Integrated silicon photonics has sparked a significant ramp-up of investment in both academia and industry as a scalable, power-efficient, and eco-friendly solution. At the heart of this platform is the light source, which in itself, has been the focus of research and development extensively. This paper sheds light and conveys our perspective on the current state-of-the-art in different aspects of application-driven on-chip silicon lasers. We tackle this from two perspectives: device-level and system-wide points of view. In the former, the different routes taken in integrating on-chip lasers are explored from different material systems to the chosen integration methodologies. Then, the discussion focus is shifted towards system-wide applications that show great prospects in incorporating photonic integrated circuits (PIC) with on-chip lasers and active devices, namely, optical communications and interconnects, optical phased array-based LiDAR, sensors for chemical and biological analysis, integrated quantum technologies, and finally, optical computing. By leveraging the myriad inherent attractive features of integrated silicon photonics, this paper aims to inspire further development in incorporating PICs with on-chip lasers in, but not limited to, these applications for substantial performance gains, green solutions, and mass production.

A ring resonator-based biochemistry sensor with a wide range, ultra-compact footprint, and high sensitivity is proposed, which utilizes a suspended slot hybrid plasmonic (SSHP) waveguide. The waveguide consists of a suspended Si nanowire separated from a Cu metal surface by a nanoscale air gap. The hybridization of fundamental mode of a Si channel waveguide with the surface plasmon polariton (SPP) mode of Cu-Si interface achieves a strong light confinement, high waveguide sensitivity (Sw), and low optical loss, showing a great potential in integrated optical sensor. The sensitivity, the detection limit and the detection range of the SSHP waveguide-based biochemistry sensor with a miniaturized radius of 1 µm are numerically demonstrated as 458.1 nm/RIU, 3.7 × 10−5 RIU and 0.225 RIU, respectively. These superior performances as well as the fully CMOS compatibility enable the integrated optical sensing applications.

Silicon photonic integrated sensors based on microring resonators are a promising candidate to achieve high-performance on-chip sensing. In this work, a novel dual-parameters sensor based on polarization multiplexing on silicon-on-insulator (SOI) platform is proposed and demonstrated experimentally, simultaneously achieving refractive index (RI) and temperature sensing with high sensitivity and large detection range (DR). The experimental results show that the RI sensitivity and temperature sensitivity of the TM-operated sensor are 489.3 nm/RIU and 20.0 pm/°C, respectively, and that of the TE-operated sensor are 102.6 nm/RIU and 43.3 pm/°C, respectively. Moreover, the DR of the fabricated sensor is 0.0296 RIU, which is 4.2 times that of the conventional TM-operated sensor based on the microring resonator. The dual-parameters sensor based on polarization multiplexing can successfully realize the simultaneous measurement of the RI and the temperature, showing potential applications of silicon photonic on-chip sensors in reality.