Chiral metamaterials have stronger optical activity than natural materials within the terahertz frequencies, so they have attracted more attention. By arranging special silicon structures at terahertz frequencies, we propose an all-silicon-based extrinsic chirality structure with high outer circular dichroism in this paper. And its circular birefringence is also better than average. The properties of our all-silicon-based metamaterials are generated due to the resonance between the circularly polarized incident wave and the special silicon structure of the surface. The circular dichroism of the device due to transmission can reach 0.54. And we obtained the maximum polarization rotation angle can achieve 50°. In addition, the chirality of the device can be dynamically changed between 0.63THz-0.79THz. Such control can be achieved merely by changing the incident tilt angle. Our research can be applied to terahertz circular polarizer and polarimeter, which has great potential in optical path construction, light detection, signal transmission and processing.
In this paper, a polarization filter based on photonic crystal fiber (PCF) with nanoscale gold film is proposed and analyzed theoretically. The cross-section of the structure is composed of four-layer air holes with a hexagonal lattice and two symmetrical air holes in the sub-internal layer are coated with gold film. We research that the PCF structure parameters affect the performances of the polarization filter through employing the finite element method. It is indicated by the numerical results that the resonance strength in y-polarization direction can reach a most value of 272.8 dB/cm at the communication wavelength of 1.55 μm. The extinction ratio can be better than 20 dB within a wavelength range from 1.45 μm to 1.75 μm when the length of the PCF is longer than 500μm. Therefore, such a length can make the communication filtering effect be realized using a shorter fiber. The calculated results can provide some references to the design of polarization micro-filter devices.
Based on the influence of surface metal materials on electric field, a terahertz metamaterial absorber with a highly symmetrical open box was designed. Aiming at the traditional square ring absorber, the absorber is made of three open square rings and a pair of symmetrical strips of silicon. Starting from the structure and material of the absorber, the absorption rate of the absorber to the three-frequency band wave is regulated by changing the size of the surface metal ring, changing the thickness of the dielectric layer, changing the dielectric constant of the dielectric layer material, and adjusting the conductivity of the silicon material after the addition of semiconductor silicon. When no semiconductor silicon is added, the absorption rate of the absorber in the low frequency band reaches 94.77% and the absorption frequency band is 0.73thz. By increasing the thickness of dielectric layer, the phenomenon of redshift is obvious, which can realize the purpose of continuous frequency band absorption. By adding the silicon strip with symmetrical structure and changing the conductivity comparison, it is found that it can close the absorption peak in the high frequency band, reducing the absorption rate to less than %, and at the same time affecting the absorption rate of the low frequency band.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.