Abstract Simultaneous temperature insensitive and large free spectral range (FSR) micro-ring resonator is reported using wide ring waveguide. The analysis has been performed using finite-difference time domain simulation. The wide waveguide facilitates the use of a small bending radius to increase the free spectral range with low bending losses. Temperature insensitivity is achieved by considering cladding region made of negative thermo-optic coefficient material, TiO2, over different guiding regions made of positive thermo-optic coefficient material, Si. We have analyzed and demonstrated that appropriate waveguide cross-section dimension provides balanced field delocalization in each material that ensures zero temperature sensitivity. The zero temperature sensitivity of the sensor is achieved while maintaining a high FSR ~45 nm. In contrast to the widely used SiO2 as the upper cladding material, for which a higher spectral shift of 73.4 pm/°C is observed, the temperature dependent wavelength shift in our proposed structure is completely eliminated. The relationship between full width at half maximum (FWHM) and temperature is also investigated, and it is shown that change of FWHM with temperature can be described by the coupling coefficient and group-index.
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