2022-12-01 スイス連邦工科大学ローザンヌ校(EPFL)
研究者らは、長さ2メートル以上の超低損失窒化ケイ素フォトニック集積回路を用いて、3×5 mm2サイズのフォトニックチップ上に初の進行波型増幅器を作製した。このチップは連続領域で動作し、通信帯域においてチップ上で7dB、ファイバー間で2dBの純利得を実現した。
将来的には、精密なリソグラフィー制御により導波路分散を最適化し、200 nm以上のパラメトリック利得帯域幅を実現することが可能である。また、窒化ケイ素の基本的な吸収損失は非常に小さいため（約0.15 dB/m）、さらなる製造上の最適化により、わずか750 mWのポンプ電力でチップの最大パラメトリック利得を70 dB以上に高めることができ、最高のファイバベース増幅器の性能を超えることができる。
＜関連情報＞
- https://actu.epfl.ch/news/photonics-chip-allows-light-amplification/
- https://www.nature.com/articles/s41586-022-05329-1
フォトニック集積型連続進行波パラメトリック増幅器 A photonic integrated continuous-travelling-wave parametric amplifier
Johann Riemensberger,Nikolai Kuznetsov,Junqiu Liu,Jijun He,Rui Ning Wang & Tobias J. Kippenberg
Nature Published:30 November 2022
DOI:https://doi.org/10.1038/s41586-022-05329-1
Abstract
The ability to amplify optical signals is of pivotal importance across science and technology typically using rare-earth-doped fibres or gain media based on III–V semiconductors. A different physical process to amplify optical signals is to use the Kerr nonlinearity of optical fibres through parametric interactions1,2. Pioneering work demonstrated continuous-wave net-gain travelling-wave parametric amplification in fibres3, enabling, for example, phase-sensitive (that is, noiseless) amplification4, link span increase5, signal regeneration and nonlinear phase noise mitigation6. Despite great progress7,8,9,10,11,12,13,14,15, all photonic integrated circuit-based demonstrations of net parametric gain have necessitated pulsed lasers, limiting their practical use. Until now, only bulk micromachined periodically poled lithium niobate (PPLN) waveguide chips have achieved continuous-wave gain16,17, yet their integration with silicon-wafer-based photonic circuits has not been shown. Here we demonstrate a photonic-integrated-circuit-based travelling-wave optical parametric amplifier with net signal gain in the continuous-wave regime. Using ultralow-loss, dispersion-engineered, metre-long, Si3N4 photonic integrated circuits18 on a silicon chip of dimensions 5 × 5 mm2, we achieve a continuous parametric gain of 12 dB that exceeds both the on-chip optical propagation loss and fibre–chip–fibre coupling losses in the telecommunication C band. Our work demonstrates the potential of photonic-integrated-circuit-based parametric amplifiers that have lithographically controlled gain spectrum, compact footprint, resilience to optical feedback and quantum-limited performance, and can operate in the wavelength ranges from visible to mid-infrared and outside conventional rare-earth amplification bands.
