Two channels of entangled twin photons generated by quasi-phase-matched spontaneous parametric down-conversion in periodically poled lithium niobate crystals

We propose the generation of two-channel time-energy entangled twin photons based on two simultaneous first-order quasi-phase-matched (QPM) spontaneous parametric down-conversion processes in a periodically poled lithium niobate (PPLN) with a monochromatic pump. The theoretical model for the generation of the entangled photons is established, and the analytical solution is obtained in a lossless crystal with an undepleted pump assumption. The generated condition of entangled photons is achieved in terms of the QPM grating period and the pump wavelength. It is shown that two channels of entangled twin photons with different wavelengths can be created by suitably choosing the PPLN grating period once the pump wavelength is fixed, which provides the potential to introduce the wavelength division multiplexed technique into quantum information systems. (c) 2008 Optical Society of America.