Integrated Whispering-Gallery-Mode Resonator for Solid-State Coherent Quantum Photonics

Achieving Robust Single-Photon Blockade with a Single Nanotip

Backscattering losses (BSL), arising from intrinsic imperfections or unavoidable external perturbations in optical resonators, can severely impact photonic devices. In single-photon systems, robust quantum correlations against BSL remain largely unexplored despite their significance for various applications. Here, we demonstrate that single-photon blockade (SPB), a purely quantum effect, can be preserved against BSL by introducing a nanotip near a Kerr nonlinear resonator with intrinsic defects. Without the tip, BSL disrupts SPB, but tuning the tip's position restores robustness even under strong BSL. Notably, quantum correlations emerge while the classical mean photon number remains suppressed due to the interplay between resonator nonlinearity and tip-induced optical coupling. Our findings highlight nanoscale engineering as a powerful tool to protect and harness fragile quantum correlations, paving the way for robust single-photon sources and backscattering-immune quantum devices.

Whispering-Gallery Mode Micro-Ring Resonator Integrated with a Single-Core Fiber Tip for Refractive Index Sensing

A micro-ring resonator structure was fabricated via the two-photon polymerization technique directly on a single-mode fiber tip and tested for refractive index sensing application. The micro-ring structure was used to excite whispering-gallery modes, and observations of the changes in the resonance spectrum introduced by changes in the refractive index of the environment served as the sensing principle. The proposed structure has the advantages of a very simple design, allowing for measurements in reflection mode, relatively easy and fast fabrication and integration with a single tip of a standard single-mode fiber, which allowed for quick and convenient measurements in the optical setup. The performance of the structure was characterized, and the resonant spectrum giving high potential for refractive index sensing was measured. Future perspectives of the research are addressed.

A Review of Photonic Sensors Based on Ring Resonator Structures: Three Widely Used Platforms and Implications of Sensing Applications

Optical ring resonators (RRs) are a novel sensing device that has recently been developed for several sensing applications. In this review, RR structures based on three widely explored platforms, namely silicon-on-insulator (SOI), polymers, and plasmonics, are reviewed. The adaptability of these platforms allows for compatibility with different fabrication processes and integration with other photonic components, providing flexibility in designing and implementing various photonic devices and systems. Optical RRs are typically small, making them suitable for integration into compact photonic circuits. Their compactness allows for high device density and integration with other optical components, enabling complex and multifunctional photonic systems. RR devices realized on the plasmonic platform are highly attractive, as they offer extremely high sensitivity and a small footprint. However, the biggest challenge to overcome is the high fabrication demand related to such nanoscale devices, which limits their commercialization.