Bai-Ou Guan

Jinan University (Guangzhou, China) · Institute of Photonics Technology

A label-free fiber-optic biosensor with a reflective microfiber Bragg grating (mFBG) configuration for in-situ DNA hybridization detection has been proposed and experimentally demonstrated. A single straight Bragg grating inscribed in the silica microfiber provides two well-defined resonances in reflection, which show different response to external...

We demonstrate four-port long-period gratings formed by winding an optical microfiber with another thinner microfiber. The surrounding thinner microfiber not only induces a strong refractive-index perturbation in the center microfiber, but also collects and leads out the light resonantly coupled from the fundamental mode to high-order modes, provid...

Microfiber Bragg gratings (mFBGs) are of great promise due to their compactness, large evanescent field effect, low stiffness, and good flexibility. A lot of researches related to the fabrication and the potential applications of mFBGs in sensing and communication have been made in the past. This review begins from the theoretical analysis based on...

Fiber grating laser sensors have been attracting interest because of their high signal-to-noise ratio and narrow linewidth that permit high resolution sensing. According to the working principle, fiber grating laser sensors can be classified into two types: wavelength encoding sensor and polarimetric heterodyning sensor. The former converts measurr...

This article presents the distinctive butyrylcholinesterase (BChE) fluorescent probe P5, designed via a targeting-site method. This method was proposed to enhance the affinity of the probe for BChE by targeting the peripheral anionic site (PAS) of BChE. By mimicking the natural substrate butyrylcholine, the structure of the probe was optimized by i...

Breast cancer often necessitates surgical interventions such as breast-conserving surgery or mastectomy. In these surgeries, sentinel lymph node (SLN) samples are often excised for histopathological examination to ascertain the presence of cancer metastasis. Despite its importance, traditional hematoxylin and eosin (H&E) staining, considerably prol...

Glass ceramics (GCs) containing PbS quantum dots (QDs) are prepared for temperature sensing. Broadband emissions are detected in the GCs when PbS QDs are precipitated from the glasses, and emissions centers are modulated from 1250 nm to 1960 nm via heat treatments. The emission centers of GCs exhibit blue-shifts when environment temperatures increa...

Efficient delivery of photons to visceral organs is critical for the treatment of deep-seated tumors taking advantage of photo-theranostics. Optical fiber can be regarded as a direct and facile photon pathway for targeting tumor lesion with negligible body invasion. However, current fiber theranostic strategies rely on the spatially separated optic...

In this paper, cascaded modal interferometers constructed by strongly-coupled seven-core fiber (SC-SCF) with different lengths are demonstrated for enhanced bending sensing based on Vernier effect. The free spectral range (FSR) of a single SC-SCF interferometer is determined by the length of SC-SCF. Two SC-SCF interferometers with different FSRs ar...

Cancer has been one of the most serious diseases, resulting in more than 10 million deaths every year. Fiber-optic sensors have great potential for diagnosing and treating cancer due to their flexibility, precise positioning, real-time monitoring, and minimally invasive characteristics. Compared to traditional central laboratory examination, fiber-...

Optical fiber-based photothermal devices show great promise for applications in in vivo detection and therapy. The integration of sensors and actuators in one fiber is a feasible method to orchestrate both functionalities. However, the photoheating-induced temperature field is not always homogeneous in the practical application, which undermines th...

Invasive fungal infections pose a significant public health threat. The lack of precise and timely diagnosis is a primary factor contributing to the significant increase in patient mortality rates. Here, an interface‐modulated biosensor utilizing an optical fiber for quantitative analysis of fungal biomarkers at the early stage of point‐of‐care tes...

In this paper, cascaded modal interferometers constructed by strongly-coupled seven-core fiber (SC-SCF) with different lengths are demonstrated for enhanced bending sensing based on Vernier effect. The free spectral range (FSR) of a single SC-SCF interferometer is determined by the length of SC-SCF. Two SC-SCF interferometers with different FSRs ar...

In this paper, cascaded modal interferometers constructed by strongly-coupled seven-core fiber (SC-SCF) with different lengths are demonstrated for enhanced bending sensing based on Vernier effect. The free spectral range (FSR) of a single SC-SCF interferometer is determined by the length of SC-SCF. Two SC-SCF interferometers with different FSRs ar...

Optical microscopy is indispensable to biomedical research and clinical investigations. As all molecules absorb light, optical-resolution photoacoustic microscopy (PAM) is an important tool to image molecules at high resolution without labeling. However, due to tissue-induced optical aberration, the imaging quality degrades with increasing imaging...

Oxyfluoride transparent glass‐ceramics (GC) are widely used as the matrix for rare‐earth (RE) ions due to their unique properties such as low phonon energy, high transmittance, and high solubility for RE ions. Tb³⁺ doped oxyfluoride glasses exhibit a large absorption cross section for ultraviolet (UV) excitation, high stability, high photoluminesce...

We report the development of a head-mounted photoacoustic fiberscope for cerebral imaging in a freely behaving mouse. The 4.5-gram imaging probe has a 9-µm lateral resolution and 0.2-Hz frame rate over a 1.2-mm wide area. The probe can continuously monitor cerebral oxygenation and hemodynamic responses at single-vessel resolution, showing significa...

A new microwave photonic signal processor for use in a frequency diverse array (FDA) to generate a dot-shaped beampattern is presented. The microwave photonic signal processor is implemented based on a dual-polarization quadrature phase shift keying (DP-QPSK) modulator and a phase modulator (PM), with the amplitude and phase of an input radio frequ...

Optical microcavities with high quality factors can significantly enhance the intracavity power density and have become a superior platform for studying quantum electrodynamics, nonlinearities, and sensing. Minimized and compact on-chip devices require the integration of microcavities with versatile functions that can be implemented by techniques c...

The use of light as a powerful tool for disease treatment has introduced a new era in tumor treatment and provided abundant opportunities for light‐based tumor theranostics. This work reports a photothermal theranostic fiber integrating cancer detection and therapeutic functions. Its self‐heating effect can be tuned at ultralow powers and used for...

Hydrogels are an important category of polymeric materials with physicochemical features such as moisturizability and biocompatibility that are ideal for developing dressings for diabetic wounds. However, conventional non-ionic hydrogel materials generally exhibit poor mechanical properties and poor adhesion, which compromise their ability to self-...

Dynamic access to quasi-bound states in the continuum (q-BICs) offers a highly desired platform for silicon-based active nanophotonic applications, while the prevailing tuning approaches by free carrier injections via an all-optical stimulus are yet limited to THz and infrared ranges and are less effective in visible bands. In this work, we present...

Hydrogen (H2) sensors are critical to various applications such as the situation where H2 is used as the clean energy for industry or the indicator for human disease diagnosis. Palladium (Pd) is widely used as the hydrogen sensing material in different types of sensors. Optical fiber H2 sensors are particularly promising due to their compactness an...

Synthetic dimension opens new horizons in quantum physics and topological photonics by enabling new dimensions for field and particle manipulations. The most appealing property of the photonic synthetic dimension is its ability to emulate high-dimensional optical behavior in a unitary physical system. Here we show that the photonic synthetic dimens...

With the recent advances in nanomaterials, photothermal therapies (PTT) enabled by deep-tissue penetration with novel nanoagents have offered a new hope for treating cancers. Nevertheless, PTT applications in conventional approaches remain translationally restricted due to their non-specificity and collateral pro-inflammatory effects during impleme...

Optical fibers can be effective biosensors when employed in early-stage diagnostic point-of-care devices as they can avoid interference from molecules with similar redox potentials. Nevertheless, their sensitivity needs to be improved for real-world applications, especially for small-molecule detection. This work demonstrates an optical microfiber...

Fiber-optic grating biosensor offers compelling advantages such as compact footprint and nature of signal reflection, and thus becomes a particularly apt candidate for cardiovascular biomarker determination. However, limit of detection (LOD), test speed, and maneuverability of such biosensor should be substantially improved before conferring those...

Helical-core fibers have been widely utilized for various applications such as orbital angular momentum manipulation, optical filtering, and sensing. In this work, we demonstrate the sensitivity enhancement of a helical-core fiber by tailoring the resonance wavelength towards the dispersion turning point (DTP) utilizing a post chemical etching proc...

A temperature-compensated refractive index (RI) sensor based on thinned strongly-coupled seven-core fiber (SC-SCF) supermode Bragg grating and interferometer is demonstrated. The SC-SCF spliced between two standard single mode fibers was first tapered to 55.0 μm and then chemically etched to a waist diameter of 15.6 μm, forming a supermode interfer...

We report the development of a head-mounted photoacoustic fiberscope for cerebral imaging in a freely behaving mouse. The 4.5-gram imaging probe has a 9-µm lateral resolution and 0.2-Hz frame rate over a 1.2-mm wide area. The probe can continuously monitor cerebral oxygenation and hemodynamic responses at single-vessel resolution, showing significa...

Humidity plays an important role in many fields, and the realization of high sensitivity and fast response simultaneously for humidity detection is a great challenge in practical application. In this work, we demonstrated a high-performance relative humidity (RH) sensor made by supporting zeolitic imidazolate framework-90 (ZIF-90)-derived porous zi...

Optical fiber acoustic sensors with miniature size and high sensitivity are attractive to develop compact photoacoustic spectroscopy. Here, a compact photoacoustic gas sensor was demonstrated by utilizing a diaphragm-based fiber-optic Fabry-Perot cavity as both the acoustic sensor and the multipass cell. A nanoscale graphite film was used as the fl...

Capacitive deionization in environmental decontamination has been widely studied and now requires intensive development to support large-scale deployment. Porous nanomaterials have been demonstrated to play pivotal roles in determining decontamination efficiency and manipulating nanomaterials to form functional architecture has been one of the most...

Plasmonic sensors leverage the enhanced near-fields associated with the constituent optical nanoantennas to achieve better sensing performance. The design and fabrication of these optical nanoantennas, especially metallic ones, are thus becoming critical steps to advance this thriving and important field. Low-cost and high-throughput nanofabricatio...

Fiber-optic devices working in the visible and near-infrared windows are attracting attention due to the rapid development of biomedicine that involves optics. In this work, we have successfully realized the fabrication of near-infrared microfiber Bragg grating (NIR-µFBG), which was operated at the wavelength of 785 nm, by harnessing the fourth har...

The optical generation of pulsed ultrasound is attractive to nondestructive testing and biological imaging, especially for those involving narrow operation space or strong electro-magnetic interference. However, conventional techniques based on the photoacoustic effect inevitably required an expensive high-energy short pulsed laser and dedicated pr...

All-optical ultrasound manipulates ultrasound waves based on laser and photonics technologies, providing an alternative approach for pulse-echo ultrasound imaging. However, its endoscopic imaging capability is limited ex vivo by the multifiber connection between the endoscopic probe and the console. Here, we report on all-optical ultrasound for in...

Wearable sensing devices, which can find tremendous applications in healthcare and automation, are attracting great attention in recent years. Herein, we report a flexible wearable optical sensor (FWOS) which consists of the microfiber Bragg grating (μFBG) as the core sensing node and a ductile PDMS film as the sensor encapsulation. Due to the stra...

Photoacoustic tomography emerged as a promising tool for noninvasive biomedical imaging and diseases diagnosis. However, most of the current piezoelectric ultrasound transducers suffer optical opacity and tissue-mismatched acoustic impedance, hindering the miniaturization and integration of the system for multiscale and multimodal imaging. Here, a...

The use of light, which is s a powerful tool for imaging and sensing, has also become one of the most prospective strategies in tumor treatment. Optical microfibers, which have engineerable waveguiding properties, are highly attractive for optical sensing and photothermal therapy on the micro/nanoscale. However, for their real‐world application, th...

Polarization fading degrades the performance of phase-sensitive optical time-domain reflectometry (φ-OTDR) seriously and has to be suppressed. A novel scheme is proposed in this paper to combat polarization fading, which features a quite simple transceiver structure by exploiting both polarization diversity through delayed polarization multiplexing...

A Bragg grating is successfully inscribed in a piece of strongly coupled seven-core fiber (SCF). There are two separate Bragg resonance notches observed in the transmission spectrum, corresponding to backward coupling of HE11-like and HE12-like supermodes of the SCF. The mode coupling mechanism of the Bragg grating is theoretically investigated via...

Using coding in phase sensitive optical time domain reflectometry (ϕ-OTDR) system has long been pursued. However, since no single sequence with ideal aperiodic autocorrelation has been found, sidelobes of aperiodic autocorrelation induce crosstalk among sensors. Finding coding schemes with as low crosstalk as possible is very meaningful. In this pa...

We reported a miniaturized single-fiber photoacoustic spectrometer for high spatiotemporal-resolution sensing and imaging of ppb-level gas molecules, with three orders of magnitude reduction of the sampling volume to picoliter and response time to 20 ms.

We developed photoacoustic fiberscopes based on optical ultrasound sensors. This new imaging modality was used for cerebral oxygenation imaging on freely moving mice for neuroscience study and the detection of brain injuries in intensive-care medicine.

This work presents a lab-on-fiber application for measuring electrochemical deionization activities. The electrically driven capacitance and adsorption processes are refractometrically recorded by the optical fiber sensors, which enable accurate evaluation of kinetic and efficiency metrics.

We present all-optical endoscopic ultrasound for in vivo, rotational-scanning (B-mode) imaging with an operating frequency of 20 MHz, an imaging depth of 2 cm, and a frame rate of 1 Hz.

Obtaining detailed insight into the photocatalytic performance of heterogeneous photocatalytic materials, is important for evaluating material properties as well as guiding material design. However, capture of the detailed matter changes on a photocatalyst surface in real time, and in situ during photocatalysis remains challenging. This work report...

Photoacoustic endoscopy shows promise in the detection of gastrointestinal cancer, inflammation, and other lesions. High-resolution endoscopic imaging of the hemodynamic response necessitates a small-sized, high-sensitivity ultrasound sensor. Here, we utilize a laser ultrasound sensor to develop a miniaturized, optical-resolution photoacoustic endo...

Accurate and timely assessment of malignant tumor in the early stage and therapy process is critical for making clear guidance and prognosis for the treatment, which can significantly elevate the cure rate of cancer patients. Fluorescent sensing and imaging of tumor have attracted extensive attention because of their advantages of high sensitivity...

Si Nanodisk Clusters In article number 2204883, Kai Chen and co‐workers demonstrate a new type of anapole state termed as extrinsic anapole with mode field spreading across the high‐index all‐dielectric nanodisk clusters, unlike the intrinsic one that is confined within individuals. The extrinsic anapole boosts two‐photon‐induced white‐light emissi...

Nanoparticle clusters provide new degrees of freedom for light control due to their mutual interaction compared with an individual one. Here, the authors demonstrate theoretically and experimentally a type of optical anapole (a nonradiating state) termed as extrinsic anapole, with mode field spreading across Si nanodisk dimers unlike the intrinsic...

An approach to photonic generation of a windowed binary phase-coded microwave waveform with suppressed spectrum sidelobes is proposed and demonstrated. An optical double sideband plus carrier signal with the carrier and the two sidebands being orthogonally polarized is generated by a dual-polarization quadrature phase shift keying (DP-QPSK) modulat...

Short-time Fourier transform (STFT) algorithm with Lorentzian fitting is popular in distributed Brillouin optical fiber sensors to acquire Brillouin frequency. However, STFT often suffers from the trade-off between Brillouin frequency measurement resolution and computation complexity. To lower the complexity of Brillouin frequency analysis and spee...

Reliable gas sensors are very important for hydrogen (H2) gas detection and storage. Detection methods based on palladium (Pd) metal are cost-effective and widely studied. When Pd is exposed to H2, it turns into palladium hydride with modified optical properties, which thus can be monitored for H2 sensing. Here, we fabricated large-area Pd nanostru...

An optoelectronic oscillator (OEO) for single-frequency microwave generation, enabled by broken parity time (PT) symmetry based on higher-order modulation using a Mach–Zehnder modulator, is proposed and demonstrated. Instead of using two physically separated mutually coupled loops with balanced gain and loss, the PT symmetry is realized using a sin...

Photothermal actuation that leverages optical fiber and plasmonic materials would not only add a practical function but also spur many important applications for the fiber-optic sensors, for example, the self-temperature governing and fiber-optic photothermal medicine probe. In this paper, we propose and demonstrate a microfiber Bragg grating devic...

A micro-nanostructure-based surface-modified fiber-optic sensor has been developed herein to selectively detect hydrogen peroxide (H2O2). In our design, phenylboronic ester-modified polymers were used as a modified cladding medium that allows chemo-optic transduction. Sensing is mechanistically based on oxidation and subsequent hydrolysis of the ph...

We investigate the two-photon fluorescence (TPF) of conjugated polymer (CP) microspheres with diameters up to tens of micrometers. Two polymers, emitting in either the violet or red, were first synthesized and characterized in terms of their one-photon fluorescence and three-dimensional internal microstructure. Under femtosecond infrared excitation...

High‐index all‐dielectric resonators have been developed into an important platform for light manipulation at the nanoscale over the past decade. Although they are widely used as 2D materials, transition metal dichalcogenides (TMDCs), as an emerging all‐dielectric material, have also been used to fabricate optical nanoantennas that support multipol...

Abstract A microwave photonic frequency divider to produce a frequency‐divided microwave signal with its frequency that is one‐third the frequency of the input microwave signal is proposed and experimentally demonstrated. The key novelty of the approach is that the phase control, a condition to realise the frequency division operation, is implement...

The detection and therapy of cancers in the early stage significantly alleviate the associated dangers. Optical devices offer new opportunities for these early measures. However, the clinical translation of the existing methods is severely hindered by their relatively low sensitivity or unclear physiological metabolism. Here, an optical microfiber...

Photoacoustic endoscopy shows promise in the detection of gastrointestinal cancer, inflammation, and other lesions. However, imaging the hemodynamic response in disease at high spatial resolution is hindered by the ultrasound detection capability. Here we developed a miniaturized, optical-resolution photoacoustic endoscope to image an inflamed rat...

The capabilities to manipulate light-matter interaction at the nanoscale lie at the core of many promising photonic applications. Optical nanoantennas, made of metallic or dielectric materials, have seen a rapid development for their remarkable optical properties facilitating the coupling of electromagnetic waves with subwavelength entities. Howeve...

Improving sensitivity is critical for the higher-order harmonic fiber Bragg grating sensors. To this aim, in this work, we have successfully introduced the phase-shift into the third harmonic fiber Bragg grating for tailoring a double-dip spectrum with a high finesse notch. The dual dips showed reversed responses for the intensity regarding the cha...

Photonics has spurred a myriad of diagnostic and therapeutic applications for defeating cancer owing to its superiority in spatiotemporal maneuverability and minimal harm. The limits of light penetration depth and elusiveness of photosensitizer utilization, however, impede the implementation of the photodiagnostic and ‐therapy for determining and a...

Detecting nitroreductase (NTR) activity in hypoxic cells and tissues in situ represents an important step toward accurate delineation of hypoxic disease loci. However, it remains challenging to develop fluorescent probes with the necessary attributes of selectivity, sensitivity, precise targeting and aqueous solubility. Herein, two kinds of fluores...

Plasmonic sensors exhibit tremendous potential to accomplish real-time, label-free, and high-sensitivity biosensing. Gold nanohole array (GNA) is one of the classic plasmonic nanostructures that can be readily fabricated and integrated into microfluidic platforms for a variety of applications. Even though GNA has been widely studied, new phenomena...

A photothermally generated microbubble on a single-mode fiber tip with tunable frequency bandwidth was demonstrated for sensitive detection of acoustic waves. The microbubble with spherical gas-water interface formed a flexible Fabry-Pérot cavity at the fiber tip and detected the acoustic waves by interferometric readout of the bubble deformation....

This paper shows a platform for reading out results of immunologic recognition by spectral integration of microfiber long-period grating and photothermal generation from immunoassay-associated plasmonic resonance. Experimental verification of chromium ion detection is also presented.

Although photonics presents the fastest and most energy-efficient method of data transfer, magnetism still offers the cheapest and most natural way to store data. The ultrafast and energy-efficient optical control of magnetism is presently a missing technological link that prevents us from reaching the next evolution in information processing. The...

Optical multiplexing1–11 by creating orthogonal data channels has offered an unparalleled approach for information encoding with substantially improved density and security. Despite the fact that the orbital angular momentum (OAM) of light involves physical orthogonal division, the lack of explicit OAM sensitivity at the nanoscale prevents this fea...