Optoelectronics/Quantum Devices

Microlaser-excited sources of indistinguishable photons for quantum networks

In this project, highly-integrated sources for quantum states of light are developed on the basis of semiconductor quantum dots. Our concept goes far beyond existing approaches in that it relies on monolithically integrated microlasers, which are intended to resonantly excite the quantum dots to emit single, indistinguishable photons. The microlasers themselves are electrically driven, which allows us to achieve a high degree of user-friendliness and miniaturization. While direct electrical charge carrier injection into quantum dots via simple p-i-n structures leads to decoherence effects, our resonant, optical excitation on the chip leads to excellent indistinguishability and suppression of the emission of multiple photons.

We meet the challenge of fabricating suitable semiconductor structures with state-of-the-art nanofabrication methods and techniques that allow us to deterministically integrate quantum dots. This enables the fabrication of low-threshold whispering-gallery microlas whose light is evanescently coupled into ridge waveguides with deterministically integrated quantum dots. Using in-situ electron beam lithography, we ensure during fabrication that quantum dots with appropriate emission wavelengths are positioned at those locations in the waveguide where they optimally couple to the waveguide mode. The waveguide systems will include beamsplitters, resonators to control the emission dynamics and maximise the photon decoupling efficiency, as well as non-linear elements for frequency conversion.

In sum, our project lays the foundation for highly functional, complex photonic quantum circuits that will be the building blocks of future quantum communication systems and photonic quantum computers.

Quick Info

AcronymOn-chip SPS
Project startOktober 2020
Funding sourceDeutsche Forschungsgemeinschaft (DFG)
Funding IDRE 2974/29-1