Gayatri Vasudevan Rajeswari, research associate in photonics at Fraunhofer Heinrich-Hertz-Institut (HHI), has received the Best Student Paper Award at the International Semiconductor Laser Conference (ISLC) 2026 for her paper “Ultra-Low Chirp DML Array for 144 Gbps per Lane over 21 km Transmission.” The award honors outstanding student-led research and underlines Fraunhofer HHI’s expertise in photonic components and high-speed optical communication systems.
Meeting the growing demand for high-capacity optical interconnects
As artificial intelligence and data-intensive applications drive global data traffic, the demand for optical interconnects with higher capacity, lower power consumption, and greater cost efficiency is growing rapidly. Directly modulated lasers (DMLs) are considered a promising technology thanks to their compact architecture, energy efficiency, and suitability for large-scale photonic integration. So far, broader deployment has been limited by frequency chirp, which impairs signal quality over longer transmission distances. Reflecting on her motivation, Gayatri Vasudevan Rajeswari says: “What fascinated me most about this research was the possibility of overcoming this long-standing limitation while preserving the simplicity and cost advantages of DML technology.”
Fraunhofer HHI key competencies show experimental results with clear impact
The award-winning work demonstrates a promising solution to this challenge. The ultra-low chirp DML array developed by Fraunhofer HHI researchers shows that directly modulated laser transmitters can achieve very high data rates and extended transmission reach without sacrificing simplicity and efficiency. In their experiments, the team demonstrated 144 Gb/s per channel transmission over distances up to 21 km of standard single-mode fiber. The laser array achieved ultra-low chirp values below 0.3, confirming the effectiveness of the approach in reducing chirp-induced impairments. The results show that low-cost DML-based transmitters can support extended-reach optical connections relevant for future high-capacity interconnects.
The paper was authored by Gayatri Vasudevan Rajeswari, Jonathan Andree, Christoph Kottke, Martin Moehrle, Ariane Sigmund, Michael Theurer, Ronald Freund, and Martin Schell. Their collaboration brought together expertise in laser design, semiconductor device fabrication, and system-level transmission experiments. The paper was presented at ISLC 2026, where Gayatri Vasudevan Rajeswari received the Best Student Paper Award. The conference proceedings will be published in IEEE Xplore.
Opening new directions for future research
The paper opens future research directions including higher per-channel data rates, larger laser arrays, wavelength-division multiplexing, reliability, and advanced modulation. The approach is relevant for next-generation 800G, 1.6T, and higher-capacity optical transceivers, e.g. for data centers, metro networks, and AI-driven communication infrastructures.
Gayatri Vasudevan Rajeswari will continue research on increasing transmission distance and speed, improving photonic integration, and exploring multi-wavelength transmitter architectures to combine high bandwidth, low chirp, and cost-effective manufacturing for future optical interconnects and communication networks.