We study subwavelength confinement of electromagnetic wave and their nonlinearity in nanometer and angstrom-scale antennas. By using a new patterning technology based on atomic layer deposition, chemical vapor deposition and simple adhesive tape-based planarization creates vertically oriented gaps in opaque metal film along the entire contour of a millimeter-sized pattern with gap widths less than a nanometer. Squeezing terahertz electromagnetic waves through these nanometer and angstrom-scale gaps leads to giant field enhancements, nonlocal electromagnetic effects and light-induced electron tunneling.

See : Physical Review Letters 115 125501 (2015) *Cover Article
Nature Communications 4, 2361 (2013) *Featured Article

We are interested in understanding extreme-subwavelength optical phenomena, in the λ/10,000 range. A good example is λ=300 μm, 1 THz wave that passes through 50 nm metallic slit, a terahertz nano-scale phenomenon. Through collaborative experimental and theoretical research program, we want to explore the heretofore virgin territory of optics in λ/10,000 regime and optics in Thomas-Fermi length scale of 0.1 nm.
See also : News and Views on Nature Photonics 3, 152 (2009)

We also pursue a deeper understanding on optics by observing electric and magnetic phenomena separately. Nontrivial magnetic-electric relationships are becoming increasingly important, while there are few suitable methods for direct measurements of the each optical field. Our research on vectorial mapping of electric/magnetic field will greatly benefit the field of nanophotonics, such as in optical metamaterial development.

See also : Optics Express, 21, 5625 (2013) & Spotlight on Optics, Nature Communications, 2, 451 (2011)