The novel concept of K-stabilizing layer is reported for the first time. The coupling coefficient (K) which determines the characteristics of distributed feedback laser diodes (DFB LDs) has been controlled by optimizing the grating depth and layer thicknesses. The coupling coefficient is less dependent on the variations of grating depth and layer thicknesses if an optimized K- stabilizing layer (lower index material like InP) is inserted between the active layer and the guide layer. The controllability of the coupling coefficient has been demonstrated by the standard deviation of the lasing wavelength and the threshold current across a wafer, 0.74 nm and 2.67 mA, respectively.
The degradation mechanisms of laser diodes are studied. It is shown that the reliability of the SDL-5410 and the SDL-2441 result in projected lifetimes of greater than 60,000 at 25 C and 200,000 at 15 C, respectively. The high maximum output power protects the laser from optically induced degradation; residual degradation is due to thermally- or field-induced recombination centers.