Self-Phase Modulation of Silicon Nanostructure Produced By Laser Induced Etching


A diode lasers of 532nm and 473nm wavelengths were used to produce silicon nanostructure by laser induced etching process for n-type silicon wafer of orientation <100>. The laser irradiation was carried out using different laser power density of (2, 5, 10 and 20 W/cm2 for recorder radiation time (4 min.). Optical fringes due to self-phase modulation are observed. Those fringe patterns depend on the size and depth of the nanostructure. It is found that fast changes in fringes when using short wavelength that indicates to further etching to produced smaller nanostructure at short irradiation time, this procedure could provide valuable details about silicon nanostructure during the etching process (in-situ). Fringes were represented by theoretical model to evaluate the size and change in the refractive index. The AFM images formation of uniform size distribution of 60 nm mean value when laser power density of 20 W/cm2 was used for 15 minutes.