InP/Si Heterogeneously Integrated Tunable Laser by Utilizing Chip-on-Wafer Bonding Method

A hybrid tunable laser consisting of the InP gain region and Si photonic integrated circuits (PICs) is demonstrated using a chip-on-wafer (CoW) bonding method. In order to investigate the feasibility of the III-V/Si heterogeneous integration with CoW bonding, integration of various InP chips on Si PICs and a reliability test of InP/Si hybrid lasers are carried out. The InP chips with different epitaxial layers for various active devices are successfully bonded on Si PICs, and photoluminescence spectra with designed peak wavelengths are observed for each InP chips. The stable continuous-wave operation of InP/Si hybrid Fabry-Perot lasers is also verified from an aging test with the total aging time of 3,000 hours. We propose an InP ridge/Si slab waveguide structure for the improvement of light output characteristics and stable wavelength tunable operation, and an InP/Si hybrid tunable laser with this structure is fabricated by the CoW bonding. The fabricated tunable laser exhibits a maximum light output power of 11.3 mW, and stable single mode operation with a sub-mode suppression ratio of higher than 53 dB and a narrow spectral linewidth of less than 60 kHz are also successfully achieved for the entire wavelength tuning range of 56 nm.