図1：直接変調レーザの3dB帯域の変遷（付加的な高速化手法の利用なし）
NTT：帯域100GHz・直接変調レーザを開発：SiC・メンブレンレーザ（動画）：
NTT: Developed 100GHz band, direct modulation laser: SiC, membrane laser:
NTT：开发了100GHz频段，直接调制激光器：SiC，膜激光器
～SiC基板上メンブレンレーザにより低消費電力で実現～
2020/10/20
NTT
東京工業大
未来産業技術研究所
- 高熱伝導率を持つSiC基板上に
- インジウムリン系化合物半導体を用いた
メンブレンレーザを開発しました。
直接変調レーザとして、3dB帯域（※4）が100GHzを超えました。
「毎秒256ギガビット（2560億ビット）の信号を2km伝送できること」を確認しました。
直接変調レーザ：
従来の問題点：
直接変調レーザは、現在、データセンタで広く使用されています。
しかし変調速度に限界があり、課題とされてきました。
今回の解決策：
- SiC・メンブレンレーザを用いれば、
- 今後のトラフィック増大にも、
- 低コスト・低消費電力に対応でき、
NTTのIOWN（＊）構想での、大容量光伝送基盤に適用できます。
成果を公開：
本成果は、英国時間10月19日に英国科学雑誌「Nature Photonics」のオンライン速報版で公開されます。
日本経済新聞
https://www.nikkei.com/article/DGXLRSP542014_Q0A021C2000000/
World’s fastest directly modulated laser exceeding 100-GHz bandwidth
October 20, 2020
World’s fastest directly modulated laser exceeding 100-GHz bandwidth
~Membrane laser on silicon carbide substrate achieves low power consumption
NTT Corporation
Tokyo Institute of Technology
Future Research of Science and Tech,has developed a membrane laser*1 that uses an indium-phosphorus compound semiconductor*2 on a silicon carbide substrate*3 with high thermal conductivity.
This laser,
the world’s first directly modulated laser with a 3-dB bandwidth*4 exceeding 100 GHz, can transmit at 256 gigabits (256 billion bits) per second over a distance of 2 km.
Directly modulated lasers
are now widely used in data centers*5, but their modulation speed is limited, which has been a problem for further increasing in transmission capacity.These results will enable us to respond to
the expected increase in traffic
with a low-cost and
low-power-consumption solution
will contribute to the realization of a high-capacity optical transmission infrastructure that supports NTT’s IOWN*6 concept.
This research
was reported in Nature Photonics on October 19, 2020. NTTPress Releases : NTT HOME
https://www.ntt.co.jp/news2020/2010e/201020a.html
Directly modulated membrane lasers with 108 GHz bandwidth on a high-thermal-conductivity silicon carbide substrate
Abstract
Increasing the modulation speed of semiconductor lasers
has attracted much attention from the viewpoint of both physics and the applications of lasers.
Here we propose a membrane distributed reflector laser on a low-refractive-index and high-thermal-conductivity silicon carbide substrate that overcomes the modulation bandwidth limit.
The laser features a high modulation efficiency because of its large optical confinement in the active region and small differential gain reduction at a high injection current density.
We achieve a 42 GHz relaxation oscillation frequency by using a laser with a 50-μm-long active region.
The cavity, designed to have a short photon lifetime,
suppresses the damping effect while keeping the threshold carrier density low, resulting in a 60 GHz intrinsic 3 dB bandwidth (f3dB).
By employing the photon–photon resonance at 95 GHz due to optical feedback from an integrated output waveguide,
we achieve an f3dB of 108 GHz and demonstrate 256 Gbit s−1 four-level pulse-amplitude modulations with a 475 fJ bit−1 energy cost of the direct-current electrical input.
Nature Photonics