Non-Hermitian photonics has emerged as a promising field for the development of high-performance optical sensors. The theoretically infinite sensitivity of non-Hermitian sensors to external perturbations in the proximity of exceptional points (EPs) is the main reason for explaining the amount of research effort about this topic. The applications of non-Hermitian sensing are various. Angular velocity sensing has been investigated for the interesting property shown by non-Hermitian optical gyroscopes of the independence of the eigenfrequency splitting (usually adopted as the output of non-Hermitian sensors) from the angular velocity to be sensed. Moreover, several non-Hermitian sensors have been proposed to detect the presence of nanoparticles in the proximity of the sensor. Moreover, refractive index and absorption sensors have also been proposed with EP-based architectures, with applications in a lot of fields. For example, label-free biosensing and chemical analysis can benefit from the increased sensitivity of non-Hermitian photonics, thus promising advancements in medical diagnostics and environmental monitoring

Due to their unique optical properties, metallic nanostructures have garnered significant interest in the field of (nano)sensors. The synergistic interaction between metallic nanostructures and the molecular recognition layer allows for the enhancement of sensitivity and specificity properties. The sensitivity of the plasmonic resonance position of metal nanostructures to their environment and the effects of electromagnetic field enhancement in the vicinity of the nanostructures have been widely utilized to develop various approaches, such as Surface Plasmon Resonance (SPR) or Surface-Enhanced Raman Spectroscopy (SERS).

In this talk, new technological and methodological approaches for interfacing the brain by photonic technologies will be shown. Tapered optical fibers are nanomachined and processed to produce optical probes and optrodes for accessing deep brain regions in animal models with spatial and temporal resolution [1-3]. These minimally invasive probes can be simultaneously exploited in both optogenetics, for manipulation of neural activity, and for recording of molecular and cellular activity in fiber photometry. It will be also shown how tapered fibers can be employed in-vivo in Raman and SERS spectroscopy experiments for tumoral tissue identification and label-free neurotechnology. 

Sensors play crucial roles in biomedical research, clinical diagnosis, food safety, pharmaceutical testing, and environmental monitoring. Among them, optical sensors based on whispering-gallery-mode (WGM) resonators have emerged as front-runners for various sensing applications due to their superior capability to significantly enhance the interactions of light with sensing targets. Similar to a whisper traveling along a circular wall, light photons propagate along a curved surface in a WGM resonator. This talk will introduce ultra-high-quality (Q) optical WGM microresonators and the diverse sensing mechanisms and strategies developed around them. The basis for resonator sensors is that the physical associations and interactions of nanomaterials on the surface of a high-Q optical WGM resonator alter the trajectory and lifetime of photons in a way that can be precisely measured and quantified. First, the discovery of using ultra-high-Q microresonators and microlasers for ultra-sensitive self-referencing detection and sizing of nanoparticles, including single virion, will be presented. Then optical gains in a microlaser to improve the detection limit beyond the reach of passive microresonators will be discussed. Various strategies, such as mechanical solitons through optomechanical effects in a microtoroid resonator, a barcode technology based on collective behaviors of multiple resonances, and AI-enhanced target classification, will be introduced for sensing applications with resonators. Recent investigations into fundamental physics, including light-matter interactions around exceptional points (EPs) in high-quality WGM resonators, have unraveled innovative strategies to achieve a new generation of optical systems, such as EPs enhanced sensors. This talk will elucidate how EP-enhanced sensing can be extended to a wide range of optical sensor systems. To conclude, an innovative handheld platform, evolved from a traditional table-top setup, will be introduced, potentially unleashing the power of resonator sensor technologies.