Partially corrugated waveguide laser diodes for use in CATV networks

Abstract

Recent CATV network systems require high power (P<SUB>o</SUB> &gt;= 20 mW), wide band (1 GHz) and low distortion light sources for use in high capacity network schemes. Furthermore, cost effective light sources are also needed for use in narrowing services. We have developed high performance, 1.3-micrometers partially corrugated waveguide laser diodes (PC-LDs) suitable for use in such CATV networks. The production yield of these PC-LDs with respect to low distortion specifications has been improved about three times over that of conventional distributed feedback (DFB) LDs, and this can be attributed to their characteristic of not being sensitive to grating phases as well as their flat electric field profile along the cavities. Excellent low distortion characteristics (a composite second-order distortion &lt;EQ -60 dBc and a composite triple beat &lt;EQ -70 dBc) for an 80-channel CATV specification were also realized for the PC-LDs over the wide power range of 10 approximately 30 mW by reducing junction capacitance of the current blocking layer. Intermodulation distortion in LDs caused by several nonlinear mechanisms was also investigated using a transfer- matrix method and an electric equivalent circuit model of LDs, taking electric field distribution along the cavity and leakage current that flows into the current blocking layer into account. Resonance oscillation and electric field nonuniformity related distortion are predominant in the lower light-output power region, while leakage current related distortion is dominant in the high-power region. Moreover, external optical feedback resistant characteristics of the PC-LDs were theoretically predicted and experimentally demonstrated. Optical feedback resistance of the PC-LDs was about ten times higher than that of conventional DFB-LDs due to their unique electric field profile along the cavity.