Second-harmonic generation imaging of semiconductor nanowires with focused vector beams

Area of Science:

• Nanotechnology
• Optics
• Materials Science

Background:

• Vertically aligned gallium arsenide (GaAs) nanowires are crucial for nanoelectronic and optoelectronic devices.
• Understanding their optical nonlinearities is essential for device optimization.
• Second-harmonic generation (SHG) is a sensitive probe of material symmetry and electronic properties.

Purpose of the Study:

• To investigate the dominant driving field for SHG in individual GaAs nanowires.
• To compare the effectiveness of focused radial polarization versus linear polarization for characterizing nanowires.
• To explore SHG as a tool for in-situ analysis within the native growth environment.

Main Methods:

• Utilizing second-harmonic generation (SHG) microscopy with focused vector beams.
• Employing radially and linearly polarized light.
• Investigating individual, vertically aligned GaAs nanowires.
• Modeling the SHG process for zinc-blende crystal structures and dipolar bulk nonlinearity.

Main Results:

• Direct evidence shows the longitudinal field along the nanowire growth axis is the primary driver of SHG.
• Focused radial polarization demonstrates superior performance for characterizing oriented GaAs nanowires compared to linear polarization.
• The study confirms the feasibility of SHG analysis in the native growth environment.

Conclusions:

• The longitudinal field is key for SHG in oriented GaAs nanowires.
• Focused radial polarization is an advanced technique for characterizing nanowire properties.
• SHG offers a powerful, non-invasive method for analyzing nanowires in their growth environment.