Luyu Wang

The development of large-scale quantum networks requires scalable interconnects operating from cryogenic to ambient temperatures. While conventional electrical interconnects pose thermal management and system complexity challenges, photonic interconnects enable efficient optical modulation and fiber transmission. Here, we present temperature-dependent characterization of a modified uni-traveling carrier photodetector (MUTC-PD) for quantum network applications. The $28~\mu $ m device exhibits stable responsivity (> 0.56 A/W), > 9 GHz bandwidth at–5 V bias, and good linearity from 5 K to 300 K. These robust characteristics identify the MUTC-PD as a promising candidate for scalable quantum photonic interconnects and provide design insights for next-generation cryogenic photodetectors.

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.

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.

Low-noise microwave oscillators are cornerstones for wireless communication, radar and clocks. The employment and optimization of optical frequency combs have enabled photonic microwave synthesizers with unrivalled noise performance and bandwidth breaking the bottleneck of those electronic counterparts. Emerging interest is to use chip-based Kerr frequency combs, namely microcombs. Today microcombs built on photonic integrated circuits feature small size, weight and power consumption, and can be manufactured to oscillate at any frequency ranging from microwave to millimeter-wave band. A monolithic microcomb-based microwave oscillator requires integration of lasers, photodetectors and nonlinear microresonators on a common substrate, which however has still remained elusive. Here, we demonstrate the first, fully hybrid-integrated, microcomb-based microwave oscillator at 10.7 GHz. The chip device, powered by a customized microelectronic circuit, leverages hybrid integration of a high-power DFB laser, a silicon nitride microresonator of a quality factor exceeding 25 × 10⁶, and a high-speed photodetector chip of 110 GHz bandwidth (3 dB) and 0.3 A/W responsivity. Each component represents the state of the art of its own class, yet also allows large-volume manufacturing with low cost using established CMOS and III-V foundries. The hybrid chip outputs an ultralow-noise laser of 6.9 Hz intrinsic linewidth, a coherent microcomb of 10.7 GHz repetition rate, and a 10.7 GHz microwave carrier of 6.3 mHz linewidth – all the three functions in one entity occupying a footprint of only 76 mm². Furthermore, harnessing the nonlinear laser-microresonator interaction, we observe and maneuver a unique noise-quenching dynamics within discrete microcomb states, which offers immunity to laser current noise, suppression of microwave phase noise by more than 20 dB, and improvement of microwave power by up to 10 dB. The ultimate microwave phase noise reaches −75/−105/−130 dBc/Hz at 1/10/100 kHz Fourier offset frequency. Our results can reinvigorate our information society for communication, sensing, imaging, timing and precision measurement.

We present InP-based evanescently-coupled waveguide modified uni-traveling carrier photodiodes (MUTC-PDs) exhibiting a breakthrough in bandwidth. The optimization of carrier transport and optical coupling is achieved through a detailed discussion on the design of the cliff layer and waveguide layer. Addressing the parasitic capacitance challenge, we introduce benzocyclobutene (BCB) beneath the PD electrodes, effectively overcoming the bandwidth bottleneck associated with the RC time constant. Devices with sizes of 2 × 7 $\upmu$ m $^{2}$ and 2× 10 $\upmu$ m $^{2}$ achieve 3-dB bandwidths over 220 GHz, along with external responsivities of 0.161 A/W and 0.237 A/W, respectively. Notably, the RF output power reaches a peak of -1.69 dBm at 215 GHz for 2 × 15 $\upmu$ m $^{2}$ PDs.

We present InP-based evanescently-coupled waveguide modified uni-traveling carrier photodiodes (MUTC-PDs) exhibiting a breakthrough in bandwidth. The optimization of carrier transport and optical coupling is achieved through a detailed discussion on the design of the cliff layer and waveguide layer. Addressing the parasitic capacitance challenge, we introduce benzocyclobutene (BCB) beneath the PD electrodes, effectively overcoming the bandwidth bottleneck associated with the RC time constant. Devices with sizes of 2 * 7 um2 and 2 * 10 um2 achieve 3-dB bandwidths over 220 GHz, along with external responsivities of 0.161 A/W and 0.237 A/W, respectively. Notably, the RF output power reaches a peak of -1.69 dBm at 215 GHz for 2 * 15 um2 PDs.

Digital alloy (DA) InAlAs on the InP substrate exhibits a lower excess noise compared to a traditional In0.52Al0.48As random alloy as the multiplication layer in avalanche photodiodes (APDs). This work implements DA InAlAs as the multiplication layer in a 1550 nm separate absorption, grading, charge, and multiplication APD and characterizes the performances through various analyses. The device reaches a maximum gain of 221 before avalanche breakdown, with a maximum gain-bandwidth product of more than 140 GHz. At 90% breakdown voltage, the dark current density is 4.1 mA/cm2, and the responsivity is 0.48 A/W at unit gain. Excess noise factors were identified, yielding an effective k value of around 0.15, which is lower than that of random alloy In0.52Al0.48As APDs (k ∼0.2). These findings show that DA InAlAs has the potential to be a promising material for high-performance APDs.

Recently, there has been a growing demand for high-speed mid-wave infrared (MWIR) photodetectors (PDs) driven by the emergence of new fields, such as free-space communication and frequency comb spectroscopy. In this study, we investigated a high-speed InAs/GaSb type-II superlattice (T2SL) MWIR uni-traveling carrier (UTC) PD with relatively low dark current and high responsivity. We also perform an inductive peaked dewar packaging on the PD to be user-friendly and allow cryogenic operation. The original on-wafer PD shows a dark current density of 54.05 A/cm ² at 300 K, along with a responsivity exceeding 0.36 A/W at 4.5 μm and a 3-dB bandwidth of 3.83 GHz at −5 V bias. The inductive-peaked device in dewar packaging demonstrates a dark current density of 1.65×10 ⁻⁵ A/cm ² at 77 K, and a responsivity of 0.39 A/W at 4 μm, and a 3-dB bandwidth of 5.29 GHz.