Patent ID: 8593638

Claim:
A method for detecting a molecule, the method comprising: introducing optical energy into a resonant microcavity, the optical energy circulating within the resonant microcavity; before detection, determining a first frequency of a first mode and a second frequency of a second mode of optical energy circulating within the resonant micro-cavity; determining a pre-detection difference between the first frequency and the second frequency; and detecting at least one molecule that binds to an outer surface of the microcavity based at least in part upon how the pre-detection difference changes to a detection difference between the first frequency and the second frequency due to the at least one molecule binding to the outer surface, the detection difference being expressed as β = ω 0 2 ⁢ ∫ ∑ i ⁢ δε ⁡ ( r i ) ⁢ E + ⁢ E - * ⁢ ⅆ v ∫ ε ⁡ ( r i ) ⁢ E + ⁢ E + * ⁢ ⅆ v + β 0 wherein β is the detection difference between the first and second frequencies due to binding of at least one molecule to the outer surface, β 0 is the pre-detection difference between the first and second frequencies due to an intrinsic property of the micro cavity, δε(r i ) is a change of relative permittivity of the microcavity due to the at least one molecule binding to the outer surface at a spatial position r i , E + is a forward propagation mode, E + * is a complex conjugate of the forward propagation mode, and E − * is a complex conjugate of a backward propagation mode.