A Whispering Gallery sphere of the order of 50-200 microns must satisfy a very sharp resonance condition if the Q of the sphere (or cavity) is high. If a biological entity is attached to the sphere through an Si-O-antigen complex, then, when an antigen attaches, there will be a small shift in the effective refractive index that the Whispering Gallery mode(s) sees. This conceit has been used for sensitive biodetection. By placing such a device within a laser cavity, it is possible to measure not a wavelength shift associated with the attachment of the biological entity, but a mode beating shift. By converting a measurement in the optical domain (wavelength shift) to a measurement in the RF (Radio Frequency) domain, i.e., a shift in the mode beating, sensitivity of measurement can be increased by several orders of magnitude.
This award is jointly supported by the Division of Electrical and Communications Systems and the Office of International Science and Engineering.
