We present a high power and low noise DFB laser design. The laser has good performance with output power over 200
mW, side-mode suppression ratio over 50 dB, and related intensity noise (RIN) less than -165 dB/Hz in a wide
frequency range. We have modeled the performance of Buried Heterostructure (BH) laser and ridge-waveguide laser.
Since the BH laser has a build-in index guiding waveguide, the laser mode is very stable, the relaxation oscillations are
suppressed, resulting in peak RIN which is much lower than that of the ridge-waveguide laser. In addition, the BH laser
has good confinement of the injected carriers in the cavity, the laser threshold current is very low, and the RIN peak is
pushed to high frequency at high bias.