Silicon photonics is a revolutionary technology in the integrated photonics field which has experienced rapid development over the past several decades. High-quality III-V semiconductor components on Si platforms have shown their great potential to realize on-chip light-emitting sources for Si photonics with low-cost and high-density integration. In this review, we will focus on semiconductor optical amplifiers (SOAs), which have received considerable interest in diverse photonic applications. SOAs have demonstrated high performance in various on-chip optical applications through different integration technologies on Si substrates. Moreover, SOAs are also considered as promising candidates for future light sources in the wavelength tunable laser, which is one of the key suitable components in coherent optical devices. Understanding the development and trends of heterogeneous integration Silicon/III-V SOA will help researchers to come up with effective strategies to combat the emerging challenges in this family of devices, progressing towards next-generation applications.

Stable narrow-linewidth lasers generated by self-injection locking systems have revolutionized applications from optical frequency metrology to astronomy. However, the dynamics for the self-injection locking system are intrinsically intertwined with thermal effects, which can generate a nonnegligible resonance drift in the microresonator and result in large detuning from the required regime. In this paper, we introduce the thermal effect, depending on the photon number, into self-injection locking systems with Rayleigh backscattering. We obtain a set of time-domain rate equations to describe the dynamics of laser-diode–cavity–microresonator systems and derive analytical formulas for effective detuning. The analytical results match well with our numerical simulations, and the effective detuning locking position moves forward as the value of the thermal effect coefficient decreases. We also analyze the dependence of the locking range and stable range on thermal effects, and our calculations show that, based on our approach, the stable range can be optimized effectively and the locking range is extended. Our results have the potential to optimize laser diode frequency stabilization experiments.

Laser based range measurement system plays an important role in both scientific and industrial areas. Soliton microcomb (SMC) based dispersive interferometry (DPI) method has shown the advantages of high speed, high precision, and compact size in ranging systems. However, due to the high repetition rate of SMCs, it results in a small non-ambiguous range (NAR), which impacts the practical application of SMC based ranging systems. Furthermore, when the measured distance is close to N times NAR, it is difficult to extract the distance information including the delay time and direction. Here, we introduce frequency scanning and prime number algorithm to an SMC based DPI ranging system. The frequency of SMC can be scanned over one free spectral range (FSR) by sweeping the pump frequency and the resonance of the microresonator synchronously. The interference spectra are recorded when the frequency is scanned every $1/{i_m}({i_m} = $ 2, 3, 5, 7…, a list of primes) FSR, and the NAR can be extended by $\sim \sqrt {2\prod {i_m}} $ times through interpolating the recorded interference spectra. We experimentally verify the feasibility of the proposed ranging system, and the NAR is extended by 3 times. Furthermore, we extract a small delay time of 6.859 fs with a standard deviation of 1.128 μm, which cannot be determined by the SMC with original repetition rate. The proposed ranging system can extend the NAR without any auxiliary rough measurement systems, and the detectable distance over the full range can be achieved.

Stabilized narrow-linewidth laser sources and soliton microcombs based on self-injection locking have driven revolutionary advancements from metrological to astronomical applications. Recently, coupled cavities have shown critical significance in optical frequency comb generation, particularly in achieving high conversion efficiency and enabling the formation of ultra-broadband soliton microcombs. In this work, we have developed a methodology for investigating self-injection locking in a laser diode-coupled-cavity system with Rayleigh backscattering. We have derived a set of rate equations to describe the system, obtained the analytical expression for effective detuning, and analyzed the critical coupling conditions and locking range for the coupled cavities. The analytical and numerical simulation results demonstrate that when the coupled-cavity structures induce mode splitting, the self-injection locking system exhibits dual-mode locking behavior. Furthermore, the auxiliary cavity introduces additional phase and losses to the coupled cavity, and the physical explanation for resonance splitting arises from the phase-balancing effect of pump detuning on the additional phase. On the other hand, the losses introduced by the auxiliary cavity can be effectively compensated by tuning the coupling strength between the waveguide and the main cavity. Therefore, we have also derived an analytical expression for the critical coupling coefficient in such laser diode-coupled-cavity systems. The proposed method can be extended to investigate self-injection locking in multi-coupled-cavity systems and provides a theoretical foundation for the realization of stabilized multi-frequency narrow-linewidth laser sources and high-efficiency, broadband soliton microcombs.