Direct creation of black silicon using femtosecond laser pulses

► Black silicon is produced by direct femtosecond laser surface structuring. ► In the visible, the reflectance of the blackened surface is less than 5%. ► Low reflectance of black silicon extends to mid-infrared wavelengths. ► Created black silicon is mechanically robust. Using a direct femtosecond laser surface structuring technique, an array of equally spaced parallel nanostructure-textured microgrooves on silicon was produced that causes a dramatic reduction of the treated silicon reflectance. The processed area appears velvet black at all viewing angles. Throughout the visible region, the reflectance of the blackened surface is less than 5%. The antireflection effect of the processed surface also extends to the mid-infrared wavelength range. Furthermore, this technique has a potential in reducing silicon reflectance at terahertz frequencies and even in millimeter wavelength range.