We have observed the second harmonic generation from a single crystal LiNbO
3 fiber with a diameter of 63 mu m. Femtosecond laser pulses Corm a modeloc
ked oscillator was focused perpendicularly onto the fiber. Scattered second
harmonic was analyzed in polarization and the conversion efficiency was es
timated. Comparing to a bulk nonlinear crystal, the striking feature of the
SHG from the microcylinder is that the nonlinear conversion takes place ou
t off phase-matching condition. For the fundamental at 850 nm the phase-mis
matching is negative, even so, a relative important conversion efficiency o
f 3.7 x 10(-4) was obtained for incident 1.1-nJ and 150-fs pulses (peak int
ensity of 1.0 x 10(9) W/cm(2)). This conversion efficiency, independent to
the phase matching, should not exhibit the sharp variation as for a bulk cr
ystal when the incident fundamental is tuned across the phase-matched wavel
ength. The fiber provides then a wide bandwidth doubler. We applied this mi
crodoubler in a second order autocorrelator.