Optical interconnects are emerging as a promising solution to address the ever growing demand for data traffic, wherein the photonic integrated circuit (PIC) technology is the key enabler. PICs are presently moving forward on parallel Si and InP platforms, but material incompatibility in these two systems has been the largest barrier towards future monolithic large-scale PICs. A compelling InP-on-Si platform marrying these two systems through heteroepitaxy could provide the combined strengths of the mature InP PIC technologies and the large-volume, low-cost silicon-based CMOS infrastructures. Meanwhile, a major driving force of optical interconnects research is device and circuit footprint reduction for scalable on-chip networks. One of the vital elements required to enable such...[ Read more ]

Optical interconnects are emerging as a promising solution to address the ever growing demand for data traffic, wherein the photonic integrated circuit (PIC) technology is the key enabler. PICs are presently moving forward on parallel Si and InP platforms, but material incompatibility in these two systems has been the largest barrier towards future monolithic large-scale PICs. A compelling InP-on-Si platform marrying these two systems through heteroepitaxy could provide the combined strengths of the mature InP PIC technologies and the large-volume, low-cost silicon-based CMOS infrastructures. Meanwhile, a major driving force of optical interconnects research is device and circuit footprint reduction for scalable on-chip networks. One of the vital elements required to enable such integrated systems is an ultra-compact, energy efficient and robust laser source emitting at communication wavelengths. III-V Quantum dots (QDs) are showing great promise for monolithically integrated lasers on such III-V-on-Si platform, benefiting from their superior optical properties and enhanced tolerance to defects. The same properties also enable further scalability of QD devices to be adapted in future energy-efficient and densely integrated PICs.

This thesis thus focuses on device implementation exploiting InP-based QDs, specifically to produce efficient InAs/InAlGaAs/InP QD lasers monolithically integrated on (001) Si substrates based on the InP-on-Si platforms and further miniaturize the laser footprint in microcavities. Moreover, the thesis research is also aimed at advanced practical performances for the QD micro-lasers such as single-mode operation, micro-transmitters and on-chip light detection.

In this thesis work, world’s first demonstrations of 1.55 μm QD lasers on Si are reported, including electrically-pumped macroscopic Fabry-Perot lasers, micro-ring lasers and optically-pumped micro-disk lasers with sub-wavelength sizes. A subset of the results achieved include an electrically-pumped lasing threshold of 1.6 kA/cm² for FP lasers and 50 mA for micro-ring lasers, stable high-temperature operations and lasing up to 70 °C. For the ultra-small lasers with 1.5 μm diameters, thresholds as low as 4 μW are achieved. Besides, the first realization of single-mode QD micro-lasers is also achieved in this work with a side-mode-suppression-ratio(SMSR) larger than 40 dB, based on which a prototype of a 4-channel micro-WDM transmitter is further presented.