Ultrashort pulse second harmonic generation in quasi-phase-matched structures

Second harmonic generation of ultrashort pulses in first- and higher-order quasi-phase-matched nonlinear structures is investigated theoretically. It is shown that using such structures high conversion efficiency can be achieved while preserving the ultrashort pulse duration. Using periodically poled bulk lithium niobate as an example, it is found that nearly complete conversion of a 900 nm wavelength 100 fs pulse to the second harmonic may be possible in a first-order structure without any broadening of the pulse width.