Time‐Modulated Optomechanics Reveal Energy Flow and Inelastic Interactions Between Acoustic Phonons in Nanomembranes
Abstract
An abrupt change in refractive index, known as a temporal interface, can cause temporal reflection, refraction, and diffraction of light, enabling the development of time-varying photonic devices. Since time-varying optics are based on ultrafast electronic excitations, the scattered light should be affected by electrons and phonons in nonequilibrium states. Here, we analyze the inelastically scattered light from ultrathin, time-varying optical media and search for spectroscopic signatures of nonthermal phonon populations. Our approach targets hypersonic gigahertz (GHz) acoustic phonons, termed Lamb modes, confined in prototypical, submicron-thick membranes: 260 nm-thick bare silicon and bilayer structures with 50 nm-thick gold layer on 200 nm-thick silicon. Femtosecond laser irradiation of the membranes modulates their optical properties and excites nonthermal, coherent Lamb modes, which are probed via inelastic light scattering of a continuous-wave laser beam. In metal-semiconductor heterostructures, the anti-Stokes signal of photoexcited Lamb modes undergoes blueshifting and an antiresonance-to-resonance temporal transition, which remains unobserved for Stokes scattering. This effect is attributed to inelastic interactions between thermoelastically excited acoustic phonons, resulting in an approximately 3.6% shift in the frequency of longitudinal acoustic phonons. Our work enables studies of heat transport, phonon dynamics, and optomechanics in time-modulated systems, using principles from time-varying optics.
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BibTeX
@article{dhiman2026timemodulated,
title = {{Time‐Modulated Optomechanics Reveal Energy Flow and Inelastic Interactions Between Acoustic Phonons in Nanomembranes}},
author = {Anuj Kumar Dhiman and Piotr Graczyk and Tobias Held and Mikolaj Pochylski and Kleoniki Sympoura and Rafal Bialek and Jacek Gapinski and Bahram Djafari-Rouhani and Baerbel Rethfeld and Bartlomiej Graczykowski and Thomas Vasileiadis},
journal = {Laser and Photonics Reviews},
year = {2026},
month = oct,
doi = {10.1002/lpor.72069},
url = {https://hal.science/hal-05834933v1},
note = {CC BY-NC 4.0},
}
RIS
TY - JOUR
TI - Time‐Modulated Optomechanics Reveal Energy Flow and Inelastic Interactions Between Acoustic Phonons in Nanomembranes
AU - Anuj Kumar Dhiman
AU - Piotr Graczyk
AU - Tobias Held
AU - Mikolaj Pochylski
AU - Kleoniki Sympoura
AU - Rafal Bialek
AU - Jacek Gapinski
AU - Bahram Djafari-Rouhani
AU - Baerbel Rethfeld
AU - Bartlomiej Graczykowski
AU - Thomas Vasileiadis
PY - 2026
DA - 2026/10/15
JO - Laser and Photonics Reviews
DO - 10.1002/lpor.72069
UR - https://hal.science/hal-05834933v1
AB - An abrupt change in refractive index, known as a temporal interface, can cause temporal reflection, refraction, and diffraction of light, enabling the development of time-varying photonic devices. Since time-varying optics are based on ultrafast electronic excitations, the scattered light should be affected by electrons and phonons in nonequilibrium states. Here, we analyze the inelastically scattered light from ultrathin, time-varying optical media and search for spectroscopic signatures of nonthermal phonon populations. Our approach targets hypersonic gigahertz (GHz) acoustic phonons, termed Lamb modes, confined in prototypical, submicron-thick membranes: 260 nm-thick bare silicon and bilayer structures with 50 nm-thick gold layer on 200 nm-thick silicon. Femtosecond laser irradiation of the membranes modulates their optical properties and excites nonthermal, coherent Lamb modes, which are probed via inelastic light scattering of a continuous-wave laser beam. In metal-semiconductor heterostructures, the anti-Stokes signal of photoexcited Lamb modes undergoes blueshifting and an antiresonance-to-resonance temporal transition, which remains unobserved for Stokes scattering. This effect is attributed to inelastic interactions between thermoelastically excited acoustic phonons, resulting in an approximately 3.6% shift in the frequency of longitudinal acoustic phonons. Our work enables studies of heat transport, phonon dynamics, and optomechanics in time-modulated systems, using principles from time-varying optics.
SN - 1863-8880
SN - 1863-8899
ER -