Berlin 2024 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 13: Poster I

HL 13.15: Poster

Monday, March 18, 2024, 15:00–18:00, Poster E

Electro-optical phase change devices based on nanocrystalline graphite heaters for integrated photonic circuits — •Niklas Vollmar¹, Anna Ovvyan², Wolfram Pernice², and Martin Salinga¹ — ¹Institute of Materials Physics, University of Münster, Wilhelm-Klemm-Str. 10, 48149 Münster, Germany — ²Kirchhoff-Institute for Physics, University of Heidelberg, Im Neuenheimer Feld 227, 69120 Heidelberg, Germany

In-memory computing with integrated photonic circuits is promising due to high bandwidth and low latency. In such systems, phase change materials (PCMs) can be used as compact and non-volatile modulators: the pronounced contrast in permittivity between their crystalline and amorphous states allow to tune the light transmission through an adjacent photonic waveguide by switching between those configurations. However, mature in-memory computing systems require to tune weights, represented by such transmission states, precisely and reproducibly. To this end, we create electro-optical phase change devices with electrical heaters based on nanometer-thin nanocrystalline graphite, which shows low-loss and can be produced in a simple graphitization process. A PCM is placed directly above stripes of graphite crossing the waveguide. Precise and reproducible tuning of the transmission state is achieved by switching individual, nanoscopic PCM pads fully, avoiding partially crystalline states. Gradual adjustments of the transmission can be achieved by configuring the states of a series of PCM pads with varying size. This way, a limited number of pads can still yield high-resolution weights.

Keywords: Phase change materials; Graphite; Integrated photonics; Optical modulator; In-memory computing