We discuss spectrotemporal measurements of laser diode pulses performed with a streak camera and a grating monochromator to yield a precise evaluation of chirping effects in Q-switched multimode emissions. We experimentally illustrate several causes of errors, depending on the grating size and period as well as on the adjustment of the collimating lens at the monochromator output. An analytical formula is derived that allows us to relate the chirp amplitude to the inclination of the modal structures in the streak image. Two configurations are proposed for a practical determination of the chirp amplitude in multimode emissions. Illustrations are provided with Q-switched AlGaAs laser diodes that exhibit chirp amplitudes larger than the mode spacing.
© 1998 Optical Society of America
Alexandre Bresson, Nikolaï Stelmakh, Jean-Michel Lourtioz, Alexandre Shen, and Claude Froehly, "Chirp Measurement of Multimode Q-Switched Laser Diode Pulses by Use of a Streak Camera and a Grating Monochromator," Appl. Opt. 37, 1022-1025 (1998)