近日，德国斯图加特大学Tobias Steinle团队研究了色散工程多通光参量放大。该研究于2025年11月5日发表在《自然》杂志上。

超短激光脉冲（小于100飞秒）的放大技术面临根本性挑战，这源于放大带宽、效率与增益之间的相互制约。传统方法依赖包含预处理与后处理步骤的复杂光学系统。光学参量放大虽能提供与非线性介质长度成正比的高光学增益，却以牺牲带宽为代价，这对具有本征宽频特性的超短脉冲尤为不利——此类脉冲的放大需要同时满足宽增益带宽、高单程增益和强非线性相互作用的要求。

研究组提出一种新型多程光学参量放大系统，通过采用色散工程介质镜，将激光束反复聚焦至非线性增益晶体。该镜面涂层能在每个多程步骤后同步补偿群延迟并抑制闲频波，从而有效阻止反向转换。相较于单程放大，该系统实现了1500倍的增益提升，光子转换效率达81%（系统总转换效率52%），放大后脉冲的时间带宽积接近傅里叶极限，且完全保持了光束空间质量。

该方案突破了增益与带宽的固有矛盾，在41分贝增益下实现12太赫兹带宽。由于不依赖特定增益介质，该技术具有普适性，可广泛应用于量子技术、阿秒物理、材料加工及超宽带低成本生物成像等领域的超快激光系统，且设备体积可控制在个位数立方厘米量级。

附：英文原文

Title: Dispersion-engineered multipass optical parametric amplification

Author: Ngele, Jan H., Steinle, Tobias, Thannheimer, Johann, Flad, Philipp, Giessen, Harald

Issue&Volume: 2025-11-05

Abstract: The amplification of extremely short laser pulses (under 100fs) presents a fundamental challenge due to the trade-off between amplification bandwidth, efficiency and gain1. Conventional methods rely on complex optical set-ups with preprocessing and postprocessing steps2. Optical parametric amplification3 offers a high optical gain that scales with the length of the nonlinear medium at the expense of bandwidth, limiting its effectiveness for extremely short and intrinsically broadband ultrashort pulses, whose amplification requires a broad gain–bandwidth, high single-pass gain and simultaneously strong nonlinear interaction. Here we introduce a new multipass4 optical parametric amplification system that leverages dispersion-engineered dielectric mirrors to repeatedly focus the laser into a nonlinear gain crystal. The coatings simultaneously compensate for the group delay5 after each multipass step and suppress the idler wave and, therefore, backconversion. This approach achieves ×1,500 higher gain compared with single-pass amplification, a photon conversion efficiency of up to 81% (52% system conversion efficiency) and near Fourier-limited time–bandwidth products of the amplified pulses, while fully preserving the spatial beam quality. Our concept breaks the gain versus bandwidth barrier and achieves 12THz at 41dB gain. As our concept does not require specific gain materials, it is versatile and broadly applicable to ultrafast6 laser systems in quantum technologies7,8,9, attosecond physics10,11,12, material processing and ultrabroadband low-cost bio-imaging systems13,14. Our concept offers device sizes in the single-digit cubic centimetre range.

DOI: 10.1038/s41586-025-09665-w

Source: https://www.nature.com/articles/s41586-025-09665-w