wavelengths as T changes from 299 K to 378 K. This blue-shift in the resonance spectrum indicates negative changes in 𝑛 𝑒𝑓𝑓 with T. In contrast, a pure silicon slot waveguide experiences positive changes in 𝑛 𝑒𝑓𝑓 with T due to the positive thermo-optic coefficient (TOC) of silicon. Therefore, this experiment suggests that the 𝑛 𝑒𝑓𝑓 of the optical mode is dominated by the refractive index of 1 and the TOC of 1 is negative. We also observe broadening of the resonance with the rise in temperature, confirmed by the monotonically decreasing quality factor (Q) with T shown in Figure .