Optically

Optically is an English adverb meaning in relation to optics or light. It is formed from the word optical and is used to indicate that a property, process, or phenomenon involves light, vision, or the interaction of electromagnetic radiation with matter.

In science and engineering, the term describes how light interacts with materials and devices. Examples include refraction, reflection, absorption, scattering, and polarization. Materials described as optically transparent transmit most visible light with little scattering; optically active substances rotate the plane of polarized light; optically anisotropic materials show direction-dependent optical properties; optically pumped devices generate light via stimulated emission.

Common usages include optically clear, optically thick or thin, and optically smooth or rough surfaces. The contrast with "optical" as an adjective is that optically is an adverb modifying a verb or adjective, while optical modifies a noun.

Measurement and analysis of optical properties rely on techniques such as spectrometry, refractometry, ellipsometry, and microscopy. These methods quantify how a material interacts with light, informing applications in coatings, lenses, sensors, and photonics.