Second-harmonic generation in tapered optical fibers

We present a theoretical study of second-harmonic generation (SHG) in tapered optical fibers in the continuous wave and monochromatic regimes. The mechanism is based on modal phase matching, where the taper is used to sweep the phase mismatch across the phase-matched condition during the propagation. Self- and cross-phase modulations are taken into account. We report general results about the conversion efficiency and demonstrate that this SHG scheme is not only robust with respect to phase modulation, but can even benefit from it. We also show that the conversion bandwidth is easily controlled by the taper design and can be realistically extended to tens of nanometers.