arXiv subjects

Linbo Shao

Publications and source records attributed to Linbo Shao.

At least 19 recordsLinked to original sources

arXiv2026

Motional-Current-Sensing Method and Simplified Closed-Loop Control Strategy for Piezoelectric-Resonator-based DC-DC Converters

Piezoelectric resonators (PRs) have been seen as a competitive alternative to magnetic components. In PR-based converters, the motional current (in the LC series branch of the equivalent circuit) is vital for control proposes but cannot be measured directly. The difficulties to detect the zero-crossing points or to measure the amplitude of the motional current has been one of the most dominating obstacles that complicates the control strategies and limits the frequency range of the PR-based converters. This work discusses a ring-dot shaped piezoelectric transformer (PT) based motional current sensing method that provides current information with low-delay, low-loss and intrinsic isolation. It is physically proven that the proposed method is robust with various non-ideal factors of the piezoceramic and circuit implementation. Based on this, an event-driven control strategy is introduced, consisting of only a finite state machine, a PI loop, a low-speed ADC and several comparators. Experiments on a step-down PR-based converter verify that the proposed approach realize ZVS for all transitions within a switching cycle with reduced hardware and software resources, enhances stability and is capable of self-startup.

physics.app-ph↗

arXiv2026

Nonlinear exceptional points in an integrated acoustic-wave oscillator for longwave infrared sensing

Exceptional points (EP) featuring enhanced responsivity and rich dynamics have attracted extensive attentions in device developments and sensing applications. However, it remains debated whether employing EP systems is beneficial in practical sensing applications. Here, we demonstrate that a nonlinear EP in our microwave-frequency acoustic-wave oscillator improves longwave infrared (LWIR) detection under practical conditions. By phase tuning the nonlinear gain, our detector can be operated at different conditions with respect to the nonlinear EP. Compared with operation away from EP, our detector at EP shows a 33-fold improvement in responsivity and an 8.75-fold extension of 3-dB bandwidth. We observe a 6-fold enhancement in signal-to-noise ratio at an input modulation frequency of 6.2 kHz. At the incident LWIR wavelength of 9.6 um, our detector at EP exhibits a noise equivalent power (NEP) of 310 pW*Hz^-1/2 at input frequency of 10 kHz, yielding a figure of merit, product of NEP and time constant, of 9.87*10^-3 pW*Hz^-3/2, a 10-fold improvement over operation away from EP. Our integrated acoustic devices offer a versatile platform for exploring noise dynamics and developing practical sensors that exploit non-Hermitian nonlinearities.

physics.optics↗

arXiv2026

Magnet-Free Nonreciprocal frequency conversion using Sequential Temporal modulation: Theory and Simulations

Nonreciprocal conversion is essential for protecting sources and enabling unidirectional signal routing in photonic, phononic, electronics, and quantum systems, yet conventional implementations rely on magnetic bias that could be challenging to integrate on chip. We propose a magnet-free scheme for frequency-domain nonreciprocity based on sequential, time-gated couplings in a three-mode system. By activating interactions in a fixed temporal order, the forward and reverse frequency conversion pathways acquire unequal dwell times in a lossy intermediate mode, producing strong nonreciprocity without requiring nonlinearities or magnetic materials. Using a harmonic-balance formulation and a Dyson-Born expansion, we derive a compact analytical expression for the isolation ratio that reveals the roles of Floquet sidebands, duty-cycle control, modulation frequency, and dissipation. The results are confirmed by direct time-domain simulations over a wide parameter range. From these results, we extract practical design rules for optimizing isolation through temporal sequencing, loss engineering, and modulation timing. The framework is general and directly applicable to integrated platforms in photonics, phononics, microwave electronics, and superconducting circuits.

physics.app-ph↗

arXiv2026

Low-loss phononic integrated circuits based on a silicon nitride-lithium niobate platform

Microwave-frequency acoustic waves in solids have emerged as a versatile platform for both classical and quantum applications. While phononic integrated devices and circuits are being developed on various material platforms, an ideal phononic integrated circuit (PnIC) platform should simultaneously support low-loss waveguide structures, high-quality-factor resonators, high-performance modulators, and efficient electromechanical transducers. Here, we establish a low-loss gigahertz-frequency PnIC platform based on patterned thin-film silicon nitride (SiN) on lithium niobate (LN) substrate. We develop low-loss PnIC building blocks including waveguides, directional couplers, and high-quality-factor (high-Q) ring resonators. As an application, we demonstrate a 1-GHz phononic oscillator based on a ring resonator, reaching a low phase noise of -159.0 dBc/Hz at a 100-kHz offset frequency. Our low-loss PnICs could meet the requirements in microwave acoustics, quantum phononics, and integrated hybrid systems combining phonons, photons, superconducting qubits, and solid-state defects.

physics.app-ph↗

arXiv2026

Resonance-enhanced integrated acousto-optic beam steering

Optical beam steering is a key technology for free-space optical communication, sensing, and imaging. Mechanical beam steering systems suffer from limited scanning speed and bulky form factors, while existing solid-state solutions rely on pixelated synthetic aperture that requires complex fabrication and control architectures. Integrated acousto-optic beam steering (AOBS) is an emerging technology that enables continuous one-dimensional beam steering using integrated acoustic transducers and fixed-wavelength laser sources. Here, we integrate AOBS with an optical ring resonator on the same thin-film lithium niobate (TFLN) platform to significantly enhance beam steering efficiency and system functionality. The resulting device achieves a resonance-enhanced beam steering efficiency of up to $26\%$ and a field of view of $18^\circ$. Moreover, by leveraging integrated electro-optic control, we dynamically lock the ring-resonator's resonance to a chirped laser frequency, enabling frequency-modulated continuous-wave (FMCW) LiDAR operation. By combining lithium niobate's piezoelectric and electro-optic properties, this work establishes a compact, efficient, and scalable beam-steering platform with co-integrated acousto-optic modulation and electro-optic control for multifunctional applications.

physics.app-ph↗

arXiv2025

Microwave-acoustic-based isolated gate driver for power electronics

Electrical isolation is critical to ensure safety and minimize electromagnetic interference (EMI), yet existing methods struggle to simultaneously transmit power and signals through a unified channel. Here we demonstrate a mechanically-isolated gate driver based on microwave-frequency surface acoustic wave (SAW) device on lithium niobate that achieves galvanic isolation of 2.75 kV with ultralow isolation capacitance (0.032 pF) over 1.25 mm mechanical propagation length, delivering 13.4 V open-circuit voltage and 44.4 mA short-circuit current. We demonstrate isolated gate driving for a gallium nitride (GaN) high-electron-mobility transistor, achieving a turn-on time of 108.8 ns comparable to commercial drivers and validate its operation in a buck converter. In addition, our SAW device operates over an ultrawide temperature range from 0.5 K (-272.6 {\deg}C) to 544 K (271 {\deg}C). The microwave-frequency SAW devices offer inherent EMI immunity and potential for heterogeneous integration on multiple semiconductor platforms, enabling compact, high-performance isolated power and signal transmission in advanced power electronics.

eess.SY↗

arXiv2025

On-chip cavity electro-acoustics using lithium niobate phononic crystal resonators

Mechanical systems are pivotal in quantum technologies because of their long coherent time and versatile coupling to qubit systems. So far, the coherent and dynamic control of gigahertz-frequency mechanical modes mostly relies on optomechanical coupling and piezoelectric coupling to superconducting qubits. Here, we demonstrate on-chip cavity electro-acoustic dynamics using our microwave-frequency electrically-modulated phononic-crystal (PnC) resonators on lithium niobate (LN). Leveraging the high dispersion of PnC, our phononic modes space unevenly in the frequency spectrum, emulating atomic energy levels. Atomic-like transitions between different phononic modes are achieved by applying electrical fields to modulate phononic modes via nonlinear piezoelectricity of LN. Among two modes, we demonstrate Autler-Townes splitting (ATS), alternating current (a.c.) Stark shift, and Rabi oscillation with a maximum cooperativity of 4.18. Extending to three modes, we achieve non-reciprocal frequency conversions with an isolation up to 20 dB. Nonreciprocity can be tuned by the time delay between the two modulating pulses. Our cavity electro-acoustic platform could find broad applications in sensing, microwave signal processing, phononic computing, and quantum acoustics.

cond-mat.mes-hall↗

arXiv2025

Injection locking of GHz-frequency surface acoustic wave phononic crystal oscillator

Low-noise gigahertz (GHz) frequencies sources are essential for applications in signal processing, sensing, and telecommunications. Surface acoustic wave (SAW) resonator-based oscillators offer compact form factors and low phase noise due to their short mechanical wavelengths and high quality (Q) factors. However, their small footprint makes them vulnerable to environmental variation, resulting in their poor long-term frequency stability. Injection locking is widely used to suppress frequency drift of lasers and oscillators by synchronizing to an ultra-stable reference. Here, we demonstrate injection locking of a 1-GHz SAW phononic crystal oscillator, achieving 40-dB phase noise reduction at low offset frequencies and unperturbed low noise at large offset frequencies. Compared to a free-running SAW oscillator, which typically exhibits frequency drifts of several hundred hertz over minutes, the injection-locked oscillator reduces the frequency deviation to below 0.35 Hz. We also investigate the locking range and oscillator dynamics in the injection pulling region. The demonstrated injection-locked SAW oscillator could find applications in high-performance portable telecommunications and sensing systems.

physics.app-ph↗

arXiv2025

Room-temperature mid-infrared detection using metasurface-absorber-integrated phononic crystal oscillator

Mid-infrared (MIR) detectors find extensive applications in chemical sensing, spectroscopy, communications, biomedical diagnosis and space explorations. Alternative to semiconductor MIR photodiodes and bolometers, mechanical-resonator-based MIR detectors show advantages in higher sensitivity and lower noise at room temperature, especially towards longer wavelength infrared. Here, we demonstrate uncooled room-temperature MIR detectors based on lithium niobate surface acoustic wave phononic crystal (PnC) resonators integrated with wavelength-and-polarization-selective metasurface absorber arrays. The detection is based on the resonant frequency shift induced by the local temperature change due to MIR absorptions. The PnC resonator is configured in an oscillating mode, enabling active readout and low frequency noise. Compared with detectors based on tethered thin-film mechanical resonators, our non-suspended, fully supported PnC resonators offer lower noise, faster thermal response, and robustness in both fabrication and practical applications. Our 1-GHz oscillator-based MIR detector shows a relative frequency deviation of $5.24 \times 10^{-10}$ Hz$^{-1/2}$ at an integration time of 50 ${\mu}$s, leading to an incident noise equivalent power of 197 pW/$\sqrt{\mathrm{Hz}}$ when input 6-${\mu}$m MIR light is modulated at 1.8 kHz, and a large dynamic range of 107 in incident MIR power. Our device architecture is compatible with the scalable manufacturing process and can be readily extended to a broader spectral range by tailoring the absorbing wavelengths of metasurface absorbers.

physics.optics↗

arXiv2024

Optical multi-beam steering and communication using integrated acousto-optics arrays

Optical beam steering enables optical detection and imaging in macroscopic or microscopic scales and long-range communication over free space. It underpins numerous optical applications, including LiDAR, biomedical imaging, and remote sensing. Despite the inherent speed of light, advanced applications increasingly require the ability to steer multiple beams simultaneously to increase imaging throughput, boost communication bandwidth, and control arrays qubits for scalable quantum computing. Therefore, there is a significant demand for non-mechanical, integrated, and scalable multi-beam steering technology. Here, we report a scalable multi-beam steering system comprising an array of acousto-optic beam steering channels and photonic integrated circuits on a thin-film lithium niobate platform. Each channel generates tens of individually controllable beams of visible wavelength by exciting acoustic waves using digitally synthesized multi-tone microwave signals. We demonstrate the system's capabilities through multi-input, multi-output free-space communications, simultaneously transmitting to multiple receivers at megabits/sec data rates. This technology can be readily scaled up to steer hundreds of optical beams from a compact chip, potentially advancing many areas of optical technologies and enabling novel applications.

physics.optics↗

arXiv2024

Low-phase-noise surface-acoustic-wave oscillator using an edge mode of a phononic band gap

Low-phase-noise microwave-frequency integrated oscillators provide compact solutions for various applications in signal processing, communications, and sensing. Surface acoustic waves (SAW), featuring orders-of-magnitude shorter wavelength than electromagnetic waves at the same frequency, enable integrated microwave-frequency systems with much smaller footprint on chip. SAW devices also allow higher quality (Q) factors than electronic components at room temperature. Here, we demonstrate a low-phase-noise gigahertz-frequency SAW oscillator on 128{\deg}Y-cut lithium niobate, where the SAW resonator occupies a footprint of 0.05 mm$^2$. Leveraging phononic crystal bandgap-edge modes to balance between Q factors and insertion losses, our 1-GHz SAW oscillator features a low phase noise of -132.5 dBc/Hz at a 10 kHz offset frequency and an overlapping Hadamard deviation of $6.5\times10^{-10}$ at an analysis time of 64 ms. The SAW resonator-based oscillator holds high potential in developing low-noise sensors and acousto-optic integrated circuits.

physics.app-ph↗

arXiv2024

Frequency-domain Parallel Computing Using Single On-Chip Nonlinear Acoustic-wave Device

Multiply-accumulation (MAC) is a crucial computing operation in signal processing, numerical simulations, and machine learning. This work presents a scalable, programmable, frequency-domain parallel computing leveraging gigahertz (GHz)-frequency acoustic-wave nonlinearities. By encoding data in the frequency domain, a single nonlinear acoustic-wave device can perform a billion arithmetic operations simultaneously. A single device with a footprint of 0.03 mm$^2$ on lithium niobate (LN) achieves 0.0144 tera floating-point operations per second (TFLOPS), leading to a computing area density of 0.48 TFLOPS/mm$^2$ and a core power efficiency of 0.14 TFLOPS/Watt. As applications, we demonstrate multiplications of two 16-by-16 matrices and convolutional imaging processing of 128-by-128-pixel photos. Our technology could find versatile applications in near-sensor signal processing and edge computing.

physics.app-ph↗

arXiv2023

Integrated Phononic Waveguides in Diamond

Efficient generation, guiding, and detection of phonons, or mechanical vibrations, are of interest in various fields including radio frequency communication, sensing, and quantum information. Diamond is an important platform for phononics because of the presence of strain-sensitive spin qubits, and its high Young's modulus which allows for low-loss gigahertz devices. We demonstrate a diamond phononic waveguide platform for generating, guiding, and detecting gigahertz-frequency surface acoustic wave (SAW) phonons. We generate SAWs using interdigital transducers integrated on AlN/diamond and observe SAW transmission at 4-5 GHz through both ridge and suspended waveguides, with wavelength-scale cross sections (~1 {\mu}m2) to maximize spin-phonon interaction. This work is a crucial step for developing acoustic components for quantum phononic circuits with strain-sensitive color centers in diamond.

physics.app-ph↗

arXiv2022

Integrated Electro-Optic Isolator on Thin Film Lithium Niobate

Optical isolator is an indispensable component of almost any optical system and is used to protect a laser from unwanted reflections for phase-stable coherent operation. The development of chip-scale optical systems, powered by semiconductor lasers integrated on the same chip, has resulted in a need for a fully integrated optical isolator. However, conventional approaches based on application of magneto-optic materials to break the reciprocity and provide required isolation have significant challenges in terms of material processing and insertion loss. As a result, many magnetic-free approaches have been explored, including acousto-optics, optical nonlinearity, and electro-optics. However, to date, the realization of an integrated isolator with low insertion loss, high isolation ratio, broad bandwidth, and low power consumption on a monolithic material platform is still absent. Here we realize non-reciprocal traveling-wave EO-based isolator on thin-film LN, enabling maximum optical isolation of 48 dB and an on-chip insertion loss of 0.5 dB using a single-frequency microwave drive at 21-dBm RF power. The isolation ratio is verified to be larger than 37 dB across a tunable optical wavelength range from 1510 to 1630 nm. We verify that our hybrid DFB laser - LN isolator module successfully protects the single-mode operation and the linewidth of the DFB laser from reflection. Our result is a significant step towards a practical high-performance optical isolator on chip.

physics.optics↗

arXiv2022

Systematic Investigation of Millimeter-Wave Optic Modulation Performance in Thin-Film Lithium Niobate

Millimeter-wave (mmWave) band (30 - 300 GHz) is an emerging spectrum range for wireless communication, short-range radar and sensor applications. mmWave-optic modulators that could efficiently convert mmWave signals into optical domain are crucial components for long-haul transmission of mmWave signals through optical networks. At these ultrahigh frequencies, however, the modulation performances are highly sensitive to the transmission line loss as well as the velocity- and impedance-matching conditions, while precise measurements and modeling of these parameters are often non-trivial. Here we present a systematic investigation of the mmWave-optic modulation performances of thin-film lithium niobate modulators through theoretical modeling, electrical verifications and electro-optic measurements at frequencies up to 325 GHz. Based on our experimentally verified model, we demonstrate thin-film lithium niobate mmWave-optic modulators with a measured 3-dB electro-optic bandwidth of 170 GHz and a 6-dB bandwidth of 295 GHz. The device also shows a low RF half-wave voltage of 7.3 V measured at an ultrahigh modulation frequency of 250 GHz. This work provides a comprehensive guideline for the design and characterization of mmWave-optic modulators and paves the way toward future integrated mmWave photonic systems for beyond-5G communication and radar applications.

physics.optics↗

arXiv2022

Thermal Modulation of Gigahertz Surface Acoustic Waves on Lithium Niobate

Surface acoustic wave (SAW) devices have wide range of applications in microwave signal processing. Microwave SAW components benefit from higher quality factors and much smaller crosstalk when compared to their electromagnetic counterparts. Efficient routing and modulation of SAWs are essential for building large-scale and versatile acoustic-wave circuits. Here, we demonstrate integrated thermo-acoustic modulators using two SAW platforms: bulk lithium niobate and thin-film lithium niobate on sapphire. In both approaches, the gigahertz-frequency SAWs are routed by integrated acoustic waveguides while on-chip microheaters are used to locally change the temperature and thus control the phase of SAW. Using this approach, we achieved phase changes of over 720 degrees with the responsibility of 2.6 deg/mW for bulk lithium niobate and 0.52 deg/mW for lithium niobate on sapphire. Furthermore, we demonstrated amplitude modulation of SAWs using acoustic Mach Zehnder interferometers. Our thermo-acoustic modulators can enable reconfigurable acoustic signal processing for next generation wireless communications and microwave systems.

physics.app-ph↗

arXiv2021

Spectral control of nonclassical light using an integrated thin-film lithium niobate modulator

Manipulating the frequency and bandwidth of nonclassical light is essential for implementing frequency-encoded/multiplexed quantum computation, communication, and networking protocols, and for bridging spectral mismatch among various quantum systems. However, quantum spectral control requires a strong nonlinearity mediated by light, microwave, or acoustics, which is challenging to realize with high efficiency, low noise, and on an integrated chip. Here, we demonstrate both frequency shifting and bandwidth compression of nonclassical light using an integrated thin-film lithium niobate (TFLN) phase modulator. We achieve record-high electro-optic frequency shearing of telecom single photons over terahertz range ($\pm$ 641 GHz or $\pm$ 5.2 nm), enabling high visibility quantum interference between frequency-nondegenerate photon pairs. We further operate the modulator as a time lens and demonstrate over eighteen-fold (6.55 nm to 0.35 nm) bandwidth compression of single photons. Our results showcase the viability and promise of on-chip quantum spectral control for scalable photonic quantum information processing.

physics.optics↗

arXiv2021

Femtosecond Pulse Generation via an Integrated Electro-Optic Time Lens

Integrated femtosecond pulse and frequency comb sources are critical components for a wide range of applications. The leading approaches for on-chip pulse generation rely on mode locking inside microresonator with either third-order nonlinearity or with semiconductor gain. These approaches, however, are limited in noise performance, wavelength tunability and repetition rates. Alternatively, sub-picosecond pulses can be synthesized without mode-locking, by modulating a continuous-wave (CW) single-frequency laser using a cascade of electro-optic (EO) modulators. This method is particularly attractive due to its simplicity, robustness, and frequency-agility but has been realized only on a tabletop using multiple discrete EO modulators and requiring optical amplifiers (to overcome large insertion losses), microwave amplifiers, and phase shifters. Here we demonstrate a chip-scale femtosecond pulse source implemented on an integrated lithium niobate (LN) photonic platform18, using cascaded low-loss electro-optic amplitude and phase modulators and chirped Bragg grating, forming a time-lens system. The device is driven by a CW distributed feedback (DFB) chip laser and controlled by a single CW microwave source without the need for any stabilization or locking. We measure femtosecond pulse trains (520 fs duration) with a 30-GHz repetition rate, flat-top optical spectra with a 10-dB optical bandwidth of 12.6 nm, individual comb-line powers above 0.1 milliwatt, and pulse energies of 0.54 picojoule. Our results represent a tunable, robust and low-cost integrated pulsed light source with CW-to-pulse conversion efficiencies an order of magnitude higher than achieved with previous integrated sources. Our pulse generator can find applications from ultrafast optical measurement to networks of distributed quantum computers.

physics.optics↗