An optical parametric oscillator as a high-flux source of two-mode light for quantum lithography

We investigate the use of an optical parametric oscillator (OPO), which can generate relatively high-flux light with strong non-classical features, as a source for quantum lithography. This builds on the proposal of Boto et al (2000 Phys. Rev. Lett. 85 2733), for etching simple patterns on multi-photon absorbing materials with sub-Rayleigh resolution, using two-mode entangled states of light. We consider an OPO with two down-converted modes that share the same frequency but differ in field polarization or direction of propagation, and derive analytical expressions for the multi-photon absorption rates when the OPO is operated below, near and above its threshold. Because of strong non-classical correlations between the two modes of the OPO, the interference patterns resulting from the superposition of the two modes are characterized by an effective wavelength that is half of their actual wavelength. The interference patterns resulting when the two modes of the OPO are used for etching are also characterized by an effective wavelength half that for the illuminating modes. We compare our results with those for the case of a high-gain optical amplifier source and discuss the relative merit of the OPO. 4 Authors to whom any correspondence should be addressed. New Journal of Physics 11 (2009) 113055 1367-2630/09/113055+17$30.00 © IOP Publishing Ltd and Deutsche Physikalische Gesellschaft