Efficient harnessing of light from nanoscale emitters deterministically placed through polymer-pen lithography at the focus of 3D-printed ellipsoidal micro-lenses

Collecting significant and measurable signals from the typically omnidirectional emission of nanoscale emitters is challenging. To improve the collection efficiency, it is essential to deterministically place the emitters in desired locations and design mode converters to match the modes of emission to those of the collection system. In this Letter, we propose the deterministic placement of nanoscale emitters using a pick-and-place technique called polymer-pen lithography. We demonstrate the concept with upconversion nanoparticles placed deterministically at the focus of three-dimensional-printed ellipsoidal micro-lenses. A significant part of the forward-going emission is collimated leading to increased collection efficiency, even at low numerical apertures of the collecting optics. The proposed approach lends itself to hybrid integration for fiber-to-chip and on-chip applications.