Specialty optical fibers for advanced sensing applications

Optical fiber technology has changed the world by enabling extraordinary growth in world-wide communications and sensing.The rapid development and wide deployment of optical fiber sensors are driven by their excellent sensing performance with outstanding flexibility,functionality,and versatility.Notably,the research on specialty optical fibers is playing a critical role in enabling and proliferating the optical fiber sensing applications.This paper overviews recent developments in specialty optical fibers and their sensing applications.The specialty optical fibers are reviewed based on their innovations in special structures,special materials,and technologies to realize lab in/on a fiber.An overview of sensing applications in various fields is presented.The prospects and emerging research areas of specialty optical fibers are also discussed.

Highly sensitive microfiber ultrasound sensor for photoacoustic imaging

An ultrasound wave is a kind of acoustic signal with a frequency greater than 20 kHz,which is widely used in diverse fields such as medical imaging diagnosis,nondestructive testing and resource exploration.A variety of ultrasound sensors have been developed for ultrasound detection.Particularly for photoacoustic imaging,specialized ultrasound sensors with high sensitivity,small size,and broad bandwidth are needed.However,achieving such sensor perform-ance still poses a great challenge to the current state-of-the-art in ultrasound sensor technology.A recent work pub-lished in Opto-Electronic Advances(DOI:10.29026/oea.2022.200076)proposes a microfiber-based ultrasound sensor that breaks the limitations of existing ultrasound sensors.Benefiting from the large evanescent field characteristic of mi-crofiber,combined with the coherent detection technology,the proposed sensor realized highly sensitive ultrasound de-tection and demonstrated excellent performance in high-resolution photoacoustic imaging.The highly sensitive and mini-aturized microfiber ultrasound sensor provides a competitive alternative for various applications,such as endoscopic photoacoustic imaging of the intestinal tract and blood vessels in animals.

RSPSSL:A novel high-fidelity Raman spectral preprocessing scheme to enhance biomedical applications and chemical resolution visualization

Raman spectroscopy has tremendous potential for material analysis with its molecular fingerprinting capability in many branches of science and technology.It is also an emerging omics technique for metabolic profiling to shape precision medicine.However,precisely attributing vibration peaks coupled with specific environmental,instrumental,and specimen noise is problematic.Intelligent Raman spectral preprocessing to remove statistical bias noise and sample-related errors should provide a powerful tool for valuable information extraction.Here,we propose a novel Raman spectral preprocessing scheme based on self-supervised learning(RSPSSL)with high capacity and spectral fidelity.It can preprocess arbitrary Raman spectra without further training at a speed of~1900 spectra per second without human interference.The experimental data preprocessing trial demonstrated its excellent capacity and signal fidelity with an 88%reduction in root mean square error and a 60%reduction in infinite norm(L__(∞))compared to established techniques.With this advantage,it remarkably enhanced various biomedical applications with a 400%accuracy elevation(ΔAUC)in cancer diagnosis,an average 38%(few-shot)and 242%accuracy improvement in paraquat concentration prediction,and unsealed the chemical resolution of biomedical hyperspectral images,especially in the spectral fingerprint region.It precisely preprocessed various Raman spectra from different spectroscopy devices,laboratories,and diverse applications.This scheme will enable biomedical mechanism screening with the label-free volumetric molecular imaging tool on organism and disease metabolomics profiling with a scenario of high throughput,cross-device,various analyte complexity,and diverse applications.

Phase-tailored assembly and encoding of dissipative soliton molecules

Self-assembly of particle-like dissipative solitons,in the presence of mutual interactions,emphasizes the vibrant concept of soliton molecules in varieties of laser resonators.Controllable manipulation of the molecular patterns,held by the degrees of freedom of internal motions,still remains challenging to explore more efficient and subtle tailoring approaches for the increasing demands.Here,we report a new phase-tailored quaternary encoding format based on the controllable internal assembly of dissipative soliton molecules.Artificial manipulation of the energy exchange of soliton-molecular elements stimulates the deterministic harnessing of the assemblies of internal dynamics.Self-assembled soliton molecules are tailored into four phase-defined regimes,thus constituting the phase-tailored quaternary encoding format.Such phase-tailored streams are endowed with great robustness and are resistant to significant timing jitter.All these results experimentally demonstrate the programmable phase tailoring and exemplify the application of the phase-tailored quaternary encoding,prospectively promoting high-capacity all-optical storage.

300 km ultralong fiber optic DAS system based on optimally designed bidirectional EDFA relays

Optical fiber distributed acoustic sensing(DAS)based on phase-sensitive optical time domain reflectometry(φ-OTDR)is in great demand in many long-distance application fields,such as railway and pipeline safety monitoring.However,the DAS measurement distance is limited by the transmission loss of optical fiber and ultralow backscattering power.In this paper,a DAS system based on multispan relay amplification is proposed,where the bidirectional erbium-doped fiber amplifier(EDFA)is designed as a relay module to amplify both the probe light and the backscattering light.In the theoretical noise model,the parameters of our system are carefully analyzed and optimized for a longer sensing distance,including the extinction ratio(ER),span number,span length,and gain of erbium-doped fiber amplifiers.The numerical simulation shows that a bidirectional EDFA relay DAS system can detect signals over 2500 km,as long as the span number is set to be more than 100.To verify the effectiveness of the scheme,a six-span coherent-detection-based DAS system with an optimal design was established,where the cascaded acoustic-optic modulators(AOMs)were used for a high ER of 104 dB.The results demonstrate that the signal at the far end of 300.2 km can be detected and recovered,achieving a high signal-to-noise ratio of 59.6 dB and a high strain resolution of 51.8■at 50 Hz with a 20 m spatial resolution.This is,to the best of our knowledge,a superior DAS sensing distance with such a high strain resolution.

Universal dynamics and deterministic motion control of decoherently seeded temporal dissipative solitons via spectral filtering effect

Temporal dissipative solitons have been widely studied in optical systems,which exhibit various localized structures and rich dynamics,and have shown great potential in applications including optical encoding and sensing.Yet,most of the soliton states,as well as the switching dynamics amongst,were fractionally captured or via self-evolution of the system,lacking of control on the soliton motion.While soliton motion control has been widely investigated in coherently seeded optical cavities,such as microresonator-based dissipative solitons,its implementation in decoherently seeded systems,typically the soliton mode-locked lasers,remains an outstanding challenge.Here,we report the universal dynamics and deterministic motion control of temporal dissipative solitons in a mode-locked fibre laser by introducing a scanned spectral filtering effect.We investigate rich switching dynamics corresponding to both the assembly and the disassembly of solitons,revealing a complete and reversible motion from chaotic states to soliton and soliton-molecule states.Significant hysteresis has been recognized in between the redshift and blueshift scan of the motorized optical filter,unveiling the nature of having state bifurcations in dissipative and nonlinear systems.The active soliton motion control enabled by filter scanning highlights the potential prospects of encoding and sensing using soliton molecules.

Recent Advances and Perspective of Photonic Bound States in the Continuum

Recent advancements in photonic bound states in the continuum(BICs)have opened up exciting new possibilities for the design of optoelectronic devices with improved performance.In this perspective article,we provide an overview of recent progress in photonic BICs based on metamaterials and photonic crystals,focusing on both the underlying physics and their practical applications.The first part of this article introduces 2 different interpretations of BICs,based on far-field interference of multipoles and near-field analysis of topological charges.We then discuss recent research on manipulating the far-field radiation properties of BICs through engineering topological charges.The second part of the article summarizes recent developments in the applications of BICs,including chiral light and vortex beam generation,nonlinear optical frequency conversion,sensors,and nanolasers.Finally,we conclude with a discussion of the potential of photonic BICs to advance terahertz applications in areas such as generation and detection,modulation,sensing,and isolation.Webelieve that continued researchinthis area will lead to exciting new advancements in optoelectronics,particularly in the field of terahertz devices.

Polarization-maintaining few mode fiber composed of a central circular-hole and an elliptical-ring core

We propose a novel waveguide design of polarization-maintaining few mode fiber(PM-FMF) supporting ≥10non-degenerate modes, utilizing a central circular air hole and a circumjacent elliptical-ring core. The structure endows a new degree of freedom to adjust the birefringence of all the guided modes, including the fundamental polarization mode. Numerical simulations demonstrate that, by optimizing the air hole and elliptical-ring core,a PM-FMF supporting 10 distinctive polarization modes has been achieved, and the effective index difference Δn_(eff) between the adjacent guided modes could be kept larger than 1.32 × 10^(-4) over the whole C +L band. The proposed fiber structure can flexibly tailored to support an even larger number of modes in PM-FMF(14-mode PM-FMF has been demonstrated as an example), which can be readily applicable to a scalable mode division multiplexing system.

Real-time dynamics of soliton triplets in fiber lasers

The evolution of soliton molecules emphasizes the complex soliton dynamics akin to matter molecules.Beyond the simplest soliton molecule-a soliton pair constituted by two bound pulses-soliton molecules with more constituents have more degrees of freedom because of the temporal pulse separations and relative phases.Here we detailedly characterize the transient dynamics of soliton triplets in fiber lasers by using the dispersive Fourier transform measurement.A particular form of leading,central,and tailing pulses is constructed to shed new light on more intriguing scenarios and fuel the molecular analogy.Especially the vibrating dynamics of the central and tailing pulses are captured near the regime of equally spaced soliton triplets,which is reminiscent of the recurrent timing jitters within multi-pulse structures.Further insights enable acess into a universal form of unequally spaced soliton triplets interpreted as 2+1 soliton molecules.Different binding strengths of intramo-lecular and intermolecular bonds are validated with respect to the diverse internal motions involved in this soliton triplet molcule.All these findings unveil the transient dynamics with more degrees of freedom as well as highlight the possible application for all-optical bit storage.

Fiber structures and material science in optical fiber magnetic field sensors

Magnetic feld sensing plays an important role in many felds of scientifc research and engineering applications.Benefting from the advantages of optical fbers,the optical fber-based magnetic feld sensors demonstrate characteristics of light weight,small size,remote controllability,reliable security,and wide dynamic ranges.This paper provides an overview of the basic principles,development,and applications of optical fber magnetic feld sensors.The sensing mechanisms of fber grating,interferometric and evanescent feld fber are discussed in detail.Magnetic fuid materials,magneto-strictive materials,and magneto-optical materials used in optical fber sensing systems are also introduced.The applications of optical fber magnetic feld sensors as current sensors,geomagnetic monitoring,and quasi-distributed magnetic sensors are presented.In addition,challenges and future development directions are analyzed.

A review of geometry-confined perovskite morphologies:From synthesis to efficient optoelectronic applications

With the continuous study of metal halide perovskite,geometry-confined technologies have been widely applied to reduce the material dimensionality and to produce pre-designed structures,which can tune optical reflectance,scattering,and absorption,thereby optimizing the performance of perovskite-based optoelectronic devices and improving their commercial competitiveness.The morphologies of perovskite active layer play a pivotal role in optoelectronic properties and the resulting device performances.In this review,we systematically summarized recent progress in the preparation and manufacture of various perovskite geometry-confined morphologies,as well as their promising advances in different optoelectronic applications,including photodetectors,solar cells(SCs),lasers,and light-emitting diodes(LEDs).In addition,the remaining challenges and further improvements of preparation unique geometry-confined perovskite morphologies for next-generation high quality optoelectronic devices are discussed.

Dynamics of cavity soliton driven by chirped optical pulses in Kerr resonators

Recent researches have demonstrated that pulsed driving is an effective method to increase the temporal overlap between cavity soliton(CS)and pump field,thereby increasing the pump-to-comb conversion efficiency.The amplitude-modulated inhomogeneity of the background wave causes the solitons to drift toward edges of the driving pulse.To eliminate the mul-tiple temporal trapping positions,induced by the spontaneous symmetry breaking,we propose the chirped pulse driving for deterministic single soliton generation.We theoretically explain the physical mechanism of the chirp pulse driving,as the combination of amplitude and phase modulation.Our numerical simulations demonstrate the chirp is responsible for the single soliton generation.A detailed investigation for dynamics of CSs sustained by chirped pulses,shows the recovery of spontaneous symmetry breaking.In addition,the desynchronized chirped pulse driving is also considered here.Considering a weak chirp parameter,the desynchronization-dependent trapping position diagram is divided into multiple areas including two CSs,a single CS,two oscillating CSs,and no CS.With a sufficient chirp parameter considered,the trapping position curve becomes a monotonous function of the desynchronized drift velocity,which indicates deterministic single soliton generation.

An optical fiber network oracle for NP-complete problems

The modern information society is enabled by photonic fiber networks characterized by huge coverage and great complexity and ranging in size from transcontinental submarine telecommunication cables to fiber to the home and local segments.This world-wide network has yet to match the complexity of the human brain,which contains a hundred billion neurons,each with thousands of synaptic connections on average.However,it already exceeds the complexity of brains from primitive organisms,i.e.,the honey bee,which has a brain containing approximately one million neurons.In this study,we present a discussion of the computing potential of optical networks as information carriers.Using a simple fiber network,we provide a proof-of-principle demonstration that this network can be treated as an optical oracle for the Hamiltonian path problem,the famous mathematical complexity problem of finding whether a set of towns can be travelled via a path in which each town is visited only once.Pronouncement of a Hamiltonian path is achieved by monitoring the delay of an optical pulse that interrogates the network,and this delay will be equal to the sum of the travel times needed to visit all of the nodes(towns).We argue that the optical oracle could solve this NP-complete problem hundreds of times faster than brute-force computing.Additionally,we discuss secure communication applications for the optical oracle and propose possible implementation in silicon photonics and plasmonic networks.