Ultrashort laser pulses are extremely important in the studies of ultrafast phenomena, so it's fundamental to know the laser pulse duration to make these studies possible. Ultrashort laser pulses cannot be measured directly, and an optical method is required to measure these pulses: the autocorrelation. Exploring the non-linear properties of a BiBO crystal, it's possible to build an autocorrelator and precisely measure the duration of an ultrashort laser pulse. Using the Second-Harmonic Generation property, the characterization of tunable spectrum laser was made, getting the relation between the pulse width and spectrum width.