The latest fiber solutions to be described for innovative applications in chemical process control, remote environment monitoring and biomedical diagnostics. Advanced fiber probes based on 4 different fiber types will be presented for their applications in very broad range of spectra 0.3-16µm – designed for all key spectroscopy methods: Transmission, ATR-absorption, Raman and fluorescence, - plus for their various combinations. The great synergy effect in fusion of spectral data from 2 (or more) spectral methods is available now when the advanced combi-fiber probes collect spectra from the same spot: Raman+DRS (Diffuse Reflection Scattering), Raman+Fluorescence, Near+Mid IR-absorption, Fluorescence + Mid ATR-absorption. The new generation of multiwavelength spectral sensors will be shown where the bundle of thin Mid IR-fibers combines radiation from the set of selected QCL into the innovative arthroscopy probe with side ATR-distal tip – for in-vivo diagnostics of osteoarthritis in car

Fiber-tip sensors have been used extensively for measuring chemical and physical parameters. Particularly, multimode fibers (MMF) tip sensors have become attractive since they open the possibility of using simple light-emitting diodes. While common techniques to fabricate MM fiber-tip sensors are labor-intensive, we developed a simple and controllable method to transfer large-area nanophotonic structures to the fiber end-face by mechanical contact, without using glue or micromanipulator. As proof of concept, a 2D photonic crystal (PhC) was successfully transferred to the tip of a multimode fiber, and its response to changes in refractive index was characterized, obtaining a sensitivity of 244 nm/RIU.

Surface enhanced Raman scattering (SERS) is a powerful biosensing technique allowing direct detection of target molecules thanks to their vibrational fingerprint Raman spectra. SERS is usually performed on nano roughened plamonic planar substrates/colloidal nanoparticles. However, the irregularities of plasmonic nanostructures lead to measurement reliability limitations. We have recently demonstrated that SERS-probes based on opto-fluidic photonic crystal fiber (PCF) composed of a silica-core surrounded by large air channels are remarkable sensing platforms leading to tremendous SERS sensitivity and excellent measurement reliability (98% in reproducibility and 95% in repeatability). However, a major limitation occurs when looking for highly reliable and easy-to-use biosensing platform. Actual SERS biosensors (planar substrate or fiber probe) require their alignment under a microscope, which could restrict on-field practical use. Here, we address this issue by developing a tapered opto-fluidic PCF allowing excellent reliability, efficient and easy coupling through a Plug-&-Play type modality. This novel type of SERS probe realized by reducing the fiber diameter, which increases the SERS sensitivity while enabling efficient light coupling to the Raman spectrometer with a relative standard deviation (RSD) of only 3.5% in reproducibility and 3.84% in repeatability. We demonstrate this easy Plug-&-Play type coupling based on a simple bare fiber connector, with a RSD of 4.5% in reproducibility measurements (i.e. removing and reconnecting the fiber SERS-probe to the Raman spectrometer without any additional alignment). We envision that this easy-to-use platform can be translated to - clinically viable SERS probes for liquid biopsy.

Noninvasive measurement of fetal oxygen saturation can provide clinicians with critical information about fetal health, and potentially contribute to improved management of childbirth. We recently proposed a novel transabdominal fetal pulse oximetry through frequency-modulated continuous-wave near-infrared spectroscopy. Here, we report our experimental results which validate one of the most important steps of our method. By shining near-infrared light on the pregnant sheep abdomen and measuring the time-resolved reflectance, we have successfully extracted the fetal heartbeat signal originating from deep tissue. This result sets up the foundation to further improve our transabdominal fetal oxygen saturation measurement method.

The brain is the most complex organ in the human body, and brain diseases are highly challenging to diagnose, monitor, and treat. Nanomaterials have emerged as a unique wireless interface with the brain in the micro/nanoscale. I will discuss our recent efforts to develop new tools using advanced nanomaterials and photonics to further understand and access the brain. These include exciting capabilities to remotely control protein activity, study neurochemical modulation, and change the blood-brain barrier permeability. These new tools provide insights into the brain microenvironment and a unique opportunity to develop strategies to treat brain diseases.

Custom fiber arrays can be used to encode 3-dimensional data for snapshot imaging techniques like imaging spectrometry or volumetric spectral domain OCT. This is achieved if array’s input is dense, while its output creates void spaces for spectral information. Here we present fiber arrays with entirely automatic development process based on 2-Photon Polymerization (2PP) additive manufacturing using Nanoscribe GmbH Quantum X system. Specifically, We developed two types of array prototypes: 10x10 to 1x100 and 20x20 - dense fiber spacing (1-2 microns fiber gap) to 20x20 – sparse fiber spacing (30-40 microns fiber gap). Fiber arrays were incorporated into prism-based imaging spectrometer system to demonstrate proof of concept spectral imaging experiments.

We present a fibre optic biosensor for SARS-CoV-2 detection based on the lossy-mode-resonance (LMR) [6] effect, generated in a single-mode fibre with a thinned cladding and coated by thin-film dielectric with appropriately selected optical properties and thickness. The detection of selected viral structural proteins in the tested sample is ensured by specific bioreceptors. As a result of the interaction with the SARS-CoV-2 antigen, optical response in the short-wave-IR range is observed, and the detection limit does not exceed 1.3*10^2 copies/ml, when converted to the viral load concentration - sufficiently for virus detection even in the first days after infection.

Surface enhanced Raman spectroscopy (SERS) allows sensitive detection of analytes, thanks to their vibrational Raman spectra. Planar SERS substrates often lack the reliability in measurement due to larger variations in signal intensity contributed by irregularities in nanostructures. In this context, photonic crystal fibers (PCFs) that combine excellent light guiding properties and the possibility to incorporate nanostructures and liquid or gas analytes into their axially aligned air holes, offer tremendous promise as an opto-fluidic SERS platform. Such sensors possess the enormous signal enhancement inherent to SERS and the flexibility of optical fibers. In addition, PCFs offer improved reproducibility, repeatability and sensitivity in measurement compared to planar substrates, due to the larger volume of interaction between the guided light and the analyte, and to highly reliable light couplings into the fiber core. Here, we present a novel design of PCF called ring core fiber (RCF), which is specifically engineered to further increase the interaction area in order to improve the sensitivity and reliability of the sensor. Preliminary experimental results showed that sensitivity of SERS sensing is improved by 115% compared to the best SuC-PCFs. Ongoing numerical simulations indicate that by further optimizing the dimensions of the ring, sensitivity could be improved by at least one order of magnitude with RCF. We envision that this new design with increased sensitivity and measurement reliability could be the next major step towards a clinically viable liquid biopsy fiber probe.

2-photon lithography enables custom fabrication of optical waveguides at a sub-micron resolution and millimeter scale. Custom optical fiber architecture is a powerful component for development of fiber coupler systems and advancement of fiber based imaging technology. Here we present an exploration of methods for 2-photon fabrication of optical fibers and fiber coupler systems.

Biological tissue is complex substance which characterization demands combination of several spectroscopic techniques. Spectroscopy enables real-time label-free chemical and structural evaluation of samples for medical diagnostics in situ and in vivo. Fiber-optic probes provide flexible, sterilizable, and compact solutions for simultaneously analyzing tissue samples with several spectroscopic modalities. Modern fiber spectroscopy seamlessly covers entire wavelength range from 0.3µm with silica fibers to 20µm with chalcogenide, silver halide PIR fibers, and hollow glass waveguides. Here we present our latest achievements in developing multispectral compact fiber-optic probes for biomedical applications. We focused on combining all four key spectroscopic modalities (NIR, MIR, Raman, and Fluorescence) in single fiber probe tip. In preliminary studies of clinical bio-samples, combination of NIR diffuse reflection or MIR absorption spectroscopy with fluorescence spectroscopy gives synergy effect in differentiation of diseased and normal tissues. In our Raman experiments, we evaluate primary signals together with fluorescence background, which helps enhance analysis accuracy. Combined with advanced chemometrics data analysis, this concept enables the development of customized spectral fiber sensors based only on several wavelengths, hence their simple design, small size, high speed, and cost savings. It is possible to make rapid measurements directly in the operation theater by using tiny (<200 µm OD) but robust monofiber disposable Raman needle probes. Our recent experiments have shown the possibility of combining mid-IR ATR absorption and Raman spectroscopy in one compact fiber-optic probe. These advances turn fiber-optic multispectral probes into universal tools for any biomedical application requiring analysis of complex tissue.

In this talk, I will give an overview of the unique applications of terahertz waves for chemical identification, material characterization, biomedical sensing and diagnostics and describe the state of the existing terahertz imaging and sensing technologies and their limitations. I will introduce a game changing technology that enables high performance, low cost, and compact terahertz spectroscopy and imaging systems for various applications. More specifically, I will introduce plasmonic terahertz imaging and spectroscopy systems, which offer several orders of magnitude higher signal-to-noise ratio levels compared to the state of the art.

Due to an unprecedented combination of high power, high efficiency, and small size, Quantum Cascade Lasers (QCLs) finding numerous applications in various mid-wave and long-wave infrared fields. The control of material composition, thickness, and doping level for each layer in the QCL superlattice offers a unique flexibility in optimizing laser characteristics to specific applications. Band gap engineering (laser core design) will be discussed in this talk in the context of spectroscopic applications, including heterogeneous laser core design that allows for either wavelength tuning in a broad spectral region around a single central wavelength or operation on multiple isolated spectral lines with significant spectral separation. The design and fabrication of QCLs with a low-cost top-metal Distributed Bragg Reflector for achieving narrow-spectrum emission will also be presented. Finally, our latest results on monolithic beam combining of multiple DBR QCLs using multi-mode interference and Y-junction couplers for increasing laser tuning range and/or increasing peak optical power will be presented. Employment of the high-power DBR QCL arrays in specific infrared applications will be discussed at the end of the talk.

In this talk we will outline current applications of QCLs to environmental, diagnostics, and biomedical applications and analyze the devices’ limitations and their potential impact if some of their present weaknesses were to be addressed. The use of QCLs and Mid-IR technologies in general will be put in the context of the applications’ needs and requirements and compared with other existing and competing solutions. The broader market implications and main commercialization opportunities will be outlined.

We report on development of a novel type of sensor for in-line analysis of nitrogen-based molecules, such as nitrate, nitrite and ammonia, in municipal wastewater. The sensor utilizes pre-concentration of analytes with ion-selective materials and subsequent optical detection in the mid-infrared spectral range. Advantages of this sensor include in-line autonomous measurements, self-calibration mechanisms and high selectivity to different nitrogen species. The sensor targets implementation at wastewater treatment plants (WWTPs) to enable control and optimization of the aeration process, thereby reducing energy consumption and cost. We will discuss challenges encountered during the transition of the technology from the lab bench to WWTPs, including operational efficiency of the optical sources, such as quantum cascade lasers (QCLs) vs. thermal sources. Extension of the sensor capabilities for sensing of additional contaminants and for bioreactor systems control will be discussed.

Microplastic particles are ubiquitous and actually many research projects deal with characterizing and quantifying the microplastic particles chemically, in number, size, and shape. The form factor influences the areas, where the particles accumulate and their potential harm in ecosystems and organs. Using microscopes (RAMAN-, QCL-IR, or µFTIR) is a well-established technique to characterize particles in environmental probes by their dimensions and chemical properties. However, measuring thicker particles challenge optical methods. A method increasing the repeatability and minimizing manual interventions by combining different modes of operation using a wide field hyperspectral QCL-IR-microscope systems is presented.

For non-invasive measurement of biological tissue, a piezoelectric photoacoustic spectroscopy system detecting ultrasound induced by irradiation of mid-infrared laser light was developed. In this work, a photoacoustic spectrum of poultry breast meat was obtained with this proposed method. Although photoacoustic spectra characterizing the optical absorption of the meat were obtained, the sensitivity was slightly less than conventional PAS. Therefore, an investigation to improve the measurement sensitivity was also performed by using standing waves in the sample. As a result, the sensitivity was successfully improved utilizing this effect, and obtained a human skin spectrum of fat and sugar absorption appeared.

Silica nanoparticle coating on 250 to 1000 um flexible quartz optical fiber facilitates side-emission of germicidal ultraviolet light (UV-C), which shows promise for disinfection of contaminated air, water, and surfaces. This work aims to develop an understanding of light interactions with the silica nanoparticles to allow more uniform side-emission of germicidal light along longer lengths of optical fibers. Two forms of light energy (refracted light and evanescent waves) are transmitted through optical fibers.

Measurements of chemicals, particles, and biological agents in water are crucial across many municipal, industrial, and residential settings. While the detection and reporting of some of these constitutes are often imposed by the regulatory agencies on fairly infrequent time periods, monitoring more regularly is essential to maintain the system's stability against changing dynamic conditions and provide safe high-quality water. This presentation will give an overview about the advantages/disadvantages/challenges of current analytical tools and provide insights into future analytical needs in the drinking water, industrial process water, and municipal wastewater sectors.

Plastic waste, especially microplastics, is a growing environmental problem. Mid infrared spectroscopy (MIR) is suitable for determining microplastics contamination. Currently, the required measuring devices are large and not robust enough for mobile and on site monitoring. Here we describe a concept using Quantum Photonics for a new class of MIR spectrometers based on the entangled photons principle. The system can be made compact and robust with readily available components. The combination with new microfluidics chips, suitable for MIR detection and artificial intelligence for automated image analysis and particle identification will open up completely new possibilities for environmental analysis and monitoring.

Agriculture is in need for new sustainable solutions in order to reduce their phytosanitary products utilization. To this end, the early detection of the necessary conditions for disease development is a key to their reduction. Combined with a laser source, such a tool can do fast measurements on a field scale and, by doing so, help farmers in containing diseases. Thus, a laser-based sensor has been developed for wetting monitoring. Using the Heiligenschein phenomenon, it has been proved effective on both hydrophilic and hydrophobic surfaces in controlled conditions.