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arXiv · 2407.18598

Disentangling thermal birefringence and strain in the all-optical switching of ferroelectric polarization

Maarten Kwaaitaal·Daniel G. Lourens·Carl S. Davies·Andrei Kirilyuk
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Abstract

Recent works have demonstrated that the optical excitation of crystalline materials with intense narrow-band infrared pulses, tailored to match the frequencies at which the crystal's permittivity approaches close to zero, can drive a permanent reversal of magnetic and ferroelectric ordering. However, the physical mechanism that microscopically underpins this effect remains unclear, as well as the precise role of laser-induced heating and macroscopic strains. Here, we explore how infrared pulses can simultaneously give rise to strong temperature-dependent birefringence and strain in ferroelectric barium titanate. We develop a model of these two coexisting effects, allowing us to use polarization microscopy to disentangle them through their spatial distributions, temporal evolutions and spectral dependencies. We experimentally observe strain-induced patterns that are an order of magnitude larger than that which can be accounted for by laser-induced heating alone, suggesting that non-thermal effects must also play a role. Our results reveal the distinct fingerprints of heat- and strain-induced birefringence, shedding new light on the process of all-optical switching of order parameters in the epsilon-near-zero regime.

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Maarten Kwaaitaal, Daniel G. Lourens, Carl S. Davies, Andrei Kirilyuk. 2024-07-26. Disentangling thermal birefringence and strain in the all-optical switching of ferroelectric polarization. https://arxiv.org/abs/2407.18598

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