Introduction
Optical metasurfaces have revolutionized wavefront engineering through subwavelength resonant nanostructures. This article explores how Silicon nanodisks actively manipulate light waves. What sets these nanodisks apart is their size.
Typically, less than 100 nanometers in diameter, this minuteness allows them to exploit unique quantum effects, enabling enhanced light matter interaction. An interaction highly useful in making Photonic Integrated Circuits. 
The Light controllers
In the preceding discussion, we established that Silicon nanodisks are the nanostructures constituting metasurfaces.Their low dissipative losses above 1.1 µm wavelength and prevalence in modern technology make silicon an attractive material choice for optical metasurfaces. The small size enhances the interaction between light and matter.
But how do they do this?
It leverage quantum effects i.e. the peculiar behaviour of electrons at the nanoscale. These quantum effects provide unique advantages, allowing precise control over the interaction with light.
Envision the nanodisks as minute building blocks, actively confining electrons and crafting customized energy levels. This quantum confinement allows engineers to tune the optical properties by adjusting the size and shape of the nanodisks. Just as tuning a musical instrument produces different sounds, tuning nanodisks enables precise control over the interaction with light, facilitating customized optical behaviour.
Read More: What is South Korea’s $471 Billion Bet on Building a Global Semiconductor industry
Fabrication of silicon nanodisks
To fabricate subwavelength lattices of silicon nanodisks, the process employs standard silicon-on-insulator technology. It involves depositing a thin layer of silicon onto an insulating substrate, typically silicon dioxide. Researchers then apply advanced lithography techniques to pattern and etch the silicon layer into nanodisk structures with various radii.
Experimental results demonstrate the full phase coverage and high transmission efficiency achieved in metasurfaces composed of arrays of silicon nanodisks. They provide complete phase coverage from 0 to 2π and achieve high transmission efficiency for various nanodisk radii. Essentially, it highlights the successful demonstration of these metasurfaces’ capability to manipulate the phase of transmitted light across the entire range, while maintaining high transmission efficiency.
Applications:
Photonic Integrated Circuits (PICs)
Silicon nanodisks are integrated into waveguides to guide and control the flow of light in PICs. Their ability to confine light within the nanoscale dimensions enhances the efficiency of information transfer in optical communication systems.
Polarizers
It act as effective polarizers in PICs, facilitating the manipulation of polarized light for diverse applications, including optical sensing and communication.
Photonic Crystal Biosensors
Metasurface biosensors. (a) Photograph. (b) The metasurface biosensor holder. Tubes are connected. Green spot is focused LED light for excitation. (c) Schematic of immobilized array of silicon nanodisks.
Silicon nanodisks contribute to the development of photonic crystal biosensors, providing a platform for highly sensitive and label-free detection of biomolecules. The nanoscale dimensions of silicon nanodisks increase the surface area available for interaction with biomolecules, enhancing the sensitivity of biosensors.
Conclusion
Silicon nanodisks represent a quantum leap in semiconductor innovation, with applications spanning from Photonic Integrated Circuits to biosensors. Their ability to manipulate light at the nanoscale opens up new possibilities in communication, sensing, and healthcare technologies. As researchers continue to explore and refine the capabilities of silicon nanodisks, we can expect further advancements that will shape the future of nanoscale electronics and photonics.
