Xi Xiao

Optical frequency comb sources have attracted significant attention for their properties of coherent waveform generation. As an alternative to Kerr micro-resonators, semiconductor mode-locked lasers are also considered as an energy efficient optical comb source. In particular, semiconductor quantum dot (QD) mode-locked lasers are one of ideal multi-wavelength laser sources for data communication and optical interconnects, attributed to unique physical properties of ultra-fast carrier dynamics and extended photon lifetime. Here, we demonstrate InAs QD 4 ^th -order colliding pulse mode-locked (CPM) laser epitaxially grown on silicon, generating stable O-band optical frequency combs with 100 GHz spacing upto 90 ℃. By adjusting operating conditions (injection current and reversed bias voltage), different optical spectral modes (Gaussian, soliton and flat-top) can be realized corresponding to different pulse train evolution. Systematical analysis in frequency-domain and time-domain shows that at low reverse bias voltage of saturable absorbers (V _SA ), the laser is frequency modulation dominated, generating weak and stretched pulses, while transfers into amplitude modulation dominated at high V _SA . At specific operation point (injection current ~ 105 mA and V _SA ~ -5 V), the zero dispersion, small frequency chirp, squared hyperbolic secant shaped pulse profile and close to limit time-bandwidth product (0.3176) reveal soliton state discovered in active semiconductor laser cavity. A flat-top optical comb with 8+1 channels within 3 dB optical bandwidth is achieved. By integrating with high speed thin-film lithium niobate (TFLN) Mach-Zender modulators, single QD CPM laser directly grown on silicon substrate can provide high capacity data transmission through 100 Gbit/s NRZ or 50 Gbaud/s PAM-4 format modulation with bit error rate (BER) reaching hard-decision forward error correct (HD-FEC) level for all channels.

Photonics-assisted wireless communication provides a powerful pathway for next-generation infrastructures, offering ultra-wide bandwidth and high spectral agility. Despite extensive research and commercial adoption of photonics-assisted schemes such as radio-over-fiber in base station scenarios, their implementation in space-constrained and power-sensitive end devices remains highly challenging. The main obstacles arise from complex transceiver architectures, as mitigating effects of drift and jitter in carriers necessitates either high-purity sources or complex digital signal processing (DSP). Here, we propose a minimalist integrated photonics-assisted terahertz wireless transceiver solution tailored for lightweight systems. By employing residual carrier modulation and injection locking, we achieve a streamlined architecture using solely off-the-shelf 4 MHz linewidth distributed feedback laser chips and a single photodetector receiver, which supports 144 Gbps high-speed transmission at sub-terahertz frequency, meanwhile operating in a DSP-free regime for carrier recovery. The system also incorporates on-chip modulator and photodiode, enabling higher-level system integration. Eliminating the long-standing hardware burden and DSP overhead, the proposed scheme paves the way for lightweight, massive adoption of high-performance photonics-assisted wireless transceivers in end devices for ubiquitous access.

Artificial Intelligence models pose serious challenges to intensive computing and high-bandwidth communication for conventional electronic circuit-based computing clusters. Silicon photonic technologies, due to their high speed, low latency, large bandwidth, and complementary metal-oxide-semiconductor compatibility, have been widely implemented for data transmission and actively explored as photonic neural networks in AI clusters. However, current silicon photonic integrated chips lack adaptability for multifunctional use and hardware-software systematic coordination, which is adverse to the development of photo-electronic AI clusters. Here, we develop a reconfigurable silicon photonic chip with 40 programmable unit cells integrating over 160 components, which, to the best of our knowledge, is the first to realize diverse functions for AI clusters with a chip, from computing acceleration and signal processing to network switching and secure encryption. Using a self-developed testing, compilation, and adjustment framework to the chip without in-chip monitoring photodetectors, we have demonstrated (1) 4 × 4 bi-direction unitary and 3 × 3 uni-direction non-unitary matrix multiplications, achieving a speed of over 1.92 TOPS with 6.22-bit precision and energy efficiency of 1.875 pJ MAC ⁻¹ , and neural networks for image recognition with a latency of 260 ps; (2) micro-ring modulator wavelength locking in the 5 to 32 Gb s ⁻¹ transmission systems; (3) 4 × 4 photonic channel switching with low to –44 dB inter-channel crosstalk; (4) silicon photonic physical unclonable functions. This optoelectronic processing system, incorporating the photonic chip and its software stack, paves the way for both advanced photonic system-on-chip design and the construction of photo-electronic AI clusters.

Telecommunication systems are evolving towards ultrawide bandwidth and low latency, supporting wired and wireless links and their non-blocking interconnection ¹ . However, a long-standing bandwidth mismatch between fibre communication and its wireless counterpart arises from fundamental disparities in signal architectures and hardware constraints ^2,3 , which prevent high-speed and compatible transmission across the two domains. This challenge further complicates unified system design and hinders the realization of high-throughput-density, congestion-free fibre–wireless links under wideband-access scenarios ⁴ . Here we present an ultra-wideband (UWB) integrated photonics scheme that facilitates fibre–wireless communication over a shared-bandwidth infrastructure. Built on electro–optic (EO) and optic–electro (OE) conversions featuring 3-dB operational bandwidths exceeding 250 GHz and cross-architecture adaptability, our system demonstrates unprecedented data transmission capabilities in both wired and wireless links. Using the same set of devices and powered by the proposed complex bidirectional gated recurrent unit (complex-biGRU) algorithm, ultrahigh single-lane data rates of 512 Gbps for short-reach fibre and, for the first time to the authors’ knowledge, 400-Gbps high-speed wireless transmission have been achieved. Furthermore, high-density access is enabled by an all-optically assisted ultra-broadband wireless scheme. Real-time multichannel 8K video transmission is successfully demonstrated across 86 channels, seamlessly using a spectral range from 138 to 223 GHz. These findings in unified telecommunication development show the potential for the development of high-speed, densified and low-latency communication networks.

Pulse-width-modulated (PWM) thermo-optic tuning in silicon photonics calls for a power supply featuring high-speed PWM power output with short settling time, high efficiency, and a compact size. However, the transient response of the traditional digital low-dropout regulators (DLDOs) is limited by the closed-loop response, which makes it difficult to meet the speed requirements of the PWM power output. This brief presents a State-Switching DLDO (SS-DLDO), specially optimized for PWM thermo-optic tuning. Two state selectors, controlled by a PWM signal, are inserted into the SS-DLDO structure to control the connections and operational states of the DLDO asynchronously. This enables the speed of PWM tuning to be decoupled from the feedback loop of the DLDO. The proposed design is fabricated in a 65nm CMOS process with an active area of 0.00634 mm2. Measurement results show that the rising-edge settling time and falling-edge settling time of the PWM power output are 16.3 ns and 14 ns, respectively, which effectively reduces the limit of the edge settling time to the achievable PWM duty cycle range. Under a 2 MHz PWM frequency, this design can achieve PWM duty cycles ranging from 5.92% to 97.2%, corresponding to output power ranging from 1.47 mW to 24.12 mW.

Quantum dot mode-locked laser-based optical frequency combs are emerging as a critical solution for achieving low-cost, high-efficiency, and large-capacity optical interconnects. The practical implementation of wavelength division multiplexing interconnects necessitates a temperature-stable OFC source with a minimum 100 GHz channel spacing to enable high-bandwidth modulation while mitigating the complexity of optical filtering and detection. By leveraging the advanced co-doping technique and a colliding pulse mode-locking scheme, here, we report a compact, ultra-wideband, highly reliable, isolator-free 100 GHz-spacing InAs/GaAs QD OFC source operating up to a record temperature of 140 °C. The comb source delivers a record 3 dB optical bandwidth of 14.312 nm, containing flat-top comb lines, each supporting 128 Gb/s PAM-4 modulation, which results in a total throughput of 3.328 Tb/s with an extremely low power consumption of 0.394 pJ/bit at 25°C. Performance remains stable at 85 °C, with negligible degradation of device critical metrics. Remarkably, accelerated aging tests under harsh conditions (85 °C with 8x threshold current injection) revealed a mean time to failure of approximately 207 years. The QD OFC source demonstrated in this work, for the first time, establishes a concrete link between fundamental research on comb sources and their practical deployment in next-generation, high-density optical interconnect systems.

Developing a high-quality, bright source of polarization-entangled photon pairs on CMOS-compatible integrated platforms, such as silicon or silicon nitride, remains a significant challenge. Here, a novel silicon chip-based nonlinear Sagnac interferometer, which mainly integrates a bidirectionally pumped microring resonator with a polarization-splitting rotator, was proposed to generate polarization-entangled photon pairs. By pumping the system with a pulsed laser at 1550 nm and a power of 78 μW, polarization-entangled photon pairs in the telecom C-band were produced through spontaneous four-wave mixing, achieving a state-of-the-art brightness of 1.6 × 107 pairs s−1 GHz−1 mW−2. Using an off-chip polarization analyzer, the visibility of polarization-correlation interference fringe was measured to be 96.6%. Quantum state tomography revealed a fidelity of 0.958 for the maximally entangled state produced by the source. These exceptional performance metrics, combined with the integrability of the device, make it highly suitable for advanced quantum applications, particularly in multi-user entanglement-based quantum communication networks.

The rapid expansion of artificial intelligence (AI) technologies, particularly in fields such as autonomous driving, image generation, and natural language processing, has driven the need for higher computational performance. Traditional digital circuits face limitations due to the slowdown of Moore's Law, necessitating alternative approaches to meet the growing computational demands. Photonic computing has emerged as a promising solution, offering fast and efficient operations with ultra-low power consumption and high bandwidth (up to pJ/MAC). However, current photonic architectures are often inflexible and limited in supporting dynamic matrix multiplications, which is crucial for AI models like Transformers. In this work, we propose a coherent photonic-electronic computing core (PECC) that overcomes these limitations by enabling operations in both amplitude and phase dimensions of the optical signal. PECC allows 2-D vector dot productions on a single wavelength and supports complex-valued multiplication operations. This core is scalable through wavelength division multiplexing (WDM) and crossbar arrays, forming the basis of a photonic-electronic tensor core (PETC). Multiple PETCs can be integrated into a Photonic-Electronic Streaming Multiprocessor (PESM) for large-scale AI computations. We experimentally demonstrate the effectiveness of the PECC and numerically simulate the performance of the PESM. For PECC, we experimentally achieved an accuracy over 5 bit at a computing speed of 32 GOPS and an accuracy of 90.0% and 91.2% on the Fashion-MNIST dataset and comparable accuracies on the Cifar-10 dataset using it as the real-valued and complex-valued neural networks. For PESM, we achieved an inference accuracy of 89.47% for the Cifar-100 dataset using Deit and could achieve a theoretical computing speed of up to 1048 TOPS in a simulated environment.

Quantum random number generators play a crucial role in securing high-demand information contexts by producing true random numbers. Nevertheless, the large volume and high-cost limit their widespread use. Here, we propose a system on chip that fully leverages the advantages of different photonic integrated platforms, where the interference optical paths and photodiodes are integrated on a standard silicon process, while the laser source on-chip is realized on a III-V platform. Using micro-lens coupling package technology, which contributes to a topnotch coupling loss lower than 2dB, the components on different platforms are combined and packaged with the amplifier circuits in a 42mm* 24mm footprint in a butterfly form. This complete miniaturized and cost-effective entropy source enables outputting a vacuum noise signal with a 3dB bandwidth of over 500MHz. After sampling and post-processing, a random number generation rate of up to 6.57Gbps is achieved. The results show a feasible way of overcoming the laser integration problem with silicon-based integrated quantum photonics. Foreseeable, commercial applications on a large scale are significantly promoted.