Light possesses momentum, and hence, force is exerted on materials if they absorb and/or scatter light. Laser techniques that use optical forces are currently attracting considerable attention. Optical manipulation for trapping, transporting small particles, and measuring the interparticle force is a representative technique. In addition, photoinduced force microscopy is a promising scanning type of microscopy using optical force. Optical force techniques have recently been used in various fields of research, such as molecular bioscience, organic photochemistry, materials engineering, and molecular fluid dynamics. In these techniques, several types of optical forces such as scattering, absorption, and gradient forces play their respective roles. In this article, we summarize the basics of optical forces and present their elementary expressions for using simplified models of light and matter systems. This will help the readers of this Special Issue to understand how different types of forces are distinguished in the basic expressions used for analyzing the optical force phenomena that appear depending on the light geometry and matter systems. After observing simplified cases of scattering and absorption forces, we introduce general formulae for the optical force and then discuss how different components appear in particular cases of laser geometry and materials.

光具有动量，因此，如果材料吸收和/或散射光，就会对材料施加力。使用光力的激光技术目前正引起相当大的关注。用于捕获、传输小颗粒和测量粒子间力的光学操作是一种代表性技术。此外，光诱导力显微镜是一种很有前途的使用光学力的扫描型显微镜。光力技术最近被用于各个研究领域，例如分子生物科学、有机光化学、材料工程和分子流体动力学。在这些技术中，散射、吸收和梯度力等几种类型的光学力发挥着各自的作用。在本文中，我们总结了光学力的基础知识，并提出了使用光和物质系统简化模型的基本表达式。这将帮助本期特刊的读者理解不同类型的力在用于分析根据光几何和物质系统出现的光学力现象的基本表达式中是如何区分的。在观察了散射力和吸收力的简化情况后，我们介绍了光学力的一般公式，然后讨论了不同分量在激光几何和材料的特定情况下是如何出现的。这将帮助本期特刊的读者理解不同类型的力在用于分析根据光几何和物质系统出现的光学力现象的基本表达式中是如何区分的。在观察了散射力和吸收力的简化情况后，我们介绍了光学力的一般公式，然后讨论了不同分量在激光几何和材料的特定情况下是如何出现的。这将帮助本期特刊的读者理解不同类型的力在用于分析根据光几何和物质系统出现的光学力现象的基本表达式中是如何区分的。在观察了散射力和吸收力的简化情况后，我们介绍了光学力的一般公式，然后讨论了不同分量在激光几何和材料的特定情况下是如何出现的。