We study the influence of pump current and absorber bias voltage on the pulse width and frequency of sustained pulsation in GaN-based multisection laser diodes. The observed frequencies and pulse widths range from 1.5 to 4.5GHz and 90 to 18 ps, respectively. Negative absorber bias is found to reduce the pulsation frequency and increase the pulse width. This behavior is explained by the tuneability of absorption and charge carrier lifetime in the absorber via the applied bias voltage. (C) 2011 The Japan Society of Applied Physics