Improved bandwidth of three channel buried crescent lasers.

The modulation bandwidth of three-channel buried crescent (TCBC) lasers was improved by reducing the ohmic contact resistance by adding a quaternary contact layer for the P-contact of the device. The ohmic resistance was reduced to 6-9 ohms with capacitance of 1.5-3 pF and inductance of 1.5-2 nH. The small signal 3 dB modulation frequency was increased to 7.2 GHz at 2.5 Ith and is still limited by the parasitic impedances of the device. Large signal digital modulation of the laser was successfully achieved at 8 Gbits/sec which is the highest frequency for direct digital modulation yet reported.