Characterization of gap-plasmon based metasurfaces using scanning differential heterodyne microscopy

Area of Science:

• Optics and Photonics
• Metamaterials
• Plasmonics

Background:

• Optical metasurfaces offer subwavelength control over light's phase, amplitude, and polarization.
• Direct measurement of phase gradients in metasurfaces is challenging but crucial for their characterization.
• Gap surface plasmon (GSP) metasurfaces are a promising class of optical devices.

Purpose of the Study:

• To develop and validate a direct phase and amplitude characterization technique for optical metasurfaces.
• To assess the efficiency and accuracy of scanning differential heterodyne microscopy (SDHM) for this purpose.
• To experimentally characterize GSP metasurfaces using the developed SDHM approach.

Main Methods:

• Numerical simulations and experimental measurements were employed.
• Scanning differential heterodyne microscopy (SDHM) was utilized for direct phase and amplitude mapping.
• Two GSP metasurface configurations (binary grating and linear phase gradient) were analyzed at 633 nm.

Main Results:

• SDHM successfully performed direct phase and amplitude characterization of the GSP metasurfaces.
• Experimental performance of the metasurfaces was compared with SDHM-reconstructed phase and amplitude profiles.
• The study verified the efficiency and accuracy of SDHM for inspecting GSP reflective metasurfaces.

Conclusions:

• SDHM is an effective technique for the direct characterization of optical metasurfaces, particularly those based on GSP.
• The validated method allows for precise inspection of phase gradients and amplitude profiles.
• This work advances the metrology for optical metasurface development and application.