[论文解读] An ultra-broadband photonic-chip-based traveling-wave parametric amplifier

Nikolai Kuznetsov, Alberto Nardi+5 more|arXiv (Cornell University)|Apr 12, 2024

Advanced Photonic Communication Systems被引用 5

一句话总结

作者在 GaP-on-insulator 光子芯片上展示了高增益、超宽带行波光学参量放大器，实现高达 35 dB 增益，围绕 1550 nm 的 ~140 nm 带宽的光纤到光纤净增益超过 10 dB。

ABSTRACT

Optical amplification, crucial for modern communication and data center interconnects, primarily relies on erbium-doped fiber amplifiers (EDFAs) to enhance signals without distortion. While EDFAs were historically decisive for the introduction of dense wavelength-division multiplexing, they only cover a portion of the low-loss spectrum of optical fibers. Pioneering work on optical traveling-wave parametric amplifiers (TWPAs) utilizing intrinsic third-order optical nonlinearity has led to demonstrations of increased channel capacity and performance. TWPAs are unidirectional, offer high gain, and can reach the 3-dB quantum limit for phase-preserving amplifiers. Despite the use of highly nonlinear fibers or bulk waveguides, their power requirements and technical complexity have impeded adoption. In contrast, TWPAs based on photonic integrated circuits (PICs) offer the advantages of substantially increased mode confinement and optical nonlinearity but have been limited in bandwidth because of the trade-off with maintaining low propagation loss. We overcome this challenge by using low-loss gallium phosphide-on-silicon dioxide PICs and attain up to 35~dB of parametric gain with waveguides only a few centimeters long in a compact footprint of 0.25 square millimeters. Fiber-to-fiber net gain exceeding 10 dB across a bandwidth of approximately 140 nm is achieved, surpassing the gain window of a standard C-band EDFA. We furthermore demonstrate the capability to handle weak signals; input powers can range over six orders of magnitude while maintaining a low noise figure. We exploit these performance characteristics to amplify both optical frequency combs and coherent communication signals. This marks the first ultra-broadband, high-gain, continuous-wave amplification in a PIC, opening up new capabilities for next-generation optical communication, metrology, and sensing.

研究动机与目标

• 激发在铒波段之外对带宽更宽、增益更高的光学放大需求。
• 证明具有强 Kerr 非线性效应的光子集成电路能够实现净参量增益。
• 在紧凑的 GaP 基 TWPA 上展示高增益、宽带宽和低噪声。
• 验证在光子芯片上对极弱信号和频率梳的放大。

提出的方法

• 使用涂覆在 SiO2 上的薄膜 GaP 以制造用于简并四波混频的色散工程螺旋波导。
• 以接近 1550 nm 的单泵驱动 TWPA，通过光学 Kerr 效应实现参量增益。
• 用 κ = Δβ + 2γP_p 建模相位匹配，并优化色散项 β2 和 β4 以最大化带宽。
• 估计片上非线性参数 γ 与有效长度 L_eff 以计算峰值增益 G_S = 1 + [sinh(-ΔβL_eff/2)]^2。
• 通过考虑插损测量 CW 放大光谱、idler 产生，以及片外净增益。
• 展示对光学频率梳和相干数据流的放大以凸显实际应用。

实验结果

研究问题

• RQ1 在接近 1550 nm 的实际泵浦功率条件下，GaP-on-insulator TWPA 可实现的净增益和带宽是多少？
• RQ2 光子芯片 TWPA 能否提供适用于频率梳和相干通信的宽带、高增益、低噪声放大？
• RQ3 色散工程和材料特性（GaP）如何在保持宽增益带宽的同时实现器件长度和占地面积的减小？
• RQ4 在实际信号场景中，GaP TWPA 的饱和、功率处理和噪声性能特性如何？

主要发现

• CW 相位匹配放大，净光纤到光纤增益高达 25 dB。
• 宽带信号和 idler 增益覆盖约 140 nm（从 ~1300 到 ~1900 nm），片外净增益超过 70 nm 的 10 dB。
• 片上饱和功率对应输入 1605 nm 时 >125 mW（片上约 220 mW），转换效率 9%。
• 片上噪声 figure 在饱和前广范围信号功率下低于 4 dB；片外噪声 figure 在小信号增益区接近 6 dB。
• 对光学频率梳（EO 梳和孤子微梳）放大实现>20 dB 的光纤到光纤净增益。
• 单泵 GaP TWPA 在饱和前的输入功率范围达到六个数量级的线性放大。