  Resistance thermometry provides a time-tested method for taking temperature
measurements that has been painstakingly developed over the last century.
However, fundamental limits to resistance-based approaches along with a desire
to reduce the cost of sensor ownership and increase sensor stability has
produced considerable interest in developing photonic temperature sensors. Here
we demonstrate that silicon photonic crystal cavity-based thermometers can
measure temperature with uncertainities of 175 mK (k = 1), where uncertainties
are dominated by ageing effects originating from the hysteresis in the device
packaging materials. Our results, a 4-fold improvement over recent
developments, clearly demonstate the rapid progress of silicon photonic sensors
in replacing legacy devices.
