Terahertz nanoresonators: Control and measurements

We discuss a new and exciting area whereby terahertz science and technology meet nano-world and thin-film technology. We first show that a lambda/30,000 nanogap on metal film can efficiently transmit terahertz electromagnetic waves whose wavelengths are in the millimeter range. It was found that the transmittance continues to increase as the frequency decreases with a dependence of 1/f. The field enhancement reaches the value of ~1000 at 0.1 THz. The accumulation of charges at metal edges via light-induced currents creates a large horizontal electric field, which in effect attracts the incoming light, while the magnetic field enhancement is only orders of unity. Turning into two-dimensional nanoresonator, we design nano-antenna arrays that allow perfect transmission. Nanoresonators on VO₂ thin films help amplify the available dynamic range for extinction and transmission when it undergoes insulator-metal phase transition.