High density of silicon nanowires (SiNWs) were synthesized by a hot-wire assisted plasma enhanced chemical vapor deposition technique. The structural and optical properties of the as-grown SiNWs prepared at different rf power of 40 and 80W were analyzed in this study. The SiNWs prepared at rf power of 40W exhibited highly crystalline structure with a high crystal volume fraction, X C of ∼82% and are surrounded by a thin layer of SiO x . The NWs show high absorption in the high energy region (E>1.8eV) and strong photoluminescence at 1.73 to 2.05eV (red–orange region) with a weak shoulder at 1.65 to 1.73eV (near IR region). An increase in rf power to 80W reduced the X C to ∼65% and led to the formation of nanocrystalline Si structures with a crystallite size of <4nm within the SiNWs. These NWs are covered by a mixture of uncatalyzed amorphous Si layer. The SiNWs prepared at 80W exhibited a high optical absorption ability above 99% in the broadband range between 220 and ∼1500nm and red emission between 1.65 and 1.95eV. The interesting light absorption and photoluminescence properties from both SiNWs are discussed in the text.