On‐Chip Single‐Molecule Fluorescence Enhancement via Slotted Gallium Phosphide Nanodisks at Anapole States

Abstract

AbstractSurface‐enhanced fluorescence of single emitters lies at the heart of single‐molecule DNA sequencers as well as quantum light sources. The state‐of‐the‐art metallic nanoapertures are impaled in a dilemma between enhancing radiative decays and minimizing nonradiative issues such as quenching and resistive heating. Here, lossless gallium phosphide slotted nanodisks are proposed that operate at anapole states by in‐plane excitation, precisely aligning the optical “hot spots” with fluidic focuses of zeptomolar sensing volume. Unlike traditional microscopic configurations, this proposed scheme excited via butt‐coupled in‐plane waveguides not only exhibits averagely 12.4× excitation enhancement growth for a single emitter located in the slot, but also enables precise manipulation of the local density of optical states which gives rise to 13.2× when QY0 = 0.003. Surprisingly, directional collection from the excitation waveguide appears in the optimal approach rather than the collection from a CMOS camera at the bottom. The overall on‐chip fluorescent enhancement is benchmarked with the four dyes’ colors, lowering the excitation power to 5.3% of contemporary zero‐mode waveguide (ZMW) devices.