Visible-telecom photon pair source based on a photonic-crystal fiber under continuous-wave pumping

The generation of interband photon pairs with wavelengths near 0.5 and 1.6 $\mu$m in a photonic-crystal fiber under low-power cw optical pumping by a diode laser with a central wavelength of 0.8 $\mu$m has been experimentally demonstrated. It has been found that the generation rate of entangled photons under cw pumping is comparable with values obtained with pulsed pumping by a femtosecond Ti:sapphire laser if the average cw pump power is an order of magnitude higher than the average pulsed pump power. The reached rates of photon generation are ensured by the used photonic-crystal fiber with a small effective mode area and a special dispersion profile. The reached low noise in the output signal is ensured by the separation of carrier frequencies of generated photons into different spectral bands.