Nanostructuring in Si using a femtosecond laser

Abstract

A femtosecond laser is used as a tool to machine a high-Q photonic bandgap crystal, which consists of a series of ∼200-nm holes on a monorail silicon-on-insulator structure. This photonic crystal has exhibited a high transmission peak with Q value of ∼700. A Q of 700 suggests that this device is a ∼ 2 nm narrow-band filter at telecommunication wavelength. Cross-sectional transmission electron microscopy was used to study the material morphology change after laser irradiation. An amorphous layer of Si was found to be adjacent to the ablated holes. This demonstrates that even when material is ablated using femtosecond pulses near the single pulse ablation threshold, sufficient heating of the surrounding material occurs to create a molten zone which solidifies so rapidly that crystallization is bypassed.A femtosecond laser is used as a tool to machine a high-Q photonic bandgap crystal, which consists of a series of ∼200-nm holes on a monorail silicon-on-insulator structure. This photonic crystal has exhibited a high transmission peak with Q value of ∼700. A Q of 700 suggests that this device is a ∼ 2 nm narrow-band filter at telecommunication wavelength. Cross-sectional transmission electron microscopy was used to study the material morphology change after laser irradiation. An amorphous layer of Si was found to be adjacent to the ablated holes. This demonstrates that even when material is ablated using femtosecond pulses near the single pulse ablation threshold, sufficient heating of the surrounding material occurs to create a molten zone which solidifies so rapidly that crystallization is bypassed.