Highly-efficient thermally-tuned resonant filters

We demonstrate spectral tunability for a microphotonic add-drop filter manufactured as ring resonator in commercial 130 nm SOI CMOS technology. The filters are provisioned with an integrated heater built in CMOS for thermal tuning. Their thermal impedance has been dramatically increased by the selective removal of the SOI handler substrate under the device footprint using silicon micromachining technology. An overall ~ 20× increase in the tuning efficiency has been demonstrated with a 100 um radii ring that requires 3.9 mW of the applied tuning power to shift the filter resonant peak across the entire free spectral range. Our result represents record tuning metrics for this class of device.