<sec>To meet the growing demand for high-frequency broadband signal processing in complex electromagnetic environments and to overcome the limitations of traditional electronic systems such as restricted bandwidth, limited response speed, and low integration density, this paper presents a reconfigurable microwave photonic channelized receiver chip implemented on a silicon photonic platform. The proposed architecture adopts a two-stage optical filtering strategy that circumvents the typical strict wavelength alignment requirements in traditional designs, thereby greatly alleviating the challenges of system integration. In the first stage, the cascaded Mach-Zehnder interferometer (MZI)-based wavelength division multiplexers (WDMs) are used to perform Gaussian-shaped filtering of the input optical spectrum with a channel spacing of approximately 200 GHz. The second stage combines an array of coupled resonator optical waveguide (CROW) filters functioning as finely tunable bandpass elements. These CROW filters utilize curved waveguide directional couplers, which are specifically designed to address the issues found in traditional multimode interference (MMI) couplers such as high insertion loss—and in straight directional couplers, which encounter significant coupling dispersion. The optimized curved coupler exhibits an insertion loss below 0.03 dB and a coupling ratio variation of less than 10% across the 1500–1600 nm wavelength band. Filter bandwidth reconfigurability is achieved via thermo-optic tuning of the balanced MZI embedded within each CROW filter, enabling dynamic adjustment of the coupling coefficients. Each filter exhibits a continuously adjustable 3 dB bandwidth ranging from 2.25 GHz to 3.12 GHz, with an excellent 20 dB/3 dB shape factor of 3.08. This performance indicates significantly improved roll-off characteristics compared with the performance of traditional filter designs, leading to enhanced suppression of image frequency components and improved signal separation fidelity.</sec><sec>A complete microwave photon channelized receiving link is constructed using an integrated WDM-CROW filter bank. System-level simulations confirm that the architecture provides excellent broadband adaptability, supporting the channelization of radio frequency (RF) signals in two operational bands: 8–28 GHz and 8–36 GHz. The system efficiently decomposes the input wideband RF signal into eight independent intermediate frequency (IF) sub-bands. Within each sub-band, an image rejection ratio (IRR) exceeding 22 dB is maintained. The corresponding IF ranges are 1.4–3.6 GHz when configured for 8–28 GHz RF input, and 2–5 GHz for 8–36 GHz input, covering critical communication and detection bands from X-band to K-band and satisfying the requirements of multi-scenario signal processing. Furthermore, we simulate the reception and reconstruction of a 5 GHz bandwidth linear frequency-modulated (LFM) signal, successfully verifying the chip’s capability in handling wideband waveforms. These results underscore the feasibility of the proposed chip as a high-performance solution for advanced applications such as radar detection and broadband electronic warfare systems, offering a novel, integrated photonic alternative to traditional channelized reception architectures.</sec>

Wideband III-nitrides, aluminum nitride (AlN), and gallium nitride (GaN) possess excellent material properties that could cater to a broad range of chip-scale photonic applications in telecommunications, microwave photonics, quantum information processing, nonlinear optics, and optical neural networks, with the freedom to extend the platform to lower wavelengths in the visible and UV owing to their bandgap. While both materials inherently hold huge potential for photonic integrated circuit (PIC) applications, the development of epitaxial thin films (< 1 μ m thickness) with low defects and superior crystal quality is of utmost importance. To this end, we develop 500 nm thick AlN and GaN films on sapphire substrate, with an XRD (002) ω -scan FWHM of 120 arcsec for AlN and 618 arcsec for GaN, and (102) ω -scan FWHM of 980 arcsec and 1020 arcsec, with a surface roughness of 0.2 nm and 0.4 nm for AlN and GaN, respectively. The crystal quality achieved for the thin films of AlN and GaN is comparable with some of the best reported in literature at these thicknesses. Using this material, we demonstrate overlay grating couplers on both AlN and GaN material platforms, achieving a peak coupling efficiency of −3.7 dB/coupler at 1545 nm in AlN and −4.6 dB/coupler at 1575 nm in GaN. The bandwidths are 48 nm for AlN and 29 nm for GaN. The coupling efficiencies are the best reported so far for both material platforms.

OEO-Based Microwave Photonics Frequency Conversion Without LO Signal Leakage

Modulation and amplification are two fundamental processes in optoelectronics. While discrete implementations have achieved widespread success, the challenge of monolithically integrating sufficient gain and electro-optic bandwidth remains a significant barrier, limiting optical systems’ miniaturization and scalability. We unify these two functions in the Er-doped thin-film lithium niobate (Er:TFLN) platform, achieving a record-high internal net gain of 38 dB in a 9.16-cm-long waveguide amplifier. Meanwhile, leveraging the host material’s strong Pockels effect, we realize ultra wide-range electro-optic modulation with a bandwidth of 53 GHz and operation up to 170 GHz, fabricated alongside waveguide amplifiers using a zero-change process. Additionally, we validate this functional fusion through two signal processing scenarios: self-amplified digital signal encoding and pre-amplified broadband radio frequency front-end receiving, demonstrating improved signal recovery quality compared to off-chip gain. The modulation-amplification integration holds broad potential for increasing system complexity and network depth in applications such as optical interconnections, Lidar, and microwave photonics.

The terahertz (THz) range, bridging microwave and infrared frequencies, enables advanced imaging, sensing, communications, and spectroscopy. Analogous to microwave photonics, terahertz photonics offers a promising optical solution to critical THz challenges-THz-optical interfacing, including THz-optic modulation and optical generation of THz waves. We address these with a monolithic integrated photonic chip enabling efficient THz-optical bidirectional interaction. Leveraging strong second-order optical nonlinearity and optical/THz confinement in thin-film lithium niobate on quartz, the chip supports efficient THz-optic modulation and continuous THz generation up to 500 GHz. The measured continuous wave THz generation efficiency of 4.8 × 10−6/W at 500 GHz also marks a tenfold improvement over existing lithium niobate-based tunable THz generation devices. We further leverage the coherent nature of the optical THz generation process and on-chip modulators to realize 65 GHz high-speed electro-THz modulation. The chip-scale THz-photonic platform enables more compact, efficient, and cost-effective THz systems for communications, sensing, and spectroscopy.

Large Bandwidth and High Power Germanium/Silicon Photodetector: A Novel Solution for 100 Gb s ^–1 Microwave Photonic Links

Broadband Phased Array Receiver Based on Microwave photonics Channelization

Temperature measurement and heat transfer investigation of horizontal gas-liquid two-phase flow based on microwave photonics

Microwave and High-Speed Photonics Applications to 6G Systems

Versatile Microwave Photonic Signal Processor Based on a Quantum-Dash Mode-Locked Laser

Deep Learning-Enhanced Microwave Photonic Sensing With Inverse-Design Assisted Fabry-Pérot Cavity

Two-Dimensional Nanoscale Position Sensing Using Microwave Photonic Signal Induced by Period-One Dynamics of Semiconductor Laser

A Microwave Photonic Processor for Convolutional Neural Networks With Increased Effective Speed of Convolution

We demonstrate a new, to the best of our knowledge, dual-wavelength distributed feedback laser platform based on a waveguide Bragg grating microcavity incorporating uniform sidewall gratings. This is the first single-section, single-contact device achieving simultaneous dual-wavelength operation at 1.55 µm, providing intrinsic stability and compactness. By adjusting the central cavity length, stable dual-mode operation is achieved within a single cavity across a broad range of frequency spacings. Devices with different cavity lengths exhibit free spectral ranges from 0.41 nm to 0.65 nm (54-86 GHz), all with side-mode suppression ratios exceeding 30 dB. The device requires only a single metalorganic vapor-phase epitaxy growth and one dry etching step, enabling a compact, thermally stable, and fabrication-tolerant solution. This work establishes a promising dual-wavelength laser platform for microwave photonics and integrated photonic systems.

Abstract This paper presents a novel design framework for photonic matrix multiplication based on programmable photonic integrated circuits that use double racetrack (DRT) resonators as building blocks. Here, we analytically demonstrate that the transfer function of the DRT resonator building block resembles that of conventional building blocks, such as directional couplers and MZI, making it suitable for implementing programmable circuits that handle complex matrix calculations. Using this new DRT resonator building block, a 3-by-3 photonic processor is implemented and validated through full-wave Finite Element Method (FEM) simulations, and scalability is further analysed using hybrid FEM-circuit modelling. Additionally, we implement a low-pass filter as a non-unitary system example, showcasing the flexibility of the approach. Results confirm high fidelity between simulated and analytical models, supporting the viability of DRT resonators for reconfigurable photonic circuits. We believe that the proposed DRT resonator building blocks have the potential to complement and integrate with other previously reported blocks, thereby enhancing fidelity and expanding the application scope of programmable photonic integrated circuits, particularly for all-optical signal processing in communication systems and for integration within microwave photonics platforms targeting emerging telecommunications technologies.

Low-noise microwave generation is crucial for advanced applications such as 6G millimeter-wave communications, satellite communications, and synthetic aperture radar systems. Traditional microwave sources encounter challenges in meeting stringent performance requirements while maintaining low size, weight, and power consumption (SWaP) at ever-increasing high frequencies. Photonic microwave generation is a promising solution to overcome these limitations, particularly when implemented with chip-scale integration using a simple yet efficient architecture. Here, we propose a chip-scale integrated photonic microwave generator (IPMG) scheme that features a low-noise hybrid InP / Si 3 N 4 comb laser based on the self-injection locking mechanism, in conjunction with the optic-electro-optic feedback to further enhance the RF generation performance. The proof-of-concept IPMG prototype has demonstrated superior performance, highlighting an ultra-narrow RF intrinsic linewidth of 0.8 Hz, low single-sideband phase noises of −92.1 dBc/Hz at 10 kHz offset and −128.3 dBc/Hz at 1 MHz offset, and excellent frequency stability with only 16 kHz fluctuations over 5 min. This work marks a substantial advancement in the development of fully integrated photonic microwave generators by unifying good performance, architectural simplicity, and low SWaP.

Abstract Integrated microwave photonic filters (IMPFs) emerge as promising candidates for advanced microwave systems owing to their distinctive combination of wide operational bandwidth, flexibility, and compact size. Nevertheless, the complex and time‐consuming manual manipulation of IMPFs remains a significant impediment to their widespread applications. Here, to the best of the knowledge, the first intelligent configuration of IMPF is experimentally demonstrated, featuring wideband center frequency tunability, flexible bandwidth reconfigurability, self‐stabilization, and excellent channel equalization simultaneously. The configuration is enabled by our proposed universal hybrid collaboration strategy, which fully unleashes the hardware potential of the optical device, thus enabling comprehensive synergy of multiple properties. Results show that the center frequency of IMPF is tuned from 2 to 48 GHz, covering microwave S band to Ka band, and the bandwidth is reconfigured from 0.66 to 4.15 GHz, with a rejection ratio of up to 37.67 dB. The roll‐off rate and shape factor reach as high as 17.50 dB GHz−1 and 0.78, respectively. Meanwhile, the maximum center frequency drift of IMPF over 3 h is reduced from 11.950 to 0.051 GHz even without a thermo‐electric cooler, indicating that the center frequency stability is enhanced by 234 times. The passband shape of the IMPF is dynamically adjusted to equalize frequency‐dependent fading, achieving up to 2.42 dB of intra‐channel fading compensation. This work highlights the potential of IMPFs based on intelligent configuration, unlocking new avenues for practical applications of microwave photonic signal processing.

The integration of GHz-frequency, high-quality factor (Q), and electrically tunable acoustic resonators holds significant potential for advancing applications in quantum information technologies, microwave photonics, and reconfigurable RF systems. However, simultaneously achieving these three characteristics within a single, scalable platform remains a fundamental challenge. Here, the experimental demonstration of a GHz quasi-BIC resonator in a piezoelectric thin-film shear horizontal (SH) wave system, achieved through a structurally simple piezoelectric-metal phononic crystal (PnC) architecture on a LiNbO3 thin film, is reported. This approach enables leaky Fabry-Perot coupling mode and localized trapping quasi-BIC mode. Without the need for deep etching or intricate patterning, a high room-temperature quality factor of ≈6.5×104 at ≈1GHz in ambient air is achieved, corresponding to an f × Q product of ≈6.4 ×1013Hz at quasi-BIC mode. Furthermore, efficient electrical tunability is demonstrated via low-voltage (0.6V) electrothermal modulation of the PnC structure, enabling a reversible transition between trapped and transmission states and yielding a high-contrast amplitude modulation of 47.75dB. This work opens new directions for scalable on-chip phononic circuits in quantum acoustics, reconfigurable RF systems, and signal processing applications.

Microcombs, formed in optical microresonators driven by continuous-wave lasers, are miniaturized optical frequency combs. Leveraging integrated photonics and laser self-injection locking, compact microcombs can be constructed via hybrid integration of a semiconductor laser with a chip-based microresonator. While the current linear self-injection locking theory has successfully addressed the linear coupling between the laser cavity and the external microresonator, it fails to describe the complicated nonlinear processes, especially for dark-pulse microcomb formation. Here, we investigate-theoretically, numerically, and experimentally-the Kerr-thermal dynamics of a semiconductor laser self-injection locked to an integrated silicon nitride microresonator. We unveil intriguing yet universal dark-pulse formation and switching behavior with discrete steps, and establish a theoretical model scrutinizing the synergy of laser-microresonator mutual coupling, Kerr nonlinearity, and photothermal effect. Numerical simulation confirms the experimental result and identifies the origins. Exploiting this unique phenomenon, we showcase an application on low-noise photonic microwave generation with phase noise purified by 23.5dB. Our study not only adds critical insight of pulse formation in laser-microresonator hybrid systems, but also enables all-passive, photonic-chip-based microwave oscillators with high spectral purity.

We report on the development and characterization of a compact visible Brillouin fiber laser. The laser is designed in a short cavity configuration and demonstrates an output power of 30 mW. Detailed analysis reveals an intrinsic linewidth of 6 Hz, indicating exceptional spectral purity. Comprehensive gain characterization was performed as a function of pump power, providing critical insight into the laser's performance and limitations. These findings contribute to the advancement of compact, highly stable visible fiber lasers for quantum technologies and microwave photonics.