近日，芬兰阿尔托大学的Zhipei Sun&Susobhan Das及其研究团队取得一项新进展。经过不懈努力，他们实现纳米级厚度倍频程相干超连续光的产生。相关研究成果已于2025年1月9日在国际知名学术期刊《光：科学与应用》上发表。

该研究团队首次报道了在纳米尺度上通过无相位匹配的频率下转换过程实现了倍频程相干光生成。在100纳米尺度上，通过硒化镓和二碘化铌氧化物晶体中的二阶非线性过程——差频生成，以离散方式展示了覆盖约565至1906纳米、光谱宽度达到40分贝的倍频程相干光生成。

与基于体材料的传统相干宽带光源相比，该器件薄了约5个数量级，且所需的激发功率低了约3个数量级。这项研究结果为可能创建紧凑、多功能和集成的超宽带光源开辟了一条新途径。

据悉，相干宽带光产生因其在计量、传感、成像、通信等领域的广泛应用而受到广泛关注。一般来说，光谱展宽是通过三阶和高阶非线性光学过程（如自相位调制、拉曼跃迁、四阶波混频、多波混频）来实现的，这些过程通常很弱，需要很长的相互作用长度和相位匹配条件来增强有效的非线性光-物质相互作用，从而产生广谱。

附：英文原文

Title: Nanoscale thickness Octave-spanning coherent supercontinuum light generation

Author: Das, Susobhan, Uddin, Md Gius, Li, Diao, Wang, Yadong, Dai, Yunyun, Toivonen, Juha, Hong, Hao, Liu, Kaihui, Sun, Zhipei

Issue&Volume: 2025-01-09

Abstract: Coherent broadband light generation has attracted massive attention due to its numerous applications ranging from metrology, sensing, and imaging to communication. In general, spectral broadening is realized via third-order and higher-order nonlinear optical processes (e.g., self-phase modulation, Raman transition, four-wave mixing, multiwave mixing), which are typically weak and thus require a long interaction length and the phase matching condition to enhance the efficient nonlinear light-matter interaction for broad-spectrum generation. Here, for the first time, we report octave-spanning coherent light generation at the nanometer scale enabled by a phase-matching-free frequency down-conversion process. Up to octave-spanning coherent light generation with a 40dB spectral width covering from ~565 to 1906nm is demonstrated in discreate manner via difference-frequency generation, a second-order nonlinear process in gallium selenide and niobium oxide diiodide crystals at the 100-nanometer scale. Compared with conventional coherent broadband light sources based on bulk materials, our demonstration is ~5 orders of magnitude thinner and requires ~3 orders of magnitude lower excitation power. Our results open a new way to possibly create compact, versatile and integrated ultra-broadband light sources.

DOI: 10.1038/s41377-024-01660-6

Source: https://www.nature.com/articles/s41377-024-01660-6