Thermal insensitivity of an ENZ-ITO clad, hollow-core micro-ring resonator

Abstract

Abstract We report on the experimental demonstration of temperature insensitivity in an epsilon-near-zero (ENZ) indium-tin-oxide (ITO) cladded, hollow-core micro-ring resonator. The permittivity of the ITO cladding was engineered to a near zero value at 1550 nm wavelength to support index guiding in the air-ITO waveguide around the C band. The air-ITO ring-resonator structure was designed using numerical simulations to support whispering gallery modes. The hollow-core microresonator structure was fabricated using two-photon lithography to 3D print a sacrificial scaffold. Guided resonator modes were observed by coupling tunable laser light to the ring resonator using a tapered fiber. The demonstrated hollow-core microresonator exhibits athermal behavior and has a temperature dependent wavelength shift of 1 pm/°C.