Abstract
The ability to manipulate light at subwavelength scales via photonic nanojets (PNJs) has revolutionized nanophotonics, yet traditional PNJs face limitations in focal length, intensity, and reproducibility. This thesis introduces collective photonic nanojets (cPNJs), generated by densely packed dielectric microcone arrays, to overcome these challenges. By leveraging interference between incident and scattered fields, cPNJs has achieved unprecedented focal lengths exceeding 60λ with the initial dielectric microcone array. Experimental studies also demonstrate that cPNJs by microcone array exhibit tunable properties through geometric optimization of array pitch, refractive index contrast, and microstructure density. These nanojets has enabled a 7-fold photoluminescence (PL) enhancement in sensor layers, highlighting their potential for optical sensing.
Building on this, we have introduced a new cPNJ platform – GaN microring arrays – based on the microcone array in this thesis. It can achieve stable super-resolution imaging with a resolution of 130 nm (∼λ/4.2) at working distances of several microns, addressing some of the limitations of conventional microsphere-assisted microscopy (MAM), or microparticle-assisted nanoscopy (MAN). Moreover, it could achieve 24-fold field enhancement. The thesis validates cPNJs as a robust, non-invasive tool for super-resolution microscopy, and PL/field enhancement. Offering a scalable and reproducible alternative to plasmonic and single-microsphere systems. This work advances dielectric nanophotonics by bridging theoretical insights with practical applications, paving the way for next-generation photonic devices in biosensing, quantum optics, and integrated photonics.