Longitudinal mode spectra and ultrashort pulse generation of InGaN multiquantum well structure laser diodes

Longitudinal modes with a mode separation of 0.04 nm were observed on InGaN multiquantum well structure laser diodes (LDs). Other peaks different from the longitudinal modes, appeared with increasing current above the threshold current. Lasing was observed up to a pulsed current duty ratio of 40%. The operating voltage of the LDs at the threshold was around 11 V. Ultrashort pulsed light from the LDs with a pulse width of 50 ps, an output power of 300 mW, and a peak wavelength of 404.2 nm was obtained. The damping constant and the frequency of the relaxation oscillation were 0.8 ns and 3 GHz, respectively.