Subsurface Damage (SSD), which is introduced to optical materials by diamond turning processes, affects the performance in optical, laser and infrared applications. For optical applications, SSD can be the source of component instability (e.g., surface stress) and flaw. The objective of the present study is to investigate the subsurface damage in silicon. Interferometry and Raman Spectroscopy are used to detect the surface finish and SSD. The surface roughness of 0.243 nm is achieved at best combination. A sharp Raman shift at 409 cm-1 is obtained, which reveals that a thin layer of Silicon has transformed to amorphous state resulting in subsurface damages. Copyright © 2017 VBRI Press.