Frontiers of Optoelectronics最新文献

In recent years, the utilization of nanoparticles with varying morphologies in optical coherence tomography (OCT) has gained prominence, primarily aimed at enhancing imaging contrast and depth. Various factors associated with nanoparticles, encompassing their shape, orientation, and distribution within biological tissues, significantly influence OCT performance. A thorough investigation of these parameters has yielded substantial findings, particularly regarding the enhancement of OCT images facilitated by the presence of nanorods (NRs). In this study, we conducted OCT imaging of chicken breast tissue employing Fe₃O₄ NRs under different polarization states, utilizing solenoids to apply a magnetic field to the nanoparticles. The results demonstrate that orienting nanoparticles can improve the Contrast-to-Noise Ratio (CNR) and signal-to-noise ratio (SNR) of OCT signal more than twofold compared to scenarios lacking specified orientation. Furthermore, this article addresses the challenge of prolonged nanoparticle distribution in tissue when using ultrasound probes, successfully reducing the distribution time from approximately 45 min to about 5 min. The findings presented herein show significant promises for advancing optical coherence tomography across a variety of applications.

Red blood cells (RBCs) are vital components of human blood, and their morphological abnormalities serve as reliable indicators of various disease pathophysiologies. As a novel label-free optical technique, Mueller matrix (MM) polarimetry is gaining recognition for its value in disease diagnosis and pathological analysis. In this study, we integrate a dual-angle MM measurement system with single-cell polarized light scattering modeling to establish specific polarization feature parameters (PFPs) characterizing cellular microphysical properties. The PFPs quantitatively describe morphological and optical changes in individual RBCs undergoing complex deformations. Experimental results demonstrate that PFPs can effectively distinguish differences in size, shape, refractive index, and surface spicules between deformed and normal RBCs. Moreover, by incorporating PFPs into a Random Forest classifier, we accurately quantify the proportion of abnormal RBCs in mixed suspensions. This study confirms the capability of polarization measurement for label-free, high-throughput analysis of RBC microphysical properties at the single-cell level.

Age is a limiting factor in the efficacy of photobiomodulation (PBM) for brain drainage and cognitive functions. Meningeal lymphatic vessels (MLVs) are "tunnels" for removal of toxins from the brain and the target of PBM. Age-related decline in the MLV functions is one of the mechanisms by which the effects of PBM on brain drainage and cognitive process are limited. Sleep is a time of natural activation of brain drainage. Recent findings have shown that PBM during sleep has greater effects on lymphatic clearance of beta-amyloid and cognitive function in young and middle-age mice. Based on these data, this study tested the hypothesis that sleep enhances the effects of PBM on MLVs and cognitive function in the aging brain. Indeed, the results revealed that PBM during sleep, but not during wakefulness, has stimulatory effects on lymphatic clearance of beta-amyloid from the brain of old mice that improves memory. In sleep deficit experiments, it was found that chronic sleep deprivation is accompanied by suppression of brain drainage and removal of metabolites from the brain, such as beta-amyloid, tau, glutamate, lactate and glucose in young, middle-aged and most significantly in old mice. The course of PBM during sleep contributed better than in wakefulness to the restoration of the brain level of tested metabolites in young and middle-aged mice, while in old mice only PBM during sleep was effective. These results open a new strategy for the use of PBM during sleep to improve the efficacy of PBM on clearance of toxic metabolites from the brain, especially in aged subjects in whom the efficacy of PBM during wakefulness is limited.

High-power fiber oscillators have been widely used in industrial processing, high-end manufacturing, biomedicine and so on. However, as the output power increase, stimulated Raman scattering (SRS) becomes the main factor limiting the performance improvement of fiber oscillators. In this paper, a chirped and tilted fiber Bragg grating (CTFBG) is used to suppress SRS in a high-power fiber oscillator. The CTFBG is fabricated on one side of a low-reflectivity FBG (LRFBG) to form a composite FBG by the femtosecond laser phase mask technology, enhancing the compactness and stability of the fiber oscillator system. SRS is effectively suppressed by CTFBG with a Raman suppression depth and width of 16 dB and 86 nm, respectively, and the Raman light ratio in the output power decreases by an order of magnitude. The output power of fiber oscillators is increased to 9 kW, which is the highest power for fiber oscillators with SRS suppression using CTFBGs, to the best of our knowledge. This work demonstrates that the composite FBG can effectively improve the performance of high-power fiber oscillators, which provides new insights into the development of fiber laser technology.

Intraoperative assessment of cerebral hemodynamics is crucial for the success of neurosurgical interventions. This study evaluates the potential of laser speckle contrast imaging (LSCI) and imaging photoplethysmography (IPPG) for contactless perfusion monitoring during neurosurgery. Despite similarities in their hardware requirements, these techniques rely on fundamentally different principles: light scattering for LSCI and light absorption for IPPG. Comparative experiments were conducted using animals (rats) when assessing the reaction of cerebral hemodynamics to adenosine triphosphate infusion. The results show different spatial and temporal characteristics of the techniques: LSCI predominantly visualizes blood flow in large venous vessels, especially in the sagittal and transverse sinuses, showing a pronounced modulation associated with the heart that cannot be explained by venous blood flow alone. In contrast, IPPG quantifies the dynamics of perfusion changes in the parenchyma, showing minimal signal in large venous vessels. We propose that LSCI signal modulation is significantly influenced by the movement of vessel walls in response to mechanical pressure waves propagating through the parenchyma from nearby arteries. A novel algorithm for LSCI data processing was developed based on this interpretation, producing perfusion indices that align well with IPPG measurements. This study demonstrates that the complementary nature of these techniques (LSCI is sensitive to blood cells displacements, while IPPG detects a change in their density) makes their combined application particularly valuable for comprehensive assessment of cerebral hemodynamics during neurosurgery.

Kerr resonator is one of the most popular platforms to produce optical frequency comb and temporal cavity soliton. As an essential method for investigating the nonlinear dynamics of Kerr resonators, traditional numerical simulations rely on solving the Lugiato-Lefever equation (LLE) using the split-step Fourier method (SSFM), which is computationally intensive and time-consuming. To address this challenge, this study proposes a recurrent neural network model with prior information feedback, enabling efficient and accurate prediction of soliton dynamics in Kerr resonator. With the acceleration of graphics processing unit (GPU), the computational efficiency improved by 20 times. We compared various recurrent neural networks and found that the gated recurrent unit (GRU) network demonstrated superior performance in this task. This work highlights the potential of artificial intelligence (AI) for modeling nonlinear optical dynamics in Kerr resonator, paving the way for designing optical frequency comb and generating ultrafast pulse.

Three-dimensional reconstruction of tissue architecture is crucial for biomedical research. Tissue optical clearing technology overcomes light scattering limitations in biological tissues, providing an essential tool for high-resolution three-dimensional imaging. Given the high degree of similarity between large model animals (e.g., pigs, non-human primates) and humans in terms of anatomical structure, physiologic function, and disease mechanisms, the application of this technology in these models holds significant value for biomedical research. While well-established tissue clearing protocols exist for tissue sections, whole organs, and even entire bodies in rodents, scaling up to large animal specimens presents substantial challenges due to dimensional effects and compositional variations. This review systematically examines the methodological translation from rodent to large animals, particularly on species-specific differences in brain architecture and parenchymal organ composition that critically impact clearing efficiency. We comprehensively summarize recent applications in large animals, focusing on representative areas including neural circuit mapping, sensory organ imaging, and other related research domains, while proposing optimization strategies to overcome cross-species compatibility barriers. We hope this review will serve as a valuable reference for advancing tissue optical clearing applications in large-animal biomedical research.

Whispering-gallery-mode (WGM) microcavities have emerged as a promising alternative to traditional ultrasound probes, offering high sensitivity and wide bandwidth. In our research, we propose a novel silica WGM microprobe device, with impressive Q factors up to 10⁷. The side-coupled approach and special encapsulation design make the device compact, robust, and capable of utilizing in both gaseous and liquid environments. We have successfully conducted photoacoustic (PA) imaging on various samples using this device which demonstrates a high sensitivity of 5.4 mPa/√Hz and a broad bandwidth of 41 MHz at -6 dB for ultrasound. And it is capable of capturing the vibration spectrum of microparticles up to a few hundred megahertz. Our compact and lightweight device exhibits significant application potential in PA endoscopic detection, near-field ultrasound sensing and other aspects.

As nonlinearity is highly correlated with their geometric dimensions, precise fabrication of optical micro/nanofibers (MNFs) has been a longstanding pursuit. Existing MNFs fabrication systems typically adopt horizontal structures, which inherently introduce inaccuracy stem from asymmetry between fiber axis/geometry and chaotic environment due to high temperature airflow, vibration, etc., leading to deviations from the expected fiber morphology, especially for complex-structured MNFs. Here, we propose and manufacture a MNFs fabrication systems, effectively reducing fiber shape deviations during the fabrication process, enabling the fabrication of precise MNFs. To demonstrate the capability of our system in manufacturing precise structure MNFs, we design and fabricate diameter-gradient microfibers with four cascaded structures over a length of approximately 120 mm and a minimum diameter of about 1 μm for on-demand nonlinearity to generate supercontinuum spectrum. Eventually, we obtain supercontinuum spectrum covering 1463-1741 nm at the - 10 dB level with an efficiency of 264.62 $\text{nm}/\text{kW}$ , exhibiting good flatness and enabling efficient spectral broadening.

Understanding the sorption dynamics between water molecules and various solid surfaces is of great interest in diverse fundamental and industrial research. For studying such dynamics in a microsystem, existing investigations mainly focus on sorption behaviors mediated by external temperature variations. Here, we demonstrate a route to in situ sensitive detection of laser irradiation-induced localized water molecule desorption at a sub-monolayer level on an oxide surface. Harnessing a tailored set of optical whispering-gallery-mode (WGM) resonances in a nanomembrane-based microtube cavity, the desorption can be tracked by resonance mode shift in real-time, and further explained using a combination of pseudo-first-order and pseudo-second-order models. Additionally, upon adjusted laser excitation locations, the axial-mode-dependent responses enable the retrieval of corresponding profiles of desorption-induced perturbation at equilibrium. This study provides new insights into molecular desorption kinetics and introduces a spatially resolved sensing technique with applications in surface science, molecular sensing, and the study of desorption dynamics at the nanoscale.