3D micro optics on top of singled-out quantum dots: Page 2 of 2

June 08, 2017 //By Julien Happich
3D micro optics on top of singled-out quantum dots
A team of German scientists has focused its efforts on improving the extraction efficiency of quantum light sources, with the hope to be able to couple such sources directly to optical fibres for quantum communications.

For their second stage of lens integration, the researchers applied a UV sensitive photoresist to the lensed QD and patterned the micro-objective using 3D femtosecond direct 780nm laser writing. "The photoresist is polymerized via two-photon absorption at 390nm in a small volume element around the laser focus, resulting in sub-micrometre resolution", the paper reveals.

Scanning electron microscope images of a QD
micro-lens (a) and the fully processed QD micro-lens/
micro-objective device (b).

As in many 3D printing technologies, moving the focus of the laser through the photoresist (following a specific CAD path corresponding to the micro-lens geometry) exposed the optical system, accurately aligned with the monolithically integrated micro-lens.

With the finalized optics, the researchers reported a broadband photon-extraction efficiency of 40+- 4% for their quantum devices, with a high suppression of multi-photon emission events. They are convinced that further development using micro-objectives with NAs close to unity could yield highly efficient plug-and-play fibre-coupled single-photon sources for quantum communications.


Related article:

905nm pulsed laser diode integrates micro lens

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