近日，美国麻省理工学院Hu, Qing团队报道了激光频率梳用超宽带空气介质双啁啾反射镜。2025年8月19日出版的《光：科学与应用》杂志发表了这项成果。

色散工程是制造集成宽带激光频率梳的关键。在长波红外范围(LWIR, 8-13μm)，基于量子级联激光器的频率梳具有吸引力，因为它们是具有高功率水平和效率的单片基本振荡器。扩展量子级联激光增益带宽的一种有效方法是通过叠加具有不同中心激光频率的多个增益介质，从而获得更平坦的宽带增益谱。然而，随着增益带宽的增加，色散成为限制梳带带宽的主要因素。因此，实现宽带梳需要能够灵活地设计宽带色散的方案。

研究组展示了最终的纳米光子色散补偿方案：一个空气介质板双啁啾反射镜，他们完全集成了量子级联激光增益部分。该方案依赖于尽可能高的索引对比度，因此在非常宽的带宽上提供每单位长度的最大校正。利用这种方法，研究组报告了在增益介质上成功演示宽带室温LWIR激光频率梳，如果没有刻意的色散补偿，通常不会形成梳。该空气介质镜是通用的，可以扩展到其他集成的激光频率梳在不同的材料平台和频段。

附：英文原文

Title: Ultrabroadband air-dielectric double-chirped mirrors for laser frequency combs

Author: Zeng, Tianyi, Dikmelik, Yamac, Xie, Feng, Lascola, Kevin, Burghoff, David, Hu, Qing

Issue&Volume: 2025-08-19

Abstract: Dispersion engineering is critical for the creation of integrated broadband laser frequency combs. In the long wavelength infrared range (LWIR, 8-13μm), frequency combs based on quantum cascade lasers are attractive since they are monolithic, fundamental oscillators with high power levels and efficiencies. One effective approach for expanding quantum cascade laser gain bandwidth is by stacking multiple gain media with different center lasing frequencies, as this leads to flatter broadband gain spectra. However, as the gain bandwidth is increased, dispersion becomes the main limiting factor for comb bandwidth. Therefore, achieving broadband combs requires schemes that can flexibly engineer the dispersion over broad bandwidths. Here, we demonstrate the ultimate nanophotonic dispersion compensation scheme: an air-dielectric slab double-chirped mirror, which we fully integrate with the quantum cascade laser gain section. This scheme relies on the highest possible index contrast and therefore provides the maximum correction per unit length over a very broad bandwidth. With this approach, we report the successful demonstration of a broadband room-temperature LWIR laser frequency comb on a gain medium that normally does not form combs without deliberate dispersion compensations. Our air-dielectric mirrors are versatile and can be extended to other integrated laser frequency combs in different material platforms and frequency bands.

DOI: 10.1038/s41377-025-01961-4

Source: https://www.nature.com/articles/s41377-025-01961-4