White Light Reflectance Spectroscopy (WLRS) Description

White Light Reflectance Spectroscopy (WLRS) is a technique where a broad-spectrum light source shines white light vertically onto a layered material. Some of this light reflects off the top surface, while the rest penetrates through and reflects from deeper layers. These reflected light waves combine and create a pattern called reflection interference, which depends on the thickness and optical properties of the layers.

In the illustration, the Light Source emits white light that hits the semi-transparent layers. The combined reflected waves, labeled Reflection Interference, are detected by the Detector nearby. By analyzing this interference, WLRS accurately determines the thickness d of the layers based on the formula for the optical path difference:

Δφ = (4 π n d) / λ

Where n is the refractive index of the layer and λ is the wavelength of the light. This non-destructive method enables precise measurement of thin films in various scientific and industrial applications.