Implementation of Chip-Level Optical Interconnect With Laser and Photodetector Using SOI-Based 3-D Guided-Wave Path

A chip-level optical interconnect module combined with a vertical-cavity surface-emitting laser (VCSEL) chip, a photodetector (PD) chip, a driver integrated circuit (IC), and an amplifier IC on a silicon-on-insulator (SOI) substrate with 3-D guided-wave paths is experimentally demonstrated. Such an optical interconnect is developed for the signal connection in multicore processors or memory-to-processor interfaces. The 3-D guided-wave path, consisting of silicon-based 45 $^{\circ}$ microreflectors and trapezoidal waveguides, is used to connect the optical signal between transmitter and receiver. In this paper, the VCSEL and PIN PD chips are flip-chip integrated on a SOI substrate to achieve complete chip-level optical interconnects. Due to the unique 3-D guided-wave path design, a higher laser-to-PD optical coupling efficiency of $-$2.19 dB and a larger alignment tolerance of $\pm 10\ \mu\hbox{m}$ for the VCSEL/PD assembly are achieved. The measured laser-to-PD optical transmission efficiency can reach $-$2.19 dB, and the maximum optical power and threshold current of VCSEL is 3.27 mW and 1 mA, respectively. To verify the data transmission, the commercial driver IC and amplifier IC are assembled upon the silicon chip, and the error-free data transmission of 10 Gbps can be achieved when the VCSEL is operated at the driving current of 9 mA.