'Research In Brief': New Developments From FBH Research

With the fourth edition of its “Research in Brief” format, Ferdinand-Braun-Institut (FBH) once again provides insights into current research activities at the institute. The compact overview brings together selected results from recent months in the fields of photonics, integrated quantum technology, III-V electronics, and III-V technology.

This issue covers topics ranging from diode lasers for future fusion power plants and highly reliable red laser diodes to miniaturized optical isolators for photonic quantum systems, as well as new concepts for high-voltage transistors, full-duplex communication, and compact picosecond laser sources.

The contributions are based on the research news published every two weeks on the FBH website. They provide regular updates on new scientific results and technological developments from the institute’s various research areas.

Photonics

• Diode laser pump sources for high-energy lasers in fusion power plants
  High-power diode lasers are paving the way to commercial fusion energy by replacing inefficient flash lamps with scalable, efficient, and reliable pump technology. We advance this transition with robust III-V technology, wavelength-stabilized diode concepts, and ultra-high-power designs, while improving efficiency, lifetime, and manufacturability toward fusion-relevant operation.
  Read more on the FBH website (https://www.fbh-berlin.de/forschung/forschungsnews/diode-laser-pump-sources-for-high-energy-lasers-in-fusion-power-plants)
• Laser facet passivation enables reliable high-power red ridge waveguide laser diodes
  We demonstrate 635 nm ridge waveguide lasers delivering up to 200 mW with high reliability through optimized facet passivation. This paves the way for high-radiance red laser diodes in demanding applications such as holography, spectroscopy, and quantum technologies.
  Read more on the FBH website (https://www.fbh-berlin.de/forschung/forschungsnews/laser-facet-passivation-enables-reliable-high-power-red-ridge-waveguide-laser-diodes)

Integrated Quantum Technology

• Miniaturized optical isolators for next-generation quantum photonic systems
  We are advancing the miniaturization of photonic systems in quantum technologies. With ultra-compact optical isolators for wavelengths from 400 to 950 nm, we address a critical gap in key components.
  Read more on the FBH website (https://www.fbh-berlin.de/forschung/forschungsnews/miniaturised-optical-isolators-for-next-generation-quantum-photonic-systems)

III-V Electronics

• Lateral rutile GeO₂ MOSFET devices for next-generation high-voltage applications
  We have demonstrated the first functional r-GeO₂ power transistor on single-crystal substrates. The ultra-wide bandgap material enables high breakdown voltages of 1280 V, excellent current modulation, and strong thermal potential – highlighting its promise for next-generation high-voltage electronics.
  Read more on the FBH website (https://www.fbh-berlin.de/forschung/forschungsnews/lateral-rutile-germanium-dioxide-mosfet-devices-for-next-generation-high-voltage-applications)
• Novel GaN-based full-duplex front-end topology for communication and sensing systems
  We demonstrate a GaN-based full-duplex front-end with analog self-interference cancellation, achieving up to 52 dB suppression at 4 GHz and high transmit power levels. The concept enables simultaneous transmission and reception without a directive device, resulting in significantly higher data rates, increased spectral efficiency, and reduced latency.
  Read more on the FBH website (https://www.fbh-berlin.de/forschung/forschungsnews/novel-gan-based-full-duplex-front-end-topology-for-communication-and-sensing-systems)

III-V Technology

• Gain-switched electrically pumped VECSEL for picosecond pulse generation at 1030 nm
  Researchers at FBH and LZH demonstrate picosecond pulse generation from a novel gain-switched electrically pumped VECSEL. The concept enables operation in the low-MHz regime without intracavity components and paves the way for compact sources targeting LiDAR, sensing, and seeding applications.
  Read more on the FBH website (https://www.fbh-berlin.de/forschung/forschungsnews/gain-switched-electrically-pumped-vecsel-for-picosecond-pulse-generation-at-1030-nm)