Nanophotonics is the study of light-matter interactions between light and nanoscale objects. The length scales involved in nanophotonics are of great scientific interest because objects on this scale give us access to new optical properties and functionalities that are not available in bulk materials.
Image credit: asharkyu/Shutterstock.com
Examples of nanophotonic devices include photonic crystals, waveguides, nanoantennas. Many nanophotonic devices are made of dielectric or metallic structures, where the device is structured to enhance to promote the light-matter interactions of interest. These often involve the creation of plasmonic resonances that can be manipulated to improve signal levels in detection and spectroscopy experiments.
Key application areas for nanophotonics include sensing, with point-of-care medical diagnostics being a particular growth area, display technologies and optoelectronic or photovoltaic devices. In addition to fabricated devices, there are examples of nanophotonic structures in the natural world, including butterfly wings and peacock features that are examples of photonic crystals containing assemblies of nanoparticles.
Nanophotonic technologies in medical devices
Nanophotonics can be used for off-line medical devices for biosensing, such as the detection of specific DNA aptamers to identify a particular disease, or for point-of-care devices. For biosensing applications, the nanophotonic device reads a change in signal when a particular biomarker binds.
Nanophotonic biosensors often make use of a change in optical response upon binding the biomarker as a detectable signal. The integration of nanophotonic technologies can help by increasing the signal levels associated with the binding event and improving the sensitivity so that even trace amounts of biomarkers can be detected.
Point-of-care diagnosis involves the use of portable devices that can be used for diagnosis directly on the patient. Many devices avoid the need for painful biopsies and can be connected to algorithms for automated analysis and diagnosis. Because many point-of-care devices are much simpler to use than specialized medical procedures such as biopsies and do not require physicians for a full diagnosis, nanophotonic-based point-of-care devices are a great way to improve efficiency in health care. These devices also present opportunities for healthcare in non-clinical settings.
Other examples of nanophotonic devices in medical settings include nanophotonics for rapid diagnosis of COVID-19 and detection of Gram-negative bacteria.
Using nanophotonics to control light
Controlling and shaping the properties of light is at the heart of optical applications. With the development of optoelectronics and optical communication, as well as the push to use light-based technologies in solar energy harvesting, finding ways to efficiently convert light into electricity has been a key focus for scientific and technological developments in the field of nanophotonics.
Silicon-based devices remain the most popular and widely used of the available solar cell technologies and materials. Although materials such as perovskites have seen better efficiency gains since their initial development, silicon-based solar cells have proven to be the most practical and viable technology to date.
Nanophotonic structures are now being integrated into solar cells, especially metallic nanoparticles, to improve their light-harvesting efficiencies and develop plasmonic solar cells. Metal nanoparticles can now be manufactured relatively cheaply, and their broad and strong absorption spectrum over a wide range of the solar spectrum makes them ideal for photovoltaics.
Nanostructuring of solar cells is another way to improve light-harvesting efficiency, and structures such as nanowires and nanoparticles can help improve light management. Efficiency gains are key to being able to shrink solar cell devices and make smaller device areas viable.
Other applications of nanophotonics in the control of light include the development of metalene technologies that allow unprecedented levels of control over light’s focus, polarization, and other properties. Metallenses can be much more compact than traditional optics and are designed to avoid creating aberrations in the beam with great promise for device miniaturization in applications such as spectroscopy and sensing or even in manufacturing of nanophotonic devices.
What is the future of nanophotonics?
One of the biggest challenges has been the manufacture of the nanophotonic devices themselves. Creating nanoscale objects requires manufacturing techniques that work at the nanoscale with nanoscale precision and accuracy.
Methods such as focused ion beam lithography combined with electron microscopy approaches that have sufficient spatial resolution to visualize components have been essential in creating some of the complex architectures required to fully exploit nanophotonic effects.
Many nanophotonic devices are now created in a bottom-up approach using ion beam deposition to create the structure layer by layer. With the use of interferometers for positional stability of ion sources and focusing optics to achieve focused beam sizes of <10 nm, the creation of complex nanophotonic structures is increasingly usual, but there are still many challenges to overcome.
Direct laser writing is another approach to nanophotonic fabrication that makes use of lasers with high peak powers and photoresists. Although many structures, including complex chiral materials, have been created using this approach, direct laser writing still faces the same challenge as focused ion beam fabrication of very slow writing speeds.
The possibilities of orders of magnitude of signal enhancement for sensing applications have driven much of the development of nanophotonics and will continue to drive fabrication approaches to fully exploit the possibilities offered by sensors capable of detecting only single molecules.
Nanophotonics; A game changer for biosensing
References and further reading
Dastmalchi, P., A. Haddadpour, and G. Veronis. 2014. Nanophotonics: Devices for Manipulating Light at the Nanoscale. Woodhead Publishing Limited.
Starkey, Tim, and Pete Vukusic. 2013. “Principles of Light Manipulation in Biological Photonic Systems.” Nanophotonics 2(4):289–307.
Anker, JN, Hall, WP, Lyandres, O., Shah, NC, Zhao, J., and Duyne, RP Van. (2008). Biodetection with plasmonic nanosensors. Nature Materials, 7, 442–453.
Yager, P., Domingo, GJ and Gerdes, J. (2008). Point-of-care diagnostics for global health. Ann. Reverend Biomed. Eng, 10, 107–144.
Ruiz-Vega, G., Soler, M. and Lechuga, LM (2021). Nanophotonic biosensors for the diagnosis of COVID-19 at the point of care and surveillance of the coronavirus. JPhys Photonics, 3(1).
Jia, Baohua. 2015. “Nanophotonic Silicon Solar Cells: Status and Future Challenges.” Nanotechnology Review 4(4):337–46.
Luo, X. (2018). Plasmonic metals for nanofabrication. Nat Sci Rev, 5(2), 137–138.
Manoccio, Mariachiara, Marco Esposito, Adriana Passaseo, Massimo Cuscun and Vittorianna Tasco. 2021. “Focused Ion Beam Processing for 3D Chiral Photonics Nanostructures.” Micromachines 12:6. https://www.mdpi.com/2072-666X/12/1/6/htm
Disclaimer: The views expressed here are those of the author expressed privately and do not necessarily represent the views of AZoM.com Limited T/A AZoNetwork the owner and operator of this website. This disclaimer forms part of the Terms and Conditions of Use for this website.