“Light Matter Coupling Strength Can Be Increased” Prove Penn University Researchers

In an important study, Penn University researchers have proved that the light-matter coupling strength which is still thought of as a constant property can now be increased, provided we implement proper finishing and fabrication techniques. The research is an important milestone in the designing of photonic devices involving the use of light instead of electricity. The study was undertaken under the guidance of Ritesh Agarwal, Asst. Professor. The members in the team were Pavan Nukala and Chang-Hee Cho, postdoctoral fellow Lambert van Vugt and graduate student Brian Piccione of Materials Science department, Penn’s school of Engineering and Applied science.


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A computer simulation of a one-dimensional cavity wave in a 200nm nanowire

Until recently, difficulty was always experienced in achieving a design having higher light matter coupling strength in the devices like the ones employed for higher temperature and low power. This is now solved by confining polaritons to nanoscale semiconductors.
Polaritons can be said to be a kind of hybrid particles. They are the combination of photons and excitons. Being quasi particles they enjoy the best properties of their parent materials. They are actually a combination of light and electricity because the excitons itself being the combination of electron and an electron hole.
Agarwal was of the opinion that when we are dealing with everyday objects, their surfaces and overall volume is very large. However, while working on a nanoscale, the ratio of number of atoms on surface to the number of atoms in volume assumes much larger role. This is what is observed with light matter strength. The property which is thought of as a constant increase significantly for sizes less than 100 nanometers. The etching techniques used by other researchers in constructing such minuscule structures had an effect of damaging the surface rendering the objects useless for experimentation purposes.
The team instead used cadmium sulfide nanowires and unlike other researchers didn’t etch the surface. The researchers relied on its self developed techniques of pacifying the surface.  The usage of silicon oxide shell prevented entrapment of excitons improving optical quality.
The research was not only focused on increasing the light matter strength but also to measure it. The team has succeeded in quantifying this coupling strength- a major boost in designing devices like nanophotonic circuit elements. The results obtained in the study are published in the journal #-Link-Snipped-#.#-Link-Snipped-#