Patent ID: 7212701

Claim:
A method for measuring the optical absorbance of a sample medium comprising: providing a light source emitting a light beam having a multitude of optical frequencies; providing a microfluidic chip comprising: a substrate defining a microfluidic channel; a microresonator being positioned within the microfluidic channel; and at least one waveguide receiving light having a frequency bandwidth greater than the spacing between the whispering gallery mode resonance frequencies, the at least one waveguide evanescently coupled to the microresonator such that supported whispering gallery mode resonance frequencies are coupled from the at least one waveguide into the microresonator and light at frequencies not resonant with the microresonator not coupling into the microresonator; disposing a sample medium into the microfluidic channel such that the sample medium substantially envelopes the microresonator; providing a reader for measuring at least a portion of the whispering gallery mode resonances coupled out of the microresonator; coupling the light beam into the at least one waveguide; and measuring the portion of the whispering gallery mode resonances coupled from the microresonator to the reader.