Inverse design of photonic meta-structure for beam collimation in on-chip sensing

Area of Science:

• Photonics and Nanotechnology
• Optofluidics
• Integrated Optics

Background:

• Metasurfaces enable miniaturization of optical elements on a plane.
• Current research prioritizes optical detection miniaturization over on-chip optical excitation.
• On-chip optofluidic sensing requires efficient and compact optical excitation sources.

Purpose of the Study:

• To design a metasurface-based planar integrated photonic source beam collimator.
• To optimize the metasurface for enhanced performance in on-chip optofluidic sensing.
• To enable miniaturized and efficient on-chip optical excitation.

Main Methods:

• Iterative inverse design approach utilizing gradient descent optimization.
• Metasurface design and simulation.
• Fabrication of metasurface beam collimators.
• Experimental characterization and comparison with conventional gratings.

Main Results:

• The optimal metasurface design enhances illumination power by a factor of 5.
• The reinforced beam exhibits improved uniformity.
• The beam spot size increased approximately 3 times for the same device footprint.
• Performance was experimentally validated against uniform binary gratings.

Conclusions:

• The designed metasurface serves as an effective planar integrated photonic source beam collimator.
• This approach significantly improves illumination power and beam uniformity for on-chip applications.
• The technology is applicable to fluorescence imaging, Raman, and IR spectroscopy.
• Enables enhanced multiplexing of light sources for high-throughput biosensing.