λ-Scale Embedded Active Region Photonic Crystal (LEAP) Lasers for Optical Interconnects

The distances optical interconnects must cover are decreasing as Internet traffic continues to increase. Since short-reach interconnect applications require many transmitters, cost and power consumption are significant issues. Directly modulated lasers with a wavelength-scale active volume will be used as optical interconnects on boards and chips in the future because a small active volume is expected to reduce power consumption. We developed electrically driven photonic crystal (PhC) lasers with a wavelength-scale cavity in which the active region is embedded in a line-defect waveguide of an InP-based PhC slab. We call this a lambda-scale embedded active region PhC laser, or a LEAP laser. The device, whose active region has six quantum wells with 2.5 x 0.3 x 0.15 mu m(3) active volume, exhibits a threshold current of 28 mu A and provides 10 fJ/bit of operating energy to 25 Gbit/s NRZ (non-return-to-zero) signals. The fiber-coupled output power is 6.9 mu W. We also demonstrate heterogeneous integration of LEAP lasers on a SiO2/Si substrate for low-cost photonic integrated circuits (PICs). The threshold current is 40.5 mu A and the output power is 4.4 mu W with a bias current of 200 mu A. These results indicate the feasibility of using PhC lasers in very-short-distance optical communications.