Plasmonic antennas for directional sorting of fluorescence emission

Area of Science:

• Photonics
• Nanotechnology
• Biomolecular engineering

Background:

• Spontaneous fluorescence emission is omnidirectional, limiting light collection and preventing molecular sorting.
• Optical antennas offer control over nanoemitter radiation but struggle with random molecular positions and orientations in solution.
• Controlling luminescence directivity is crucial for advanced biomolecular screening applications.

Purpose of the Study:

• To achieve full directional control of fluorescence emission from molecules in aqueous solution using a novel optical antenna.
• To demonstrate a micrometer-size dispersive antenna capable of directing fluorescence beams at specific wavelengths and angles.
• To establish physical optics guidelines for controlling fluorescence directivity by tuning antenna parameters.

Main Methods:

• Fabrication of an optical antenna comprising a gold film with a nanoaperture surrounded by periodic shallow grooves.
• Characterization of fluorescence emission from molecules in water solution using the fabricated antenna.
• Analysis of interference phenomena to explain and control fluorescence beaming directivity.

Main Results:

• Demonstrated full directional control of fluorescence emission from molecules in water.
• Achieved wavelength-specific fluorescence beaming with controllable angular width.
• Established a correlation between groove-nanoaperture distance and fluorescence directivity.

Conclusions:

• The developed optical antenna enables precise control over fluorescence emission direction, overcoming limitations of omnidirectional radiation.
• This technology functions as a micrometer-size dispersive antenna, allowing for photon sorting based on wavelength and direction.
• The photon-sorting capability offers a novel pathway for high-sensitivity screening of molecular species in solution.