Tunable photon-phonon interaction

by mixing acoustic waves ​

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Heedeuk Shin

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Department of Physics, POSTECH

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Recently, new photon-phonon phenomena have been explored in micro- or nano-scale systems by controlling strong correlations between optical and acoustic waves. One such phenomenon is stimulated Brillouin scattering (SBS), one of the most potent nonlinear effects in optical fibers. We have observed the SBS process in silicon photonic structures, demonstrating optical amplification and active acoustic modulation in silicon for the first time[1-3]. Additionally, we have introduced a novel acoustic resonance tuning method by mixing high-order Lorentzian responses using weakly coupled phononic-crystal acoustic cavities[4]. Typically, actively altering the properties of mechanical oscillators is challenging because their stiffness, surface stress, and dimensions are determined by the materials and geometries chosen. However, we achieved coherent mixing of second- and third-order Lorentzian responses, allowing for precise tuning of the resonance's bandwidth and peak frequency. This innovative resonance tuning method can be broadly applied to Lorentzian-response systems and optomechanics, particularly for actively compensating for environmental fluctuations and fabrication errors.

[1] Nature Communications 4, 1944 (2013)
[2] Nature Photonics 10, 463-467 (2016)
[3] Nano Letters 21, 7270–7276 (2021)
[4] Nano Letters (https://doi.org/10.1021/acs.nanolett.4c00335)