Abstract
Integrated microresonators with low thermal drift of resonant wavelength are imperative photonic devices to provide stable multiplexing/filtering functions on silicon substrates with large thermo-optic coefficient. To realize athermal microresonators with high quality factor and small footprint, we present an undercut Ta2O5-based microdisk resonator on the Si substrate using a facile lift-off process on the sputtered film and chemical etching. Dependences of surface morphology, crystalline property, refractive index and extinction coefficient of Ta2O5 film on the annealing temperature are studied to reveal favorable parameters for the microresonator production. The produced 40 μm-diameter Ta2O5 microdisk resonator exhibits low thermal drift (7.40 pm/°C), high quality factor (1.65 × 104) and wide free spectral range (11.5 nm). The measured thermo-optic coefficient at the wavelength 1550 nm is 3.0 × 10−6/°C. The thermal stability is further enhanced by using the TiO2 film with the negative thermo-optic coefficient. The study of Ta2O5/TiO2 composite microdisk resonators achieves high thermal stability as best as 0.26 pm/°C.
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