Temporal Dynamics of Fiber Optical Poling

A germanium-doped silica fiber can be transformed into a second harmonic (SH) generation device resorting to optical poling [1]. By injecting fundamental frequency (FF) 1064 nm pulses along with a SH 532 nm seed it is possible to induce a quadratic nonlinearity, which is stable over time and can be cancelled only by injecting UV or visible light. Repeated experiments have demonstrated that the commercial Corning HI980 fiber can be poled using a Nd:YAG laser emitting pulses with a duration of 800 ps, repetition rate of 7.1 kHz and an average power of 40 mW (corresponding to a peak power of 7 kW) [2], [3]; a few minutes are sufficient to start writing the quadratic nonlinearity which saturates to its maximum value after about 2 hours.