A high-brightness source of polarization-entangled photons optimized for applications in free space
Steinlechner, F., Trojek, P., Jofre, M., Weier, H., Perez, D., Jennewein, T., Ursin, R., Rarity, J., Mitchell, M., Torres, J., Weinfurter, H., Pruneri, V. · MPG.PuRe (Max Planck Society) · 2012
We present a simple but highly efficient source of polarization-entangled photons based on spontaneous parametric down-conversion (SPDC) in bulk periodically poled potassium titanyl phosphate crystals (PPKTP) pumped by a 405 nm laser diode. Utilizing one of the highest available nonlinear coefficients in a non-degenerate, collinear type-0 phase-matching configuration, we generate polarization entanglement via the crossed-crystal scheme and detect 0.64 million photon pair events/s/mW, while maintaining an overlap fidelity with the ideal Bell state of 0.98 at a pump power of 0.025 mW.