Automatic active alignment of substrate-free thin-film filters on a photonic platform using single photon detectors

verfasst von

P. Gehrke, A. K. Rüsseler, J. Matthes, L. Fütterer, E. Raffalt, A. Günther, R. Johanning, G. A. Hoffmann, A. Wienke, D. Kracht, M. Kues

Abstract

We present an automated active alignment procedure for assembling miniaturized photonic quantum circuits specifically designed to handle single-photon-level signals (i.e. low photon count). This process is exemplarily used for producing a polarization-based encode-and-measure quantum key distribution emitter. For this, we use the integration of miniaturized substrate-free thin-film filter elements into laser-induced deep-etched pockets on a photonic platform. The filter elements function as splitters to combine/divide four beams with different linear polarization states, as required for the BB84 quantum communication protocol. Bare-die laser diodes bonded to the same platform are used to create the single-photon level signals. The single filter chips are placed under an angle of 45 degrees to the propagation direction of the photon radiation vertically into the deep-etched pockets and fixed on the platform surface with UV-curable adhesive. The resulting signal is subsequently coupled into a single-mode fiber. For active alignment, a single photon avalanche detector is used in a feedback loop with a precision-optics assembly system, exploiting six degrees of freedom for the alignment of the assembly with stacked translation and rotation stages. The single photon detector is connected to an oscilloscope where a single voltage peak signals the detection of a photon. Aligning the filter elements changes the number of photons detected. The average voltage is a measure for the number of photons detected per integration time and used for the active alignment loop. This technique enables the active alignment of optical components for single photon-level signals, otherwise not detectable with conventional power meters.

Organisationseinheit(en)

Institut für Transport- und Automatisierungstechnik
Institut für Mikroproduktionstechnik
PhoenixD: Simulation, Fabrikation und Anwendung optischer Systeme
Institut für Photonik

Externe Organisation(en)

Laser Zentrum Hannover e.V. (LZH)

Typ

Aufsatz in Konferenzband

Publikationsdatum

19.03.2025

Publikationsstatus

Veröffentlicht

Peer-reviewed

Ja

ASJC Scopus Sachgebiete

Elektronische, optische und magnetische Materialien, Physik der kondensierten Materie, Angewandte Informatik, Angewandte Mathematik, Elektrotechnik und Elektronik

Elektronische Version(en)

https://doi.org/10.1117/12.3042937 (Zugang: Geschlossen)