Ultra-long-working-distance spectroscopy of single nanostructures with aspherical solid immersion microlenses

In light science and applications, equally important roles are played by efficient light emitters/detectors and by theoptical elements responsible for light extraction and delivery. The latter should be simple, cost effective, broadband,versatile and compatible with other components of widely desired micro-optical systems. Ideally, they should alsooperate without high-numerical-aperture optics. Here, we demonstrate that all these requirements can be met withelliptical microlenses 3D printed on top of light emitters. Importantly, the microlenses we propose readily form thecollected light into an ultra-low divergence beam (half-angle divergence below 1°) perfectly suited for ultra-long-working-distance optical measurements (600 mm with a 1-inch collection lens), which are not accessible to date withother spectroscopic techniques. Our microlenses can be fabricated on a wide variety of samples, includingsemiconductor quantum dots and fragile van der Waals heterostructures made of novel two-dimensional materials,such as monolayer and few-layer transition metal dichalcogenides