Common-path interferometric detection of protein monolayer on the BioCD

Xuefeng Wang, Ming Zhao, D. D. Nolte

Research output: Contribution to journalArticlepeer-review

29 Scopus citations


The bio-optical compact disk (BioCD) is an optical biosensor that performs common-path molecular interferometry of patterned proteins on a disk spinning at high speed. The common-path configuration makes it ultrastable and allows surface height precision below 10 pm. In this paper we show that two complementary interferometric quadrature conditions exist simultaneously that convert the modulus and phase of the reflection coefficient, modulated by protein patterns on the disk surface, into intensity modulation at the detector. In the far field they separate into spatially symmetric and antisymmetric intensity modulation in response to the local distribution of protein. The antisymmetric response is equivalent to differential phase-contrast detection, and the symmetric response is equivalent to in-line (IL) common-path interferometry. We measure the relative sensitivities of these orthogonal channels to printed protein patterns on disk structures that include thermal oxide on silicon and Bragg dielectric stacks. The scaling mass sensitivity of the IL channel on oxide on silicon was measured to be 0.17 pg/mm.

Original languageEnglish (US)
Pages (from-to)7836-7849
Number of pages14
JournalApplied optics
Issue number32
StatePublished - Nov 10 2007

ASJC Scopus subject areas

  • Atomic and Molecular Physics, and Optics
  • Engineering (miscellaneous)
  • Electrical and Electronic Engineering


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