Fiber Probe Research Articles

Accurate measurement of wavelength-Dependent beam parameters of a supercontinuum light source focused by a lensed fiber probe

In this work, an supercontinuum (SC) light is focused by an optical lensed fiber (OLF). We demonstrate a new method to meticulously analyze multi-wavelength beam parameters of the OLF probe and the focused SC beam by applying a spectrometer to measure the variation of back-coupling efficiency for different wavelengths. By contrast, inevitable and relatively small errors in the OLF parameters that are obtained by using the conventional method lead to significant errors in the spatial information of the focused SC beam. Therefore, this method is expected to be a necessary calibration procedure for a system with an OLF probe. The SC beam focused by our OLF has little chromatic aberration in the beam size and the focal length in a range of approximately 120 μm.

Use of a Single-Fiber Optical Probe for the Detection of Tumor Fluorescence in High-Grade Glioma.

High-grade glioma (HGG) is the most common primary brain tumor in adults. The overall median survival is between 14 and 16 months. Fluorescence-guided surgery by detection of protoporphyrin IX (PpIX) fluorescence has been shown to improve the extent of resection, translating to improved progression-free survival. Microscope-based fluorescence detection techniques are associated with several pain points, some of which may be addressed by using contact-based spectroscopy. We aimed to investigate the accuracy of an optical fiber at detecting PpIX fluorescence by performing real-time spectroscopy in patients with HGG. Adult patients undergoing fluorescence-guided surgery for suspected HGG were recruited prospectively. Intraoperatively, samples from cortex, white matter, and tumor were taken. These samples were interrogated using standard white and blue light microscope techniques and the optical fiber. These specimens were then assessed by neuropathology to determine whether the tumor tissue was present within them. We collected 89 samples from 28 patients. There was an equal ratio of men to women, with a median age of 66.5 years. The accuracy of the probe for detecting PpIX fluorescence was 75.9%, compared with 56.6% for the operating microscope, with a significant improvement in sensitivity (χ2 = 11.84, P < .001). The optical fiber probe was more accurate than the operating microscope for detecting PpIX fluorescence. This technology has potential value in improving the accuracy of fluorescence-guided surgery and has potential practical benefits relating to surgical workflow.

Simple and Efficient Laser-Induced Evaporation Assembly Method to Fabricate SERS Optical Fiber Probe for Detection of PAHs

Simple and Efficient Laser-Induced Evaporation Assembly Method to Fabricate SERS Optical Fiber Probe for Detection of PAHs

Numerical Analysis of Optical Fiber Refractive Index in the Miniaturized Graded‐Index Fiber Probe

ABSTRACTWe analyze the impact of the refractive index of optical fibers on the focusing properties of a miniaturized graded‐index (GRIN) fiber probe. The ABCD ray transfer matrix and characteristic parameters are employed to characterize the working distance, focusing spot size, and the depth of field effectively. The three‐dimensional (3‐D) function diagrams and two‐dimensional (2‐D) graphs are used to illustrate the impact of the no‐core fiber (NCF) refractive index and the center refractive index of GRIN fiber on the focusing properties. Numerical analysis results show that when the length of the NCF is 0.36 mm and the GRIN fiber is 0.1 mm, the variation of the refractive index of the NCF between 1.44 and 1.52 leads to the variation of the working distance in the range of 0.02 mm, while the focusing spot size varies in the range of 5 μm. A comparison of 12 probe samples reveals that a 0.02 difference in the center refractive index of GRIN fiber could result in a 0.16 mm variation in working distance and a variation in focusing spot size of over 3 μm. The experimental results indicate that alterations in the length of the fibers have a considerable effect on the focusing properties of the probe. In contrast, the range of variation in focusing properties with fiber refractive index is relatively limited.

Upconverting thermal history paint for investigations of short thermal events

The main goal of the work was to develop phosphorescent coating for investigations of surface temperature distribution resulted from short duration and high energy thermal events such as small rocket engine testing. For that purpose, we developed thermal history paint with upconverting Gd2O3: Er3+, Yb3+, Mg2+ nanopowder. The developed paint was heated by Joule effect with precise control over temperature and heating time. Photoluminescence signal of cooled samples was excited with 980 nm laser and collected in automatic manner with use of an optical fibre probe connected to photospectrometer. The results show that irreversible changes of paint emission are temperature and heating time specific for calcination temperatures from 700 °C to 1150 °C. Calibration curves were prepared for heating times of 10, 60 and 180 seconds. Finally, 2D surface temperature samples were determined with use of upconverting thermal history paint and compared to IR camera and pyrometric measurements. The results indicate that uncertainty of temperature measurement below 10 °C was achieved for temperatures above 1000 °C. It has been demonstrated that developed thermal history paint allows for measurements of 2D surface temperature distribution with high spatial resolution and good agreement to standard measurements techniques like thermal camera and pyrometer.

Detection of picometer scale vibration based on the microsphere near-field probe

We introduce an innovative vibration detection method utilizing a microsphere near-field probe, affixed to an optical fiber probe. Notably, when the microsphere probe is positioned at a distance of approximately 100 nm from the vibrating objects, it exhibits a substantial increase in detection sensitivity, enabling the detection vibration as small as 5 pm. This enhancement arises from the strong near-field interaction between the sample and probe, where the evanescent wave dominates. This effect is confirmed for the first-time through both theoretical analysis and experimental validation. This innovative probe has great potential for applications in cellular acoustics, vibrational detection of biomolecules and their complexes, in situ measurements, and imaging of microstructures and nanostructures.

Controlling spatial optical illuminations in optogenetics using an angled optical fiber tip

The advent of optogenetic tools has revolutionized neuroscience research through its spatiotemporally precise activation of specific neurons by illuminating light on opsin-expressing neurons. A long-standing challenge of in vivo optogenetics remains in delivering light to multiple brain sites simultaneously and maintaining high spatial resolution. Optical fiber-based technologies have been proposed to address these challenges. This work presents the fabrication and characterization of an innovative angled optical fiber probe based on a double-sided angled tip (DSAT) structure. A custom griding setup was used for the reproducible fabrication of a smooth DSAT probe. The designed probe enables precise spatial control of light propagation in brain tissue in which DSAT at angled tip 55° achieving a maximum lateral illumination position of ± 420 μm away from the optical axis and a peak irradiance of 478.5 mW/mm2, using a 5 mW of 473 nm laser light. Also, the designed DAST probe was simulated based on ray tracing method and obtained the practical tip angle to evaluate the propagation of light rays emitted from the DSAT at various input optical angles ranging from 0° to 12.5° to predict their irradiance and positions in the modelled tissue. The results indicate the probe generates two elliptical rings each containing two spots with higher optical concentration. Consequently, this device provides four optical spots with irradiance peaks that enable simultaneous illumination of four different locations in the brain tissue. Obtained experiment results are in good agreement with simulation results which can be used for multipoint illumination of brain tissue in optogenetics applications.

Neural stimulation and modulation with sub-cellular precision by optomechanical bio-dart

Neural stimulation and modulation at high spatial resolution are crucial for mediating neuronal signaling and plasticity, aiding in a better understanding of neuronal dysfunction and neurodegenerative diseases. However, developing a biocompatible and precisely controllable technique for accurate and effective stimulation and modulation of neurons at the subcellular level is highly challenging. Here, we report an optomechanical method for neural stimulation and modulation with subcellular precision using optically controlled bio-darts. The bio-dart is obtained from the tip of sunflower pollen grain and can generate transient pressure on the cell membrane with submicrometer spatial resolution when propelled by optical scattering force controlled with an optical fiber probe, which results in precision neural stimulation via precisely activation of membrane mechanosensitive ion channel. Importantly, controllable modulation of a single neuronal cell, even down to subcellular neuronal structures such as dendrites, axons, and soma, can be achieved. This bio-dart can also serve as a drug delivery tool for multifunctional neural stimulation and modulation. Remarkably, our optomechanical bio-darts can also be used for in vivo neural stimulation in larval zebrafish. This strategy provides a novel approach for neural stimulation and modulation with sub-cellular precision, paving the way for high-precision neuronal plasticity and neuromodulation.

TEMPERATURE MONITORING FOR LASER METAL DEPOSITION USING NEAR-INFRARED SPECTROSCOPY

Temperature monitoring during laser metal deposition (LMD) aids process control to ensure high-quality production. However, the fluctuating emissivity of the melt pool limits the accuracy of the existing non-contact temperature measuring devices. Thus, this work explores a new temperature monitoring technique, where the thermal radiation emitted by the processing zone was collected with a near-infrared (NIR) spectrometer and fitted to Planck's law to determine the temperature. This work has established the optimised angle and distance of the fiber probe from the LMD processing area to maximise the spectral signal acquisition. The temperature determined from the technique was cross-validated with a thermocouple, resulted in a small deviation of 2.39%. The applicability of the spectroscopic method for continuous temperature monitoring of the LMD process has been demonstrated. The optimised placement for the fiber probe end was determined at the 45˚ angle relative to the surface of the substrate and positioned 5 cm away from the molten pool. The temperature during the LMD process decreased gradually then stabilised after approximately 17 mm track length, resembling those reports in prior studies. Our findings support the practicality of the proposed temperature monitoring approach in LMD.

Impact of kV-cone beam computed tomography dose on DNA repair mechanisms: A pilot study

PurposeIn head and neck squamous cell carcinoma (HNSCC), early complications of the radiotherapy (RT) are observed from the beginning of the treatment to a few months after its end. During external radiotherapy treatment, several patient-dependent parameters can cause a modification of the dose distribution compared to the planned distribution due to variation in patient positioning, anatomy, or intra-fractional movements for example. To verify these parameters during treatment sessions, one of the most commonly used solutions is the cone-beam computed tomography (CBCT). Nowadays, the use of CBCT may constitutes a significant part of the total dose at the end of treatment (up to 10 cGy per session) and more often the volume irradiated by imaging is larger than the one irradiated by the treatment, leading to unintentional irradiation of nearby organs.In this study, we asked whether the imaging low dose added to a following fraction dose (2Gy) may affect the biological response in terms of DNA repair. Material and methodsUsing an IVInomad dosimeter and scintillating fiber probes specially designed for this exploratory study, we exposed fibroblasts cells from head and neck cancer (HNC) patients to a CBCT dose followed by a radiotherapy fraction dose. DNA double strand breaks and DNA repair were assessed by immunofluorescence using the biomarkers gamma H2AX (γH2AX) and pATM. ResultsThe median dose of CBCT was measured between 17 to 21 mGy per session. The kinetics of both biomarkers were found to be strongly dependent on the individual factor in radiosensitive patients. For HNC patients, a prior CBCT dose applied few minutes before the 2Gy dose may have a sublinear effect on the DNA repair mechanisms and potentially on observed health tissue toxicity. ConclusionThe preliminary results obtained highlight the importance of individual and tissue factors for recognizing and repairing DSB during a treatment by radiotherapy using CBCT.

A Nanosecond level current pulse capture taper optical fiber probe based on micron level NV color center diamond

Abstract This work demonstrates a micron-sized nanosecond current pulse probe using a quantum diamond magnetometer. A micron-sized diamond crystal affixed to a fiber tip is integrated on the end of a conical waveguide. We demonstrate real-time visualization of a single 100 nanosecond pulse and discrimination of two pulse trains of different frequencies with a coplanar waveguide and a home-made PCB circuits. This technique finds promising applications in the display of electronic stream and to be used as a pulse discriminator to Simultaneously receive and demodulate multiple pulse frequencies. This method of detecting pulse current is expected to provide further detailed analysis of the internal working state of the chip.

Optical fiber SPR probe platform combined with oriented antibody optimized modification for ultrasensitive and portable detection of human thyroglobulin

Thyroglobulin (Tg) is an essential indicator for monitoring differentiated thyroid cancer. However, there are still significant challenges in achieving fast, accurate, and efficient point-of-care testing (POCT). This paper presented an optical fiber bioprobe platform technology based on the ultrasensitive sensing principle of surface plasmon resonance (SPR), aiming to achieve an efficient and precise immunoassay of Tg. The fiber probes were modified with Tg antibodies to form fiber Tg probes. After optimization of the oriented antibody modification, the detection sensitivity of fiber Tg probes increased by 3 times, facilitating one-step direct detection of μg-level sample concentrations such as thyroid tissue fluid samples. For ng-level sample concentrations such as blood samples, a two-step measurement method was used to amplify the surface load signal. Through Tg detection studies in different concentration ranges and background environments, our fiber Tg probes exhibited a sensitivity of 81.99 pm / (ng / mL) and a limit of detection of 1.4 ng / mL, and were able to complete ng-level detection in serum backgrounds. The fiber Tg probe holds immense potential in the diagnosis and postoperative monitoring of thyroid cancer. Additionally, being a miniature, disposable, reliable, and portable quantitative optical immunoassay tool, it can serve as a rapid detection instrument for various target proteins and pathogens by simply altering the modified antibody.

Fiber-optic drug delivery strategy for synergistic cancer photothermal-chemotherapy

Chemotherapy is one of the conventional treatments for cancer in clinical practice. However, poor delivery efficiency, systemic toxicity, and the lack of pharmacokinetic monitoring during treatment are the critical limitations of current chemotherapy. Herein, we reported a brand-new antitumor drug delivery strategy that harnesses an optical fiber endoscopically therapeutic probe. The fiber probe carries photosensitizers in the fiber core and antitumor agents on the fiber surface mediated by a temperature-responsive hydrogel film, giving rise to an activable photothermal-chemotherapy that orchestrates the localized hyperthermia and thermal-stimuli drug release to the tumor lesion. Furthermore, the dynamical drug release and in-situ temperature can be real-time supervised through the built-in fiber sensors, including the reflective Mach–Zehnder interferometer and fiber Bragg grating, to visualize the therapy process and thus improve the safety of treatment. Compared with conventional methods, the fiber-optic drug delivery can adequately take advantage of the chemotherapeutics through collaboratively recruiting the photoheating-mediated enhanced permeability and the hydrogel particle-assisted high drug retention, shedding new light on a “central-to-peripheral” drug pervasion and retention mechanism to destroy tumors completely. The fiber-optic chemotherapy strategy incorporates precise drug delivery, accurate controllability of drug release, high drug permeability and retention in tumor, low off-target rate, and real-time drug release and temperature feedback, performing a straightforward and precise photothermal-chemotherapy pathway. More than that, the proposed strategy holds tremendous promise to provide a revolutionized on-demand drug delivery platform for the highly efficient evaluation and screening of antitumor pharmaceuticals.

Myoglobin saturation as an intracellular indicator for transfusion need in oncology patients.

This study aims to demonstrate the potential of myoglobin saturation as an indicator of oxygen delivery adequacy to help determine the need for red cell transfusion. Modern blood management approaches have been established to optimise use of red blood cells for transfusions in patients with anaemia. However, most approaches make recommendations to transfuse based on haemoglobin or haematocrit levels and do not directly address adequacy of oxygen delivery. Intracellular oxygen determined by myoglobin saturation directly measures oxygen delivery at the tissue level. A custom built spectrometer system with an optical fibre probe was used in this pilot study to measure muscle cell myoglobin saturation noninvasively from the first digital interosseous muscles in patients undergoing planned red blood cell transfusion. Patients were recruited from both the in-patient and out-patient oncology service at a major university medical centre. Measurements were made immediately before, immediately after, and 24 h following transfusion. Clinical data and tissue oxygen values from the Somanetics INVOS system were also collected. Myoglobin saturation, and thus cellular oxygen increased in some, but not all patients receiving a transfusion, and was most pronounced in patients who initially had low myoglobin saturation compared with the group as a whole. Clinical decisions to transfuse based on haemoglobin or haematocrit thresholds alone are likely insufficient to optimise use of red blood cell transfusions. The combination of haemoglobin or haematocrit with myoglobin saturation may optimally determine who will benefit physiologically from a transfusion.

3D printed UV-sensing optical fiber probes: manufacturing, properties, and performance

UV sensing 3D printed optical fiber hydrogels provide a flexible and precise method of remotely of detecting exposure to UV radiations. The optical fibers were created using digital light processing 3D printing technique with hydrogel composites, including micro-sized photochromic dyes (pink, blue and their combination). When exposed to ultraviolet (UV) radiation, these dyes exhibited specific absorption characteristics, resulting in significant decreases in both reflection and transmittance mode spectra at 560 nm, 620 nm, and 590 nm. Optical fibers of lengths 1, 2, and 3 cm were manufactured in two orientations: vertical and horizontal. Scanning electron microscopy, Fourier transform infrared spectroscopy, and X-ray diffraction were utilized to characterize the printed fiber probes. The optical performance of the fibers was tested using customized measurement setups. The reflection and transmission of the printed fibers reduced as the length increased due to optical losses. Reflection and transmisson loss of 20–40% can be observed when the length is increased from 1 to 3 cm. The maximum loss in reflection is observed for pink fiber in the presence of UV irradiation. Also, the type of powder used impacted the response and retraction time, whereas the mixed fiber showed the highest response time of 12–20 s under various conditions. The pink dye added fiber probes shows quick response to UV radiation. An increase in the response time is observed with increasing fiber length. The impact of printing orientation on the transmission and reflectance mode operations of optical fibers was assessed. In addition, the stability of the fiber probes are assesed using a green laser having wavelength 532 nm. This work comprehensively examines the optical properties, manufacturing procedures, and sensing capacities of UV-sensitive photochromic optical fiber sensors.

Optical Fiber Probe with Integrated Micro-Optical Filter for Raman and Surface-Enhanced Raman Scattering Sensing.

Optical fiber Raman and surface-enhanced Raman scattering (SERS) probes hold great promise for in vivo biosensing and in situ monitoring of hostile environments. However, the silica Raman scattering background generated within the optical fiber increases in proportion to the length of the fiber, and it can swamp the signal from the target analyte. While filtering can be applied at the distal end of the fiber, the use of bulk optical elements has limited probe miniaturization to a diameter of 600 µm, which in turn limits the potential applications. To overcome this limitation, femtosecond laser micromachining was used to fabricate a prototype micro-optical filter, which was directly integrated on the tip of a 125 µm diameter double-clad fiber (DCF) probe. The outer surface of the microfilter was further modified with a nanostructured, SERS-active, plasmonic film that was used to demonstrate proof-of-concept performance with thiophenol as a test analyte. With further optimization of the associated spectroscopic system, this ultra-compact microprobe shows great promise for Raman and SERS optical fiber sensing.

Quantitative detection of tapered fiber SERS probes prepared in batches by electrostatic adsorption self-assembly method

The tapered fiber Surface-enhanced Raman scattering (SERS) probe is a highly sensitive SERS substrate for on-site detection. However, fiber probes prepared by the current technology lack interchangeability and are difficult to meet the practical quantitative detection demands. In this paper, we develop a batch preparation technology of tapered fiber SERS probes, with good interchangeability between each of the 20 tapered fiber SERS probes prepared in batches. Furthermore, we propose and demonstrate a spectral data assimilation method, through which the differences in interchangeability between different batches can be eliminated. Using 10 batches of spectral data assimilated with this method, we obtain a high-precision calibrated quantitative relationship curve with a fitting degree of 0.99464, with recovery rates of the two thiram spiked samples 106.88% and 95.75%, respectively. The batch preparation technology and the spectral data processing method provide a new option for practical quantitative detection.

A Fabry-Perot interferometer based on probe-embedded bubble for ultrasensitive strain measurement

A high-sensitivity Fabry-Perot interferometer (FPI) strain sensor based on tapered single-mode fiber (SMF) probe embedded in microbubble is proposed and verified. The two reflective surfaces of this FPI are composed of the two tapered SMF ends and assembled within a bubble. The distance between the reflection face can be flexibly adjusted to enhance the strain sensitivity of the sensor. Experimental result shows that the strain sensitivity of proposed FPI sensor reaches to 142.2 pm/με. Meanwhile, the sensor demonstrates low temperature sensitivity of 2.19 pm/°C, which achieves an extremely low temperature-strain crosstalk of less than 16.6 nε/°C. Moreover, the proposed FPI sensor possesses advantages of high sensitivity, low-cost and compact length, which shows potential in areas of micro strain measurement.

Assembly and characterization of an optical fiber probe for use in a portable Raman spectrometer

This study describes the assembly and testing of an optical fiber Raman probe for use in a portable spectrometer using a 785 nm laser. The Raman probe was tested on edible vegetable oils (extra virgin olive, canola, sunflower, corn, and soybean), with the distal end of the probe immersed in each sample. The spectra of a dipyrone tablet and a mothball were also obtained. The silica peaks were subtracted by taking a spectrum with the probe tip immersed in water. The spectra of the samples exhibited characteristic peaks from vibrations of unsaturated fatty acids between 900 and 1800 cm−1, as well as characteristic peaks of silica from 600 to 1200 cm−1. The spectra of the samples after subtraction of the silica spectrum (probe in water) showed characteristic peaks without alterations in position or relative intensities compared without the probe. Exploratory analysis by principal component analysis was able to identify peaks of the constituent fatty acids in the oils and associate them with the oil type. A classification model based on partial least squares regression allowed for the classification of oil spectra with an accuracy of 77%. This study demonstrated the feasibility of coupling a probe to a portable Raman spectrometer with the goal of monitoring and controlling industrial processes.

Ultra‐Stable Phonon Laser Through Closed‐Loop Feedback Control for Optomechanical Sensing

AbstractThe resonant amplification of the optical and mechanical components in cavity optomechanical systems enhances the performance of sensing applications, which rely on precise frequency control and narrowed mechanical linewidth. This study proposes a direct closed‐loop feedback technique for a narrow linewidth phonon laser based on optomechanical self‐oscillation. By continuously pumping a mechanical resonator with a laser, a phonon laser is achieved with an oscillation frequency of 17.58 MHz, exhibiting a narrow linewidth of just 0.44 mHz and an effective mechanical Q of 4 × 1010, while preserving the linear frequency response. The oscillator phase is fed back to the pump laser, yielding a mechanical frequency stability of 7.2 × 10−11 and providing a real‐time output of direct current voltage corresponding to the oscillator frequency changes. The system's real‐time sensing capability is tested using fiber probes and polystyrene particles, demonstrating a performance approach to the theoretical resolution limit. This work opens new avenues for real‐time precision measurement technology and can be extended to different optomechanical systems.