Ultra-long-working-distance Spectroscopy of Single Nanostructures with Aspherical Solid Immersion Microlenses

In this work, we present aspherical micro-lenses which redirect emitted photons from semiconductor nanostructure into an ultra-narrow light cone of NA=0.016 - the outcoming light can be collected by a 1 inch-diameter lens at the distance of 590 mm from the sample [1]. The resulting working distance is more than 70 times longer than the one offered by conventional microscope objectives. Micro-lenses were fabricated by Two-Photon Polymerisation Direct Laser Writing (TPP-DLW), the technique which allows for three-dimensional printing of micro-objects made of transparent non-conductive resin that withstands cryogenic temperatures [2].

We demonstrate the usability of the proposed solid immersion lenses with single self-assembled quantum dots containing a single magnetic ion. Finally, we show that our solution works for monolayers of transition metal dichalcogenides (TMDs), in particular, MoSe₂ and WSe₂ thus confirming the feasibility of broadband operation of fabricated lenses. Presented micro-lenses could be especially useful for single nanostructure spectroscopy in very high magnetic fields - due to the absence of metal elements - as well as in microwave cavities or optical dilution refrigerator systems.

[1] Light Sci. Appl. 9, 48 (2020).
[2] Opt. Express 26, 11513 (2018).