Efficient and compact sol-gel TiO₂ thermo-optic microring resonator modulator

Abstract

Thermo-optic (TO) modulators play an increasingly important role in wavelength routers, lidar, optical computing, and other reconfigurable photonic systems. Highly efficient TO tunable microring resonators (MRRs) were first demonstrated based on a sol-gel TiO2 platform in the 1310-nm waveband owing to the synergistic effect between the TiO2 core and SU-8 cladding with both the negative thermo-optical coefficients. The MRR modulator with SU-8 polymer as the top cladding layer exhibits a thermal tuning efficiency of 33.0 pm/mW, which is more than 14 times higher than that with silica top cladding. Its rise/fall times of 9.4 us/24 us and a Pπ power of 7.22 mW were achieved, indicating a relatively high TO modulator figure of merit among noncrystalline material platforms allowing monolithic integration on different substrates. These results yield a strong promise for applying the sol-gel TiO2 platform in photonic integrated circuits and suggest a new angle of view to design compact and efficient TO modulators in wearable devices, visible/infrared communication, and biophotonic applications.

A Universal Approach to High‐Index‐Contrast Flexible Integrated Photonics

“…That is because that TiO 2 also holds excellent properties, including low optical loss, wide transparency window, high refractive index, and large negative thermooptic coefficient, which allows efficient and compact modulation and switching in flexible photonic circuits. [17] Instead of using a symmetry structure to construct flexible MRRs without being influenced by external mechanical deformation, MRRs can be used as sensitive bendable and stretchable strain sensors by placing the device in a multilayer structure, in which multiple neutral planes can be generated for different functions use. Our previous work [28,49] quantitatively analyzed the strainoptical coupling mechanism.…”

“…[13][14][15] However, a low-refractive-index contrast between the polymer core structures and cladding substrates cannot allow strong optical confinement, which often leads to the large size of the fabricated devices and is not conducive to high-density integration. In comparison with polymers, silicon-based materials, [16] inorganic oxides, [17,18] and chalcogenide glass [19] materials show high refractive index and low absorption loss, enabling a large degree of freedom in obtaining functional optical structures for strong optical confinement on flexible substrates. [20][21][22][23] It is innately advantageous to realize compact, flexible photonic devices using an inorganic-organic hybrid structure consisting of inorganic core material and organic cladding substrate.…”