Hair-thin optical fiber endoscopes have opened new paradigms for advanced imaging applications, such as optical coherence tomography, which a large depth-of-field is desirable to trade off lateral and axial resolutions. This requirement can be achieved using needle-like Bessel beams, generated by micro-lenses bonded onto fiber tips. In this paper, we compare Fresnel zone plate and axicon mask on fiber tips shaping light into Gaussian foci and Bessel beams, and demonstrate that the axicon-fiber device is capable of imaging a resolution target with large depth-of-field. We also show that our fabrication method is capable of fabricating fiber-imaging devices with multi-layer lens stacks.

Calcium phosphate glass based single-mode and multi-mode bioresorbable optical fibers were in-house manufactured. Ex-vivo studies were then conducted to test the suitability of these fibers for time gated diffuse optics spectroscopy, photodynamic therapy and diffuse correlation spectroscopy applications which can be respectively employed for the diagnosis, treatment, and monitoring of malignant tissues. The results demonstrated the potential of calcium phosphate glass-based fiber optic devices towards the realization of an implantable multi-functional class of devices with functionalities ranging from cancer detection to monitoring of the healing process all integrated into a single bioresorbable platform. Acknowledgement: This project has received funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant agreement No 860185

Water electrolysis in Proton Exchange Membrane Water Electrolysis (PEMWE) cells is important for sustainable energy conversion. The efficiency and longevity of these cells depend on operating conditions such as the temperature of the membrane. We employ a fiber-based sensor using lanthanide-doped nanoparticles as nanothermometers to measure the temperature at the cell’s membrane for different operational conditions. In the future, this sensor can be used to optimize the cell’s operational parameters and is also applicable in strong electromagnetic fields, for example in battery technology or magnetic resonance tomography.

Addressing the pressing need for rapid and sensitive infectious disease diagnostics, we introduce DIgitAl plasMONic nanobubble Detection (DIAMOND), an innovative strategy harnessing plasmonic nanobubbles generated through laser-induced nanoparticles. Using gold nanoparticles in an optofluidic system, DIAMOND enables compartment-free digital counting and homogeneous immunoassays, demonstrating respiratory syncytial virus detection at single RNA copy per microliter. This breakthrough technology offers single-nanoparticle detection, direct virus sensing at room temperature, and simplified liquid handling, establishing itself as a versatile platform for expedited and highly sensitive diagnostics, with the added benefit of achieving detection within just 10 minutes. Concurrently, our research advances plasmonic nanobubble generation by anchoring sub-10 nm AuNPs onto thiol-rich Qβ virus-like particles, significantly enhancing photocavitation and reducing laser fluency. In a significant step forward, we are expanding the horizons of DIAMOND, now enabling single protein detection at attomolar concentrations, representing a remarkable advancement in our capabilities.

Rapid and sensitive assessment of biomedical compounds as well as environmental markers have become a critical pursuit of our community. Implementation of a combination of complementary and orthogonal sensing schemes, such as, fiber-coupled Raman and THz spectroscopy and imaging systems could revolutionize the sensing field even outside the laboratory by providing fast, reliable, non-contact, non-invasive acquisitions in the domains of environmental sensing and biomedical diagnostics.

We report a fiber-optic sensor that can be deployed through a standard 250-µm injection needle (25 gauge) for minimally invasive measurements of deep-tissue biomechanical properties in vivo. We have demonstrated the sensor’s ability to provide distinct readouts of muscle stiffness when the hind limb of a rat is relaxed and stretched. To ensure minimal tissue damage and distortion, we have integrated optical proximity sensing within the same fiber for real-time, precise control of the sensor position. To facilitate clinical translation, we have designed the sensor to be disposable and autoclavable and have developed a strategy for mass production.

We report on fluorescence enhancement using a suspended core photonic crystal fiber (PCF) as an optofluidic platform. By employing metallic nanoparticles and an organic spacer, we achieved a thirty-fold signal enhancement of Cy5 dye at picomolar concentrations. The combination of fluorescence enhancement and PCF offers robustness, ease of use, and high sensitivity. This comprehensive study explores fluorescence enhancement using PCF, highlighting the significant enhancement achieved through metallic nanoparticles and organic spacers associated by the long length of light-analyte interactions offered by the PCF. These findings might contribute to the development of highly sensitive optical fiber-platforms for biomedical applications.

A compact fiber-optic probe for combinational vibrational spectroscopy was developed and evaluated. The probe is capable of simultaneous acquisition of mid-infrared ATR and Raman spectra from the same spot in the region 3100-2600 cm-1 which contains predominantly the responses of C-H stretching vibrations of hydrocarbon residues that has been widely employed in organic, analytic, biological, and polymer chemistry.

Infrared imaging from space provides critical information about Earth’s surface and atmosphere for weather prediction, study of the world’s ecosystems, detection and monitoring of natural disasters such as volcanoes and wildfires. In the recent decade, JPL IR group has been developing high performance imagers that are based on the novel infrared detector technology. In my presentation I will discuss our advances in mid- and long- wavelength infrared FPAs and their use in remote sensing instruments.

Owing to the recent technological advances in mid-infrared (3-15 µm; MIR) laser technology, especially cascade laser spectroscopy (CSL) has evolved into a state-of-the-art tool for the selective and sensitive quantification of trace analytes in liquid, solid, and gaseous state in a wide variety of sensing scenarios. High output power, narrow linewidths, single-mode operation, low power consumption, broad tunability and compact dimensions are just some of the most outstanding features of cascade lasers. The unique combination with mid-infrared fiberoptic facilitates the development of innovative MIR catheter technologies for analyzing cartilage damage in-vivo during arthroscopic surgery.

There is a multibillion-dollar market for gas monitoring and the demand for solutions continues to grow. Managing methane leaks is critical for energy operations, monitoring nitrogen species in agriculture has ramifications for crop health, and toxic gases in multiple industries can create hazardous working conditions. Many systems rely on optical techniques, light sources and photonic detectors working together to produce measurements. When considering the wavelengths to utilize, operating in the mid-infrared region presents advantages such as higher sensitivity, longer lifetimes, and more consistent measurements. Components have been known to be expensive and difficult to integrate but recent developments present new opportunities. This presentation will cover the basic principles of photonic gas measurements, the state of current and future mid-infrared components, and the science behind the benefits of mid-infrared for gas analysis.

The mid-IR wavelength range, and the fundamental vibrational absorption fingerprint region it encompasses, can be utilised for a variety of environmental and medical monitoring applications requiring the detection of specific covalently bonded molecules, for example, in atmosphere or in a patient’s breath. Mid-IR transmitting chalcogenide fibres, based on the elements: sulfur, selenium, and tellurium, have a characteristically high optical non-linearity and thus can be tailored to also generate mid-IR supercontinuum light that covers this fingerprint region. The process of designing, fabricating, and characterising chalcogenide glass fibres via differential scanning calorimetry, microscopy, ellipsometry, and optical fibre loss measurements is detailed.

This paper explores how a fluorescent dye can be immobilized in a polymer film at the distal end of an optical fibre to serve as a fibre optical chemical sensor for organic solvents in water. The sensing principle is based on a shift in the fluorescence peak of the dye.

Here we present our latest fiber-optic techniques in spectral range from UV to mid-infrared for research and industrial applications. Depending on the chemical process or materials to be analyzed, fiber probes can be based on 4 different fiber types selected for the required spectral range and used for Transmission, Reflection, ATR-absorption, Raman & Fluorescence spectroscopies. Advanced fiber optic combi probes are capable to utilize two and more spectroscopic methods at the same time assembled in the same probe shaft - such as Mid-FTIR+Fluorescence, Raman+Near IR, Raman+Mid-FTIR, Raman+mid-FTIR-Near IR and others. It improves selectivity and precision of the analysis for media content in process control.

Optical fiber shape sensing has diverse applications in medical and industrial fields. However, commercially available fiber shape sensors are costly and complex. The development of eccentric fiber Bragg grating (eFBG) sensors provides a cost-effective alternative with unique capabilities. Existing eFBG shape sensing methods calculate curvature using Bragg signal intensity variations. Yet, uncontrolled bending and polarization-dependent losses cause spectral distortions affecting eFBG intensity ratios. To overcome this, we developed a data-driven deep-learning technique for accurate shape prediction. Our approach significantly improves shape prediction, achieving millimeter-level accuracy for curvatures of 3 cm to 70 cm in a 30 cm eFBG sensor. This promising research advances low-cost and accurate fiber sensors, impacting medical and industrial sectors requiring precise and cost-effective shape sensing.

The development of rapid and precise methods for detecting metal ions has emerged as a critical concern. In this study, we present a novel and highly miniaturized glass capillary system designed for the specific, rapid, and cost-effective detection of heavy metal ions, focusing on chromium (Cr3+) as a representative example. Applied capillaries were made of fused silica (tailored and drawn in-house), and their used pieces accommodated volumes as low as 2.9 µL. The measurement setup consisted of the laser source and optical detector collecting spectra in the wavelength range of 200-900 nm. The specificity of the detection in the system was provided by the engineered green fluorescent protein (eGFP, developed in-house), which undergoes conformational changes upon interaction between its engineered metal-binding loop - and specific metal ion. Consequently, the fluorescence emission of eGFP is either emitted or enhanced. The obtained results clearly demonstrate distinct changes in fluorescence intensity corresponding to varying concentrations (50 pM to 50 µM) of metal ions. Detection of 500 pM was feasible even with the mere presence of ng of the receptor protein - eGFP.

In this study, simulated by using Finite-Difference Time-Domain method, and applied to spin-coating titanium dioxide (TiO2) solution onto the indium tin oxide (ITO) conductive glass films, and gold nanoparticles (AuNPs) are modified on the TiO2 glass films by using self-assembly method. The sensing element is immersed in five different concentrations of glucose solution, including 0 mg/dl, 50 mg/dl, 100 mg/dl, 150 mg/dl and 200 mg/dl. The results show that the resonance wavelength λSPR was shifted by changing the polarization state of the incident light for the purpose of copper ion (Cu2+) concentration sensing.

Wideband wavelength swept lasers (WSLs) are widely used as light sources for dynamic fiber optic sensors. In this study, we implemented an ultra-wideband wavelength-swept laser (WSL) that achieved a 10 dB bandwidth over 430 nm using a single polygonal scanning mirror-based wavelength tunable filter. The wavelength scanning range with a 1.8kHz scanning frequency is 1136.0~1567.2nm. Comparing the WSL output signal in the temporal and spectral domains resulted in an error of 0.7 nm in the mid-crossing region of the two gain media. To confirm WSL performance, the transmission band was measured by changing the electric field applied to the cholesteric liquid crystal cell, and it was confirmed that the transmitted beam according to the applied electric field matched each other in the spectral and temporal domains.

Surface enhanced Raman spectroscopy (SERS) is a powerful analytical technique that can detect trace quantities of analyte. However, fabricating cost–effective and homogeneous SERS substrates for diverse applications remains a significant challenge. Herein, a simple bottom-up technique is reported for developing a unique SERS substrate by exploiting the plasmonic coupling of low-cost aluminium foil (ALF) and 3-dimensional (3D) gold nanoparticle aggregates induced by cucurbit[5]uril (CB[5]) .

In this study, the feasibility of a volatile organic compounds (VOC) gas sensor was confirmed through a porous cholesteric liquid crystal film (CLCF) coated on the cross-section of an optical fiber ferrule. The device was fabricated by injecting the CLCF mixture between two ferrules and then UV cured. After separating the two ferrules, porous CLCF was prepared by immersing the CLCF-coated ferrule in acetone. To measure the change in the reflection spectrum of the device for each VOC gas, a broadband wavelength swept laser with a 10dB bandwidth of ~430nm was used. In conclusion, it was found that the reflection band was continuously red-shifted for acetone gas and THF gas.