  The recent discovery of semiconducting two-dimensional materials has led to
the prediction of a revolution in the field of optoelectronics, driven by the
introduction of a series of new components that are just a few atoms thick. Key
remaining challenges for producing practical devices from these materials lie
in improving the coupling of light into and out of single atomic layers, and in
making these layers robust to the influence of their surrounding environment.
We present a solution to tackle both of these problems simultaneously, by
deterministically placing a micro-lens directly onto the surface of these
materials. These lenses are dynamically tuned to increase the coupling of
light, whilst controlling chromatic aberration, before being set in place with
UV light. We show that this approach enhances photoluminescence of tungsten
diselenide (WSe2) monolayers by up to 300%, and nearly doubles the imaging
resolution of the system. Furthermore, this solution fully encapsulates the
monolayer, preventing it from physical damage and degradation in air. The
optical solution we have developed could become a key enabling technology for
the mass production of ultra-thin optical devices, such as quantum light
emitting diodes.
