Gray-Tone Lithography Implementation of Drexhage's Method for Calibrating Radiative and Nonradiative Decay Constants of Fluorophores

TL;DR

This paper introduces a fast, accurate gray-tone lithography method to calibrate fluorophore decay rates by controlling emitter-surface distance, demonstrated through Drexhage experiments with various emitters.

Contribution

A novel gray-tone UV-lithography technique for fabricating dielectric spacers enabling precise fluorophore decay rate calibration via Drexhage experiments.

Findings

Decay rates depend on emitter-mirror distance as predicted by local density of states

Quantitative radiative and nonradiative decay rates are extracted from experiments

Method is applicable across visible and near-infrared wavelengths

Abstract

We present a straightforward method to realize non-planar dielectric structures with a controlled height profile for use in calibration of fluorophores. Calibration of fluorescence quantum efficiency and intrinsic radiative and nonradiative decay rates of emitters is possible by using changes in the local density of optical states, provided one can control the emitter-surface distance with nanometer accuracy. We realize a method that is accurate yet fast to implement. We fabricate PMMA wedges (4 mm x 4 mm x 2 \mu m) by gray-tone UV-lithography of Shipley S1813G2. Its applicability as dielectric spacer is demonstrated in Drexhage experiments for three different emitters in the visible and near-infrared wavelength regime. The decay-rate dependence of the fluorescent state of emitters on the distance to a silver mirror is observed and compared to calculations based on the local density of states. Quantitative values for (non)radiative decay rates and quantum efficiencies are extracted. Furthermore, we discuss how Drexhage experiments can help to scrutinize the validity of effective material parameters of metamaterials in the near field regime.