Sensitive, label-free, and selective sensors are of importance for a wide variety of applications, in particular medical diagnostics, and environmental monitoring. Microtoroid optical resonators, when combined with frequency locking, balanced detection, and data processing techniques, are capable of single molecule detection. We have developed such a system called FLOWER (frequency locked optical whispering evanescent resonator). We discuss our latest work on using FLOWER for a variety of applications including medical diagnostics for ovarian cancer and Alzheimer’s disease, chemical threat sensing, and drug screening. In addition, we discuss our next generation sensing platforms.

Single-mode optical waveguides are one of the fundamental photonic components and the building block for compact multicore bundles. The cross-talk of a waveguide bundle might scramble the information and reduce the resolution. To get the highest possible resolution on a fixed field of view (FOV), we propose to optimize the core to core spacing via assessing the reconstruction accuracy of the output images of the bundle processed by a deep neural network (DNN), where the obtained bundle is 3D printed via direct laser writing. We demonstrate the DNN based optimization scheme and the fabrication of a waveguide bundle of 10-µm core-to-core spacing to image various digit layouts in a (120 µm)^2 FOV.

Total internal reflection fluorescence (TIRF) is a popular type of illumination used in fluorescence microscopy for surface imaging of biospecimens; however, the commonly used objective-based TIRF illumination can induce artifacts that degrade the image. We previously demonstrated a fiber bundle that reshaped an input beam to achieve artifact-free TIRF illumination with coherent or incoherent light sources. Here we demonstrate an improved design using a photonic lantern, which will increase the power throughput by reducing coupling losses at the input facet. The improved power efficiency will facilitate new capabilities such as super-resolution imaging.

Matrix metalloproteinase 9 (MMP9) is present in normal physiological events in the human body. However, it is also known for being involved in inflammation process related to different diseases, such as arthritis and metastasis. Thus, this protein can be used as a biomarker for diseases monitoring and therapies control and assessments. The goal of this study is to demonstrate that novel multiplexed R-NPs optical transducers independent arrays, (also called BICELLs, Biological Sensing Cells) can discriminate small concentrations of MMP9. We achieved a LoD of 84 ng/mL. This data can be improved by increasing the resolution of the characterization system and optimizing the biofunctionalization strategy. These results are promising and encourage us to perform prospective works addressed to replicate this experiment using a fluidic system for multiplexed real-time optical response, so as to facilitate the monitoring of the different selected biomarkers (thank to multiplexed configuration of R-NPS arrays), necessary to provide patients with a more accurate diagnosis and treatments, and therefore to boost up personalized medicine.

Fiber couplers based on hollow metallic fibers were designed and fabricated to branch and combine mid-infrared laser light with low loss. The fiber coupler was fabricated by side-polishing and bonding two hollow metallic fibers bent at an arbitrary curvature. The branching ratio is precisely aligned by the position shift amount of the two fibers in the optical axis direction. The fabricated coupler showed a branching ratio of 0 - 50% and an excess loss of less than 1 dB.

We propose a novel non-invasive approach to transabdominally measure fetal oxygen saturation via time-domain near-infrared spectroscopy. We employ the frequency-modulated continuous-wave technique to measure the time-resolved reflectance of near-infrared light shining on the maternal abdomen. The time-of-flight reflectance reveals path-lengths of different photons traveling through the tissue, facilitating the separation of signal from the shallow maternal layer and the deep fetal layer. Using two optical wavelengths, oxygen saturation of the fetus can be measured. This technique has the potential to improve labor outcomes by providing an important assessment of fetal health intrapartum.

Recently, 3D imaging endoscopes have made their way into endoscopy and enable three-dimensional visualization. While many of them require optics with mounts increasing the fibers diameter, two-photon polymerization enables mount-free fabrication of optical elements directly on the tip of fibers. Using multicore fibers combined with diffractive optical elements (DOE) enables the phase to be taken into account in measurements in addition to intensity, enabling 3D imaging. While each multicore fiber has an individual distribution of phase differences, an individual DOE is required, which can be fabricated rapidly and stitching-free with high precision using maskless 3D lithography.