Mengjie Yu

Optomechanical transduction harnesses the interaction between optical fields and mechanical motion to achieve sensitive measurement of weak mechanical quantities with inherently low noise. Lithium niobate combines low optical loss, strong piezoelectricity, a high intrinsic f × Q _m factor, and low thermal conductivity, making it promising for exploring optomechanical platforms targeting thermal sensing applications. Here, we demonstrate an integrated optomechanical platform on thin-film lithium niobate with precisely engineered optical, mechanical, and thermal fields within a compact 40 μm-diameter footprint. The platform integrates suspended microring resonators with ultrathin central membranes, reducing effective mass and thermal capacitance while maintaining a high intrinsic optical quality factor Q _o of 10 ⁶ and a mechanical quality factor Q _m of 1117, which increases to 5.1 × 10 ⁴ upon optomechanical oscillation. The two-step etching suppresses thermal dissipation into the silicon substrate and enhances thermal sensitivity, achieving a temperature coefficient of frequency of −124 ppm K ⁻¹ , a measurable loaded thermal response time of 7.2 μs, and a noise-equivalent power of 6.2 nW Hz ^−1/2 at 10 kHz and room temperature. This compact and scalable platform opens new opportunities for high-sensitivity thermal sensing and power detection and supports heterogeneous integration with infrared absorbers for uncooled infrared detection, thereby paving the way toward large-format infrared sensing arrays with low-noise, all-optical readout.

Coherent conversion between microwave and optical fields underpins technologies ranging from high data-rate optical communications and photonic computing to precision sensing, frequency metrology, and emerging quantum networks that link superconducting quantum processors over optical fiber. Non resonant electro-optic (EO) modulation provides a deterministic, broadband, chip-scale route to such conversion, coherently bridging microwave signals in the gigahertz domain with optical fields at hundreds of terahertz for signal transduction and coherent frequency comb generation. However, compared with all-optical nonlinear interactions, the inherently weak EO interaction demands substantially long effective interaction lengths for efficient conversion, placing stringent requirements on microwave attenuation, phase matching, and optical propagation loss to maintain coherent phase accumulation. Here, we overcome these challenges by extending coherent traveling-wave EO interactions to unprecedented lengths on ultralow-loss thin-film lithium niobate EO circuits. Our 9 cm traveling-wave modulators achieve sub-volt half-wave voltages up to 23 GHz and below 1.5 V up to 38 GHz. Cascaded and folded recycling architectures extend the EO interaction length to 36 cm within a 2.4 cm2 footprint, enabling a phase-modulation depth of 86.6π and 32% comb efficiency. The resulting cavity-free EO comb comprises more than 550 lines within a 52 nm (6.5 THz) 10-dB bandwidth at an 11.78 GHz line spacing, with a single comb spectrum extending across the S-, C-, and L-bands. In a complementary 30.7 GHz-drive architecture, an optical loss per modulation depth as low as 0.02 dB/π enables 187 mW of comb power with 77% pump-to-comb conversion efficiency, while wavelength multiplexed operation further extends the accessible coherent bandwidth to over 23 THz. Together, these results establish a scalable traveling-wave architecture for extending coherent microwave optical interaction toward the meter scale, opening new regimes of EO transduction, frequency synthesis, and quantum networking.

The mid-infrared (MIR) spectral regime is central to applications including remote sensing, precision spectroscopy, higher harmonic generation, and free-space optical communication. However, coherent and broadband MIR modulation remains challenging owing to high optical loss, limited bandwidth, and large drive voltages in existing platforms. Here, we overcome the challenges by deploying a suspended thin-film lithium-niobate (TFLN) based electro-optic (EO) platform co-designed with high-performance traveling-wave microwave (MW) electrodes. We demonstrate a record-low V _{π , D C} of 2.3 to 4.3 V over a broadband MIR bandwidth from 2.4 to 3.6 μm, and a 2.3-dB EO bandwidth of 40 GHz (extracted 3-dB bandwidth of 52 GHz), yielding a figure-of-merit of 19.3 GHz/V–more than an order of magnitude higher than the state-of-the-art. We demonstrate, for the first time, high-frequency V _{π , M W} of 4.5-6.5 V in the 27-34 GHz range, and frequency-agile MIR EO frequency comb generation with a 10-dB optical bandwidth over 0.8 THz using a suspended phase modulator of 4-cm active modulation length. We further validate the platform in a free-space optical communication link. Our results establish a monolithic MIR photonic platform capable of powerful EO modulation and spectral synthesis, and present a significant step towards reconfigurable MIR sensing and communication systems on chip.

Quantum noise limits the sensitivity of optical measurements, but squeezed states of light enable quantum-enhanced metrology, sensing, and information processing. Most on-chip squeezed-light sources rely on Kerr (χ(3)) nonlinearities, remain limited by pump power and excess loss constraints. Quadratic (χ(2)) platforms instead provide stronger parametric interactions, lower pump power requirements, and greater spectral engineering flexibility. Here, we demonstrate strong, broadband squeezed-light generation on a thin-film lithium niobate (TFLN) photonic chip using a dual-resonant optical parametric amplifier implemented in a single periodically poled LN (PPLN) microresonator. Near-full-depth domain inversion is achieved simultaneously with highly over-coupled resonances, exhibiting escape efficiencies exceeding 90% and intrinsic quality factors above 2.5 million in a 0.6mm2 X-cut TF-PPLN resonator, enabling efficient squeezing at 1587nm when pumped at 793.5 nm. Operating in the continuous-wave regime, we directly measure −0.81 dB of squeezing below the shot-noise limit with a pump power of 27mW, together with +4.29 dB of anti-squeezing. From these measurements, we infer an on-chip squeezing level of −7.52 dB±0.22 dB (95% confidence interval: [−7.96,−7.10] dB), and an on-chip anti-squeezing level of +9.62 dB±0.25 dB . We demonstrate single-mode squeezing at degeneracy with a squeezed-light spectrum exceeding 10.3 THz. This work reports the highest squeezing ratio among integrated χ(2) cavity platforms and the first quasi-phase matched, fully resonant χ(2) cavity squeezer on chip, establishing a scalable route to fully integrated power-efficient squeezed-light sources for quantum-enhanced sensing and metrology.

The ability to process and act on data in real time is increasingly critical for applications ranging from autonomous vehicles, three-dimensional environmental sensing, and remote robotics. However, the deployment of deep neural networks (DNNs) in edge devices is hindered by the lack of energy-efficient scalable computing hardware. Here, we introduce a fanout spatial time-of-flight optical neural network (FAST-ONN) that calculates billions of convolutions per second with ultralow latency and power consumption. This is enabled by the combination of high-speed dense arrays of vertical-cavity surface-emitting lasers (VCSELs) for input modulation with spatial light modulators of high pixel counts for in-memory weighting. In a three-dimensional optical system, parallel differential readout allows signed weight values for accurate inference in a single shot. The performance is benchmarked with feature extraction in You-Only-Look-Once (YOLO) for convolution at 100 million frames per second (MFPS), and in-system backward propagation training with photonic reprogrammability. The VCSEL transmitters are implementable in any free-space optical computing systems to improve the clockrate to over gigahertz, where the high scalability in device counts and channel parallelism enables a new avenue to scale up free space computing hardware.

Modern problems in high-performance computing, ranging from training and inferencing deep learning models in computer vision and language models to simulating complex physical systems with nonlinearly-coupled equations, require exponential growth of computational resources. Photonic analog systems are emerging with solutions of intrinsic parallelism, high bandwidth, and low propagation loss. However, their application has been hindered by the low analog accuracy due to the electro-optic distortion, material nonlinearities, and signal-to-noise ratios. Here we overcome this barrier with a quantization-aware digital-photonic mixed-precision framework across chiplets for accelerated AI processing and physical simulation. Using Lithium Niobate photonics with channel equalization techniques, we demonstrate linear multiplication (9-bit amplitude-phase decoupling) in homodyne optical logics with 6-bit precision at the clock rate of 128 giga-symbol-per-second (128 GS/s), enabling AI processing with 6 ns latency. Codesign hardware-algorithms, including iterative solvers, sparse-dense quantization, and bit-sliced matrix multiplication, explore photonic amplitude and phase coherence for complex-valued, physics-inspired computation. In electromagnetic problems, our approach yields 12-bit solutions for partial differential equations (PDEs) in scattering problems that would conventionally require up to 32-bit and often even 64-bit precision. These results preserve digital-level fidelity while leveraging the high-speed low-energy photonic hardware, establishing a pathway toward general-purpose optical acceleration for generative artificial intelligence, real-time robotics, and accurate simulation for climate challenges and biological discoveries.

The mid-infrared (MIR) spectral regime is central to applications including remote sensing, precision spectroscopy, higher harmonic generation, and free-space optical communication. However, coherent and broadband MIR modulation remains challenging owing to high optical loss, limited bandwidth, and large drive voltages in existing platforms. Here, we overcome these challenges by deploying a suspended thin-film lithium-niobate (TFLN) based electro-optic (EO) platform co-designed with high-performance traveling-wave microwave (MW) electrodes. We demonstrate a record-low Vpi,DC of 2.3 to 4.3 V over a broadband MIR bandwidth from 2.4 to 3.6 um, and a 2.7 dB EO bandwidth of 40 GHz (extracted 3 dB bandwidth of 50 GHz), yielding a figure of merit of 17.4 GHz/V, more than an order of magnitude higher than the state of the art. We demonstrate, for the first time, high-frequency Vpi,MW of 4.5 to 6.5 V in the 25 to 35 GHz range, and frequency-agile MIR EO frequency comb generation with a 10 dB optical bandwidth over 0.8 THz using a suspended phase modulator of 4 cm active modulation length. We further validate the platform in a free-space optical communication link. Our results establish a monolithic MIR photonic platform capable of powerful EO modulation and spectral synthesis, and represent a significant step toward reconfigurable MIR sensing and communication systems on chip.

The mid-infrared (MIR) spectral region is central to sensing, spectroscopy, and free-space optical communication, yet coherent and broadband electro-optic (EO) control remains limited by material loss, bandwidth constraints, and high switching voltages. Existing approaches based on quantum cascade laser modulation, nonlinear frequency conversion, or bulk EO devices suffer from fundamental trade-offs between efficiency, bandwidth, and scalability. Here we report a suspended thin-film lithium niobate (TFLN) MIR EO platform co-designed with velocity- and impedance-matched traveling-wave microwave electrodes. We achieve record-low half-wave voltages of 2.3–4.3 V across 2.4–3.6 μm and EO bandwidths up to 50 GHz, corresponding to a record voltage-bandwidth figure-of-merit of 17.4 GHz/V. High-frequency operation with 4.5–6.5 V is demonstrated at 25–35 GHz, together with 30-GHz-line-spacing MIR EO frequency comb generation spanning 0.8 THz. We further validate the platform in a free-space communication link, establishing a scalable high-performance MIR optoelectronic platform.

Optomechanical transduction harnesses the interaction between optical fields and mechanical motion to achieve sensitive measurement of weak mechanical quantities with inherently low noise. Lithium niobate combines low optical loss, strong piezoelectricity, high intrinsic f × Q_m factor, and low thermal conductivity, making it promising for exploring optomechanical platforms targeting thermal sensing applications. Here, we developed an integrated optomechanical platform on thin-film lithium niobate with precisely engineered optical, mechanical, and thermal fields within a compact 40 μm × 40 μm footprint. The platform integrates suspended microring resonators with ultrathin central membranes, reducing mechanical stiffness and effective mass while maintaining a high optical factor Qo of 10^6 and mechanical quality factor Qm of 1117, which increases to 5.1 × 10^4 after oscillation. The design suppresses thermal dissipation into the silicon substrate and enhances thermal sensitivity, achieving a temperature coefficient of frequency of −124 ppm/K and a noise-equivalent power of 6.2 nW/√Hz at 10 kHz at room temperature. This compact and scalable platform opens new opportunities for high-sensitivity thermal sensing, supports heterogeneous integration with infrared absorbers for uncooled infrared detection, and enables fully integrated, all-optical on-chip readout, paving the way toward large-format, low-noise infrared sensing arrays.