Figure 8

The binding of molecules on the surface of a resonator shifts the resonant frequency. (A) For a passive resonator (resonator without gain medium), too much overlap with the original resonant mode makes it difficult to distinguish the shifted resonance since the resonant frequency shift induced by the attached molecule is smaller than the linewidth. (B) For an active resonator (resonator gain medium), the resonant shift is clearly resolved due to large separation of the shifted resonance from its original position in the spectrum. The narrow linewidth due to the optical gain (g) improves the sensor resolution by reducing the smallest detectable shift in the resonance.

© De Gruyter