近日，美国南加州大学的Demetrios N. Christodoulides&Georgios G. Pyrialakos及其研究团队取得一项新进展。经过不懈努力，他们对光子气体的焦耳-汤姆逊膨胀过程进行观测。相关研究成果已于2025年1月14日在国际知名学术期刊《自然—物理学》上发表。
该研究团队演示了一个由光子-光子相互作用介导的全光学焦耳-汤姆逊膨胀过程，在该过程中，光学气体的温度急剧下降至零。研究人员在各种耦合多芯非线性波导配置中的实验表明，如何将经历膨胀诱导冷却的光从任意输入状态以接近100%的效率引导至基模。
研究人员证明了膨胀后状态的稳定性是通过一个不可逆的能量转换过程来确保的。本研究探索的全光学热力学现象可能催生出创新技术，使各种不相关但相同的光源能够合并成一个统一的空间相干状态，为直接光束合成提供了一条途径。
据悉，近年来，一个自洽的光学热力学框架应运而生，为理解、驾驭和利用多模非线性系统的复杂集体动力学提供了系统的方法论。这些进展使得人们现在能够考虑光学中的一系列长期存在的问题，包括将多模系统中的全部功率导入其基态的前景，而目前尚不存在实现这一目标的方法。
附：英文原文
Title: Observation of Joule–Thomson photon-gas expansion
Author: Kirsch, Marco S., Pyrialakos, Georgios G., Altenkirch, Richard, A. Selim, Mahmoud, Beck, Julius, Wolterink, Tom A. W., Ren, Huizhong, Jung, Pawel S., Khajavikhan, Mercedeh, Szameit, Alexander, Heinrich, Matthias, Christodoulides, Demetrios N.
Issue&Volume: 2025-01-14
Abstract: In recent years, a self-consistent optical thermodynamic framework has emerged that offers a systematic methodology to understand, harness and exploit the complex collective dynamics of multimode nonlinear systems. These developments now allow consideration of a series of long-standing problems in optics, including the prospect of funnelling the entire power flowing in a multimode system into its ground state, for which no methodology currently exists. Here we demonstrate an all-optical Joule–Thomson expansion process mediated by photon–photon interactions whereby the temperature of the optical gas drops abruptly to zero. Our experiments in various configurations of coupled multicore nonlinear waveguide arrangements illustrate how light undergoing expansion-induced cooling can be channelled from arbitrary input states into the fundamental mode with near-unity efficiency. We show that the stability of the post-expansion state is ensured through an irreversible process of energy conversion. The all-optical thermodynamic phenomena explored in this study may enable innovative techniques where various uncorrelated but identical sources are merged into a unified spatially coherent state, offering a route for direct beam combining.
DOI: 10.1038/s41567-024-02736-1
Source: https://www.nature.com/articles/s41567-024-02736-1