Metasurface-Integrated Photonic Platform for Versatile Free-Space Beam Projection with Polarization Control.

Area of Science:

• Photonics and Nanotechnology
• Integrated Optics
• Metasurfaces

Background:

• Densely integrated photonic circuits are crucial for optical signal processing.
• Interfacing integrated circuits with free-space optics enables novel applications like chip-scale sensing and atomic manipulation.
• A significant challenge is bridging the mode scale mismatch within planar fabrication limits.

Purpose of the Study:

• To create a versatile nanophotonic platform for efficient coupling between integrated photonic circuits and free-space optical modes.
• To overcome the mode scale mismatch using metasurfaces and mode converters.
• To enable controlled free-space optical beam manipulation directly from a chip.

Main Methods:

• Integration of a dielectric metasurface with an extreme photonic mode converter.
• Conversion of high-index photonic modes to a collimated Gaussian beam.
• Modification of the beam by a planar, integrated, low-loss metasurface for controlled polarization, phase, and intensity.

Main Results:

• Efficient coupling to free-space radiation at 780 nm wavelength with controlled polarization, phase, and intensity.
• Demonstration of high numerical aperture, diffraction-limited focusing to a sub-micron spot.
• Simultaneous conversion from linear to elliptical polarization achieved.

Conclusions:

• The developed nanophotonic platform facilitates efficient chip-to-free-space optical interfacing.
• Batch fabrication of all device components enables scalable, low-cost hybrid photonic systems.
• Potential applications include bio-sensing, nonlinear signal processing, and quantum sensing.