Optical Fiber Tip Research Articles

Modern concepts on the mechanisms of endovasal laser coagulation in varicose vein disease

Mechanisms of endovasal laser coagulation (EVLC) applied in varicose vein disease are not fully understood.Purpose. To analyze currently applied EVLC mechanisms so as to prevent hemorrhagic complications and paresthesia caused by these mechanisms.Methods. This review analyses modern theories on EVLC mechanisms when applied in varicose vein disease in the lower extremities.Results. Published experimental and clinical trials, including histological ones, have shown that the degree of vein damage during EVLC session depends on many factors, such as wavelength, intensity, and optical fiber speed. Damage to veins during EVLC procedure depends on various factors, such as direct contact of the vein wall with an optical fiber tip, carbonization of blood elements leading to the increased intravenous blood temperature and to the formation of gas bubbles as well as heat convection on the vein wall through the blood.Conclusion. Destruction of the vein wall during EVLC procedure is the result of a synergistic effect of various damaging factors. Currently, 2-μm laser irradiation is being implemented into clinical practice. This technique provides better vein coagulation under less power values which promotes less postoperative complications.

Tunable Nanoislands Decorated Tapered Optical Fibers Reveal Concurrent Contributions in Through-Fiber SERS Detection.

Creating plasmonic nanoparticles on a tapered optical fiber (TF) tip enables a remote surface-enhanced Raman scattering (SERS) sensing probe, ideal for challenging sampling scenarios like biological tissues, site-specific cells, on-site environmental monitoring, and deep brain structures. However, nanoparticle patterns fabricated from current bottom-up methods are mostly random, making geometry control difficult. Uneven statistical distribution, clustering, and multilayer deposition introduce uncertainty in correlating device performance with morphology. Ultimately, this limits the design of the best-performance remote SERS sensing probe. Here we employ a tunable solid-state dewetting method to create densely packed monolayer Au nanoislands with varied geometric parameters in direct contact with the silica TF surface. These patterns exhibit analyzable nanoparticle sizes, densities, and uniform distribution across the entire taper surface, enabling a systematic investigation of particle size, density, and analyte effects on the SERS performance of the through-fiber detection system. The study is focused on the SERS response of a widely employed benchmark molecule, rhodamine 6G (R6G), and serotonin, a highly relevant neurotransmitter for the neuroscience field. The numerical simulations and limit of detection (LOD) experiments on R6G show that the increase of the total near-field enhancement volume promotes the SERS sensitivity of the probe. However, we observed a different behavior for serotonin linked to its interaction with the nanoparticle's surface. The obtained LOD is as low as 10-7 M, a value not achieved so far in a through-fiber detection scheme. Therefore, our work offers a strategy to design nanoparticle-based remote SERS sensing probes and provides new clues to discover and understand intricate plasmonic-driven chemical reactions.

Silica‐Rich Sol‐Gel Ink for Two‐Photon Direct Laser Writing of Microscale Structures and Optical Elements

AbstractInnovative materials enable two‐photon polymerization for precise additive fabrication of intricate optical components. Existing polymeric inks suffer from poor optical performance due to their high organic content. Silica‐rich sol‐gel ink (75 wt%, under ambient conditions) is presented for high‐precision three‐dimensional (3D) printing of microscale structures and optical devices. A photoinitiator with high‐efficiency nonlinear absorption is introduced to initiate two‐photon polymerization. Utilizing a commercial direct laser writing system, 3D‐printing is demonstrated including the optimization of printing parameters and ink characterization. The optical performance of the printed microscale elements using the new sol‐gel ink surpasses commercially available polymeric inks on key metrics: Printed elements exhibit extremely low surface roughness, 3nm; visible and near‐IR light transmission is greater than 90%; Printed elements present enhanced mechanical and chemical resistance to common organic solvents; Structures exhibit low isotropic shrinkage, <10%; Elements withstand continuous‐wave laser intensities exceeding 7 × 105 W cm−2. Direct writing onto an optical fiber tip with no need for surface functionalization is presented, with the demonstration of a tall waveguide taper (≈1:5 aspect ratio) with low losses and modal crosstalk, and a freestanding photonic lantern mode multiplexer. The new ink can be utilized in a variety of applications and across many materials, requiring compact, durable, and complex optical elements.

Citrate polymer optical fiber for measuring refractive index based on LSPR sensor

Fiber optic localized surface plasmon resonance (LSPR) sensors have become an effective tool in refractive index (RI) detection for biomedical applications because of their high sensitivity. However, using conventional optical fiber has caused limitations in implanting the sensor in the body. This research presents the design and construction of a new type of polymer-based LSPR sensors to address this issue. Also, finite element method (FEM) is used to design the sensor and test it theoretically. The proposed polymer optical fiber (POF) based on citrate is biocompatible, flexible, and degradable, with a rate of 22% and 27 over 12 days. The step RI structure utilizes two polymers for light transmission: poly (octamethylene maleate citrate) (POMC) as the core and poly (octamethylene citrate) (POC) as the cladding. The POF core and cladding diameters and lengths are 700 µm, 1400 µm, and 7 cm, respectively. The coupling efficiency of light to the POF was enhanced using a microsphere fiber optic tip. The obtained results show that the light coupling efficiency increased to 77.8%. Plasma surface treatment was used to immobilize gold nanoparticles (AuNPs) on the tip of the POF, as a LSPR-POF sensor. Adsorption kinetics was measured based on the pseudo-first-order model to determine the efficiency of immobilizing AuNPs, in which the adsorption rate constant (k) was obtained be 8.6 × 10–3 min−1. The RI sensitivity of the sensor in the range from 1.3332 to 1.3604 RIU was obtained as 7778%/RIU, and the sensitivity was enhanced ~ 5 times to the previous RI POF sensors. These results are in good agreement with theory and computer simulation. It promises a highly sensitive and label-free detection biosensor for point-of-care applications such as neurosciences.

Advanced fiber optic sensors for quantitative nitrite detection: Comparative analysis of plasmonic tilted fiber Bragg gratings and fiber optic tips with ion-imprinted polymers

The presence of nitrite, a prevalent contaminant in natural environments, presents a significant environmental and human health concern. Hence, it is imperative to develop a sensor with the ability to quantitatively detect nitrite. This study focuses on the design and development of i) probe 1: tilted fiber Bragg gratings (TFBGs) and ii) probe 2: fiber optic tip-based plasmonic sensors utilizing ion-imprinted polymers. The concentration of nitrite was assessed at various levels using both sensing configurations. The outcomes indicated that the TFBGs-based sensor exhibited a sensitivity and limit of detection (LOD) of 0.469 nm/ln(μg/mL) and 0.142 μg/mL in the linear detection range of 0.5–50 μg/mL. The fiber optic tip-based sensor exhibited a sensitivity and LOD of 1.16 nm/ln(μg/mL) and 0.176 μg/mL within the 1–50 μg/mL linear detection range. The obtained sensing results reveal that the sensors presented in this study are able to accurately detect nitrite at various concentrations in a quantitative manner. Moreover, an assessment was conducted to examine the selectivity and reusability of the sensor individually, yielding satisfactory results.

Numerical and experimental demonstrations of optical trapping and manipulation of a selective red blood cell using a photonic hook based on broken symmetry tapered fiber probe

Optical tweezers and trapping technologies have a crucial impact on scientific research by precisely manipulating mesoscale objects at wavelength scales. The development of simple fiber-based optical tweezers foreseeing sorting and manipulation of a single cell has been firstly encouraged by biomedical requirements. The ability to manipulate mesoscale objects with high flexibility and precision is essential for a wide class of different fields. The ability to precisely arrange cells into desired structures is important for numerous biomedical and physical applications. This study experimentally reports for the first time a simple and low-cost strategy to produce an optical fiber-based photonic hook for achieving new unprecedented functionalities to selective particle manipulation in a lab-on-tip platform. We show perspectives opened by combining the fields of structured light in the form of the photonic hook and optical manipulation method. This enables new applications for optical trapping setups based on structured fields in the form of the photonic hook produced by an optical fiber tip with broken symmetry, where it becomes possible to manipulate and sort cells selectively.

Femtosecond Laser 3D Nano‐Printing for Functionalization of Optical Fiber Tips

AbstractFunctionalized optical fiber tips featuring miniature sizes and diverse functions have broken the limitations of traditional optical fiber with fixed shapes and single materials, significantly enriching the application scenarios in communication, sensing, imaging, and other fields. However, the unconventional shape presents challenges in manufacturing arbitrarily sophisticated 3D micro/nano structures on optical fiber tips. Femtosecond laser 3D nano‐printing (FL‐3DNp) technology injects new vitality into the functionalization of fiber tips due to its high‐precision, customizable structure, and real 3D processing abilities, as well as advantages of non‐vacuum, maskless, and plentiful materials. This paper extensively compares the key performance parameters of various micro‐nano manufacturing technologies for functionalizing optical fiber probes and focuses on the FL‐3DNp technology. In addition, the latest research progresses are systematically presented from the perspective of structure and application. Finally, the current research challenges and future development directions in this emerging field are discussed, aiming at providing scientific and industrial guidance for FL‐3DNp in functionalizing optical fibers.

Radiation hardness of open Fabry-Pérot microcavities

High-finesse microcavities offer a platform for compact, high-precision sensing by employing high-reflectivity, low-loss mirrors to create effective optical path lengths that are orders of magnitude larger than the device geometry. Here, we investigate the radiation hardness of Fabry-Pérot microcavities formed from dielectric mirrors deposited on the tips of optical fibers. The microcavities are irradiated under both conventional (∼ 0.1 Gy/s) and ultrahigh (FLASH, ∼ 20 Gy/s) radiotherapy dose rates. Within our measurement sensitivity of ∼ 40 ppm loss, we observe no degradation in the mirror absorption after irradiation with over 300 Gy accumulated dose. This result highlights the excellent radiation hardness of the dielectric mirrors forming the cavities, enabling new optics-based, real-time, in-vivo, tissue-equivalent radiation dosimeters with ∼ 10 micron spatial resolution (our motivation), as well as other applications in high-radiation environments.

3D Printed Micro-Nano Waveguide Ultrashort Bragg Grating on Optical Fiber Tip as a Contact Liquid Reagent Temperature Sensor

3D Printed Micro-Nano Waveguide Ultrashort Bragg Grating on Optical Fiber Tip as a Contact Liquid Reagent Temperature Sensor

Microstructured Cantilever Probe on Optical Fiber Tip for Microforce Sensor

Benefiting from the great advances of the femtosecond laser two-photon polymerization (TPP) technology, customized microcantilever probes can be accurately 3-dimensional (3D) manufactured at the nanoscale size and thus have exhibited considerable potentials in the fields of microforce, micro-vibration, and microforce sensors. In this work, a controllable microstructured cantilever probe on an optical fiber tip for microforce detection is demonstrated both theoretically and experimentally. The static performances of the probe are firstly investigated based on the finite element method (FEM), which provides the basis for the structural design. The proposed cantilever probe is then 3D printed by means of the TPP technology. The experimental results show that the elastic constant k of the proposed cantilever probe can be actively tuned from 2.46 N/m to 62.35 N/m. The force sensitivity is 2.5 nm/µN, the Q-factor is 368.93, and the detection limit is 57.43 nN. Moreover, the mechanical properties of the cantilever probe can be flexibly adjusted by the geometric configuration of the cantilever. Thus, it has an enormous potential for matching the mechanical properties of biological samples in the direct contact mode.

3D Printing of Glass Micro-Optics with Subwavelength Features on Optical Fiber Tips.

Integration of functional materials and structures on the tips of optical fibers has enabled various applications in micro-optics, such as sensing, imaging, and optical trapping. Direct laser writing is a 3D printing technology that holds promise for fabricating advanced micro-optical structures on fiber tips. To date, material selection has been limited to organic polymer-based photoresists because existing methods for 3D direct laser writing of inorganic materials involve high-temperature processing that is not compatible with optical fibers. However, organic polymers do not feature stability and transparency comparable to those of inorganic glasses. Herein, we demonstrate 3D direct laser writing of inorganic glass with a subwavelength resolution on optical fiber tips. We show two distinct printing modes that enable the printing of solid silica glass structures ("Uniform Mode") and self-organized subwavelength gratings ("Nanograting Mode"), respectively. We illustrate the utility of our approach by printing two functional devices: (1) a refractive index sensor that can measure the indices of binary mixtures of acetone and methanol at near-infrared wavelengths and (2) a compact polarization beam splitter for polarization control and beam steering in an all-in-fiber system. By combining the superior material properties of glass with the plug-and-play nature of optical fibers, this approach enables promising applications in fields such as fiber sensing, optical microelectromechanical systems (MEMS), and quantum photonics.

Fabrication of multilevel metalenses using multiphoton lithography: from design to evaluation.

We present a procedure for the design of multilevel metalenses and their fabrication with multiphoton-based direct laser writing. This work pushes this fast and versatile fabrication technique to its limits in terms of achievable feature size dimensions for the creation of compact high-numerical aperture metalenses on flat substrates and optical fiber tips. We demonstrate the design of metalenses with various numerical apertures up to 0.96, and optimize the fabrication process towards nanostructure shape reproducibility. We perform optical characterization of the metalenses towards spot size, focusing efficiency, and optical functionality with a fiber beam collimation design, and compare their performance with refractive and diffractive counterparts fabricated with the same technology.

Design of compact integrated diamond nitrogen–vacancy center quantum probe

An integrated quantum probe for magnetic field imaging is proposed, where the nitrogen–vacancy (NV) center fixed at the fiber tip is located on the periphery of flexible ring resonator. Using flexible polyimide (PI) as the substrate medium, we design a circular microstrip antenna, which can achieve a bandwidth of 140 MHz at Zeeman splitting frequency of 2.87 GHz, specifically suitable for NV center experiments. Subsequently, this antenna is seamlessly fixed at a three-dimensional-printed cylindrical support, allowing the optical fiber tip to extend out of a dedicated aperture. To mitigate errors originating from processing, precise tuning within a narrow range can be achieved by adjusting the conformal amplitude. Finally, we image the microwave magnetic field around the integrated probe with high resolution, and determine the suitable area for placing the fiber tip (SAP).

Design and full analysis of a metafiber-based photothermal bio-probe with perfect conversion efficiency

The metafiber, which involves fabricating metasurfaces at optical fiber tips, has shown potential as an integrated optical sensing or photothermal conversion platform. In this study, we present a metafiber-based photothermal bio-probe with a high optical absorption efficiency of 99.83%. Physical mechanisms underlying the efficiency are elucidated using coherent perfect absorption and multiple reflection theories. In our simulation, the probe exhibits ultra-fast heating/cooling rates, high temperature localization, steep temperature gradients, and robust response to environmental factors. In particular, only 1.0 mW of incident power is needed to generate the temperature gradient required for cell capture or drug delivery, while the corresponding temperature near the fiber tip is still safe for biological tissue. These advantages make our designed bio-probe as an ideal platform in various of applications, such as living cells capture, drug delivery, and local hyperthermia.

Хирургический лазер 450 нм в лечении заболеваний верхних дыхательных путей

The use of modern laser systems has contributed to the enhancement of the quality and immediate outcomes of surgical treatment for patients with chronic laryngeal diseases. The benefits of laser surgery, such as asepsis, bloodlessness, and rapid onset of clinical effects, are ensured by the device technical characteristics and the physical properties of the generated waves. In laryngological practice, laser radiation with a wavelength of 450±10 nm is actively employed, and its efficacy continues to be studied. We present our experience with the surgical treatment of 10 patients with various pharynx and larynx disorders. All patients underwent surgical interventions using a domestically produced high-energy laser device with a wavelength of 450±10 nm and a maximum average power of 10 W. Subsequently, therapy results were compared with those using similar devices. The high efficacy of the domestic high-energy laser device with a wavelength of 450±10 nm and maximum average power of 10 W was demonstrated in key technical characteristics relative to its counterparts. We successfully performed surgical interventions on ENT organs, confirming the high resection and photoangiolytic properties of the laser device, which, with the specified physical characteristics, is in demand for the surgical treatment of laryngeal diseases, competitive, and easy to use. Additionally, due to its configuration with interchangeable fiber-optic tips, the domestic device offers greater versatility. Its distinguishing features include the simplicity and ease of performing surgical interventions characterized by minimal trauma and the absence of intraoperative bleeding. In the postoperative period, less significant inflammatory phenomena and earlier healing of surgical wounds were observed. FOR CITATION: Krivopalov A.A., Shamkina P.A., Korkmazov M.Yu., Panchenko P.I., Glushchenko A.I., Zhurba V.M., Chuchin V.Yu. 450 nm diode laser in the treatment of upper respiratory tract diseases. Russian Medical Inquiry. 2024;8(8):484–492 (in Russ.). DOI: 10.32364/2587-6821-2024-8-8-7.

Broadband optical vortex beam generation using flat-surface nanostructured gradient index vortex phase masks

We developed a new kind of compact flat-surface nanostructured gradient index vortex phase mask, for the effective generation of optical vortex beams in broadband infrared wavelength range. A low-cost nanotechnological material method was employed for this work. The binary structure component consists of 17,557 nano-sized rods made of two lead–bismuth–gallium silicate glasses which were developed in-house. Those small rods are spatially arranged in such a way that, according to effective medium theory, the refractive index of this internal structure is constant in the radial direction and linearly changes following azimuthal angle. Numerical results demonstrated that a nanostructured vortex phase mask with a thickness of 19 μm can convert Gaussian beams into fundamental optical vortices over 290 nm wavelength bandwidth from 1275 to 1565 nm. This has been confirmed in experiments using three diode laser sources operating at 1310, 1550, and 1565 nm. The generation of vortex beams is verified through their uniform doughnut-like intensity distributions, clear astigmatic transformation patterns, and spiral as well as fork-like interferograms. This new flat-surface component can be directly mounted to an optical fiber tip for simplifying vortex generator systems as well as easier manipulation of the generated OVB in three-dimensional space.

Distributed interferometric fiber tip biosensors for a multi-channel and label-free biomolecular interaction analysis.

This paper describes fabrication and implementation of distributed optical fiber tip biosensor probes for simultaneously measuring label-free biomolecular interactions at multiple locations. Biosensor probes at the tip of a single-mode fiber are Fabry-Perot etalons that are functionalized with a capture layer for a specific biomolecule. A coherence multiplexing method is implemented to separate data collected from distributed biosensors in a single data stream. Multiplexing is achieved by using fiber tip biosensors of varying etalon lengths with the same or different capture layers for each biosensing channel. Experiments demonstrating simultaneous multi-channel recording of protein-to-protein interaction sensorgrams with fiber tip biosensor probes are presented.

Optical fiber probe with a concave cavity for non-contact trapping

We demonstrate a non-contact trapping of a yeast cell by an optical fiber probe with a micron-size concave cavity both theoretically and experimentally. We fabricate the optical fiber tip with a micron-size concave cavity by the improved tube etching method. The size of the concave cavity can be controlled by the etching parameters, such as the etching time, the etching solution, and so on. The output fields from the fiber tips with concave cavities of two geometrical sizes (microns and tens of microns) are computed and analyzed. Then the optical forces on a yeast cell by these concave fiber tips (CFTs) are calculated and discussed. The theoretical results predicate that a micron-size CFT can be used for non-contact trapping of a yeast cell. We observe the non-contact trapping of a yeast cell by a micron-size CFT in the experiments and measure the trapping forces. The optical trapping and manipulation based on these micron-size CFTs may provide versatile applications in bio-science and medical research.

Dental Diode Lasers for Implant Uncovering: A Case Series.

Diode lasers are increasingly being utilized as an alternative to conventional soft tissue surgery. While originally diode lasers referred to wavelengths ranging from 810 through 980 nm, a visible diode laser with a 445-nm wavelength has emerged as an additional wavelength for soft tissue surgery. The goal of this case series was to demonstrate the clinical results of both visible and near infrared (NIR) wavelengths when utilized for second stage implant surgery. Ten patients with 23 implants were treated at Stony Brook University, Department of Periodontology for implant uncovering using both visible and nonvisible (NIR) diode lasers. The uncovering was done utilizing 445-nm, 970-nm, and 980-nm wavelengths at a power setting of 2 W in either continuous or pulsed modes. The fiber-optic tips were initiated using blue articulating paper. Either topical benzocaine or infiltration anesthesia was utilized prior to soft tissue removal with the initiated tip. All patients healed uneventfully without any postoperative complications. Visible and NIR diode lasers provide an alternative and safe method to uncover submerged at implants at second stage surgery.

Surface Functionalised Optical Fibre for Detection of Hydrogen Sulphide.

Dysregulated production of hydrogen sulphide in the human body has been associated with various diseases including cancer, underlining the importance of accurate detection of this molecule. Here, we report the detection of hydrogen sulphide using fluorescence-emission enhancement of two 1,8-naphthalimide fluorescent probes with an azide moiety in position 4. One probe, serving as a control, featured a methoxyethyl moiety through the imide to evaluate its effectiveness for hydrogen sulphide detection, while the other probe was modified with (3-aminopropyl)triethoxysilane (APTES) to enable direct covalent attachment to an optical fibre tip. We coated the optical fibre tip relatively homogeneously with the APTES-azide fluorophore, as confirmed via x-ray photoelectron spectroscopy (XPS). The absorption and fluorescence responses of the control fluorophore free in PBS were analysed using UV-Vis and fluorescence spectrophotometry, while the fluorescence emission of the APTES-azide fluorophore-coated optical fibres was examined using a simple, low-cost optical fibre-based setup. Both fluorescent probes exhibited a significant increase (more than double the initial value) in fluorescence emission upon the addition of HS- when excited with 405 nm. However, the fluorescence enhancement of the coated optical fibres demonstrated a much faster response time of 2 min (time for the fluorescence intensity to reach 90% of its maximum value) compared to the control fluorophore in solution (30 min). Additionally, the temporal evolution of fluorescence intensity of the fluorophore coated on the optical fibre was studied at two pH values (7.4 and 6.4), demonstrating a reasonable overlap and confirming the compound pH insensitivity within this range. The promising results from this study indicate the potential for developing an optical fibre-based sensing system for HS- detection using the synthesised fluorophore, which could have significant applications in health monitoring and disease detection.