We experimentally demonstrate that one can exploit nonlinear phase shifts produced in type I phase-mismatched second-harmonic generation to produce intensity-dependent polarization evolution with 100-fs pulses. An amplitude modulator based on nonlinear polarization rotation provides passive amplitude-modulation depth of up to ∼50%. Applications of the amplitude and phase modulations to mode locking of femtosecond bulk and fiber lasers are promising and are discussed.
© 2000 Optical Society of America
X. Liu, F. O. Ilday, K. Beckwitt, and F. W. Wise, "Femtosecond nonlinear polarization evolution based on cascade quadratic nonlinearities," Opt. Lett. 25, 1394-1396 (2000)