QuoAlA—quantum entangled photon pair source based on AlGaAs Bragg reflection waveguides

© Fraunhofer IAF
SEM image of the facet of a cleaved AlGaAs Bragg reflection ridge waveguide
© Fraunhofer IAF
Simulated profile of a Bragg reflection light wave mode in an AlGaAs Bragg reflection ridge waveguide.

In the project “QuoAlA”, researchers at Fraunhofer IAF are working on compact on-chip sources for entangled photons, which are a crucial component for the realization of quantum technological applications, such as high-precision sensor technology and secure quantum communication.

The focus is on fundamental research of AlGaAs-based photon sources and their epitaxial manufacturing. The goal is to produce photon pairs with a high quality of entanglement at an exactly defined wavelength. The target wavelength is 1550 nm, which is within the telecom range(1500-1600 nm). For this purpose, the researchers rely on the extensive expertise of Fraunhofer IAF in epitaxy as well as process technology for the realization of waveguide structures in various III-V semiconductor materials.

The semiconductor material AlGaAs has nonlinear properties. In a material with nonlinear properties, a photon can spontaneously split into two photons at high light intensity due to an optical effect. Such light particle pairs can be quantum mechanically entangled. Furthermore, AlGaAs Bragg reflection waveguides allow the integration of other optical and electronic components on chip level and offer the potential for an especially compact design.

The project “QuoAlA” is funded by the Federal Ministry of Education and Research within the framework program of the Federal Government “Quantum technologies—from basic research to market” as “WiVoPro” (Scientific Preliminary Project) (FKZ: 13N15480).


QuoAlA – Quantum entangled photon pair sources at telecom wavelength based on AlGaAs Bragg reflection waveguides



2020 – 2023


BMBF (FKZ: 13N15480)


Fraunhofer IAF


  • Optimization of the fabrication of layer structures with regard to setting the target wavelength as precisely as possible
  • Fabrication of thinner (< 2,0 µm) and wider (> 5,0 µm) ridge waveguides
  • Demonstration of the generation of photon pairs with a high quality of entanglement at a wavelength of 1550 nm

Further information

At Fraunhofer IAF

Press Release

For information on the launch of the project, see the press release:


Project website


More information (in German) on the project can be found on the project website: