This PDF file contains the front matter associated with SPIE Proceedings Volume 11635 including the Title Page, Copyright information, and Table of Contents.

Mid-infrared (MIR) direct fiber lasers beyond 4 μm wavelength will deliver optimum beam quality of bright, spatially and temporally coherent light, routeable in MIR fiber-optics. They are being developed for applications including narrow-band biomolecular sensing, medical laser surgery at new, long wavelengths and for pulsed seeding of long wavelength MIR-supercontinua in MIR glass fiber for all-fiber, compact systems for broad-band MIR medical sensing and hyperspectral imaging. Low phonon energy, selenide chalcogenide glasses are the optimum glass host for lanthanide ion doping for emission across the 3 to 10 μm wavelength MIR region. Here, we report our recent advances including: >1 mW incoherent emission in the 4-5 μm wavelength region and demonstration of gain beyond 4 μm in Pr³⁺ doped chalcogenide glass fiber, and proposed quasi three-level lasing beyond 4 μm in Tb³⁺ doped chalcogenide glass fibers. Encouragingly, since 2020, lasing in both Pr³⁺ and Tb³⁺ selenide chalcogenide bulk glasses has been reported. Our overall goal is for new portable, MIR spectroscopic systems based on chalcogenide optical fibers for in vivo sensing, imaging and treatment in healthcare, including for early diagnosis of disease.

Based on current studies with pulsed Nd-YAG lasers at 213, 266 and 355 nm, the measured UV-induced losses of multi-mode stepindex fibers can be described by multiple Gaussian shaped UV-defects. For best fitting, the peak value, center peak wavelength and Full-Width-Half-Maximum (FWHM) were variable parameter for the different absorption bands, similar to those defined by literature values. On the other hand, the damaging of multimode UV-fibers by broadband UV light-sources is still of particular interest. In addition to deuterium sources, where these losses are already described in the German DIN 58145 standard, pulsed Xe-lamps are used e.g. in spectroscopic applications for process control. Using both light-sources, the status of long-term degradation in UV fibers due to defects in their synthetic high-OH silica core and cladding will be described. However, this paper, focusses on results with the pulsed Xe-lamp and presents data for fiber-optic systems in spectroscopic applications. Transferring the above approach including the fit-function, analyses in high-OH and low-OH are carried out using broadband lightsources, regarding basic attenuation plus spectral and temporal damaging over several days. With the different light-sources, the peak values and the form of the absorption bands differ strongly, which can be explained by the overlapping of the absorption bands due to their spectral widths (especially the NBOHC at 260 nm). After discussing the differences related to different core diameters and lightsources, it is shown for the first time that the UV-induced losses are independent of the propagation angle within a step-index fiber.

Plasma outside deposition (POD) allows the incorporation of high fluorine contents in silica glass to manufacture multi-mode fibers. Due to all silica design and excellent material attributes, these so-called Fluosil fibers cover a wide spectrum of applications over a broad wavelength rage from UV to NIR including medical laser surgery, industrial materials processing, automotive, sensing, spectroscopy, and fiber bundles. These characteristics have allowed fiber designs to become more and more sophisticated in recent years. An overview of the current capabilities, characterization techniques, and fiber trends will be presented. Heraeus supports these new developments by offering a growing number of materials, preforms and services.

Review of the latest progress of special optical fiber applications in laser optics, IR-Imaging and spectrometry. The advanced fiber solutions will be presented for Quantum Cascade Lasers in Mid-IR range. A high coupling efficiency of optical fiber and Hollow Waveguides to QCL is demonstrated. A novel combined fiber optic multispectral probe for tissue diagnostics is demonstrated and discussed. Flexible solutions for thermal imaging in mid-IR range are proposed on the base of high quality optical fibers.

Beam-shaping through optical fibers facilitates miniaturized light delivery in fields such as endoscopy, communication, etc. As the stability of optical beam delivery and collection depends a lot on the fiber stability, the impact of fiber deformations on mode-coupling for different types of fibers should be analyzed. To this end, we present a numerical simulation tool modeling optical field propagation through fibers with arbitrary refractive index profiles, focusing on fiber twisting, tapering, and bending. Our simulation tool is compared against the state-of-the-art simulation software evaluating computational efficiency, versatility, and user-friendliness. The simulation tool is gratis, open-source, fast, and supports optional CUDA acceleration.

We have developed a compact background and fluorescence free endoscopic Raman probe using shifted-excitation Raman difference spectroscopy (SERDS) with an optical fibre featuring a negative curvature excitation core and a coaxial ring of multimode collection cores. The probe consists of a single optical fibre with an outer diameter below 0.25 mm packaged in sub-millimetre tubing making it compatible with the working channels of standard endoscopic tools. The light in the fibre is guided in air and therefore interacts little with silica, enabling an almost background-free transmission of the excitation light and collection using a single optical fibre. In addition, we used the SERDS technique and a tunable 785 nm laser to separate the fluorescence and the Raman spectrum from highly fluorescence samples, demonstrating the suitability of the probe for biomedical applications.

Optical, and especially fiber-optic techniques for the sensing of pH have become very attractive and considerable research progress in this field has been made over a number of years. The determination of the pH level across a broad range of applications today, e.g. in life sciences, environmental monitoring, industry and widely in biologically research is now accessible from such optical sensors. This arises because familiar sensors are often limited in terms of their response time and drift, which reduces the use of the current group of such fiber-optic sensors in wider applications. A new compact sensor design has been developed in this work, based on a specially-formed fiber-optic tip that was coated with a pH-sensitive dye, covalently linked to a hydrogel matrix to provide high stability. The sensor developed has a very fast response time (to 90% of saturation, Δt₉₀) of < 5 seconds, a sensing uncertainty of about ± 0.04 pH units and given the covalently bonded nature of the dye, leeching is reduced and the probe is very stable over many days of use. During extended continuous use over ~12h in pH 7, this stability was confirmed, with drift of < 0.05 pH/h. Preliminary experiments in an important biological application, monitoring over pH levels from pH 5 to pH 8.5, are shown and discussed.

We have developed different portable tools based on phosphorescence lifetime and intensity measurements to be used together with syringes, needles, and catheters to measure oxygen partial pressure deep inside tissue with the aim to improve the assessment of acute compartment syndrome (ACS). Due to their portability and universality, the tools will also be useful in other hypoxia-related conditions such as vascular diseases, diabetic wounds, cancer, and traumatic injuries. We will present designs as well as results from in vivo porcine model studies.

Optical coherence tomography (OCT) with a robust depth-resolved attenuation compensation method for a wide range of imaging applications is proposed and demonstrated. The proposed novel OCT attenuation compensation algorithm introduces an optimized axial point spread function (PSF) to modify existing depth-resolved methods and mitigates under and overestimation in biological tissues, providing a uniform resolution over the entire imaging range. The preliminary study is implemented using A-mode numerical simulation, where this method achieved stable and robust compensation results over the entire depth of samples. The experiment results using phantoms and corneal imaging exhibit agreement with the simulation result evaluated using signal-to-noise (SNR) and contrast-to-noise (CNR) metrics.

Atrial fibrillation (AFib or AF) is the leading cause of heart arrhythmia in the U.S and it causes damage to the heart tissue. It can be detected using an electrocardiogram (ECG or EKG). However, there are some limitations to using ECG sensors such as external electrodes, fault electrical signals, short time monitoring of patients, and failure to detect the abnormal heart rhythm. In addition, some patients with symptoms which are present for a limited time and then stop, need to be continuously monitored. A human implantable electrocardiogram sensor is a key instrument to monitor, diagnose, and detect the heart problem such as AFib, heart attack, and coronary artery diseases. In this paper, a 2-coil inductive wireless power transfer (WPT) system, having three different shapes including circular, elliptical, and square coils, is designed, and optimized at a resonant frequency of 13.56 MHz to overcome low power transfer efficiency (PTE). Six different combinations of coils are proposed to induce WPT. The transmitter and receiver coils are in alignment together and their PTE are compared. At close distance between aligned coils, the maximum PTE is 56.2 % for square-square coil at the resonant frequency of 13.56 MHz. The distance and frequency parameters are used to optimize the square-square coil with maximum PTE. The optimization results showed that the PTE of the square-square coil is maximum at 0 mm distance between coils. The optimized coil with maximum PTE was utilized in the implantable ECG sensor and the electrical signals were successfully recorded.

Distributed sensing optical fibers have been recognized for their unparalleled ability in discriminating and measuring environmental variables on strain, temperature, and vibration behaviors. For its ubiquitous industrial values in monitoring dynamic events in pipelines, railroads, perimeter surveillance, subsea, highway and so forth, distributed acoustic sensing (DAS) market is expected to grow steadily in the next few years. However, the inferior thermal stability of standard optical fiber coating, along with the native weakness Rayleigh scattering reflectivity, make the traditional telecommunication grade fibers-based DAS component suboptimal for mid-temperature environment deployment such as oilfield exploration and detection. Here, we report DAS fibers prototype with enhanced backscattering reflection and improved thermal robustness for feasible mid-temperature application. Typically, the 8/125/200 μm DAS fiber is fabricated from a G.652 compliant single-mode preform, coated with dual-layer of proprietary UV curable and high optical transparent write-through coatings, and further followed by a post-draw UV processing technology to increase the elastic scattering reflectivity in the optical fiber. Depending on the selected coating materials and fiber designs, developed DAS fibers are demonstrated with low level of OTDR attenuation, enhanced elastic backscattering signal amplitude about 15+ dB above Rayleigh level, and exceptional thermal reliability against elevated temperature conditions.

Whispering gallery mode (WGM) optical microresonators with high quality (Q) factors have been widely used to sense biomolecules due to their small mode volume and narrow linewidth resonance. Previously, we reported a frequency locked optical whispering evanescent resonator (FLOWER) system for real time single macromolecule detection. Here, we explore the detection limit of FLOWER via numerical simulation based on coupled mode theory. These results predict that frequency locked microcavities with ultra-high-Q can detect resonance shifts as small as 0.05 attometers at 1 millisecond time interval and are limited by shot noise and laser intensity noise.

A vacuum-ultraviolet (VUV) spectroscopy system is proposed for measurement of acetone in human breath that has been attracting attention as a biomarker of body fat metabolism and diagnosis of diabetes. A strong absorption peak of acetone at 195 nm is detected by using a simple system consisting of a deuterium lamp source, a hollow-core fiber gas cell, and a fiber-coupled compact spectrometer corresponding the VUV region. The hollow-core fiber functions as a long path and extremely small volume gas cell and enables sensitive measurement of trace components in exhaled breath. For breath analysis, we applied multiple regression analysis using absorption spectra of O₂, H₂O, and the acetone standard gas as explanatory variables to quantitate the concentration of acetone in breath. We applied standard addition method based on human breath and as a result, it was found that the measurement accuracy was 0.074 ppm in standard deviation (SD) for healthy human breath with the acetone concentration of around 0.8 ppm and precision was 0.026 ppm SD. We also tried to monitor body fat burn based on breath acetone and confirmed that breath acetone increased after exercises because acetone is a volatile byproduct of lipolysis..

Ni-Ti tube is used as a supporting tube for the infrared hollow fiber to obtain flexibility and strong mechanical strength. The loss of Hollow optical fiber is inversely proportional to the cube of the inner diameter. Considering this, it is expected that the large-diameter hollow optical fiber has a low loss. Even with a large inner diameter of 800 μm, the Ni-Ti tube with a wall thickness of 0.1 mm can be bent with a small force to a bending radius of 15 mm. Therefore, 800-μm-bore hollow optical fiber based on Ni-Ti tube was fabricated. In order to reduce roughness of inner surface of Ni-Ti tube which causes the additional transmission loss, an acrylic-silicon resin material is used as a buffer layer to the inner wall of Ni-Ti tube for a low-loss characteristic. For the dielectric inner-coating layer, cyclic olefin polymer (COP) is used to lower the transmission loss. The COP layer is formed by using liquid-phase coating method. The hollow fibers with optimized COP inner film thickness for CO₂ laser light were fabricated and reasonable transmission losses was demonstrated.

Recently, we have proposed a refractive-index(RI)-sensing optical comb by placing a multi-mode interference (MMI) fiber sensor inside a fiber comb cavity. In this method, change of RI is read out as a repetition frequency frep via photonic RF conversion, and is precisely measured based on a RF frequency standard. If a surface of the intracavity MMI sensor is chemically modified for biosensing, it will be further used for biosensing. In this paper, we chemically modified the surface of the intracavity MMI fiber sensor with biotin and then read the chemical reaction with avidin as a change in frep.

We present spectral characteristics of the phase shifts in refractive index based phase-shifting interferometer. The conventional mechanical movement method cannot provide the same phase change for different wavelengths, which occurs phase information distortion in the incoherent interferometer. The refractive index-based phase-shifting method can adjust the uniform phase shift over a wide spectral window. Spectral phase-shifting errors of the proposed method were compared with those of the mechanical phase-shift method. The proposed method can be applied to eliminate unwanted phase-shifting errors and to obtain correct phase information of optical tomographic images.

To obtain uniform power distribution on the ATR prism for biomedical spectroscopy system, the power intensity mapping on the prism is precisely measured by using a newly developed probing technique. It is found that the distribution of QCL based system is less uniform than that of the FT-IR based system due to the high coherency of the laser beam. To homogenize the distribution, a lens is introduced to diffuse the light and the incident beam is inclined to increase the number of reflections in the prism. As a result, we confirmed that the measurement error of in-vivo experiments is suppressed.

A numerical modelling to theoretically investigate and analyse the characteristic of the surface functionalised optical fibre based sensor to detect volatile organic compounds (VOCs) biomarker is introduced in this paper. A 125-micron diameter of coreless silica fibre (CSF) connected to single-mode fibre (SMF) at both ends to achieve a structure of SMF-CSF-SMG is proposed to detect VOCs biomarkers for diabetes such as acetone and isopropanol. The coreless fibre region is considered to be a sensing region where the multimode interference (MMI) occurs having a higher light interaction at the interface between the fibre and sensing medium which leads to the enhancement of sensitivity. The sensing region undergoes surface functionalisation with Au-silane for the sensor to be selectively detect VOCs biomarker with electrostatic absorption. The length of the sensing region is numerically optimised to achieve a reimaging distance where the highest possible of coupling efficiency occurs and the maximum output signal can be obtained. Coupling efficiency spectra at different volume fractions of gold nanoparticles with various acetone and isopropanol concentrations are also presented. A sensitivity of the Au-silane functionalised optical fibre sensor is achieved by using the analysis of wavelength shift interrogation. The results show the spectra undergoes red-shift phenomenon in the near-infrared region (NIR) when concentrations of acetone and isopropanol are increased. The functionalisation of Au-silane on the optical fibre sensor provides a higher sensitivity compared to the unfunctionalised sensor as it shows more dramatic shifts of absorption spectra when there is a change in VOCs biomarker concentration.

In this work, the capability of a wave plate is exploited to modify the state of polarization, as it provides a controlled phase shift between the two polarization components of propagating light. A half-wave plate is used to stabilize the state of polarization of light (632.8 nm) at the distal end of a multimode fiber of core diameter 62.5 μm.

This article presents a packaged optical fiber axicon tip generating high-quality Bessel beam and Bessel beam optical interferometry for measuring the Refractive Index of hazardous liquid like HCL, H₂SO₄ at 1550nm. The measurement resolution of our system is 1×10^-3± 0.0007. The packaged axicon feeds with broadband amplified spontaneous emission source through an optical circulator. Packaged axicon tip is dipped in different concentrations of liquid samples. The light reflects from the air-glass and glass-liquid interfaces, couples back to the optical fiber axicon tip, interferes with the reference beam generated at the air-axicon interface. The interference spectra are recorded in an optical spectrum analyzer via the third port of the circulator. The interference spectra are analyzed by applying fast Fourier transform. The FFT differentiates the power reflected from different interfaces which helps in solving the Fresnel equation to calculate the solution's RI as the glass RI is known.

Contaminated drinking water is a global health issue, particularly for third-world countries. Fluoride is a widely found contaminant whose prolonged exposure in quantities greater than 1.5 mg/L causes various health hazards, including dental fluorosis and stiffness in the backbone or joints. State-of-the-art techniques for detecting fluoride in water include titrimetric, potentiometric, spectrophotometric, and chromatographic systems. Although these techniques provide fair accuracy, these systems face mass adaptability constraints due to their resource-intensive nature. This suggests a need to develop sensors that can provide rapid, portable, and accurate fluoride detection in drinking water. Here, we demonstrate a fluoride sensor by employing the principle of phase shift cavity ring down spectroscopy (PS-CRDS) in fiber cavities. In PS-CRDS, the magnitude of phase shift between output and input sinusoids is a measure of an absorption event within the cavity. We realize the sensor by building a cavity using fiber Bragg gratings. We insert a tapered fiber of < 10 μm waist within the cavity as a sensing head. We inject a 2 mL sample solution along with 2 mL of pre-stored SPADNS−zirconyl acid complex reagent for enhancing absorption at 633 nm into a customized fluidic cell. The cell holds the tapered portion of the cavity. We then quantify fluoride in the sample using PS-CRDS with the detection limit of less than 2 ppm. We anticipate that the current work with a modified chemistry protocol can be extended to a rapid and accurate biosensor for detecting a variety of diseases, including tuberculosis and pneumonia.

Advances in polarimetric techniques are of high interest in multiple scientific fields. Polarimetry characterizes optical and material properties such as anisotropy and structure, which relate to physical, chemical and functional properties of materials used in optoelectronic, polymer, plasmonic, bio-related and pharmaceutical applications. Laser-based infrared (IR) spectroscopic methods beyond classical Fourier-transform infrared (FTIR) spectroscopy enable previously impossible polarimetric investigations from macroscopic to nanoscopic length scales. This contribution focuses on new polarimetry techniques for detailed analyses of structural and material properties of thin films and surfaces. Specifically, we show applications of two laboratory-based instruments that employ tunable quantum cascade lasers (QCLs) from Daylight Solutions as brilliant light sources. Regarding far-field IR spectroscopic measurements, a novel laser ellipsometer (built in cooperation with Sentech Instruments) simultaneously measures spectral amplitude and phase information via single-shot detection of four different polarization states. The device reaches temporal resolutions in the μs to ms range at high spectral (< 0.5 cm⁻¹ ) and lateral resolutions (≤ 125μm). At the nanoscale, photothermal atomic force microscopy (AFM)-IR (Anasys, Bruker), based on a QCL and a polarizing unit, enables polarimetry with lateral resolutions of a few 10 nm.

This work addresses the need to spectrally analyze of the absorption of middle-infrared (mid-IR) radiation in single living cells, with subwavelength spatial resolution, to identify molecular groups in them. The challenge is considerable, no lens can be used, so to realize such a device, a near-field probe was developed, from an optical fiber that is transparent in the mid-IR, non soluble in water, non-toxic and mechanically suitable. Incorporation of this probe in a scanning microscope, and use on a specially contained single living cell in water, allowed to achieve subwavelength imaging. Our fiber-material of choice is silver halides, i.e. AgCl_xBr_1-x, made in the Applied Phyics Group of Tel-Aviv University. In spite of being bulky they were mechanically adapted to scanning microscopy. Theoretical and experimental investigations into the dampening of the motion of the probe in water were performed. A grid-like holder for containing living-cells for near-field microscopy has been introduced. The operating principle of this grid is based on sinking the cells inside the holes of the grid and letting them only negligibly protrude out of the holes (compared to the height-range of motion of the tip), in air and water. The result is a demonstration of the operation of the SNIM on different types of objects, including yeast cells, in water.

Scanning Tunneling Microscopy (STM) can easily image hydrogen-passivated silicon(001) with atomic resolution, but images often contain artifacts such as double tips, blunt tips or unstable tips. Nevertheless, a trained human eye can recognize surface details such as dimer rows, step edges, depassivated silicon, etc. A Neural Network could classify the surface better than the human eye. One advantage of a deep learning algorithm is that it can analyze, in parallel, information from multiple channels such as topography, tunneling current, forward and reverse scans. Our scanning software also collects Tunnel Barrier Height information that contributes extra information about the electronic properties of the surface at each point. This identification will be integrated into ZyVector – our STM controller product -- to provide more accurate depiction of the surface than is available in the STM image, and to automate Hydrogen Depassivation Lithography (HDL) patterning.

We demonstrate a state-of-the-art nanoIR instrument that integrates a broadband mid-IR OPO/DFG system from APE GmbH with a scanning probe system from Bruker. This broadband laser covers an extended wavelength range, and works in both broadband and narrowband modes. The broadband mode covers the range of 670-4000 cm^-1 (2.5-15 μm) allowing fast acquisition of s-SNOM spectrum. The narrowband mode covers the range of 670-2200 cm^-1 (4.5-15 μm), giving access to key molecular vibrational modes commonly used for chemical identification in the “fingerprint” region. With its higher spectral resolution, the narrowband enables s-SNOM imaging at defined IR wavelength, as well as AFM-IR spectroscopy and imaging. The comprehensive capabilities and performance of this combined system are highlighted by the high quality results obtained from several representative samples including 2D material, polymer film and biological sample.

The direct interfacing of photonic crystal fiber to metallic nanoantenna has widespread application in nano-scale imaging, optical lithography, nanoscale lasers, quantum communication, in-vivo sensing and medical surgery. I will present the design, fabrication, and characterization of fiber-plasmonic probes for nanoscale chemical imaging. The proposed Fiber-based Tip-Enhanced Raman Spectroscopy (F-TERS) combines the spatial (<1 nm) and chemical resolution of TERS with the ease of use of Scanning Near-field Optical Microscopy. F-TERS can operate in virtually any gaseous and liquid environment, enabling new avenues of nanoscale chemical data collection from any sample analysis in most real-world environments.

In this work, we present the development of an infrared scanning near-field optical microscope (IR-SNOM) for thermal imaging. As an example, we explore thermal imaging of quantum cascade lasers (QCLs). QCLs are attractive infrared (IR) sources for chemical detection due to their tunability and wide emission range spanning from mid-wavelength to longwavelength infrared radiation (MWIR and LWIR). However, they require high performance cooling systems and have limited use at low power in continuous wave (CW) operation due to the potential for thermal failure of the device. Thermal imaging can help identify mechanisms and points of failure during laser operation. Because the size of the features of QCLs (~1 μm) are much smaller than the wavelength of the emitted thermal radiation, IR-SNOM is an ideal technique to image the spatial thermal profile of QCLs during operation to guide design improvement.

For a long time FTIR and laser-based spectroscopies have been used for high resolution molecular spectroscopy studies. The recent development of Dual-Comb Spectroscopy at high resolution (<0.001 cm^-1) makes this technique a powerful tool for gas phase studies. The IRis-F1 is a dual-comb spectrometer building on quantum cascade laser frequency combs. We show that it is very well adapted for measurements of line shape parameters. Despite its weak abundance, methane effect on climate and atmospheric chemistry is important. We measured with IRis-F1 the half-widths of absorption lines of methane diluted in nitrogen, and compared with results obtained by other spectroscopies.

In this paper, we present a thorough comparison of mid-infrared techniques, focusing on the two dominant solutions: QCL and FTIRs. Consequently, we will cover the technical challenges the DCS technique has to overcome to be superior to the FTIR technique. Pushing the DCS technique, we manage to get µs time resolution for up to 131 ms acquisition time as well as < 1 ms time-resolution for reactions which take > 10s. Furthermore, we have improved the spectral coverage of QCL DCS covering more than 100 cm^-1 . Overall, the combination of high-speed, spectral bandwidth and high-brightness of this highly coherent source puts DCS at an advantage compared to FTIRs for a plethora of applications, such as liquid analysis (e.g. protein analysis, dioxin measurement, stopped flow), fiber applications and high-resolution spectroscopy. As such, we will give a comprehensive review of applications which are targeted today using QCL DCS. This covers bio-, environmental/gas, combustion as well as water analysis.

Microplastics (MP) have been found all over the planet and it is quite difficult to model the impact on the biosphere due to the low throughput of conventional measurement techniques. They actually restrict the number of measurable samples in appropriate time frames. Even the fastest conventional methods to quantify MP such as Fourier-Transform-IRmicroscopes (μFTIR) or Raman microscopes do not provide the required speed for measuring the desirable number of samples. By combining a wide field quantum cascade laser (QCL) based microscope with an automated vibrational spectroscopy data base (siMPle) identification and quantification of the particles fit into normal laboratory routine time slots. The MIDIR transmission spectra of environmental samples on standard and cost-effective Aluminum oxide filters were measured and evaluated using the adaptable data base design^{1 2} . The results turned out to be very similar to the common techniques, and particles assigned by FT-IR to one material, were connotated to the same using the laser-based method. Furthermore, the spatial resolution of the laser-based system is slightly superior to the one of μFTIR and the size distribution determined was found similar to results from even slower Raman-microscopy especially for small particle size smaller than 50 μm. Amongst others a treated waste water sample of 12*12 mm² was measured in less than 36 minutes delivering 8,294,400 spectra with 2 cm^-1 resolution, while the time to analyze the data remains the same order of magnitude, the pure measurement is more than ten times faster compared to using state of the art FT-IR-microscopes.

Infrared spectroscopy is a powerful tool for identification and quantification of functional molecular groups. Molecular gas lasers have long been used for such purposes due to their early development and mature manufacturing technology. Over the past few decades, Quantum Cascade Lasers (QCLs) have popularized due to their continuously tunable wavelength, climbing peak power, and steadily improving manufacturing economics. However, for many applications in the longwave infrared (LWIR) spectral region, carbon dioxide (CO₂) lasers retain a clear advantage over QCLs by providing higher power, greater spectral purity and extended coherence length. This combination allows for detection of volatile organic compounds indicative of many diseases such as early-stage lung cancer, an advanced prognosis of which can increase the 5-year survival rate by 37.5%. In addition to medical applications, CO₂ lasers also retain their niche in environmental sensing by providing a robust photoacoustic airborne measurement platform for air quality and climate research. Furthermore, recent advances in thermally balanced gas laser architectures have enabled reliable mobile leak monitoring of the insulation gas Sulfur Hexafluoride (SF₆) used in medium to ultra-high-voltage electricity transmission lines. With the installed base of SF6 expected to grow 75% by 2030 due to the increase of green energy infrastructure via solar panels and wind turbines – both of which rely on electrical connections, switches, and circuit breakers – this task has gained new urgency due to an upper leak estimate of 15% over the full life cycle of the insulation gas.

The US Food and Drug Administration (FDA) has high regulatory and quality requirements for the development and more importantly production of pharmaceuticals. Ideally, the production process is continuously monitored and recorded noninvasively to allow immediate control action if necessary. There are a multitude of established optical detection systems for classical stainless steel bioreactors using fiber optic probes, light guides, light sources and detectors for absorbance, fluorescence and Raman detection techniques. These systems are steam-sterilizable in place, reusable but are complex and expensive. Such systems are not well suited to use on the growing market of pre-sterilized disposable bioreactors, since there is a lack of sterile interface technology. A novel disposable and pre-sterilized flow cell has been developed, which can be easily connected to disposable bioreactors by sterile tube connections. The disposable BioFlowCell is clamped into a reusable flow cell holder, which is equipped with light guides, a light source and a detection unit. By this modular construction, spectroscopic techniques, like UV/Vis, fluorescence, turbidity by scattered light, near infrared or Raman spectroscopy are now usable for modern disposable bioreactors. We report on the suitability for in-line monitoring of mammalian cell cultures by detecting optical absorbance at 260, 280, 340 and 450 nm wavelengths to study aromatic amino acids, NADH and flavins simultaneously in a BioFlowCell with multiple pathlengths. Further, we studied in a second optical flowcell design, if light scattering and absorption in turbid samples can be used for biomass concentration measurements, as well as size or the viability of cells during continuous bioprocess experiment lasting several days.

Monitoring water quality by detecting chemical and biological contaminants is critical to ensuring the provision and discharge of clean water, hence protecting human health and the ecosystem. Among the available analytical techniques, infrared (IR) spectroscopy provides sensitive and selective detection of multiple water contaminants. In this work, we present an application of IR spectroscopy for qualitative and quantitative assessment of chemical and biological water contaminants. We focus on in-line detection of nitrogen pollutants in the form of nitrate and ammonium for wastewater treatment process control and automation. We discuss the effects of water quality parameters such as salinity, pH, and temperature on the IR spectra of nitrogen pollutants. We then focus on application of the sensor for detection of contaminants of emerging concern, such as arsenic and Per- and polyfluoroalkyl substances (PFAS) in drinking water. We demonstrate the use of multivariate statistical analysis for automated data processing in complex fluids. Finally, we discuss application of IR spectroscopy for detecting biological water contaminants. We use the metabolomic signature of E. coli bacteria to determine its presence in water as well as distinguish between different strains of bacteria. Overall, this work shows that IR spectroscopy is a promising technique for monitoring both chemical and biological contaminants in water and has the potential for real-time, inline water quality monitoring.

Wastewater is a complex matrix containing a wide range of chemical and biological markers of human activity. Relating concentrations of these “waste” materials in wastewater influent streams to population-scale use, consumption, or rates of exposure, can provide important qualitative and/or quantitative information on the combined activity of inhabitants within a given wastewater catchment. This approach has become known as wastewater-based epidemiology (WBE) and is widely applied for monitoring community use of selected pharmaceuticals, illicit drugs, tobacco and alcohol. However, many other potential applications are emerging that can contribute useful knowledge on human health, exposure to industrial chemicals, infectious diseases or pathogens, antibiotic resistance and other catchment-based activities.This presentation will discuss the role pf sensor-based approaches for the field’s future development.

Microplastics’ occurrence is a major contributor to aquatic pollution and threat to marine ecosystems because these contaminants persist in the environment for hundreds of years. Although there have numerous workflows focusing on identification and characterization of microplastics, standardized methods are lacking. Infrared (IR) Microscopy has been widely used to identify and differentiate microplastics. It has proven to be an excellent technique for quick and accurate analysis; however, lack of standardization in methods and measurement parameters have made incredibly challenging to compare and replicate studies in a systematic manner. In this work, we have laid out systematic experimental methods and parameters for accurate and reproducible microplastics studies using IR Microscopy. We also investigated the lowest measurable size of microplastics using the technique with statistical analysis and multiple experimental approaches to support the findings.