In integrated photonics, when light passes through a sample, absorption is a weak effect. That’s because as light travels in a silicon wire, a tiny bit of it “bleeds” out, beyond its surface; when a sample is deposited, it’s this tiny evanescent part of the light that experiences absorption. Now, recall a ring resonator traps light, which means light circulates many times around it before finally escaping. In light of this, can you imagine another role for the ring resonator in Lab-on-a-Chip sensing, besides routing wavelengths of light to detectors? Which role might be more important?