Diffraction-based molecular detection is achieved by etching optical gratings into thermal oxide on silicon. The gratings perform as a stable common-path diffractive optical balance (DOB) designed to operate near a missing diffraction order. The biosensor is operated in an off-null condition with a phase bias to produce a high-contrast responsivity that is linear in accumulated molecules but with a low background. The DOB linear responsivity is a factor of 20 larger than the reflectometric responsivity of planar thermal oxide.
© 2012 Optical Society of America
Optics at Surfaces
Original Manuscript: July 13, 2012
Revised Manuscript: August 29, 2012
Manuscript Accepted: August 29, 2012
Published: September 26, 2012
Xuefeng Wang, Ming Zhao, and David D. Nolte, "Molecular layer detection on a diffractive optical balance," Opt. Lett. 37, 4098-4100 (2012)