Compact on-chip crystalline resonator integration with etching of tapered fiber waveguide

Whispering-gallery-mode crystalline resonators currently maintain the best quality factor (Q) record; however, compact on-chip packaging is still a challenge, although various coupling architectures have been developed. Here, a chemical etching method is proposed to fabricate a miniaturized tapered fiber waveguide on silicon substrate. The Marangoni effect is implemented to reduce the surface roughness of the cone region. The optical loss of 0.1 dB/mm is obtained, and the Q of the on-chip crystalline resonator exceeds 10⁸. Additionally, thermoelectric cooler (TEC) is implanted in the package to actively customize the temperature, and the temperature response of 18 pm/°C is consistent with the theoretical calculation.