Second harmonic generation in an optically poled fiber

The second harmonic signal at the output of an optically poled fiber was studied as a function of the input fundamental frequency power and polarization state. For an injected average power of 3 mW at 1064 nm, the measured output power at 532 nm was 10 μW. The second harmonic intensity profile was a bright green ring even if the pump was injected in the fundamental HE11 mode: we believe that the second harmonic was carried by a combination of the EH11 and HE31 modes.