Microcombs are revolutionizing optoelectronics by providing parallel, mutually coherent wavelength channels for time-frequency metrology and information processing. To implement this essential function in integrated photonic systems, it is desirable to drive microcombs directly with an on-chip laser in a simple and flexible way. However, two major difficulties have prevented this goal: (1) generating mode-locked comb states usually requires a significant amount of pump power and (2) the requirement to align laser and resonator frequency significantly complicates operation and limits the tunability of the comb lines. Here, we address these problems by using microresonators on an AlGaAs on-insulator platform to generate dark-pulse microcombs. This highly nonlinear platform dramatically relaxes fabrication requirements and leads to a record-low pump power of <1 mW for coherent comb generation. Dark-pulse microcombs facilitated by thermally controlled avoided mode crossings are accessed by direct distributed feedback laser pumping. Without any feedback or control circuitries, the comb shows good coherence and stability. With around 150 mW on-chip power, this approach also leads to an unprecedentedly wide tuning range of over one free spectral range (97.5 GHz). Our work provides a route to realize power-efficient, simple, and reconfigurable microcombs that can be seamlessly integrated with a wide range of photonic systems.

Integrated microwave photonic filters (IMPFs) are capable of offering unparalleled performances in terms of superb spectral fineness, broadband, and more importantly, the reconfigurability, which encounter the trend of the next-generation wireless communication. However, to achieve high reconfigurability, previous works should adopt complicated system structures and modulation formats, which put great pressure on power consumption and controlment, and, therefore, impede the massive deployment of IMPF. Here, we propose a streamlined architecture for a wideband and highly reconfigurable IMPF on the silicon photonics platform. For various practical filter responses, to avoid complex auxiliary devices and bias drift problems, a phase-modulated flexible sideband cancellation method is employed based on the intensity-consistent single-stage-adjustable cascaded-microring (ICSSA-CM). The IMPF exhibits an operation band extending to millimeter-wave (≥30GHz), and other extraordinary performances including high spectral resolution of 220 MHz and large rejection ratio of 60 dB are obtained. Moreover, Gb/s-level RF wireless communications are demonstrated for the first time towards real-world scenarios. The proposed IMPF provides broadband flexible spectrum control capabilities, showing great potential in the next-generation wireless communication.

A hybrid integrated 16-channel silicon transmitter based on co-designed photonic integrated circuits (PICs) and electrical chiplets is demonstrated. The driver in the 65 nm CMOS process employs the combination of a distributed architecture, two-tap feedforward equalization (FFE), and a push–pull output stage, exhibiting an estimated differential output swing of 4.0V_pp. The rms jitter of 2.0 ps is achieved at 50 Gb/s under nonreturn-to-zero on–off keying (NRZ-OOK) modulation. The PICs are fabricated on a standard silicon-on-insulator platform and consist of 16 parallel silicon dual-drive Mach–Zehnder modulators on a single chip. The chip-on-board co-packaged Si transmitter is constituted by the multichannel chiplets without any off-chip bias control, which significantly simplifies the system complexity. Experimentally, the open and clear optical eye diagrams of selected channels up to 50 Gb/s OOK with extinction ratios exceeding 3 dB are obtained without any digital signal processing. The power consumption of the Si transmitter with a high integration density featuring a throughput up to 800 Gb/s is only 5.35 pJ/bit, indicating a great potential for massively parallel terabit-scale optical interconnects for future hyperscale data centers and high-performance computing systems.

A low-loss hybrid plasmonic transverse magnetic (TM)-pass polarizer has been demonstrated utilizing polarization-dependent mode conversion. Taking advantage of the silicon hybrid plasmonic slot waveguide (HPSW), the unwanted transverse electric (TE) fundamental mode can be efficiently converted first to a TM higher-order mode and then suppressed by a power combiner, while the retained TM fundamental mode can pass through with negligible influence. Since the HPSW feature both strong structural asymmetry and a small interaction area in the cross-section between the metal and optical field, the optimized insertion loss of the device is as low as 0.4 dB. At the wavelength of 1550 nm, the extinction ratio is 28.3 dB with a moderate footprint of 2.38μm×10μm. For the entire C band, the average reflection of the TE mode is suppressed below ?14dB, and the extinction ratio is over 18.6 dB. This work provides another more efficient and effective approach for better on-chip polarizers.

Optical microring resonators are extensively employed in a wide range of physical studies and applications due to the resonance enhancement property. Incorporating coupling control of a microring resonator is necessary in many scenarios, but modifications are essentially added to the resonator and impair the capability of optical enhancement. Here, we propose a flexible coupling structure based on adiabatic elimination that allows low-loss active coupling control without any modifications to the resonators. The self-coupling coefficient can be monotonically or non-monotonically controllable by the proposed coupler, potentially at a high speed. The characteristic of the coupler when implemented in silicon microring resonators is investigated in detail using substantiated analytical theory and experiments. This work provides a general method in coupling control while ensuring the resonance enhancement property, making active coupling control in a resonator-waveguide system feasible.