Design of Lateral-Current-Injection-Type Membrane Distributed-Feedback Lasers for On-Chip Optical Interconnections

For application to on-chip optical interconnections, lateral-current-injection (LCI) membrane distributed-feedback (DFB) lasers, which are expected to be potential components for such an application, were investigated from the aspects of low threshold current operation and high-speed direct modulation capability. First, the stripe width dependence of the carrier injection delay time was evaluated from small-signal response measurements of LCI Fabry-Perot lasers prepared on a semi-insulating InP substrate, and it was found that a narrower stripe width was advantageous for shorter carrier injection delay time as well as higher internal quantum efficiency. Second, semiconductor core layer thickness dependences of the lasing properties of LCI-membrane-DFB lasers, such as the threshold current, output power, relaxation oscillation frequency, and a 3-dB bandwidth, were investigated theoretically. A strong optical confinement effect in the semiconductor membrane structure enabled the design of an LCI-membrane-DFB laser with a low threshold current of 0.16 mA, an output power of more than 0.16 mW, and a high relaxation oscillation frequency of 8.9 GHz at a bias current of only 1 mA. From these values, the LCI-membrane-DFB laser can be a good candidate for a low-pulse-energy (<;100 fJ/bit) light source, for high-speed (>10 Gb/s) transmission, and for on-chip optical interconnections.