School Seminar Program

Engineering Nonlinear Response at Nanoscale

Dr Mohsen Rahmani
Nonlinear Physics Centre, RSPE, ANU

At the beginning of the 20th century, researchers struggled to understand how electricity worked and how they might harness it. Today we are standing in a similar position as we contemplate the emergence of photonics and how it will continue its exponential growth over the coming years. It is no surprise that many consider photonics to be the technology revolution of the 21st Century, while 2015 is the UNESCO world year of light. The high frequency nature of light gives unmatched information capacity leaving no doubt that light is the ultimate means of conveying information. But when it comes to real world systems, in today`s technology, optical and electric signals have to be converted between each other many times, which introduces delays and additional power consumption. Nonlinear optics holds a great potential to circumvent these current limitations via eliminating the need for electronics altogether, whereby light is directly controlled by light. This is the heart of modern photonic functionalities, including diversifying lasers and light, material interaction and more importantly information technology. Unfortunately, this very weak effect must be built over long interaction distances within a nonlinear medium to get a significant effect, which together with difficulties of nanoscale integration makes nonlinear optics an unsuitable option in miniaturized nanoscale chips.

In this seminar, I will discuss recent progress in extracting decent nonlinear responses at the nanoscale. In fact, nanoscale metallic particles are demonstrated to be excellent candidates because of their high optical nonlinearities. But the current argument in this favour is that loss issue and relatively low heat resistance of metallic structures against high power lasers bring this progress to the bottleneck. I will then outline the newly explored potentials of dielectrics and semiconductors, as well as hybrid systems, which offer unique opportunities for generating large nonlinear effects due to remarkable heat resistance and very low losses in combination with multipolar characteristics of both electric and magnetic resonant optical modes.

Dr Mohsen Rahmani graduated with PhD from National University of Singapore. After spending two years at Imperial College London as a research associate, Dr. Rahmani has recently joined The Australian National University to pursue his research activities in Nonlinear Physics Centre. Dr. Rahmani’s initial research direction was focused on the linear optical properties of wavelength scale structures. At the fundamental level, he studied the concepts of surface plasmon resonances and various couplings and interactions. He also actively contributed to design and development of several micro/nanodevices for ultra-sensitive detection of bio/chemical molecular vibrational modes from visible to infrared frequencies. His current interest and contribution is devoted to the nonlinear properties of nanoscale structures.

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