Second harmonic generation (SHG) and sum frequency spectroscopy (SFS) have provided unique opportunities to probe surfaces and interfaces. They have found broad applications in many disciplines of science and technology. In recent years, there has been significant progress in the development of SHG/SFS technology that has significantly broadened the applications of SHG and SFS. In this article, we review the recent progress of the field with emphasis on SFS.

中文翻译：

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和频光谱学的最新进展

二次谐波产生（SHG）和和频谱（SFS）为探测表面和界面提供了独特的机会。他们在许多科学和技术学科中发现了广泛的应用。近年来，SHG / SFS技术的开发取得了重大进展，极大地扩展了SHG和SFS的应用范围。在本文中，我们将重点介绍SFS，以回顾该领域的最新进展。