A dichroic coating is a thin-film optical layer applied to surfaces such as glass or mirrors. It is engineered to selectively reflect certain wavelengths of light while allowing others to pass through. This property is achieved by stacking multiple layers of materials with different refractive indices, creating constructive and destructive interference for specific wavelengths. In cybersecurity and physical security contexts, dichroic coatings can be used in surveillance equipment, optical sensors, and secure communication devices to filter or direct light precisely. This enhances the performance of optical systems by improving signal clarity, reducing glare, or preventing unwanted detection. Dichroic coatings are also common in lasers, cameras, and display technologies.