Objective-free excitation of quantum emitters with a laser-written micro parabolic mirror

The efficient excitation of quantum sources such as quantum dots or single molecules requires high numerical aperture optics, which is often a challenge in cryogenics or in ultrafast optics. Here, we propose a 3.2 mu m wide parabolic mirror, with 0.8 mu m focal length, fabricated by direct laser writing on CdSe/CdS colloidal quantum dots, capable of focusing the excitation light to a sub-wavelength spot and of extracting the generated emission by collimating it into a narrow beam. This mirror is fabricated viain situvolumetric optical lithography, which can be aligned to individual emitters, and it can be easily adapted to other geometries beyond the paraboloid. This compact solid-state transducer from the far-field to the emitter has important applications in objective-free quantum technologies.