Four-section sampled-grating DBR (SGDBR) lasers, including two sampled grating DBRs, gain and phase tuning
sections, were designed by a InGaAlAs / InP strained multiple quantum well microstructure. The lengths of gain and
phase sections are 280 μm and 150 μm, respectively. One SGDBR, accommodating 10 sample periods with a total length
of 270 μm, is situated adjacent to the gain, and another SGDBR, containing 11 sample periods with a total length of 330
μm, is to the right of phase section.
The estimated threshold current and characteristic temperature, T0 , were 10 mA and 166 °K respectively. High
T0 reflects excellent electron confinement of the MQW structure. The optical coupling strength and the cavity-mode
spacing of DBR lasers were carefully chosen. With appropriate tuning mechanisms, the tunable SGDBR lasers produced
172 transmission channels, each with side-mode suppression ratios higher than 40 dB. Under 100 mA current driving, the
lasers could be operated with a bandwidth of 20 GHz and the channel switching could be completed within 1 nS.
Moreover, from the observations on the relative intensity noises as well as on the eye diagram, the lasers do exhibit
excellent dynamic characteristics.