Inflection Point: A New Perspective on Photonic Nanojets

TL;DR

This paper introduces a novel perspective on photonic nanojets by analyzing the inflection point between regions of rapid and slow light change, supported by numerical simulations and theoretical analysis, revealing new ways to control light focusing.

Contribution

It presents a new approach to understanding photonic nanojets through the inflection point concept, combining numerical and theoretical methods for light manipulation.

Findings

Identification of the inflection point as key to PNJ behavior

Demonstration of photonic hook generation via inflection point control

Modulation of PNJ and PH using different illumination strategies

Abstract

When light propagates through the edge or middle part of microparticle's incoming interface, there is a basic rule that light converges and diverges rapidly or slowly at the output port. These two parts are referred to as region of rapid change (RRC) and region of slow change (RSC), respectively. Finding the boundary point between RRC and RSC is the key to reveal and expound this rule scientifically. Based on the correlation between light convergence-divergence and the slope of emergent light, combined with the relationship between natural logarithm and growth in physical reality and the second derivative of a function in practical significance, we determine the boundary point between RRC and RSC, namely the inflection point. From such perspective, photonic nanojet (PNJ) and near-field focusing by light irradiation on RSC and RRC, as well as the position of the inflection point under different refractive index contrast and the field distribution of light-focusing, are studied with finite-element-method-based numerical simulation and ray-optics-based theoretical analysis. By illuminating light of different field intensity ratios to the regions divided by the inflection point, we demonstrate the generation of photonic hook (PH) and the modulation of PNJ/PH in a new manner.