Twist Angle-Controlled Near-Field Heat Transfer between Hyperbolic Photonic Surfaces

Twisted bilayer photonic structures have received extensive investigations over the past years and have been proven to be a powerful platform in creating photonic tunability for emergent photonic phenomena and device architectures. Quite recently, the concept has been introduced in the near-field regime to tune the radiative heat transfer between two nonequilibrium objects but with no experiment reported yet. In this work, we perform a deep investigation about this subtle physical effect between uniaxial polar crystals (calcite, α-sapphire, and α-quartz) possessing strong anisotropic photonic dispersions in the thermal infrared bands both theoretically and experimentally. Super Planckian emission was explicitly observed under the excitation of surface phonon polaritons (SPhPs). Utilizing these localized modes, particularly the hyperbolic photonic surface modes, we demonstrated that the couplings and tunneling possibility of evanescent photons could be largely modulated by twisting the in-plane optical axis (OA) of one of the crystals. In the context of near-field interaction, a prominent heat flux modulation with a ratio exceeding 16% was obtained between the sapphire pair with great experiment–theory agreement. This work reveals the potential of twist angle-controlled NFRHT for exploring exotic thermophotonic phenomena and devices.