This PDF file contains the front matter associated with SPIE Proceedings Volume 12372, including the Title Page, Copyright information, Table of Contents and Conference Committee lists.

The paper presents the design and preliminary experimental validation of a fiber laser with direct emission in the yellow. The active material is a Dy-doped custom-made phosphate fiber, which is pumped by high-power blue diode lasers emitting at 450 nm. A suitable model has been developed to optimize the laser behavior and validated with a low-power version of the laser cavity with femtosecond written Bragg grating mirrors.

Optical Backscatter Reflectometry (OBR) is capable of converting a simple and inexpensive single mode fiber (SMF) into an effective spatially distributed sensor of temperature and strain based on the concepts of Optical Frequency Domain Reflectometry (OFDR). A 2D sensing map of applied forces over a defined surface may be created by employing different spatial configurations of SMFs. This can be beneficial in biological applications such as measuring bite force. In this paper a 2D pressure sensing map based on distributed fiber optic sensing is provided. The two dimensional technique is performed by bending the optical fiber along the surface to acquire ten lines embedded in silicone material, thereby generating a carpet of 2 by 6 cm. The highly resolved sensing map is created by spacing fiber lines 2 mm apart with a sensing range of 2 mm across the fiber. The embedded fiber detects distributed strain, which is subsequently transformed into a pressure map. The dependence of strain on the toughness of silicone material was observed. The map's pressure sensitivity coefficient has been effectively identified. The setup has been validated for surface measurement of wavelength shift values over 9 sensor carpet locations with a total of 310 sensing points. Since the sensor is embedded or attached to irregular forms and geometries, the distinctiveness of sensing surfaces allows for enhanced responsiveness to curvature due to its mechanical characteristics.

We reported a design and evaluation of an optical coherence tomography (OCT) sensor-integrated 27 gauge vertically inserted razor edge cannula (VIREC) for pneumatic dissection of Descemet’s membrane (DM) from the stromal layer. The VIREC was inserted vertically at the apex of the cornea to the desired depth near DM. The study was performed using ex vivo bovine corneas (N = 5) and rabbit corneas (N = 5). A clean penumodissection of a stromal layer was successfully performed using VIREC without any stomal blanching on bovine eyes. The “big bubble” was generated in all five tests without perforation. Only micro bubbles were observed on rabbit eyes. The results proved that VIREC can be an effective surgical option for “big bubble” DALK.

In the treatment of acute cerebral infarction, it is important to remove the thrombus quickly without side effects such as intracranial hemorrhage. We have been developing a new therapy way of acute cerebral infraction using laser to solve some weaknesses of current devices and medicines. We use 532nm pulsed laser to remove clot without damage of vessel wall, but it is difficult to adjust position of the tip of catheter to a clot within an effective range. Then, we developed real time monitoring function to evaluate it. In a real-time monitoring function, we used 785nm CW laser added on 532nm pulsed laser, evaluated the 785nm laser which is reflected the tip of the optical fiber. A power of the reflected 785nm is based on the Fresnel equations, and time change levels of reflected 785nm reflects how bubbles generated by pulsed lasers disappear. In the result of evaluation of in vitro studies, it turned out that how its change is affected by the surrounding environment (e.g., hardness and viscosity around the catheter tip). If the area around the catheter tip is filled with liquid, the signal will disappear quickly and simply, and if there is a blood clot, it will be less likely to disappear and its shape is more complex and the key to these phenomena is how the shock generated by the pulsed laser propagates, and we hypothesize that it is a type of rebound due to cavitation.

Tumour hypoxia is a critical factor in treatment failure and resistance, and its accurate measurement with diffuse reflectance spectroscopy (DRS) could be used for prognostic and response monitoring purposes. In this in vivo characterisation study, we sequentially measured oxygenation trends over the entire course of tumour growth in mice using a multi-depth, fibre-optic DRS probe. Results demonstrated a clear downtrend in oxygenation over time. This progression was not always linear, with significant heterogeneity over time and between mice. Our findings will be further validated against gold standards prior to investigating whether hypoxia can be used to predict radiotherapy responses.

One interesting feature of optical frequency comb (OFC) is a function of frequency conversion between region and electric regions. While such feature has been used for generation of correct electric signal in microwave or millimeter region, it can be further used for fiber biosensing; namely, biosensing OFC. In this paper, we demonstrated detection of SARS-CoV-2 antigen based on a combination of dual fiber combs, an intracavity multi-mode-interference fiber sensor, and sensor surface modification of SARS-CoV-2 antibody.

Lens-less endoscopy based on multi-core fibers (MCFs) with aperiodic core arrangements enables 3D imaging deep inside tissue with reduced imaging artifacts such as higher-order diffraction. With a scalable iterative stack-and-draw process, we fabricated and characterized (e.g. cross-talk) two aperiodic MCFs: (i) a 250 µm fiber with 420 cores and (ii) a 333 µm fiber with 1281 cores. Since lens-less endoscopy is sensitive to dynamic bending, two different approaches to twist the fibers were evaluated: i) rotation of the fiber preform during fiber drawing and (ii) post-production twisting of the MCF within a fiber processing station.

Real-time dosimetry with optical fibre can add to the range of dosimeters available for proton therapy applications. Perfluorinated fibre has demonstrated linearity in radiation-induced attenuation with doses delivered at different energies and it has shown to be highly sensitive and dependent on the wavelength of the probing light source with its highest sensitivity obtained at a wavelength of 460 nm This paper presents the potential of perfluorinated polymer fibre in proton dosimetry applications.

The DIN standard 58145 “Measuring method for determination of solarization effect of fused silica optical fibers” was introduced over 5 years ago to standardize the quality control for UV fibers. A deuterium lamp with a lens-based imaging system, coupling a light power density of approx. 200 µW/(cm2 nm) at 214 nm into the fiber under test, was specified as light-source. With time, the availability of new powerful broadband light-sources stimulated new applications. Further, improvements in deuterium lamps and imaging coupling systems resulted in higher light power densities. It was quickly determined that these new conditions induced different spectral and temporal UV losses, which needed to be studied. As a result, the cw-power coupled into the fibers under test, referenced at 214 nm in the original set-up, increased. We observed that two measurement systems, both assembled by the DIN standards recommendations, showed significant deviations in solarization effects at 215 nm (E’ center) and 265 nm (NBOH center). Therefore, we investigated ideal lens coupling conditions, influence of lens aging (solarization) and the influence of N2 purging of light-source and detector on permanent and transient solarization effects in fibers. A closer analysis and selective change of the spectral power between 190 nm and 260 nm wavelength coupled into silica-based fibers with undoped high-OH silica core is presented and an improved system for solarization measurements on UV fibers is recommended.

Due to the increased use of laser in various analytical instrumentation and microscopy, laser speckle has become an issue, where the speckle reduces the contrast of the images produced. This paper describes an optical fiber-based speckle reducer where the speckle is reduced within the fiber. This allows the de Speckler to be directly attached to any fiber based light source making it easy to use. We will be presenting speckle reduction data along with images produced.

The phrase "fiber laser" is a ubiquitous but insufficiently detailed description, as powers can range from microwatts to kilowatts. Fiber core diameters can vary from 3-micron core diameter ultra-high NA fibers for supercontinuum generation to 85 micron or greater PCF fibers to generate high pulse energies. With appropriate nonlinear optics, fiber lasers can reach wavelengths ranges from the UV to the LWIR and pulse widths can range from ultrafast femtosecond lasers to continuous output. The appropriate selection of laser can minimize cost, maximize efficiency, and ease assembly challenges in biomedical systems. The advantages and design limitations of single-mode, LMA, and PCF fiber lasers, as necessary to understand the available system impact of fiber laser source selection and including methods to reach directly inaccessible wavelength ranges, maximize net efficiency, or shape the light inside of a fiber are discussed.

The paper presents the development and investigation of distributed and a quasi-distributed fiber optic sensors for the real-time monitoring of radiations during cancer treatments. Both sensors rely on ad-hoc developed nanoparticle-doped optical fibers with enhanced sensitivity to radiation. The distributed sensor is interrogated with an OFDR-based instrument and allows the reconstruction of the spatial dose distribution along the fiber. The quasi-distributed sensor is implemented through fiber Bragg gratings inscribed with a femtosecond laser in the few-mode section of a single mode-multi mode-single mode interferometer.

Monitoring UV fluorescence from tissue and biological samples is highly relevant because several molecules can emit in this spectral region. Applications such as tumor evaluation through cell tracking proliferation for instance, rely on the use of these fluorescent molecules as biomarkers through its UV autofluorescence. Although optical fiber devices can be readily used for this task, these are typically fabricated with special fibers in order to avoid the high UV transmission losses of conventional silica fibers. In this work, we demonstrate the use of down-conversion phosphors attached to conventional fiber optic tips to fabricate probes for UV monitoring. The phosphors are irradiated by the target UV fluorescence signal thus producing emission in the visible spectral range that is captured and transmitted through the silica fiber probe to a spectrometer. We use europium (Eu) activated phosphors to generate the down-conversion effect, in particular, commercially available red emitters embedded in a transparent polymer matrix. This blend is obtained by a simple mixing procedure and is subsequently deposited via dip-coating on the fiber end face to create a fluorescent end cap. We describe the fabrication procedure of the probes as well as their performance for UV fluorescence monitoring.

The exploration of solar system bodies is now for decades a focus of activities of space agencies around the world. The motivation ranges from gaining a better understanding of the geology of e.g. planets and moons to the search for traces of (former) life. The developed spectroscopic sensors reach from passive infrared spectrometers employed e.g. on orbiters to active laser spectroscopies such as NIR spectroscopy, Raman spectroscopy or Laser-Induced Breakdown Spectroscopy employed on robotic missions. Space, weight and power restrictions as well as robustness against harsh environmental conditions are inherent prerequisites for space missions and lead to specific design solutions for these instruments. In this review an overview is given, presenting the application and design of selected spectroscopic sensors and techniques employed in past missions. Thereafter, emerging sensors concepts and technologies are presented which are currently investigated for use in future space missions.

A straightforward multi-scale infrared (IR) spectroscopic characterization of anisotropic polymer nanofibers for material research and biomedical applications is presented. Polarization dependent IR spectroscopies with spatial resolutions from a few mm down to a few 10 nm (by atomic force microscopy-based infrared spectroscopy, AFM-IR) and time resolutions from the min to µs range (by infrared dual-comb polarimetry, IR-DCP) are used. Compared to AFM-IR, which measures the absorption via the photothermal expansion, and IR ellipsometry, which measures amplitudes of sand p-polarized radiation and their phase differences, IR-DCP measures separately s-and p-polarized amplitudes and phases

Block Engineering’s pulsed external-cavity Quantum Cascade Lasers (QCLs) combine the optical brightness of lasers with very broad wavelength tuning to provide a breakthrough capability for spectroscopy. Over the past decade QCLs have been refined, become accepted as a spectroscopy tool, and applied to heretofore challenging sampling scenarios such as transmission through liquids or scattering off of low-reflectivity surfaces. More recent miniaturization of hardware and electronics are now enabling QCLs to become embedded in portable and hand-held instruments. This presentation will briefly review the current state of the art of QCL technology and describe systems recently developed for portable medical diagnostics and hyperspectral imaging.

Optical Whispering Gallery Mode (WGM) microresonators have shown great promise in sensing applications. Various efforts have been made to package WGM sensors in order to enhance their robustness for field applications. Previously, polydimethylsiloxane (PDMS) and other low index polymers have been employed for packaging of WGM sensors. However, the long curing time of PDMS and the rigidity of polymers pose other difficulties, thereby limiting their performance. Hydrogels, with shorter polymerization time and increased flexibility, transparency and biocompatibility, offer a great alternative to current packaging materials. The flexibility and optical transparency of hydrogels, in conjunction with the capability to functionalize them for specific applications, provide superior functionality and improved stability of WGM sensors. Herein we propose the use of laponite nanoclay and N, N, dimethylacrylamide (DMAA) based hydrogel for the packaging of WGM sensors. Microbubble resonators were used for the demonstration of hydrogel-based packaging. The hydrogel was synthesized by mixing DMAA in exfoliated nanoclay suspension at different concentrations with sodium persulfate as an initiator and Tetramethylethylenediamine (TEMED) as an accelerator. The microbubble resonators were packaged on 3D-printed chips and were characterized through their transmission spectra.

In the proposed work, titanium dioxide (TiO2) coated on an etched fiber Bragg grating (eFBG) sensor has been used for sensing the industrial chemicals such as glycerin. The FBGs were etched with hydrofluoric acid at a 40% concentration to interact with the outer medium before applying an optically active thin material layer for improved sensing. Raman spectroscopy and FESEM are used to characterize the sensor. An increase in the interaction of the evanescent field interacting with the analyte caused by the metal oxide layer increases sensitivity by approximately 24%. The sensitivities achieved with the bared eFBG sensor and the TiO2-coated eFBG sensor are 10.18 nm/RIU and 13.4 nm/RIU, which is better than any other earlier reported work for sensing glycerin.

Hydrogen has attracted much attention as a source of clean and sustainable energy. However, one of the drawbacks of handling hydrogen as a power source is its volatility and flammability. Moreover, hydrogen leakages in gas pipelines or tanks can generate highly explosive gas mixtures in air, if the hydrogen concentrations exceed 4 %. Therefore, in order to increase the security, monitoring of hydrogen concentrations in hydrogen infrastructures is mandatory. Remote sensing systems using passive fiber optical sensors are predestined for these kinds of applications. In this paper, a sensor based on evanescent field fiber Bragg grating (FBG), coated with palladium (Pd) nanoparticles is proposed. Thereby, the intensity change of the sensor signal correlates with the hydrogen concentration. The detection range of the sensor is between 0.5% to 5% H2 in nitrogen or synthetic air atmosphere and therefore shows great potential for the detection of hydrogen leakages below the explosive limit of 4%.

The paper presents the realization of a prototype of a compact, cost-effective, and real-time photonic system for the early detection of quality variations in flowing water and for its sanitization. The detection is based on a multi-functional fiber Surface Plasmon Resonance (SPR) sensor, while the disinfection is obtained with a combination of short-wavelength light in the UV-blue region.

To achieve the UN Sustainable Development Goal of universal access to clean water and sanitation, we need to rethink centralized water systems with global net-zero carbon and sustainability in mind. One approach is to develop scalable off-grid systems that are reliable and easy to use and maintain. A major challenge for such systems is translating the standard laboratory-based monitoring of centralized systems to a more sustainable and scalable model for regularly and routinely monitoring system outputs, which consist of complex mixtures with varying concentrations of molecules and ions in water. Here, we demonstrate a preliminary sensor that, once fully developed, could allow for point-of-use measurements with a single output to monitor. Rather than developing multiple sensors to monitor the levels of each individual component in the water, our label-free, array-based design mimics the biological system of taste. The sensor is comprised of an array of nano-tastebuds made of tailored plasmonic metasurfaces. The combination of different signals from each nano-tastebud to the same sample yields a unique fingerprint for that sample. Through training, these fingerprints build an identification model. By integrating a fully developed sensor into decentralized water systems, we seek to provide non-expert end-users with an easy-to-read output capable of warning of imminent system failures.

Rapid advances in design, materials, and fabrication technologies over the past decade have allowed scientists to construct novel sensors to map and investigate the marine environment in new ways. This paper investigates the potential of nanoplasmonic sensors to further improve our understanding of marine ecosystems by providing information on pressing physical, chemical, and biological ocean parameters.

Arsenic is a significant drinking water contaminant whose prolonged consumption can cause cancer, skin lesions, and cardiovascular diseases. The environmental protection agency (EPA) declares 10 ppb and lower as an acceptable limit for arsenic in drinking water. Several technologies, such as biomolecules, nanoparticles, nanowires, carbon nanotubes, and quantum dots have been deployed under optics to develop viable optical sensors for arsenic detection in water. Although these approaches offer decent accuracy, they require trained laboratory personnel and state-of-the-art lab facilities, impose several adaptability constraints, and take hours in results production. Therefore, there is a need for an economical and easy-to-fabricate optical sensor that can provide rapid, precise, and portable detection of arsenic in drinking water. Here, we demonstrate a novel fiber sensor that employs phase shift cavity ring down spectroscopy (PS-CRDS) to record phase shift measurements in fiber cavities. In PS-CRDS, the cavity ring down time is proportional to the phase shift between the reference modulating signal and the cavity output, a measure of sensing event (absorption due to arsenic) inside the cavity. The sensor utilizes a tapered fiber of waist ˂ 12 µm as a sensing head. We place the tapered fiber in a fluidic cell and insert the assembly inside the optical cavity. Furthermore, we chemically treat the solution with Azure B to add specificity toward arsenic detection. Azure B acts as a chromogenic reagent that enhances the absorption loss of arsenic in water samples at 633 nm. We inject 3 mL of arsenic-contaminated water and Azure B solution into the fluidic cell and record phase shift measurements. We experimentally demonstrate that the sensor has a minimum detection limit of 5 ppb and a sensitivity of 0.0133o /ppb. We anticipate our work will lead to rapid, portable, and accurate optical sensors for physical, chemical, and biological applications.

We suggest a prototype of a fiber-optic sensor system that is based on a simple singlemode-multimode-singlemode fiber structure and serial OTDR. The sensor has simple structure, made of affordable components, exploits easy measuring principle, immunes to EMI or RFI, and has confident response to measure key environment variables at a very long span. From the experimental results, the relationship between the temperature of water and output signal of the temperature sensor can be determined. After some maths, we can determine the temperature of the water by measuring the optical power loss of the at the SMS structure in a temperature range of 30 to 70 °C. This SMS structure is shown to carry out vibration measurement for 0.1-60 Hz frequencies with high accuracy. The OTDR exploited allows carrying out far-field measurements when SMS structure is spliced in long fiber-optic link.

Ascorbic acid, genreally known as Vitamin ‘C’, is a nutrient, which is responsible for numerous biological functions like collagen formation, iron absorption, growth and repair of cells, tissues, bones, cartilages, teeth etc. It plays a promising role in providing a healthy immunity against bacterial and viral infections. It also helps in making several chemical messenger and hormones, thus playing importance in the nervopus system of body. Thus, ascorbic acid is a biomarker for the detection of various malfunctionings of the body like weakened immunity, scurvy, cardiovascular diseases, Alzheimer’s and Parkinson’s disease. In this work, a straightforward and effectual sensor model is proposed to detect the presence of ascorbic acid samples found in human body. Etched single mode fiber-multimode fiber-single mode fiber (E-SMS) is used for developing the sensor with the application of localized surface plasmon resonance (LSPR) phenomenon. For achieving LSPR and better sensitivity, the E-SMS are coated with gold nanoparticles (AuNPs). The different concentration of ascorbic acid solution alters the refractive index and the spectrum thus recorded and evaluated. The experimental results shows that the proposed E-SMS-based LSPR biosensors can detect the presence of ascorbic acid in human body and thus have significant application in the field of biosensing.