Berlin 2024 – wissenschaftliches Programm

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HL: Fachverband Halbleiterphysik

HL 37: Poster IV

HL 37.18: Poster

Mittwoch, 20. März 2024, 18:00–20:30, Poster F

Monolithic 850 nm VCSEL Array for QKD via the decoy state protocol — •Katharina Dahler, Michael Zimmer, Michael Jetter, and Peter Michler — Institut für Halbleiteroptik und Funktionelle Grenzflächen, Center for Integrated Quantum Science and Technology (IQST) and SCoPE, University of Stuttgart, Allmandring 3, 70569 Stuttgart.

The need for secure data communication has increased in recent years. In contrast to classical key distribution, the use of quantum key distribution (QKD) offers fundamental advantages, such as complete secrecy. However, QKD poses numerous challenges with regard to the use of single photons. With this in mind, the decoy-state protocol offers the possibility of realizing QKD with classical light sources such as attenuated semiconductor lasers.

Here, we present the electro-optical characterization of an array of eight VCSELs emitting at 850 nm, capable to be used in a faint pulse source enabling QKD via the BB84 and decoy state protocol. The VCSEL structure was fabricated on a 4-inch GaAs wafer using metal-organic vapor-phase epitaxy (MOVPE), and the VCSELs are arranged in a coplanar contact design. Polarization control of the laser emission is achieved by monolithically integrated surface gratings in the light opening window of the VCSELs. Structures with surface grating reliefs were fabricated for additional modal control. The electro-optical device characteristics as well as a detailed investigation of the polarization states of the VCSELs realized with the aforementioned surface gratings are presented.