High-frequency ultrasound imaging, due to its penetrability and micrometer-level resolution, is a critical modality for nondestructive testing (NDT) of integrated circuit (IC) packaging. However, the substantial acoustic impedance mismatch between the coupling medium (water) and the silicon substrate creates a severe measurement bottleneck: strong surface reflections drastically reduce the energy transmitted into the chip, degrading the signal-to-noise ratio (SNR) and resolution of internal interconnects. To overcome this physical limitation and enhance the measurement capability of scanning acoustic microscopy (SAM), we have designed a precise anti-reflection coating based on the theory of the evolution from electromagnetic transmission lines to acoustic transmission lines. By modeling the acoustic propagation path as an equivalent circuit, we designed and fabricated a three-layer composite structure (Parylene C/Au/Parylene C) specifically optimized for the particular frequency (70 MHz in this study). Experimental validation on commercial IC chips demonstrates that this "instrumentation conditioning" approach significantly improves signal integrity. Specifically, the coating yielded a 52% increase in the amplitude of internal echoes (from 142 to 216 mV). Furthermore, C-scan imaging revealed a 93% average improvement in the mean gradient of internal metal wires across multiple layers, enabling high-fidelity 3-D reconstruction of interconnection structures that were previously indistinguishable from noise. This method offers a robust, low-cost solution to the intrinsic attenuation problem in high-frequency acoustic measurement, significantly extending the detection depth and clarity for IC reliability analysis.

Crosstalk, a detrimental phenomenon in ultrasonic arrays, compromises resolution, penetration depth, and diagnostic reliability. This study examines the impact of kerf filling materials on crosstalk suppression and imaging performance via integrated numerical simulations and experimental validation. Two fillers with contrasting acoustic properties were evaluated: rigid epoxy resin (Epo-Tek 301) and soft silicone rubber (RTV-664). RTV-664, exhibiting lower acoustic impedance and higher attenuation, demonstrated reduced mechanical coupling between adjacent elements. To validate this, a 128-element linear array was designed and fabricated, with its electrical, transceiver, and crosstalk characteristics systematically assessed through finite element simulations, phantom experiments, and "in vivo" imaging. Results indicate that RTV-664 reduced crosstalk in first- to third-order adjacent elements by an average of 33.4% across the 4-8 MHz bandwidth, aligning with simulated predictions. Imaging tests further confirmed that RTV-664-based arrays achieved broader bandwidth, enhanced field uniformity, and superior image quality, including improved resolution, penetration depth, signal-to-noise ratio (SNR), and contrast-to-noise ratio (CNR). These findings underscore the critical role of kerf filling materials selection in crosstalk mitigation, offering theoretical insights and experimental evidence for optimizing ultrasonic array design toward high-performance medical imaging.

Ultrasonic attenuation affects the quality of ultrasonic imaging and material characterization significantly, especially at ultrahigh frequencies (>100 MHz), where higher attenuation brings about additional challenges. However, the reliable ultrasonic attenuation coefficients are scarce in this frequency range. In this study, we propose a method of measuring ultrasound attenuation coefficient at ultrahigh frequencies. By the spectral analysis of multiple ultrasonic echoes, the aggregate attenuation coefficient was extracted. Ultrasonic diffraction attenuation and transmission loss at the material interface are calibrated by using circular flat transducer acoustic fields and acoustic transmission line theory, respectively. The attenuation coefficient of silicon at approximately 150 MHz was measured to be 10.52 dB/cm. This article presents a novel approach for evaluating ultrasonic attenuation in the ultrahigh-frequency range, reducing experimental errors and equipment costs. The proposed methodology also contributes to the development and characterization of ultrahigh-frequency ultrasonic transducers.

The ultrahigh-frequency (UHF) ultrasonic transducers are widely used in the fields of biomedical microscopy and nondestructive testing. However, the operating frequency and electroacoustic conversion efficiency of UHF transducers have potential for further improvement. This work presents design, simulation, and fabrication of focused 300-MHz UHF ultrasonic transducers. The UHF ultrasonic transducers were designed and simulated by equivalent circuit model and finite element analysis. Furthermore, the effect of lens aperture and ultrasonic frequency on the distribution of sound field was studied. To improve their performance, the UHF ultrasonic transducers were fabricated by using lithium niobate (LiNbO3) piezoelectric material and quartz glass focal lens. As a result, the pulse-echo measurements show that the center frequencies of the echoes were 238.7, 119.8, and 73.1 MHz from the lens, near field, and the focal point, respectively. According to the axial sound pressure distribution of the focusing transducer and the echoes, the ultrasound attenuation in water was calculated of 1.74 (+/- 0.16) x 10-3 x f2 (dB/cm). In addition, the image of 10-mu m tungsten wire target illustrated that the lateral and axial resolutions of the UHF ultrasonic transducers were 28.9 and 31.4 mu m, respectively. This study highlights strategies for optimizing transducer performance and improving imaging resolution in scanning acoustic microscope (SAM) systems.

Ultra-high frequency (>100 MHz) acoustic waves feature biocompatibility and high sensitivity and allow biomedical imaging and acoustic tweezers. Primarily, excellent spatial resolution and broad bandwidth at ultra-high frequency is the goal for pathological research and cell selection at the cellular level. Here, we propose an efficient approach to visualize mouse brain atrophy by self-focused ultrasonic sensors at ultra-high frequency with ultra-broad bandwidth. The numerical models of geometry and theoretically predicted acoustic parameters for half-concave piezoelectric elements are calculated by the differential method, which agrees with measured results (lateral resolution: 24 μm, and bandwidth: 115% at –6 dB). Compared with the brain slices of 2-month-old mouse, the atrophy visualization of the 6-month-old mouse brain was realized by C-mode imaging with an acoustic microscopy system, which is a potential prospect for diagnosis and treatment of Alzheimer's disease (AD) combined with neuroscience. Meanwhile, the acoustic properties of the brain slices were quantitatively measured by the acoustic microscopy. These encouraging results demonstrate the promising application for high-resolution imaging in vitro biological tissue with ultra-high frequency self-focusing ultrasonic sensors.

Cardiovascular disease (CVD) is a kind of high life-threatening illness for humans. Intravascular ultrasound (IVUS) technology could highly help the physicians to know the condition of human's vessel wall. In this work, the novel lead zinc niobate-lead titanate (PZN-PT) single crystals-based IVUS transducers were prepared. The electrical properties of PZN-PT single crystals were investigated with high d33 of 2531 pC/N and dielectric constant. The high piezoelectric response could improve the transmission and receive properties of IVUS transducers. Moreover, the high dielectric constant (8050) could highly help the miniaturization of IVUS transducer. The IVUS transducers have a center frequency at 43.5 MHz and a -6dB bandwidth of 62.3%. It promising the PZN-PT based IVUS transducers are suitable for the clinical diagnosis field for CVD.

Acoustic microscopes and acoustic tweezers have great value in the application of microparticle manipulation, biomedical research and non-destructive testing. Ultrahigh frequency (UHF) ultrasonic transducers act as the key component in acoustic microscopes, and acoustic tweezers and acoustic lenses are essential parts of UHF ultrasonic transducers. Therefore, the preparation of acoustic lenses is crucial. Silicon is a suitable material for preparing acoustic lenses because of its high acoustic velocity, low acoustic attenuation and excellent machinability. In previous research, silicon lenses were mainly prepared by etching. However, etching has some drawbacks. The etching of large sizes is complex, time-consuming and expensive. Furthermore, vertical etching is preferred to spherical etching. Thus, a new method of ultra-precision machining was introduced to prepare silicon lenses. In this paper, silicon lenses with an aperture of 892 μm and a depth of 252 μm were prepared. Then, UHF ultrasonic transducers with a center frequency of 157 MHz and a −6-dB bandwidth of 52% were successfully prepared based on silicon lenses. The focal distance of the transducers was 736 μm and the F-number was about 0.82. The transducers had a lateral resolution of 11 μm and could distinguish the 13 μm slots on silicon wafers clearly.

The ultrahigh-frequency (UHF) ultrasonic transducers are active in various fields, including nondestructive evaluation in the semiconductor industry, microscopic biological organization imaging in biomedicine, particle manipulation, and so on. In these fields ultrahigh-frequency (UHF) ultrasonic transducers play a critical role in the performance of related equipment. This article will focus on the topic of ultrahigh-frequency ultrasonic transducers’ preparation, and reviews three aspects: material selection, focus design, and acoustic energy transmission matching. Provides a summary of the current research status, and puts forward some views on the future development of UHF ultrasound devices.

In order to effectively and flexibly control acoustic pattern, an efficient optimization design method of acoustic liquid lens (ALL) is developed by the frame of particle swarm optimization (PSO) algorithm. The ALL is composed of ethanol and dimethicone, and its parameters include ethanol concentration (EC), volume fraction of dimethicone (VFD), and total volume (TV). Based on the established finite element model and orthogonal design method, the data of acoustic pattern and ALL can be obtained by using COMSOL Multiphysics. Based on the simulation data, the neural network models are constructed to characterize the relationship between the parameters of ALL and the performance of acoustic pattern. The optimization design criteria of ALL are constructed based on the performance parameters of acoustic pattern, including focal distance (FD), transverse resolution (TR), and longitudinal resolution (LR). Based on the optimization criteria, the modified PSO algorithm is utilized to optimize the design parameters of ALL in the developed method. According to the desired FD, TR, and LR of acoustic pattern (20, 1, and 17 mm), the optimized EC, VFD, and TV of ALL are about 0.838, 0.165, and 164.4 [Formula: see text]. The performance parameters of acoustic pattern verified by simulation and experiments agree with the desired ones. In addition, using 6 MHz ultrasonic transducer with the optimized ALL, the ultrasonic imaging of tungsten wires and porcine eyeball further demonstrates the effectiveness and feasibility of the developed method.

An optimization design strategy based on finite element method (FEM) and particle swarm optimization (PSO) algorithm is developed to fabricate high-performance 1-3 piezocomposite ultrasonic transducer. In this strategy, the structure and performance of ultrasonic transducer are simulated by FEM based PZFlex software to analyze the effect of design parameters (ceramic volume fraction and kerf width) on its performance. Due to the time-consuming of FEM simulation, based on the data obtained by simulations, artificial neural network models are established to describe the mapping relation of the design parameters and performance parameters (center frequency and high electromechanical coupling coefficient). The multi-objective optimization criterion is constructed for ultrasonic transducer, and then the modified PSO algorithm are adopted to optimize design parameters. According to the optimized design parameters, the FEM simulation and experiment are conducted to validate the effectiveness of the developed strategy. The simulation and experiment results are in agreement with the designed performance, which indicates that the developed strategy can be used to optimize design parameters for fabricating high-performance ultrasonic transducer. In addition, the imaging experiments of tungsten wires and RMB coin prove the high imaging performance of the ultrasonic transducer fabricated by the developed strategy.

Although high-frequency (≥ 100 MHz) ultrasound has demonstrated its capability in a variety of applications, the fabrication of high frequency ultrasonic transducers with both high sensitivity and broad bandwidth remains challenging. One main reason is the mismatch of acoustic impedance between piezoelectric materials and the loading medium. Due to reliance on both specific acoustic impedance of matching materials and precise thickness control, the conventional quarter wavelength (1/4 λ) matching layer design is impractical for high-frequency transducers. Based on the transmission line theory and Mason model, we interfaced polymer-metal-polymer matching layers for transducers over 100 MHz. The modeling result comparison between transducers without matching layer and those with two conventional matching layers demonstrated that the matching performance of polymer-metal-polymer matching layers could be as good as the one of conventional matching layers. Meanwhile, unlike conventional 1/4 λ matching layer design, our design is independent on materials with specific acoustic impedance, while precise thickness control of polymer and metal can be achieved by deposition. The polymer-metal-polymer matching layers scheme paves the way to high frequency ultrasonic transducers.

0.63[0.9BiFeO3–0.1DyFeO3]–0.37PbTiO3 (BDF-PT) multiferroic ceramics with large piezoelectric response (d33 = 88 pC/N) and high Curie temperature (TC = 420 °C) were fabricated around the morphotropic phase boundary through traditional solid-state reaction method. The phase symmetry, microstructure, ferroelectricity and piezoresponse of BDF-PT ceramics were characterized systematically. Based on its high Curie temperature and appropriate piezoelectric properties, the BDF-PT ceramic was used to fabricate nondestructive testing ultrasonic transducer. The Krimholtz, Leedom and Matthaei (KLM) model was applied to design the ultrasonic transducer. The transducer fabricated was characterized to have a center frequency of 7 MHz and a low insertion loss of − 13 dB. This transducer was utilized to test metal stacks with different thicknesses; the experimental results show that the BDF-PT ceramics have great potential for nondestructive testing ultrasonic transducer applications.

超声以其无创性在生物医学及工业无损检测等领域备受关注,超声换能器作为实现超声应用的关键载体,需具备高的空间分辨率和特定的声场分布.常见的单阵元换能器需通过设计优化来满足上述需求,聚焦是最直接且有效的工艺方法.针对不同类型、不同工艺研制的超声换能器,提出了多种聚焦工艺,以实现换能器性能优化.

0.63[0.9BiFeO 3 - 0.1DyFeO 3 ] - 0.37PbTiO 3 (named as PT37) multiferroic ceramics with large piezoelectric response (d33=88pC/N) and a high Curie temperature (Tc=420°C) were fabricated around the morphotropic phase boundary through traditional solid-state reaction method. The phase symmetry, microstructure, ferroelectricity and piezo-electric properties of PT37 were characterized systematically. Based on its high Curie temperature and ideal piezoelectric properties, a Krimboltz, Leedom, and Mattaei (KLM) model-based simulation software PiezoCAD was used to design structure parameters of the transducer. Characterized by electrical and acoustic properties, the fabricated single element transducer had a center frequency of 7MHz and a low insertion loss of -13dB. The transducer was capable of measuring metal stack of different thickness. These results shows that the PT37 ceramics have great capability for ultrasonic non-destructive testing.

In this paper, a PZT/epoxy piezo-composite transducer with functionally graded design was proposed, which facilitated high sensitivity and broad bandwidth. The functionally graded piezocomposite was fabricated using a modified dice and fill method. Finite-element simulation was performed to study the vibration modes of the piezocomposite and to predict the transducer performances. To evaluate the performances experimentally, the proposed and conventional transducer based on monolithic PZT ceramic with similar dimension was fabricated and characterized systematically. We determined that the functionally graded transducer has a slightly higher center frequency (537 MHz), broader -6-dB bandwidth (22.5%), and a much lower insertion loss (-13.57 dB) compared to the conventional transducer (5.26 MHz, 183%, and -17.72 dB, respectively). The experimental results are in good agreement with the simulation ones. This preliminary investigation suggests that the functionally graded design is a promising approach to enhance the performance of ultrasonic transducers in high-sensitivity applications.

A simple optical frequency comb generator with Nyquist temporal waveform by using of an intensity modulator (IM) in a Sagnac Loop is proposed. By properly adjusting the polarization of the output from the Sagnac loop, a quasi-rectangular-shaped 5-tone OFC with Nyquist temporal waveform is theoretically and experimentally demonstrated. But it is impossible to generate Nyquist pulses with more than 3 comb lines using a single IM as reported before. In our scheme, only one RF signal with a relatively low power is needed, which effectively increases the system reliability and decrease the system complexity and cost.

A flat optical frequency comb generator utilizing a single dual parallel Mach–Zehnder modulator (DPMZM) is detailed investigated both in theory and experiment. In the scheme, the two sub-modulators of DPMZM are biased at the maximum and minimum transmission points respectively. By adjusting the RF signals power, two optical frequency combs with even harmonics or odd harmonics can be generated. So at the end of DPMZM, 5 and 7-line flat OFCs with a side-comb suppression ratio (SCSR) higher than 18dB are theoretically and experimentally generated. The optical frequency comb generator scheme is relatively simple and valuable due to only one bias voltage may be controlled.