Soliton molecules(SMs),bounded and self-assembled of particle-like dissipative solitons,exist with versatile mutual interactions and manifest substantial potential in soliton communication and optical data storage.How...Soliton molecules(SMs),bounded and self-assembled of particle-like dissipative solitons,exist with versatile mutual interactions and manifest substantial potential in soliton communication and optical data storage.However,controllable manipulation of the bounded molecular patterns remains challenging,as reaching a specific operation regime in lasers generally involves adjusting multiple control parameters in connection with a wide range of accessible pulse dynamics.An evolutionary algorithm is implemented for intelligent control of SMs in a 2μm ultrafast fiber laser mode locked through nonlinear polarization rotation.Depending on the specifications of the merit function used for the optimization procedure,various SM operations are obtained,including spectra shape programming and controllable deterministic switching of doublet and triplet SMs operating in stationary or pulsation states with reconfigurable temporal separations,frequency locking of pulsation SMs,doublet and SM complexes with controllable pulsation ratio,etc.Digital encoding is further demonstrated in this platform by employing the self-assembled characteristics of SMs.Our work opens up an avenue for active SM control beyond conventional telecom bands and brings useful insights into nonlinear science and applications.展开更多
Water photoacoustic microscopy(PAM)enables water absorption contrast mapping in deep biological tissue,which further allows a more detailed architecture analysis and facilitates a better understanding of metabolic and...Water photoacoustic microscopy(PAM)enables water absorption contrast mapping in deep biological tissue,which further allows a more detailed architecture analysis and facilitates a better understanding of metabolic and pathophysiological pathways.The strongest absorption peak of water in the near-infrared region occurs at 1930 nm,where the first overtone of the O-H bond lies.However,general light sources operating in this band hitherto still suffer from low optical signal-to-noise ratio and suboptimal pulse widths for photoacoustic signal generation.These lead to not only PAM contrast deterioration but also a high risk of sample photodamage.Consequently,we developed a hybrid optical parametrically-oscillating emitter(HOPE)source for an improved water PAM image contrast,leading to noninvasive and safer bioimaging applications.Our proposed source generates 1930 nm laser pulses with high spectral purity at a repetition rate of 187.5 kHz.The pulse width is flexibly tunable from 4 to 15 ns,and the maximum pulse energy is 700 nJ with a power stability of 1.79%.Leveraging these advancements,we also demonstrated high-contrast water PAM in multifaceted application scenarios,including tracking the dynamic of water distribution in a zebrafish embryo,visualizing the water content of a murine tumor xenograft,and mapping the fluid distribution in an edema mouse ear model.Finally,we showcased 1750-nm/1930-nm dual-color PAM for quantitative imaging of lipid and water distributions with reduced cross talk and imaging artifacts.Given all these results,we believe that our HOPE source can heighten water PAM’s relevance in both biological research and clinical diagnostics.展开更多
Current gradient-index(GRIN)lens based proximal-driven intracoronary optical coherence tomography(ICOCT)probes consist of a spacer and a GRIN lens with large gradient constant.This design provides great flexibility to...Current gradient-index(GRIN)lens based proximal-driven intracoronary optical coherence tomography(ICOCT)probes consist of a spacer and a GRIN lens with large gradient constant.This design provides great flexibility to control beam profiles,but the spacer length should be well controlled to obtain desired beam profiles and thus it sets an obstacle in mass catheter fabrication.Besides,although GRIN lens with large gradient constant can provide tight focus spot,it has short depth of focus and fast-expanded beam which leads to poor lateral resolution for deep tissue.In this paper,a type of spacer-removed probe is demonstrated with a small gradient constant GRIN lens.This design simplifies the fabrica-tion process and is suitable for mass production.The output beam of the catheter is a narrow nearly collimated light beam,referred to as pencil beam here.The full width at half maximum beam size varies from 35.1μm to 75.3μm in air over 3-mm range.Probe design principles are elaborated with probe/catheter fabrication and performance test.The in vivo imaging of the catheter was verified by a clinical ICOCT system.Those results prove that this novel pencil-beam scanning catheter is potentially a good choice for ICOCT systems.展开更多
In two-photon microscopy,low illumination powers on samples and a high signal-to-noise ratio(SNR)of the excitation laser are highly desired for alleviating the problems of photobleaching and phototoxicity,as well as p...In two-photon microscopy,low illumination powers on samples and a high signal-to-noise ratio(SNR)of the excitation laser are highly desired for alleviating the problems of photobleaching and phototoxicity,as well as providing clean backgrounds for images.However,the high-repetition-rate Ti:sapphire laser and the low-SNR Raman-shift lasers fall short of meeting these demands,especially when used for deep penetrations.Here,we demonstrate a 937-nm laser frequency-doubled from an all-fiber mode-locked laser at 1.8μm with a low repetition rate of∼9 MHz and a high SNR of 74 dB.We showcase two-photon excitations with low illumination powers on multiple types of biological tissues,including fluorescence imaging of mouse brain neurons labeled with green and yellow fluorescence proteins(GFP and YFP),DiI-stained and GFP-labeled blood vessels,Alexa Fluor 488/568-stained mouse kidney,and second-harmonic-generation imaging of the mouse skull,leg,and tail.We achieve a penetration depth in mouse brain tissues up to 620μm with an illumination power as low as∼10 mW,and,even for the DiI dye with an extremely low excitation efficiency of 3.3%,the penetration depth is still up to 530μm,indicating that the low-repetition-rate source works efficiently for a wide range of dyes with a fixed excitation wavelength.The low-repetition-rate and high-SNR excitation source holds great potential for biological investigations,such as in vivo deep-tissue imaging.展开更多
Lipid imaging by conventional photoacoustic microscopy subjects to direct contact sensing with relatively low detection bandwidth and sensitivity,which induces superficial imaging depth and low signalto-noise ratio(SN...Lipid imaging by conventional photoacoustic microscopy subjects to direct contact sensing with relatively low detection bandwidth and sensitivity,which induces superficial imaging depth and low signalto-noise ratio(SNR)in practical imaging scenarios.Herein,we present a photoacoustic remote sensing microscopy for lipid distribution mapping in bio-tissue,featuring noncontact implementation,broad detection bandwidth,deep penetration depth,and high SNR.A tailored high-energy pulsed laser source with a spectrum centered at 1750 nm is used as the excitation beam,while a cofocused 1550 nm continuous-wave beam is used as the probe signal.The pump wavelength is selected to overlap the first overtone of the C-H bond in response to the intensive absorption of lipid molecules,which introduces a much-enhanced SNR(55 dB)onto photoacoustic remote sensing(PARS)signals.Meanwhile,the optical sensing scheme of the photoacoustic signals provides broadband detection compared to the acoustic transducer and refrains the bio-samples from direct contact operations by eliminating the ultrasonic coupling medium.Taking merits of the high detection sensitivity,deep penetration depth,broadband detection,and high resolution of the PARS system,high-quality tissue scale lipid imaging is demonstrated in a model organism and brain slice.展开更多
Highly sensitive and broadband ultrasound detection is important for photoacoustic imaging,biomedical ultrasound,and ultrasonic nondestructive testing.The elasto-optical refractive index modulation induced by ultrasou...Highly sensitive and broadband ultrasound detection is important for photoacoustic imaging,biomedical ultrasound,and ultrasonic nondestructive testing.The elasto-optical refractive index modulation induced by ultrasound arouses a transient phase shift of a probe beam.Highly sensitive phase detection with a high Q factor resonator is desirable to visualize the ultraweak transient ultrasonic field.However,current phase-sensitive ultrasonic detectors suffer from limited bandwidth,mutual interference between intensity and phase,and significant phase noise,which become key to limiting further improvement of detection performance.We report a phase-sensitive detector with a bandwidth of up to 100 MHz based on dual-comb multiheterodyne interferometry(DCMHI).By sensing the phase shift induced by the ultrasound without any resonators in the medium,the DCMHI boosted the phase sensitivity by coherent accumulation without any magnitude averaging and extra radio frequency amplification.DCMHI offers high sensitivity and broad bandwidth as the noise-equivalent pressure reaches 31 mPa∕pHz under 70 MHz acoustic responses.With a large repetition rate difference of up to 200 MHz of dual comb,DCMHI can achieve broadband acoustic responses up to 100 MHz and a maximum possible imaging acquisition rate of 200 MHz.It is expected that DCMHI can offer a new perspective on the new generation of optical ultrasound detectors.展开更多
Photoacoustic microscopy(PAM)operating within the 1.7-μm absorption window holds great promise for the quantitative imaging of lipids in various biological tissues.Despite its potential,the effectiveness of lipid-bas...Photoacoustic microscopy(PAM)operating within the 1.7-μm absorption window holds great promise for the quantitative imaging of lipids in various biological tissues.Despite its potential,the effectiveness of lipid-based PAM has been limited by the performance of existing nanosecond laser sources at this wavelength.In this work,we introduce a 1725-nm hybrid optical parametric oscillator emitter(HOPE)characterized by a narrow bandwidth of 1.4 nm,an optical signal-to-noise ratio(OSNR)of approximately 34 dB,and a high spectral energy density of up to 480 n J/nm.This advanced laser source significantly enhances the sensitivity of photoacoustic imaging,allowing for the detailed visualization of intrahepatic lipid distributions with an impressive maximal contrast ratio of 23.6:1.Additionally,through segmentation-based analysis of PAM images,we were able to determine steatosis levels that align with clinical assessments,thereby demonstrating the potential of our system for high-contrast,label-free lipid quantification.Our findings suggest that the proposed 1725-nm HOPE source could be a powerful tool for biomedical research and clinical diagnostics,offering a substantial improvement over current technologies in the accurate and non-invasive assessment of lipid accumulation in tissues.展开更多
Neural networks(NNs),especially electronic-based NNs,have been rapidly developed in the past few decades.However,the electronic-based NNs rely more on highly advanced and heavy power-consuming hardware,facing its bott...Neural networks(NNs),especially electronic-based NNs,have been rapidly developed in the past few decades.However,the electronic-based NNs rely more on highly advanced and heavy power-consuming hardware,facing its bottleneck due to the slowdown of Moore's law.Optical neural networks(ONNs),in which NNs are realized via optical components with information carried by photons at the speed of light,are drawing more attention nowadays.Despite the advantages of higher processing speed and lower system power consumption,one major challenge is to realize reliable and reusable algorithms in physical approaches,particularly nonlinear functions,for higher accuracy.In this paper,a versatile parametric-process-based ONN is demonstrated with its adaptable nonlinear computation realized using the highly nonlinear fiber(HNLF).With the specially designed modelocked laser(MLL)and dispersive Fourier transform(DFT)algorithm,the overall computation frame rate can reach up to 40 MHz.Compared to ONNs using only linear computations,this system is able to improve the classification accuracies from 81.8%to 88.8%for the MNIST-digit dataset,and from 80.3%to 97.6%for the Vowel spoken audio dataset,without any hardware modifications.展开更多
We demonstrate a versatile bismuth-doped fiber pulse source that is seeded by a mode-locked fiber laser operating in different regimes with different net dispersions in the same cavity,including the square-wave noise-...We demonstrate a versatile bismuth-doped fiber pulse source that is seeded by a mode-locked fiber laser operating in different regimes with different net dispersions in the same cavity,including the square-wave noise-like pulse regime with anomalous net dispersion at 1331 nm and the multi-pulse soliton regime with normal net dispersion at 1320 nm.The versatile pulse evolutions and the multi-pulse dynamics in these two regimes are investigated under different pump powers or polarization states.The seed pulses are then amplified by a bismuth-doped fiber amplifier,which boosts the pulse energy to 21 nJ with a slope efficiency of 21.3%without power saturation and is anticipated to be useful for practical applications.展开更多
The slow axial scanning rate in multiphoton microscopy(MPM)has traditionally limited the speed of three-dimensional(3D)imaging.Recently,a lot of techniques have been proposed to speed up the axial scan;however,there i...The slow axial scanning rate in multiphoton microscopy(MPM)has traditionally limited the speed of three-dimensional(3D)imaging.Recently,a lot of techniques have been proposed to speed up the axial scan;however,there inherently exists an upper limit of the achievable maximum scanning rate restricted by full sampling.To overcome this limitation,we developed an approach to realize multiplane compressive imaging in MPM that empowers conventional laser scanning microscopies with rapid axial scanning capacity in a sub-sampling way.To realize the technique,we achieved two technical breakthroughs:first,we proposed a concept to axially encode the beam with binary intensities;second,compressive sensing theory was introduced to the axial direction in MPM based on the axial-coded point spread function.This 3D imaging technology is termed arbitrary illumination microscopy with encoded depth(AIMED),enabling a nearly double volumetric imaging speed with subcellular resolution for mouse brain neurons in experiments and performing approximately eight times faster in simulation.The axial compressive ability of AIMED can be readily extended to other microscopic modalities for achieving axially compressive 3D imaging.Our concepts demonstrated provide insights into the entire field of advanced volumetric microscopy.展开更多
Period-doubling bifurcation,as an intermediate state between order and chaos,is ubiquitous in all disciplines of nonlinear science.However,previous experimental observations of period doubling in ultrafast fiber laser...Period-doubling bifurcation,as an intermediate state between order and chaos,is ubiquitous in all disciplines of nonlinear science.However,previous experimental observations of period doubling in ultrafast fiber lasers are mainly restricted to self-sustained steady state,controllable manipulation and dynamic switching between period doubling and other intriguing dynamical states are still largely unexplored.Here,we propose to expand the vision of dissipative soliton periodic doubling,which we illustrate experimentally by reporting original spontaneous,collisional,and controllable spectral period doubling in a polarization-maintaining ultrafast fiber laser.Specifically,the spontaneous period doubling can be observed in both single-and double-pulses.The mechanism of the switchable state and periodic doubling was revealed by numerical simulation.Moreover,state transformation of individual solitons can be resolved during the collision of triple solitons involving stationary,oscillating,and period doubling.Further,controllable deterministic switching between period doubling and other dynamical states,as well as exemplifying the application of period-doubling-based digital encoding,is achieved under programmable pump modulation.Our results open a new window for unveiling complex Hopf bifurcation in dissipative systems and bring useful insights into nonlinear science and applications.展开更多
Soliton explosions,among the most exotic dynamics,have been extensively studied on parameter invariant stationary solitons.However,the explosion dynamics are still largcly unexplored in breathing dissipative solitons ...Soliton explosions,among the most exotic dynamics,have been extensively studied on parameter invariant stationary solitons.However,the explosion dynamics are still largcly unexplored in breathing dissipative solitons as a dynamic solution to many nonlincar systems.Here,we report on the first observation of a breathing dissipative soliton explosion in a nct-normal-dispersion bidirectional ultrafast fiber lascr.The breathing soliton explos ionscould be stimulated by the soliton buildup process or alteration of polarization settings.Transient breathing soliton pairs with intensive repulsion that is sensitive to initial conditions can also be triggered by multiple soliton explosions in the soliton buildup process instead of being triggered by varying polarization settings.The high bchavior similarity also exists in the breathing soliton buildup and explosion process owing to the common gain and loss modulation.In addition,dissipative rogue waves were detected in the breathing soliton explosion,and the collision of breathing soliton significantly enhanced the amplitude of rogue waves,which is characteristic of the breathing solitons in a bidirectional fiber laser.These results shed new insights into complex dissipative soliton dynamics.展开更多
Coherent Raman scattering(CRS)microscopy is widely recognized as a powerful tool for tackling biomedical problems based on its chemically specific label-free contrast,high spatial and spectral resolution,and high sens...Coherent Raman scattering(CRS)microscopy is widely recognized as a powerful tool for tackling biomedical problems based on its chemically specific label-free contrast,high spatial and spectral resolution,and high sensitivity.However,the clinical translation of CRS imaging technologies has long been hindered by traditional solid-state lasers with environmentally sensitive operations and large footprints.Ultrafast fibre lasers can potentially overcome these shortcomings but have not yet been fully exploited for CRS imaging,as previous implementations have suffered from high intensity noise,a narrow tuning range and low power,resulting in low image qualities and slow imaging speeds.Here,we present a novel high-power self-synchronized two-colour pulsed fibre laser that achieves excellent performance in terms of intensity stability(improved by 50 dB),timing jitter(24.3 fs),average power fluctuation(<0.5%),modulation depth(>20 dB)and pulse width variation(<1.8%)over an extended wavenumber range(2700-3550 cm^(−1)).The versatility of the laser source enables,for the first time,high-contrast,fast CRS imaging without complicated noise reduction via balanced detection schemes.These capabilities are demonstrated in this work by imaging a wide range of species such as living human cells and mouse arterial tissues and performing multimodal nonlinear imaging of mouse tail,kidney and brain tissue sections by utilizing second-harmonic generation and twophoton excited fluorescence,which provides multiple optical contrast mechanisms simultaneously and maximizes the gathered information content for biological visualization and medical diagnosis.This work also establishes a general scenario for remodelling existing lasers into synchronized two-colour lasers and thus promotes a wider popularization and application of CRS imaging technologies.展开更多
We demonstrate a high-energy all-fiber short wavelength gain-switched thulium-doped fiber laser for volumetric photoacoustic(PA)imaging of lipids.The laser cavity is constructed by embedding a short piece of gain fibe...We demonstrate a high-energy all-fiber short wavelength gain-switched thulium-doped fiber laser for volumetric photoacoustic(PA)imaging of lipids.The laser cavity is constructed by embedding a short piece of gain fiber between a pair of fiber Bragg gratings(FBGs).Through using three pairs of FBGs with operation wavelengths at1700,1725,and 1750 nm,three similar lasers are realized with a cavity length of around 25 cm.Under a maximum pump energy of 300μJ at 1560 nm,laser pulse energies of 58.2,66.8,and 75.3μJ are,respectively,achieved with a minimum pulse width of<16.7 ns at a repetition rate of 10 kHz.Volumetric imaging of lipids is validated through scanning a fat beef slice with a PA microscopy system incorporated with the newly developed source,and a lateral resolution of 18.8μm and an axial resolution of 172.9μm are achieved.Moreover,the higher shooting speed of the developed source can potentially allow for increasing at twice the frame rate of current intravascular PA imaging.展开更多
Parallelized fluorescence imaging has been a long-standing pursuit that can address the unmet need for a comprehensive three-dimensional(3D)visualization of dynamical biological processes with minimal photodamage.Howe...Parallelized fluorescence imaging has been a long-standing pursuit that can address the unmet need for a comprehensive three-dimensional(3D)visualization of dynamical biological processes with minimal photodamage.However,the available approaches are limited to incomplete parallelization in only two dimensions or sparse sampling in three dimensions.We hereby develop a novel fluorescence imaging approach,called coded light-sheet array microscopy(CLAM),which allows complete parallelized 3D imaging without mechanical scanning.Harnessing the concept of an“infinity mirror”,CLAM generates a light-sheet array with controllable sheet density and degree of coherence.Thus,CLAM circumvents the common complications of multiple coherent light-sheet generation in terms of dedicated wavefront engineering and mechanical dithering/scanning.Moreover,the encoding of multiplexed optical sections in CLAM allows the synchronous capture of all sectioned images within the imaged volume.We demonstrate the utility of CLAM in different imaging scenarios,including a light-scattering medium,an optically cleared tissue,and microparticles in fluidic flow.CLAM can maximize the signal-to-noise ratio and the spatial duty cycle,and also provides a further reduction in photobleaching compared to the major scanning-based 3D imaging systems.The flexible implementation of CLAM regarding both hardware and software ensures compatibility with any light-sheet imaging modality and could thus be instrumental in a multitude of areas in biological research.展开更多
The optical scanning holography(OSH)technique can capture all the three-dimensional volume information of an object in a hologram via a single raster scan.The digital hologram can then be processed to reconstruct indi...The optical scanning holography(OSH)technique can capture all the three-dimensional volume information of an object in a hologram via a single raster scan.The digital hologram can then be processed to reconstruct individual sectional images of the object.In this paper,we present a scheme to reconstruct sectional images in OSH with enhanced depth resolution,where a spatial light modulator(SLM)is adopted as a configurable point pupil.By switching the SLM between two states,different Fresnel zone plates(FZPs)are generated based on the same optical system.With extra information provided by different FZPs,a depth resolution at 0.7μm can be achieved.展开更多
Water plays a vital role in biological metabolism and it would be essential to trace the water content non-invasively,such as leveraging the vibrational absorption peak of the O-H bond.However,due to the lack of an ef...Water plays a vital role in biological metabolism and it would be essential to trace the water content non-invasively,such as leveraging the vibrational absorption peak of the O-H bond.However,due to the lack of an efficient laser source,it was challenging to image the water content in the deep tissue with micron-level spatial resolution.To address this problem,we develop a high-power hybrid optical parametrically-oscillating emitter(HOPE)at 1930 nm,at which the vibrational absorption peak of the O-H bond locates.The maximum pulse energy is over 1.74μJ with a pulse repetition rate of 50 kHz and a pulse width of 15 ns.We employ this laser source in the optical-resolution photoacoustic microscopy(OR-PAM)system to image the water content in the phantom and the biological tissue in vitro.Our 1930-nm OR-PAM could map the water content in the complex tissue environment at high spatial resolution,deep penetration depth,improved sensitivity,and suppressed artifact signal of the lipid.展开更多
Childhood obesity is one of the biggest public health challenges globally.It is associated with various adverse health consequences throughout life.Prevention and early intervention represent the most reasonable and c...Childhood obesity is one of the biggest public health challenges globally.It is associated with various adverse health consequences throughout life.Prevention and early intervention represent the most reasonable and costeffective approaches.Considerable progress has been achieved in the management of obesity in children and adolescents;yet,implementation in the real world remains a challenge.This article aimed to present an overview of the diagnosis and management of obesity in children and adolescents.展开更多
The role of gut microbiota in modulating the durability of cOVID-19 vaccine immunity is yet to be characterised.In this cohort study,we collected blood and stool samples of 121 BNT162b2 and 40 CoronaVac vaccinees at b...The role of gut microbiota in modulating the durability of cOVID-19 vaccine immunity is yet to be characterised.In this cohort study,we collected blood and stool samples of 121 BNT162b2 and 40 CoronaVac vaccinees at baseline,1 month,and 6 months post vaccination(p.v).Neutralisation antibody,plasma cytokine and chemokines were measured and associated with the gut microbiota and metabolome composition.展开更多
基金supported by the Research Grants Council of the Hong Kong Special Administrative Region of China(Grant Nos.HKU 17212824,HKU 17210522,HKU C7074-21G,HKU R7003-21,and HKU 17205321)the Innovation and Technology Commission of the Hong Kong SAR Government(Grant Nos.MHP/073/20 and MHP/057/21),and the Health@InnoHK program.
文摘Soliton molecules(SMs),bounded and self-assembled of particle-like dissipative solitons,exist with versatile mutual interactions and manifest substantial potential in soliton communication and optical data storage.However,controllable manipulation of the bounded molecular patterns remains challenging,as reaching a specific operation regime in lasers generally involves adjusting multiple control parameters in connection with a wide range of accessible pulse dynamics.An evolutionary algorithm is implemented for intelligent control of SMs in a 2μm ultrafast fiber laser mode locked through nonlinear polarization rotation.Depending on the specifications of the merit function used for the optimization procedure,various SM operations are obtained,including spectra shape programming and controllable deterministic switching of doublet and triplet SMs operating in stationary or pulsation states with reconfigurable temporal separations,frequency locking of pulsation SMs,doublet and SM complexes with controllable pulsation ratio,etc.Digital encoding is further demonstrated in this platform by employing the self-assembled characteristics of SMs.Our work opens up an avenue for active SM control beyond conventional telecom bands and brings useful insights into nonlinear science and applications.
基金supported by the Research Grants Council of the Hong Kong Special Administrative Region(SAR)of China(Grant Nos.HKU 17210522,HKU C7074-21G,HKU 17205321,and HKU 17200219)ITF MHKJFS Projects(Grant Nos.MHP/073/20 and MHP/057/21)the Health@InnoHK Program of the Innovation and Technology Commission of the Hong Kong SAR Government.
文摘Water photoacoustic microscopy(PAM)enables water absorption contrast mapping in deep biological tissue,which further allows a more detailed architecture analysis and facilitates a better understanding of metabolic and pathophysiological pathways.The strongest absorption peak of water in the near-infrared region occurs at 1930 nm,where the first overtone of the O-H bond lies.However,general light sources operating in this band hitherto still suffer from low optical signal-to-noise ratio and suboptimal pulse widths for photoacoustic signal generation.These lead to not only PAM contrast deterioration but also a high risk of sample photodamage.Consequently,we developed a hybrid optical parametrically-oscillating emitter(HOPE)source for an improved water PAM image contrast,leading to noninvasive and safer bioimaging applications.Our proposed source generates 1930 nm laser pulses with high spectral purity at a repetition rate of 187.5 kHz.The pulse width is flexibly tunable from 4 to 15 ns,and the maximum pulse energy is 700 nJ with a power stability of 1.79%.Leveraging these advancements,we also demonstrated high-contrast water PAM in multifaceted application scenarios,including tracking the dynamic of water distribution in a zebrafish embryo,visualizing the water content of a murine tumor xenograft,and mapping the fluid distribution in an edema mouse ear model.Finally,we showcased 1750-nm/1930-nm dual-color PAM for quantitative imaging of lipid and water distributions with reduced cross talk and imaging artifacts.Given all these results,we believe that our HOPE source can heighten water PAM’s relevance in both biological research and clinical diagnostics.
基金financial supports from the National Natural Science Foundation of China(Grant No.81927805)Shenzhen Municipal Science and Technology Plan Project,China(Grant No.JCYJ20160427183803458)。
文摘Current gradient-index(GRIN)lens based proximal-driven intracoronary optical coherence tomography(ICOCT)probes consist of a spacer and a GRIN lens with large gradient constant.This design provides great flexibility to control beam profiles,but the spacer length should be well controlled to obtain desired beam profiles and thus it sets an obstacle in mass catheter fabrication.Besides,although GRIN lens with large gradient constant can provide tight focus spot,it has short depth of focus and fast-expanded beam which leads to poor lateral resolution for deep tissue.In this paper,a type of spacer-removed probe is demonstrated with a small gradient constant GRIN lens.This design simplifies the fabrica-tion process and is suitable for mass production.The output beam of the catheter is a narrow nearly collimated light beam,referred to as pencil beam here.The full width at half maximum beam size varies from 35.1μm to 75.3μm in air over 3-mm range.Probe design principles are elaborated with probe/catheter fabrication and performance test.The in vivo imaging of the catheter was verified by a clinical ICOCT system.Those results prove that this novel pencil-beam scanning catheter is potentially a good choice for ICOCT systems.
基金Research Grants Council of the Hong Kong Special Administrative Region of China(HKU C7074-21GF,HKU 17205321,HKU 17200219,HKU 17209018,CityU T42-103/16-N)and Health@InnoHK program of the Innovation and Technology Commission of the Hong Kong SAR Government.
文摘In two-photon microscopy,low illumination powers on samples and a high signal-to-noise ratio(SNR)of the excitation laser are highly desired for alleviating the problems of photobleaching and phototoxicity,as well as providing clean backgrounds for images.However,the high-repetition-rate Ti:sapphire laser and the low-SNR Raman-shift lasers fall short of meeting these demands,especially when used for deep penetrations.Here,we demonstrate a 937-nm laser frequency-doubled from an all-fiber mode-locked laser at 1.8μm with a low repetition rate of∼9 MHz and a high SNR of 74 dB.We showcase two-photon excitations with low illumination powers on multiple types of biological tissues,including fluorescence imaging of mouse brain neurons labeled with green and yellow fluorescence proteins(GFP and YFP),DiI-stained and GFP-labeled blood vessels,Alexa Fluor 488/568-stained mouse kidney,and second-harmonic-generation imaging of the mouse skull,leg,and tail.We achieve a penetration depth in mouse brain tissues up to 620μm with an illumination power as low as∼10 mW,and,even for the DiI dye with an extremely low excitation efficiency of 3.3%,the penetration depth is still up to 530μm,indicating that the low-repetition-rate source works efficiently for a wide range of dyes with a fixed excitation wavelength.The low-repetition-rate and high-SNR excitation source holds great potential for biological investigations,such as in vivo deep-tissue imaging.
基金supported by the Research Grants Council of the Hong Kong Special Administrative Region of China(Grant Nos.HKU 17210522,HKU C7074-21G,HKU 17205321,HKU 17200219,HKU 17209018,and CityU T42-103/16-N)the Health@InnoHK Program of the Innovation and Technology Commission of the Hong Kong SAR Government.
文摘Lipid imaging by conventional photoacoustic microscopy subjects to direct contact sensing with relatively low detection bandwidth and sensitivity,which induces superficial imaging depth and low signalto-noise ratio(SNR)in practical imaging scenarios.Herein,we present a photoacoustic remote sensing microscopy for lipid distribution mapping in bio-tissue,featuring noncontact implementation,broad detection bandwidth,deep penetration depth,and high SNR.A tailored high-energy pulsed laser source with a spectrum centered at 1750 nm is used as the excitation beam,while a cofocused 1550 nm continuous-wave beam is used as the probe signal.The pump wavelength is selected to overlap the first overtone of the C-H bond in response to the intensive absorption of lipid molecules,which introduces a much-enhanced SNR(55 dB)onto photoacoustic remote sensing(PARS)signals.Meanwhile,the optical sensing scheme of the photoacoustic signals provides broadband detection compared to the acoustic transducer and refrains the bio-samples from direct contact operations by eliminating the ultrasonic coupling medium.Taking merits of the high detection sensitivity,deep penetration depth,broadband detection,and high resolution of the PARS system,high-quality tissue scale lipid imaging is demonstrated in a model organism and brain slice.
基金supported by the Council of the Hong Kong Special Administrative Region of China(Grant Nos.HKU 17205321,HKU 17200219,HKU 17209018,E-HKU701/17,HKU C7047-16G,and CityU T42-103/16-N)the National Natural Science Foundation of China(Grant No.N_HKU712/16).
文摘Highly sensitive and broadband ultrasound detection is important for photoacoustic imaging,biomedical ultrasound,and ultrasonic nondestructive testing.The elasto-optical refractive index modulation induced by ultrasound arouses a transient phase shift of a probe beam.Highly sensitive phase detection with a high Q factor resonator is desirable to visualize the ultraweak transient ultrasonic field.However,current phase-sensitive ultrasonic detectors suffer from limited bandwidth,mutual interference between intensity and phase,and significant phase noise,which become key to limiting further improvement of detection performance.We report a phase-sensitive detector with a bandwidth of up to 100 MHz based on dual-comb multiheterodyne interferometry(DCMHI).By sensing the phase shift induced by the ultrasound without any resonators in the medium,the DCMHI boosted the phase sensitivity by coherent accumulation without any magnitude averaging and extra radio frequency amplification.DCMHI offers high sensitivity and broad bandwidth as the noise-equivalent pressure reaches 31 mPa∕pHz under 70 MHz acoustic responses.With a large repetition rate difference of up to 200 MHz of dual comb,DCMHI can achieve broadband acoustic responses up to 100 MHz and a maximum possible imaging acquisition rate of 200 MHz.It is expected that DCMHI can offer a new perspective on the new generation of optical ultrasound detectors.
基金Research Grants Council of the Hong Kong Special Administrative Region of China(HKU 17212824,HKU 17210522,HKU C7074-21G,HKU R7003-21,HKU 17205321)Innovation and Technology Commission of the Hong Kong SAR Government(MHP/073/20,MHP/057/21,Health@Inno HK program)Shenzhen Science Technology and Innovation Commission(SGDX20220530111403022)。
文摘Photoacoustic microscopy(PAM)operating within the 1.7-μm absorption window holds great promise for the quantitative imaging of lipids in various biological tissues.Despite its potential,the effectiveness of lipid-based PAM has been limited by the performance of existing nanosecond laser sources at this wavelength.In this work,we introduce a 1725-nm hybrid optical parametric oscillator emitter(HOPE)characterized by a narrow bandwidth of 1.4 nm,an optical signal-to-noise ratio(OSNR)of approximately 34 dB,and a high spectral energy density of up to 480 n J/nm.This advanced laser source significantly enhances the sensitivity of photoacoustic imaging,allowing for the detailed visualization of intrahepatic lipid distributions with an impressive maximal contrast ratio of 23.6:1.Additionally,through segmentation-based analysis of PAM images,we were able to determine steatosis levels that align with clinical assessments,thereby demonstrating the potential of our system for high-contrast,label-free lipid quantification.Our findings suggest that the proposed 1725-nm HOPE source could be a powerful tool for biomedical research and clinical diagnostics,offering a substantial improvement over current technologies in the accurate and non-invasive assessment of lipid accumulation in tissues.
基金Research Grants Council of the Hong Kong Special Administrative Region of China(HKU 17212824,HKU 17210522,HKU C7074-21G,HKU R7003-21,HKU 17205321)Innovation and Technology Commission—Hong Kong(MHP/073/20,MHP/057/21,Health@Inno HK programc)。
文摘Neural networks(NNs),especially electronic-based NNs,have been rapidly developed in the past few decades.However,the electronic-based NNs rely more on highly advanced and heavy power-consuming hardware,facing its bottleneck due to the slowdown of Moore's law.Optical neural networks(ONNs),in which NNs are realized via optical components with information carried by photons at the speed of light,are drawing more attention nowadays.Despite the advantages of higher processing speed and lower system power consumption,one major challenge is to realize reliable and reusable algorithms in physical approaches,particularly nonlinear functions,for higher accuracy.In this paper,a versatile parametric-process-based ONN is demonstrated with its adaptable nonlinear computation realized using the highly nonlinear fiber(HNLF).With the specially designed modelocked laser(MLL)and dispersive Fourier transform(DFT)algorithm,the overall computation frame rate can reach up to 40 MHz.Compared to ONNs using only linear computations,this system is able to improve the classification accuracies from 81.8%to 88.8%for the MNIST-digit dataset,and from 80.3%to 97.6%for the Vowel spoken audio dataset,without any hardware modifications.
基金supported by the Key-Area Research and Development Program of Guangdong Province(No.2023B0909010002)the Introduced Innovative Team Project of Guangdong Pearl River Talents Program(No.2021ZT09Z109)+2 种基金the Research Grants Council of the Hong Kong Special Administrative Region of China(Nos.HKU 17212824,HKU 17210522,HKU C7074-21G,HKU R7003-21,and HKU 17205321)the Innovation and Technology Commission of the Hong Kong SAR Government(Nos.MHP/073/20,MHP/057/21,and Health@InnoHK program)the Shenzhen Science Technology and Innovation Commission(SZSTI)(No.SGDX20220530111403022)。
文摘We demonstrate a versatile bismuth-doped fiber pulse source that is seeded by a mode-locked fiber laser operating in different regimes with different net dispersions in the same cavity,including the square-wave noise-like pulse regime with anomalous net dispersion at 1331 nm and the multi-pulse soliton regime with normal net dispersion at 1320 nm.The versatile pulse evolutions and the multi-pulse dynamics in these two regimes are investigated under different pump powers or polarization states.The seed pulses are then amplified by a bismuth-doped fiber amplifier,which boosts the pulse energy to 21 nJ with a slope efficiency of 21.3%without power saturation and is anticipated to be useful for practical applications.
基金supported by the Research Grants Council of the Hong Kong Special Administrative Region of China(Grant Nos.HKU 17210522,HKU C7074-21G,HKU R7003-21,HKU 17205321,and HKU 17200219)the Innovation and Technology Commission of the Hong Kong SAR Government(Grant Nos.MHP/073/20,MHP/057/21,and Health@Inno HK program)+2 种基金the National Natural Science Foundation of China(Grant No.62305274)the Natural Science Foundation of Xiamen City,China(Grant No.3502Z202371001)the Fujian Provincial Natural Science Foundation(Grant No.2024J01056)。
文摘The slow axial scanning rate in multiphoton microscopy(MPM)has traditionally limited the speed of three-dimensional(3D)imaging.Recently,a lot of techniques have been proposed to speed up the axial scan;however,there inherently exists an upper limit of the achievable maximum scanning rate restricted by full sampling.To overcome this limitation,we developed an approach to realize multiplane compressive imaging in MPM that empowers conventional laser scanning microscopies with rapid axial scanning capacity in a sub-sampling way.To realize the technique,we achieved two technical breakthroughs:first,we proposed a concept to axially encode the beam with binary intensities;second,compressive sensing theory was introduced to the axial direction in MPM based on the axial-coded point spread function.This 3D imaging technology is termed arbitrary illumination microscopy with encoded depth(AIMED),enabling a nearly double volumetric imaging speed with subcellular resolution for mouse brain neurons in experiments and performing approximately eight times faster in simulation.The axial compressive ability of AIMED can be readily extended to other microscopic modalities for achieving axially compressive 3D imaging.Our concepts demonstrated provide insights into the entire field of advanced volumetric microscopy.
基金supported by National Natural Science Foundation of China(12374402)Research Grants Council of the Hong Kong Special Administrative Region of China(HKU 17210522,HKU C7074-21G,HKU 17205321,HKU 17200219,MHP/073/20,MHP/057/21)Health@InnoHK program of the Innovation and Technology Commission of the Hong Kong SAR Government.
文摘Period-doubling bifurcation,as an intermediate state between order and chaos,is ubiquitous in all disciplines of nonlinear science.However,previous experimental observations of period doubling in ultrafast fiber lasers are mainly restricted to self-sustained steady state,controllable manipulation and dynamic switching between period doubling and other intriguing dynamical states are still largely unexplored.Here,we propose to expand the vision of dissipative soliton periodic doubling,which we illustrate experimentally by reporting original spontaneous,collisional,and controllable spectral period doubling in a polarization-maintaining ultrafast fiber laser.Specifically,the spontaneous period doubling can be observed in both single-and double-pulses.The mechanism of the switchable state and periodic doubling was revealed by numerical simulation.Moreover,state transformation of individual solitons can be resolved during the collision of triple solitons involving stationary,oscillating,and period doubling.Further,controllable deterministic switching between period doubling and other dynamical states,as well as exemplifying the application of period-doubling-based digital encoding,is achieved under programmable pump modulation.Our results open a new window for unveiling complex Hopf bifurcation in dissipative systems and bring useful insights into nonlinear science and applications.
基金National Natural Science Foundation of China(N_HKU712/16):Rcsearch Grants Council,University Grants Committee of the Hong Kong Special Administrative Region,China(CityU T42-103/16-N,E-HKU701/17,HKU17200219,HKU17209018,HKU C7047-16G).
文摘Soliton explosions,among the most exotic dynamics,have been extensively studied on parameter invariant stationary solitons.However,the explosion dynamics are still largcly unexplored in breathing dissipative solitons as a dynamic solution to many nonlincar systems.Here,we report on the first observation of a breathing dissipative soliton explosion in a nct-normal-dispersion bidirectional ultrafast fiber lascr.The breathing soliton explos ionscould be stimulated by the soliton buildup process or alteration of polarization settings.Transient breathing soliton pairs with intensive repulsion that is sensitive to initial conditions can also be triggered by multiple soliton explosions in the soliton buildup process instead of being triggered by varying polarization settings.The high bchavior similarity also exists in the breathing soliton buildup and explosion process owing to the common gain and loss modulation.In addition,dissipative rogue waves were detected in the breathing soliton explosion,and the collision of breathing soliton significantly enhanced the amplitude of rogue waves,which is characteristic of the breathing solitons in a bidirectional fiber laser.These results shed new insights into complex dissipative soliton dynamics.
基金supported by the Germany/Hong Kong Joint Research Scheme sponsored by the Research Grants Council of Hong Kongthe Germany Academic Exchange Service of Germany(G-HKU708/14,DAAD-57138104)+5 种基金the European Union’s Horizon 2020 research and innovation program under the Marie Sklodowska-Curie Grant Agreement No.766181,project“DeLIVER”the Research Grants Council of the Hong Kong Special Administrative Region,China(HKU 17205215,CityU T42-103/16-N,EHKU701/17,and HKU C7047-16G)the National Natural Science Foundation of China(N_HKU712/16)Innovation and Technology Fund(GHP/050/14GD)support for the Article Processing Charge by the Deutsche Forschungsgemeinschaftthe Open Access Publication Fund of Bielefeld University.
文摘Coherent Raman scattering(CRS)microscopy is widely recognized as a powerful tool for tackling biomedical problems based on its chemically specific label-free contrast,high spatial and spectral resolution,and high sensitivity.However,the clinical translation of CRS imaging technologies has long been hindered by traditional solid-state lasers with environmentally sensitive operations and large footprints.Ultrafast fibre lasers can potentially overcome these shortcomings but have not yet been fully exploited for CRS imaging,as previous implementations have suffered from high intensity noise,a narrow tuning range and low power,resulting in low image qualities and slow imaging speeds.Here,we present a novel high-power self-synchronized two-colour pulsed fibre laser that achieves excellent performance in terms of intensity stability(improved by 50 dB),timing jitter(24.3 fs),average power fluctuation(<0.5%),modulation depth(>20 dB)and pulse width variation(<1.8%)over an extended wavenumber range(2700-3550 cm^(−1)).The versatility of the laser source enables,for the first time,high-contrast,fast CRS imaging without complicated noise reduction via balanced detection schemes.These capabilities are demonstrated in this work by imaging a wide range of species such as living human cells and mouse arterial tissues and performing multimodal nonlinear imaging of mouse tail,kidney and brain tissue sections by utilizing second-harmonic generation and twophoton excited fluorescence,which provides multiple optical contrast mechanisms simultaneously and maximizes the gathered information content for biological visualization and medical diagnosis.This work also establishes a general scenario for remodelling existing lasers into synchronized two-colour lasers and thus promotes a wider popularization and application of CRS imaging technologies.
基金Research Grants Council of the Hong Kong Special Administrative Region,China(City U T42-103/16-N,EHKU701/17,HKU 172000219,HKU 17209018,HKU C7047-16G)National Natural Science Foundation of China(N_HKU712/16)。
文摘We demonstrate a high-energy all-fiber short wavelength gain-switched thulium-doped fiber laser for volumetric photoacoustic(PA)imaging of lipids.The laser cavity is constructed by embedding a short piece of gain fiber between a pair of fiber Bragg gratings(FBGs).Through using three pairs of FBGs with operation wavelengths at1700,1725,and 1750 nm,three similar lasers are realized with a cavity length of around 25 cm.Under a maximum pump energy of 300μJ at 1560 nm,laser pulse energies of 58.2,66.8,and 75.3μJ are,respectively,achieved with a minimum pulse width of<16.7 ns at a repetition rate of 10 kHz.Volumetric imaging of lipids is validated through scanning a fat beef slice with a PA microscopy system incorporated with the newly developed source,and a lateral resolution of 18.8μm and an axial resolution of 172.9μm are achieved.Moreover,the higher shooting speed of the developed source can potentially allow for increasing at twice the frame rate of current intravascular PA imaging.
基金financially supported by the Research Grants Council of the Hong Kong Special Administrative Region of China(HKU 17209017,17259316,17207715,C7047-16G,HKU 17209018,E-HKU701/17,CityU T42-103/16-N,and HKU 17205215)the Innovation and Technology Support Program(ITS/204/18 and GHP/024/16GD)+1 种基金the University Development Funds of the University of Hong KongNatural Science Foundation of China(N_HKU712/16).
文摘Parallelized fluorescence imaging has been a long-standing pursuit that can address the unmet need for a comprehensive three-dimensional(3D)visualization of dynamical biological processes with minimal photodamage.However,the available approaches are limited to incomplete parallelization in only two dimensions or sparse sampling in three dimensions.We hereby develop a novel fluorescence imaging approach,called coded light-sheet array microscopy(CLAM),which allows complete parallelized 3D imaging without mechanical scanning.Harnessing the concept of an“infinity mirror”,CLAM generates a light-sheet array with controllable sheet density and degree of coherence.Thus,CLAM circumvents the common complications of multiple coherent light-sheet generation in terms of dedicated wavefront engineering and mechanical dithering/scanning.Moreover,the encoding of multiplexed optical sections in CLAM allows the synchronous capture of all sectioned images within the imaged volume.We demonstrate the utility of CLAM in different imaging scenarios,including a light-scattering medium,an optically cleared tissue,and microparticles in fluidic flow.CLAM can maximize the signal-to-noise ratio and the spatial duty cycle,and also provides a further reduction in photobleaching compared to the major scanning-based 3D imaging systems.The flexible implementation of CLAM regarding both hardware and software ensures compatibility with any light-sheet imaging modality and could thus be instrumental in a multitude of areas in biological research.
基金This research was supported in part by the Research Grants Council of the Hong Kong Special Administrative Region,China,under Projects HKU 7138/11E and 7131/12EH.Ou is also grateful to the National Science Foundation of China(Grant 61107018)the Fundamental Research Funds for the Central Universities(ZYGX2011J033),which allow her to enter into this collaborative research.
文摘The optical scanning holography(OSH)technique can capture all the three-dimensional volume information of an object in a hologram via a single raster scan.The digital hologram can then be processed to reconstruct individual sectional images of the object.In this paper,we present a scheme to reconstruct sectional images in OSH with enhanced depth resolution,where a spatial light modulator(SLM)is adopted as a configurable point pupil.By switching the SLM between two states,different Fresnel zone plates(FZPs)are generated based on the same optical system.With extra information provided by different FZPs,a depth resolution at 0.7μm can be achieved.
基金This project is funded by Research Grants Council of the Hong Kong Special Administrative Region,China(HKU 17200219,HKU 17209018,E-HKU701/17,CityU T42-103/16-N,and HKU C7047-16G)Natural Science Foundation of China(N_HKU712/16)。
文摘Water plays a vital role in biological metabolism and it would be essential to trace the water content non-invasively,such as leveraging the vibrational absorption peak of the O-H bond.However,due to the lack of an efficient laser source,it was challenging to image the water content in the deep tissue with micron-level spatial resolution.To address this problem,we develop a high-power hybrid optical parametrically-oscillating emitter(HOPE)at 1930 nm,at which the vibrational absorption peak of the O-H bond locates.The maximum pulse energy is over 1.74μJ with a pulse repetition rate of 50 kHz and a pulse width of 15 ns.We employ this laser source in the optical-resolution photoacoustic microscopy(OR-PAM)system to image the water content in the phantom and the biological tissue in vitro.Our 1930-nm OR-PAM could map the water content in the complex tissue environment at high spatial resolution,deep penetration depth,improved sensitivity,and suppressed artifact signal of the lipid.
基金The Science and Technology Project of Jilin Province,China,Grant/Award Number:20200201421JC。
文摘Childhood obesity is one of the biggest public health challenges globally.It is associated with various adverse health consequences throughout life.Prevention and early intervention represent the most reasonable and costeffective approaches.Considerable progress has been achieved in the management of obesity in children and adolescents;yet,implementation in the real world remains a challenge.This article aimed to present an overview of the diagnosis and management of obesity in children and adolescents.
基金The study was supported by the Health and Medical Research Fund(HMRF)Commissioned Research Grant(COVID193002)(F.K.L.C.)Enhanced start-up research grant of CUHK(H.M.T.)+2 种基金Hui Hoy&Chow Sin Lan Charity Fund Limited(S.C.N.)the National Research Foundation of Korea(NRF)grant funded through the Korea government(NRF-2018M3A9H4055203)(C.K.P.M.)Emergency Key Program of Guangzhou Laboratory(Grant No.EKPG22-30-6)(C.K.P.M.).
文摘The role of gut microbiota in modulating the durability of cOVID-19 vaccine immunity is yet to be characterised.In this cohort study,we collected blood and stool samples of 121 BNT162b2 and 40 CoronaVac vaccinees at baseline,1 month,and 6 months post vaccination(p.v).Neutralisation antibody,plasma cytokine and chemokines were measured and associated with the gut microbiota and metabolome composition.
