  Thermal effects are well known to influence the electronic and optical
properties of materials through several physical mechanisms and are the basis
for various optoelectronic devices. The thermo-optic (TO) effect - the
refractive index variation with temperature (dn/dT), is one of the common
mechanisms used for tunable optical devices, including integrated optical
components, metasurfaces and nano-antennas. However, when a static and fixed
operation is required, i.e., temperature invariant performance - this effect
becomes a drawback and may lead to undesirable behavior through drifting of the
resonance frequency, amplitude, or phase, as the operating temperature varies
over time. In this work, we present a systematic approach to mitigate thermally
induced optical fluctuations in nanophotonic devices. By using hybrid
subwavelength resonators composed from two materials with opposite TO
dispersions (dn/dT<0 and dn/dT>0), we are able to compensate for TO shifts and
engineer meta-atoms and metasurfaces with zero effective TO coefficient
(dn/dT~0). We demonstrate temperature invariant resonant frequency, amplitude,
and phase response in meta-atoms and metasurfaces operating across a wide
temperature range and broad spectral band. Our results highlight a path towards
temperature invariant nanophotonics, which can provide constant and stable
optical response across a wide range of temperatures and be applied to a
plethora of optoelectronic devices. Controlling the sign and magnitude of TO
dispersion extends the capabilities of light manipulation and adds another
layer to the toolbox of optical engineering in nanophotonic systems.
