Publication database

Breast cancer screening with mammography is less effective in women with dense breast tissue, prompting the use of ultrasound (US) imaging. While two- (2D) and three-dimensional (3D) US improve cancer detection, their low specificity leads to frequent unnecessary biopsies. Operator dependence on 2D US has led to the development of 3D automated breast volume scanners (ABVS), but challenges remain in distinguishing benign from malignant lesions. We developed a 3D photoacoustic and ultrasound (PAUS)–ABVS system that integrates a large field-of-view, 768-element transducer to improve diagnostic accuracy. In a clinical study of 61 patients with 36 benign and 30 malignant lesions, multispectral photoacoustic imaging was used to measure blood volume and oxygen saturation within lesions. When combined with standard US BI-RADS (breast imaging reporting and data system) scores, the system achieved a sensitivity of 96.7% and specificity of 66.7%. This performance matched the best outcomes of 2D PAUS and outperformed conventional US. Our results suggest that the PAUS-ABVS can support more accurate breast cancer diagnosis while reducing unnecessary biopsies.

Image-guided phototheranostics, including photothermal therapy and photoacoustic imaging using plasmonic nanoparticles, has attracted attention due to its remarkable photothermal conversion effects. In particular, considering the several benefits of biocompatibility, unique plasmon resonance, and tunable optical properties, gold nanoparticles of various shapes have been widely utilized as phototheranostic agents. However, applications in the near-infrared window have been limited due to the tendency of anisotropic gold nanoparticles to transform into spherical shapes under repetitive laser irradiation, which cause a shift in the localized surface plasmon resonance peak and reduces photothermal stability. To address these limitations, we introduce an Fe layer between Au nanodiscs to synthesize Au/Fe/Au trilayer uniform structured nanodiscs (AuFeAuNDs) using nanoimprint lithography. This approach aims to improve photostability and endow a magnetic targeting ability, enabling more accurate spatiotemporal regulation. The AuFeAuNDs primarily function as photothermal therapy agents and also serve as chemodynamic agents via the Fenton reaction specifically within the tumor microenvironment, which induces ferroptosis. Moreover, the AuFeAuNDs trigger immunogenic cell death following photothermal therapy. This study demonstrates applications of magnetic-targeted AuFeAuNDs for photoacoustic imaging-guided, spatiotemporal-controlled photothermal therapy, chemodynamic therapy, and immune modulation to bolster anti-tumor immune responses in cancer treatment.

This paper presents the precipitation of copper (Cu) from a surfactant-added glyoxylic acid copper (GACu) complex ink, in femtosecond laser multiple pulse-induced thermochemical processes to achieve high-resolution Cu direct writing. The study specifically examines the impact of the surfactant, n-decanoylsarcosine sodium, (NDSS), on the nonlinear optical absorption properties of GACu complex ink. Findings reveal that the addition of NDSS did not alter the molecule binding and single-photon absorption properties of the ink. However, nonlinear optical absorptions evaluated through the open aperture z-scan method displayed differences between the NDSS-added and non-added GACu complex inks when subjected to femtosecond laser pulse irradiation. These results suggest that Cu nanoparticles were generated from the GACu complex ink via nucleation and surfactant-mediated growth, leading to the saturable absorption of the subsequent irradiated laser pulses. By employing a pulse repetition frequency of 5 MHz and a pulse number of 2 × 104, a minimum dot diameter of 1.6 ± 0.1 μm with stable reproductivity was attained with NDSS-added ink, corresponding to the laser spot diameter, without excessive precipitation due to thermal diffusion. This comprehensive understanding of the surfactant NDSS and pulse number effects on the Cu precipitation process holds potential for the direct writing of various materials. Furthermore, this insight offers a novel approach for affordable and scalable manufacturing with minimized environmental impact.

As lasers expand further into industrial, research, medical, and military applications, end users are placing increased scrutiny on system cooling requirements. All lasers require a form of thermal management. The appropriate method depends on both the laser design and its operating environment: If the heat load fluctuates, for example, a user must account for both the laser’s range and rate of change.

Regardless of scale and power, overheating can lead to efficiency losses, wavelength drift, and shortened operating lifetime. Low-power lasers operating in stable environments with broad temperature tolerances can often rely on simple air cooling. On the other hand, higher-power systems, or those with tight tolerances, require more advanced methods. Today, system wall-plug efficiencies range from 0.1% to nearly 80%, and power levels can span from milliwatts in measurement and marking applications to multiple kilowatts in heavy manufacturing. Cooling design is therefore not a peripheral consideration. Instead, it is a critical factor that is central to ensuring reliability and performance across all systems and applications.

Fabry–Perot (FP) ultrasound sensors are a class of optical ultrasound sensors used in photoacoustic tomography (PAT) and other applications. Conventionally, an FP ultrasound sensor comprises an ultrasonically compressible planar microcavity, locally interrogated by a focused Gaussian beam. One way to increase the sensitivity could be to replace this beam with a Bessel beam. The rationale is twofold. First, as a Bessel beam’s wavefront better matches the modes of the planar microcavity, this could increase the -factor, leading to higher sensitivity. Second, as a Bessel beam provides a focused spatial structure—a central core surrounded by concentric rings—it might retain the ability to locally interrogate the sensor. To explore this idea, we developed an experimental system featuring a custom FP ultrasound sensor interrogated by a Bessel beam and evaluated its on-axis sensitivity, directivity, and image resolution when performing PAT. For comparison, we measured the same characteristics using a conventional focused Gaussian beam with a spot size similar to the core of the Bessel beam. As anticipated, the Bessel beam provided a higher ultrasonic on-axis sensitivity. However, the directivity and spatial resolution were degraded, suggesting that the Bessel beam yielded a larger acoustic element. We conclude that it is feasible to increase the sensitivity of an FP ultrasound sensor using a Bessel beam. Further work is required to establish whether differently designed Bessel beams could concurrently offer a smaller acoustic element.

Abstract Polarization is a fundamental property of light that can be engineered and controlled efficiently with optical metasurfaces. Here, we employ chiral metasurfaces with monoclinic lattice geometry and achiral meta-atoms for resonant engineering of polarization states of light. We demonstrate, both theoretically and experimentally, that a monoclinic metasurface can convert linearly polarized light into elliptically polarized light not only in the linear regime but also in the nonlinear regime with the resonant generation of the third-harmonic field. We reveal that the ellipticity of the fundamental and higher-harmonic fields depends critically on the angle of the input linear polarization, and the effective chiral response of a monoclinic lattice plays a significant role in the polarization conversion.

Abstract Early-stage stroke monitoring enables timely intervention that is crucial to minimizing neuronal damage and increasing the extent of recovery. By monitoring collateral circulation and neovascularization after ischemic stroke, the natural recovery process can be better understood, optimize further treatment strategies, and improve the prognosis. Photoacoustic computed tomography (PACT), a non-invasive imaging modality that captures multiparametric high-resolution images of vessel structures, is well suited for evaluating cerebrovascular structures and their function. Here 3D multiparametric transcranial PACT is implemented to monitor the early stage of a photothrombotic (PT)-stroke model in living rats. New vessels in the PT-induced region are successfully observed using PACT, and these observations are confirmed by histology. Then, using multiparametric PACT, it is found that the SO2 in the ischemic area decreases while the SO2 in newly formed vessels increases, and the SO2 in the PT region also recovers. These findings demonstrate PACT\'s remarkable ability to image and monitor cerebrovascular morphologic and physiological changes. They highlight the usefulness of whole-brain PACT as a potentially powerful tool for early diagnosis and therapeutic decision-making in treating ischemic stroke.

Structural organization of harmonophores used in hematoxylin (H) and eosin (E) staining is studied with polarimetric multimodal second-harmonic generation (SHG), third-harmonic generation (THG) and multiphoton excitation fluorescence (MPF) microscopy in rat tail tendon histology sections. The polarimetric microscopy imaging reveals that hemalums (complexes of hematoxylin and aluminum) are well aligned with C_6h symmetry along the collagen fibers in H-stained tissue, while eosin Y is partially aligned along the fibers in E-stained tissue and also follows organization of C_6h symmetry. When both hemalum and eosin are used for H&E staining, the dye molecules interact and align noncentrosymmetrically with C₆ symmetry along the collagen fibers, while the stained nuclei appear isotropically organized. The polar alignment of the hemalum and eosin complexes increases the achiral second order susceptibility tensor component ratio

in H&E-stained tissue. The alignment of hemalum and eosin molecules, and their complexes in collagenous tissue, must be considered in nonlinear microscopy and polarimetric analysis of H&E-stained histopathology.

Intra-volume glass scribing for cutting is one of the most advanced applications of nondiffractive laser beams. However, ever-growing requirements from the industry for complexity, miniaturization, and quality of fabricated parts have pushed the technology forward. Most of the methods developed to improve glass scribing rely on spatial and temporal pulsed beam shaping. As another degree of freedom to manipulate light, polarization has received little attention so far. In this work, we investigate the effect of linear and circular polarizations on the volumetric modification and scribing of soda-lime glass using a zero-order Bessel beam in the MHz burst regime. We demonstrate that at a certain burst energy, transverse microcracks align with the linear polarization orientation. Furthermore, we show that the polarization state affects the modified glass separation, processing speed, efficiency, and quality.

A localized energy deposition in a thin layer of liquid between two solid glass plates excites waves in the liquid, solids, and their interfaces. Of particular interest is an elastic surface wave (Rayleigh wave) on the liquid–solid interface that travels faster than the shock wave in the liquid. The surface deformation caused by the Rayleigh wave expands the layer of liquid, thereby locally reducing the pressure below the cavitation threshold. The created tension nucleates many cavitation bubbles, which later collapse due to the passage of the trailing shock wave in the liquid. Interestingly, the bubbles are not arranged homogeneously but on concentric rings centered on the location of the energy deposition. We explain the formation of the concentric rings with the interaction between neighboring bubbles. The fluid–structure interaction is modeled with a coupled finite volume solver that couples a multi-phase compressible fluid region (water and bubble gas) with an elastic solid (glass). We find that the nucleation of bubbles in such a geometry relaxes the tension in their immediate vicinity and thereby suppresses the growth of neighboring bubble nuclei. This idea is confirmed by a Rayleigh–Plesset model of a bubble driven by a far-field pressure obtained from the finite volume simulation. The observed ring patterns are thus the result of the successive activation of statistically distributed nucleation sites into explosively expanding cavitation bubbles in an axisymmetric geometry, whose strong interaction on short distances leads to a hindrance of bubble growth in radially distinct regions.