Designing surface lattice resonances to enhance the luminescence from silicon nanocrystals

Periodic arrays of nanoparticles whose period is commensurate with the wavelength of light can sustain collective resonances known as surface lattice resonances (SLR). SLR are associated with sharp and intense resonances and are appealing for fluorescence enhancement. In this communication, we design an array of double bowtie antennas for fluorescence enhancement of any large Stokes-shift emitter. A single emitter is located in the center of the central antenna. Each antenna is composed of two perpendicular bowties: an aluminum bowtie along the X-axis designed to enhance the excitation rate of the emitter and a gold bowtie along the Y-axis design to enhance the emission rate. Our goal is to enhance simultaneously excitation, emission and directivity within a single design. First, we study the properties of a single double bowtie (”nanoclover”) antenna for fluorescence enhancement. Then, we discuss the properties of one-dimensional arrays (chains) of nanoclovers. We evidence a subradiant mode sustained by the chain, leading to an increased absorption and detrimental to fluorescence enhancement. A strategy to circumvent this issue is proposed.