Regensburg 2025 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 39: Poster III

HL 39.24: Poster

Wednesday, March 19, 2025, 15:00–18:00, P3

Monolithic 850 nm VCSEL array for Quantum Key Distribution 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, Germany

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 regarding 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 a monolithic 850 nm vertical-cavity surface-emitting laser (VCSEL) array, for QKD via the BB84 and decoy state protocol. The complete VCSEL array consists of eight individual VCSELs arranged in a coplanar contact design, with four VCSELs serving as signal states and four as decoy states. A highly homogeneous growth is needed due to the requirement of indistinguishable light pulses regarding the emission wavelength. In order to realize the four necessary polarization states and to counteract the electro-optical effect, each VCSEL features a monolithically integrated surface grating in the top layer of its light emission window. Electro-optical device characteristics regarding light polarization via surface gratings and spectral homogeneity of the VCSEL array are presented.

Keywords: Vertical-cavity surface-emitting laser (VCSEL); Quantum Key Distribution; Decoy State Protocol; Monolithically integrated surface grating