SciTech Connect

Title: Chiral THz metamaterial with tunable optical activity

Chiral THz metamaterial with tunable optical activity Optical activity in chiral metamaterials is demonstrated in simulation and shows actively tunable giant polarization rotation at THz frequencies. Electric current distributions show that pure chirality is achieved by our bi-Iayer chiral metamaterial design. The chirality can be optically controlled by illumination with near-infrared light. Optical activity, occurring in chiral materials such as DNA, sugar and many other bio-molecules, is a phenomenon of great importance to many areas of science including molecular biology, analytical chemistry, optoelectronics and display applications. This phenomenon is well understood at an effective medium level as a magnetic/electric moment excited by the electric/magnetic field of the incident electromagnetic (EM) wave. Usually, natural chiral materials exhibit very weak optical activity e.g. a gyrotropic quartz crystal. The optical activity of chiral metamaterials, however, can be five orders of magnitude stronger. Chiral metamaterials are made of sub-wavelength resonators lacking symmetry planes. The asymmetry allows magnetic moments to be excited by the electric field of the incident EM wave and vice versa. Recently, chiral metamaterials have been demonstrated and lead to prospects in giant optical activity, circular dichroism, negative refraction and reversing the Casmir force. These fascinating optical properties require strong chirality, which may be designed through the microscopic structure more » of chiral metamaterials. However, these metamaterials have a fixed response function, defined by the geometric structuring, which limits their ability to manipulate EM waves. Active metamaterials realize dynamic control of response functions and have produced many influential applications such as ultra-fast switching devices, frequency and phase modulation and memory devices. Introducing active designs to chiral metamaterials will give additional freedom in controlling the optical activity, and therefore enable dynamic manipulation of electromagnetic waves. This should prove useful for many potential applications. In this work, we show an active chiral metamaterial design with tunable giant optical activity. Our numerical simulations show the proposed chiral metamaterial has exceptionally strong polarization rotation with low transmission losses at THz frequencies, which makes it a very efficient material for tunable polarization rotators. Our preliminary experimental results (now shown here) show good agreements with numerical simulations. « less
Authors: ; ; ; ; ;
Publication Date:
OSTI Identifier:1024367
Report Number(s):LA-UR-10-02334; LA-UR-10-2334
TRN: US201119%%329
DOE Contract Number:AC52-06NA25396
Resource Type:Conference
Resource Relation:Conference: Metamorphose VI, 2010 ; September 13, 2010 ; Karlsruhe, Germany
Research Org:Los Alamos National Laboratory (LANL)
Sponsoring Org:DOE
Country of Publication:United States
Language:English
Subject: 36; ASYMMETRY; CHEMISTRY; CHIRALITY; DICHROISM; DNA; ELECTRIC CURRENTS; ELECTRIC FIELDS; ELECTROMAGNETIC RADIATION; MAGNETIC MOMENTS; MEMORY DEVICES; MODULATION; MOLECULAR BIOLOGY; OPTICAL ACTIVITY; OPTICAL PROPERTIES; POLARIZATION; REFRACTION; RESONATORS; RESPONSE FUNCTIONS; ROTATION; SACCHAROSE; SYMMETRY