Photonic angle-of-arrival measurement with phase noise suppression

Long-range distributed fiber-optic acoustic sensor with 100 kHz linewidth laser and frequency domain signal-and-kernel phase noise compensation

This paper presents a novel free-space optical Angle-of-Arrival (AOA) estimation method based on arrayed waveguide coherent mode decoding, aiming to surpass the inherent limitations of traditional AOA detection technologies, which face significant challenges in achieving miniaturization, low complexity, and high reliability. The method utilizes the AOA-related phase differences generated by the propagation and interference of incident light in an arrayed input waveguide, forming multi-beam interference fringes at the output end of the slab waveguide. This pattern is then sampled by an arrayed output waveguide to produce an intensity sequence, which is then fed into a trained CNN–Attention Regressor for AOA estimation. This study innovatively applies the method to decoding the spatial angular information of optical signals. Simulation results demonstrate the exceptional performance of our approach, achieving a Mean Absolute Error (MAE) of 0.0142° and a Root Mean Square Error (RMSE) of 0.0193° over a 40° field of view. This precision is significantly superior to conventional peak–linear calibration methods and other common neural network architectures, and exhibits remarkable robustness against simulated phase noise and manufacturing tolerances. This research demonstrates the powerful synergy between integrated photonics and deep learning, paving the way for a new class of highly integrated, robust, and high-performance on-chip optical sensors.

Terahertz (THz) waves play a crucial role in numerous imaging applications, from industrial inspection to medical diagnostics. However, most current THz imaging techniques operate in the pulsed mode, remaining entrenched in the “super-resolution versus practical-level frame rate” dilemma. In this work, we present system-level rapid, super-resolution, and large-field-of-view THz compressive imaging. In the system, by implementing high-speed sampling with low phase noise through CW radiation based on an optical frequency comb, and exploring a VO 2 /mica film THz spatial modulator with advanced trigger threshold (0.37mJ/cm 2 ) and higher modulation depth (80.4%), we simultaneously break the long-standing trade-off between spatial resolution and temporal speed in THz imaging systems. We experimentally achieve rapid super-resolution THz compressed sensing (CS) imaging with a super-resolution (< λ /65) at video-frame rates (2 fps) over a large field of view of 100mm 2 . This work represents a significant step toward application-oriented THz imaging, and holds tremendous promise in biomedical diagnostics, nondestructive testing, and pharmaceutical industries.

Traditional zero-compensation techniques employed to improve sub-sampling phase-locked loop (SSPLL) stability often exacerbate spur degradation or incur excessive area overhead, rendering them unsuitable for high-resolution image sensor applications. This paper proposes a novel SSPLL based on capacitor multiplication technology. This capacitor multiplication technology employs dual charge pumps (CP1 and CP2) in a coordinated operational scheme where their charge/discharge states are inversely synchronized. The effective capacitance of the loop filter is thereby amplified without expanding the physical layout area dedicated to capacitive components. Meanwhile, the continued use of zero-compensation technology ensures the stability of the SSPLL. The proposed SSPLL is designed and verified in a 55 nm CMOS process. At a 1.2 GHz output frequency, simulation results show a spot phase noise of −131.5 dBc/Hz at 1 MHz offset, accompanied by an integrated RMS jitter of 549 fs across the 10 kHz to 40 MHz spectrum, spurs suppressed to −51.3 dB, while maintaining a power efficiency of 3.81 mW and a compact layout area of 0.064 mm2. All the above results show that by introducing the novel dual-CP charge multiplication technology, the SSPLL can achieve low jitter and low power consumption performance while reducing the layout area, providing a new technical approach for its application in high-resolution image sensors.

Microresonator-based dual-comb technology has emerged as a transformative tool for precision measurements, driving advances in ultrafast distance measurement, high-resolution spectroscopy, and optical coherence tomography. In dual-comb heterodyne systems, measurements critically depend on the long-term stability of the combs—an inherent challenge for free-running microcombs due to their susceptibility to phase noise and frequency drift. While active stabilization schemes can enforce comb synchronization, their reliance on external feedback mechanisms inevitably reintroduces the very complexity these integrated systems aim to eliminate—creating a paradoxical barrier to practical applications, particularly in compact, field-deployable platforms. To address these challenges, we present a low-noise Kerr frequency comb device integrated within a coin-sized, electrically driven butterfly package. By leveraging self-injection locking to a high-Q, large-mode-volume fiber Fabry–Perot resonator, we achieve an unprecedented reduction in phase noise: reaching −129dBc/Hz at 10 kHz, −142dBc/Hz at 100 kHz, and −158dBc/Hz at the noise floor, approaching the quantum noise limit. This compact device exhibits key practical advantages, including low-power consumption, long-term operational stability, and turnkey functionality. Crucially, the high coherence of the generated comb enables a locking-free dual-comb system capable of achieving single-micron-level ranging accuracy and spectroscopic precision with errors below 1%—performance comparable to fully stabilized dual-mode-locked laser systems. Our work demonstrates Kerr combs with a low fundamental noise limit enabled by a novel platform structure, to our knowledge, and establishes a new paradigm for high-performance, compact frequency comb sources. These advances pave the way for the widespread adoption of Kerr comb technology in real-world applications beyond laboratory settings, spanning precision metrology, communications, and remote sensing.

As an important method for exoplanet detection, the key to the radial velocity (RV) method lies in the high-precision measurement of stellar RV. Coherent-dispersion spectrometer (CODES), which obtains the RV by analyzing the Doppler phase shift of stellar absorption line interference spectrum, shows significant potential in the application of the RV method due to its high energy utilization efficiency and excellent environmental stability. However, the background white light in the stellar absorption spectrum makes phase noise to the CODES, which leads to a significant decrease and fluctuation in the RV inversion precision. To remove the phase noise caused by background white light, the Dual-domain background white light prediction network (DDBWP-Net) is proposed by integrating spatial and frequency domain processing. In DDBWP-Net, firstly, the main energy of the background white light and the absorption line is separated through frequency-domain processing, and then the global high-frequency and low-frequency features of the background white light interference spectrum are extracted. Secondly, the global high-frequency and low-frequency features are fused deeply by introducing the channel attention mechanism, enhancing the integrity of the feature representation. Thirdly, the multi-scale local detail features of the background white light interference spectrum are extracted by utilizing the spatial convolution based on the double-layer residual structure. Finally, the prediction result of the background white light interference spectrum is reconstructed. The experimental results show that the RV inversion error is mainly distributed in the range of 0-0.15 m/s, with the mean error of 0.08 m/s and the root mean square error of 0.13 m/s, after removing the background white light predicted by DDBWP-Net from the original absorption line interference spectrum. Moreover, with different absorption lines and different fixed optical path differences, the error distribution shows good uniformity. This indicates that DDBWP-Net can predict background white light accurately, and has strong stability and robustness, providing solid technical support for CODES to achieve high-precision exoplanet detection.

Abstract Erbium-doped waveguide lasers have attracted great interests in recent years due to their compact footprint, high scalability and low phase noise. In this work, by using a high-external-gain erbium-doped thin-film lithium niobate waveguide as the gain medium, a fiber-Bragg-grating based Fabry–Perot-type laser is demonstrated with the low pump threshold of few-milliwatts, narrow bandwidth of 0.1 nm, high external output power above 2 mW and maximum optical signal-to-noise ratios above 50 dB. Laser linewidth measurements by self-delayed homodyne and heterodyne detections reveal the underlying multi-longitudinal-mode laser structure and the average intrinsic linewidth as low as ∼50 kHz for the individual longitudinal-modes. Theoretical modeling of the waveguide laser is also conducted with high consistence with the experimental measurements. The demonstrated high-power erbium-doped waveguide laser on thin-film lithium niobate can find diverse applications in optical communication and laser sensing.

A novel, to the best of our knowledge, optoelectronic oscillator (OEO) based on parity-time (PT) symmetry is proposed and experimentally demonstrated. In the proposed PT-symmetric OEO, a PT-symmetric structure with a phase modulator and an interleaved optical filter is incorporated to achieve the balance between the loop gain and loss in the OEO cavity, which significantly improves the side-mode suppression ratio (SMSR) of the generated microwave signals. In the experiment, a 10-GHz microwave signal has been successfully generated by the proposed PT-symmetric OEO, the side-mode suppression ratio of the RF output can reach 62.5 dB, and the phase noise can reach -148.88 dBc/Hz at 10-kHz offset via a 4.4-km OEO loop. Furthermore, the significant contrast between the generated 10-GHz signal's SMSR and phase noise is presented by using different fiber lengths. A YIG filter is incorporated into the OEO loop to verify the PT-symmetric effects at various oscillation frequencies. Experiment results indicate that the single-frequency oscillation can be tuned from 8 to 11 GHz with the SMSR beyond 50 dB and phase noise better than -130 dBc/Hz at 10 kHz offset via a 1-km OEO loop.

RIS-assisted LoRa networks with diversity: Impact of hardware impairments and phase noise

ABSTRACT A millimeter‐wave (MMW) voltage‐controlled oscillator (VCO) with parallel feedback architecture is proposed in this paper. A diplexer with large frequency ratio is exploited to act as a fundamental frequency stabilization and third‐harmonic frequency extraction component, simultaneously. It consists of an X‐band microstrip bandpass filter (BPF) and a Ka‐band substrate integrated waveguide (SIW) BPF. The characteristics of the proposed diplexer possess a decent performance of high isolation between the two output ports. To verify the proposed architecture, a Ka‐band VCO prototype is designed, fabricated, and measured. The observed outcomes indicate that the frequency tuning range is from 26.19 to 26.76 GHz, and the designed VCO achieves a superior phase noise (PN) of −128.7 dBc/Hz and the corresponding figure of merit (FOM) indicates −203.8 dB/Hz at 1‐MHz offset frequency.

Surpassing the phase noise in continuous-variable quantum key distribution via Gaussian filter

A PRF-Based Multibaseline fitting model for temperature prediction.

Phase Noise Mitigation in Higher Order Probabilistic Constellation Shaping for High-Capacity Optical Communications

Phase noise reduction when using a polarization camera for speckle interferometry

This work proposes a photonics-aided W-band integrated sensing and communication (ISAC) system using photonics-aided frequency multiplication to suppress phase noise. Conventional dual-laser architectures suffer from phase noise accumulation, degrading both communication reliability and sensing resolution. To address this, we integrate photonics-aided frequency multiplication with orthogonal frequency-division multiplexing (OFDM), enabling a unified signal structure that simultaneously encodes communication data and radar waveforms without redundant resource allocation. Theoretical analysis reveals phase noise cancellation through coherent beating of symmetrically filtered sidebands in the photodetector (PD). Results demonstrate concurrent delivery of probability shaping (PS)-256QAM OFDM signals with a symbol error rate below 4.2 × 10−2 and radar sensing with a 13.6 dB peak-to-sidelobe ratio (PSLR). Under a 1 MHz laser linewidth, the system achieves a 3.2 dB PSLR improvement over conventional methods, validating its potential for high-performance ISAC in beyond-5G networks.

Integrating quantum key distribution (QKD) with classical data transmission over the same fiber is crucial for scalable quantum-secured communication. However, noise from classical channels limits QKD distance. We demonstrate the longest-distance continuous-variable QKD (CV-QKD) over 120km (20dB loss) in the asymptotic regime, and over 100km (17dB loss) in the finite-size regime, both coexisting with a fully populated coarse wavelength division multiplexing system. Natural mode filtering of the local oscillator and phase noise mitigation enabled this without additional filtering or wavelength reallocation. Benchmarking against a commercial discrete-variable QKD system and considering finite-size effects confirms the feasibility of CV-QKD as a plug-and-play solution for typical 80-100km long-haul optical networks. Our results set a record fiber distance for CV-QKD, showing its potential for cost-effective, large-scale deployment in existing network infrastructure.

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.

Mode locking is an essential process through which resonant modes achieve stable synchronization via nonlinear interactions. This self-organization allows photonic and electronic sources to produce pulsed waveforms and is vital for applications in ultrafast and high-field optics as well as frequency comb generation. Here, we report a mechanism to include photon-electron-phonon interactions, demonstrating the excitation of mode-locked optomechanical microcombs in a graphene-deposited silica microresonator, determined by the synergy of optomechanical back action and graphene saturable absorption. The circulating optical field induces mechanical oscillations that modulate the light wave, while Pauli blocking in graphene locks a single optomechanical mode, forming a localized coherent optical wave packet within a single microcavity. In addition, using frequency division techniques, the mode-locked optomechanical microcomb achieves repetition stability with phase noise reduced to −110.5 decibels relative to the carrier per hertz at a 1-hertz offset and an Allan deviation as low as 3 × 10−12 @ 20 seconds, comparable to a standard rubidium clock.

Abstract Strong coupling between quasiparticles enables breakthroughs in quantum technologies. Surface acoustic waves (SAWs), carrying coherent gigahertz‐frequency phonons, provide a platform to achieve strong coupling between SAW phonons and quasiparticles like magnons. SAWs devices also utilize the delta‐E or delta‐G effect for magnetic field sensing, achieving an ultra‐low limit of detection (LoD) down to tens of picotesla. Concomitant disadvantages include unidirectional response, millimeter size, complex structure, and fabrication still remain. The strong magnon‐phonon coupling has great potential to overcome these challenges for weak magnetic detection. Here, an ultra‐compact and highly sensitive SAW magnetic field sensor based on a strongly coupled magnon‐phonon system is demonstrated, featuring a thin FeGaB film embedded in an acoustic cavity. In the strong coupling regime, the SAW frequency exhibits anti‐crossing and responds dramatically to external magnetic fields, enabling high sensitivities. Notably, within the anti‐crossing region, a frequency sensitivity of 600 kHz/Oe and a phase sensitivity of 44 °/Oe are achieved. Combined with phase noise evaluation, the LoD is determined to be 126 pT/Hz0.5 @ 10 Hz and 27 pT/Hz0.5 @ 100 Hz. Besides its fundamental significance for hybrid quasiparticles, this work proposes a brand‐new sensing mechanism for developing miniaturized, highly sensitive, and low‐LoD SAW magnetic field sensors.