Entangled-photon ellipsometry
Alexander V. Sergienko, Ayman F. Abouraddy, Kimani C. Toussaint, Bahaa E. A. Saleh, Malvin Carl Teich · Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIE · 2003
We present a novel quantum interferometric technique to perform ellipsometric measurements. Classical ellipsometric measurements are limited in their accuracy by virtue of the need for an absolutely calibrated source and detector. Mitigating this limitation requires the use of a well-characterized reference sample. Our technique relies on the use of a non-classical optical source, namely polarization-entangled twin photons generated by spontaneous parametric down-conversion from a nonlinear crystal, in conjunction with a coincidence-detection scheme. We have demonstrated that entangled-photon ellipsometry eliminates the necessity of constructing an interferometer altogether and is thereby self-referencing. The underlying physics that leads to this remarkable result is the presence of fourth-order (coincidence) quantum interference of the photon pairs in conjuction with polarization entanglement.