School Seminar Program
Towards low-loss optical metamaterials
Dr. Andrey Miroshnichenko
Nonlinear Physics Centre
Generic natural materials exhibit various dielectric permittivity at optical frequencies. In contrast, the magnetic permeability is always close to its free space value in the optical range. Thus, in all conventional optical materials and devices, only the electric component of light is directly controlled. Recently, however, the emergence of metamaterial research has fundamentally altered the situation. Artificial magnetism can now be achieved at higher frequencies by specially designed “meta-atoms” – functional units of the metamaterial that are smaller than the wavelength. The canonical subwavelength “meta-atom” is a split ring resonator (SRR) that consists of an inductive metallic ring with a gap. The basic principle behind this design is that SRR can support a principal eigenmode with a circular current distribution that gives rise to a magnetic moment. But, the intrinsic losses put a fundamental limit for downscaling the SRRs for obtaining an efficient magnetic response in the optical range. Spherical silicon nanoparticles with sizes of a few hundreds nanometers can be considered as an attractive alternative. According to theoretical predictions based on Mie theory they can exhibit strong magnetic resonances in the visible spectral range. The basic mechanism of excitation of such modes inside the nanoparticles is very similar to that of SRRs, but with one important difference that silicon nanoparticles have much smaller losses. The magnetic resonance arises due to excitation of a particular mode inside the particles with a circular displacement current of the electric field. The spectral position of the magnetic resonance can be tuned throughout the whole visible spectral range from violet to red by changing the nanoparticle size in the range from 100 to 200 nm. Recently, we have fabricated silicon nanoparticles by laser ablation technique and experimentally demonstrated that such nanoparticles, indeed, have a strong magnetic dipole resonance in visible spectral range. It makes silicon nanoparticles the best candidates for lossless magnetic response at high frequencies. The regular arrays of such bi-spherical elements will allow for development of all-dielectric optical 3D metamaterials.
Andrey Miroshnichenko obtained his PhD in 2003 from the Max-Planck Institute for Physics of Complex Systems in Dresden, Germany. In 2004 he moved to Australia to join the Nonlinear Physics Centre at ANU. During this time Dr. Miroshnichenko made fundamentally important contributions to the field of photonic crystals and bringing the concept of the Fano resonances to photonics. In 2007 Dr. Miroshnichenko was awarded by APD Fellowship from the Australian Research Council. It allowed him to initiate the research on a new class of tunable photonic structures infiltrated with liquid crystals. Last year he was awarded by Future Fellowship from the Australian Research Council. The current topics of his research are nonlinear nanophotonics, resonant interaction of light with nanoclusters, including optical nanoantennas and metamaterials.
Refreshments will be held in the Tea Room after the Seminar (around 5pm)