“…In all cases, it has to be minimized to enable efficient and high‐speed optical modulation. Expressing P π and τ in terms of material‐based parameters, while including the thermal expansion effect, leads to the following expression: [
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where n eff is the effective refractive index of propagation in the material, ∂n eff / ∂T is the thermo‐optic coefficient, α L is the thermal expansion coefficient, C p is the specific heat capacity, ρ is the mass density, λ is the wavelength of operation, and A is the effective heated area. To draw out a fair comparison between the reported devices and the above‐described structure, we have chosen to calculate the wavelength‐ and configuration‐independent figure‐of‐merit, FOM = P π τ / (λA) .…”