and multi-physics simulations. Brillouin spectroscopy methods reveal a family of densely spaced Brillouin-active phonon modes below 100 MHz with coupling strengths that approach those of conventional silica fiber. The experimental results are corroborated by multi-physics simulations, revealing that relatively strong optomechanical coupling is mediated by a combination of electrostriction and radiation pressure within the nano-scale silica-air matrix; the nontrivial mechanical properties of this silica-air matrix facilitate the large optomechanical response produced by this system. Simulations also reveal an incredible sensitivity of the Brillouin spectrum to fiber critical dimensions, suggesting opportunity for enhancement or suppression of these interactions. Finally, we relate the measured and calculated couplings to the noise properties of the fiber as the foundation for phase- and polarization-noise estimates in hollow-core fiber. More generally, such Brillouin interactions are an important consideration in both the high and low optical intensity limits.
Highlights
In contrast to conventional step-index fibers, hollow-core photonic bandgap fibers (HC-PBF) produce guidance of light in air through Bragg reflection from a periodic silica-air matrix [1,2,3]
We show that the majority of Brillouin active phonon modes in HC-PBF produce strong depolarized phonon-mediated four-wave mixing (Ph-FWM), meaning that these measurements provide a powerful new window into the stimulated Brillouin interactions in HC-PBF
Through a combination of experiments and multi-physics simulations, we have shown that hollow core photonic bandgap fiber supports a family of densely spaced Brillouin-active phonon modes below 100 MHz with coupling strengths approaching those of conventional silica fiber
Summary
In contrast to conventional step-index fibers, hollow-core photonic bandgap fibers (HC-PBF) produce guidance of light in air through Bragg reflection from a periodic silica-air matrix [1,2,3] This unique form of guidance has enabled powerful new opportunities for both classical and quantum applications. Strong coupling to atomic vapors, enabled by hollow-core fibers, has brought new concepts for single photon nonlinearities and interactions [7,8,9,10], including switching and memories [11] Such applications require reduced interactions with the silica-air matrix, as both stimulated and spontaneous light scattering processes adversely impact quantum coherence [12,13,14,15,16,17,18,19,20].
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