We applied laser-diode sheetlike end pumping to a multimode Nd:YVO<sub>4</sub> laser and observed high-speed (>400-MHz) modulation of the intensity of chaotic pulsation near 1 MHz. The frequencies of modulation were the beat frequencies for pairs of closely spaced lasing modes. Asymmetric optical confinement and the resultant modal interference are shown to lead to oval-hollow-mode operation in which modal beat notes induce high-speed modulation, the frequency range of which is 2 orders of magnitude higher than the intrinsic relaxation oscillation frequency. Good numerical reproduction of the observed chaotic pulsations and their high-speed modulation was obtained with model equations in which such effects as nonlinear gain coupling among modes and field interference between pairs of modes were included. High-speed pulsations in nonchaotic lasers were also demonstrated.
© 2002 Optical Society of America
Kenju Otsuka, Tsong-Shin Lim, Jing-Yuan Ko, and Hironori Makino, "Self-induced high-speed modulation in microchip solid-state lasers with asymmetric end pumping," Opt. Lett. 27, 1696-1698 (2002)