High extinction ratio terahertz wire-grid polarizers with connecting bridges on quartz substrates.

A terahertz (THz) wire-grid polarizer with metallic bridges on a quartz substrate was simulated, fabricated, and tested. The device functions as a wide-band polarizer to incident THz radiation. In addition, the metallic bridges permit the device to function as a transparent electrode when a DC bias is applied to it. Three design variations of the polarizer with bridges and a polarizer without bridges were studied. Results show the devices with bridges have average s-polarization transmittance of less than -3 dB and average extinction ratios of approximately 40 dB across a frequency range of 220-990 GHz and thus are comparable to a polarizer without bridges.

Emulating Nonreciprocity with Spatially Dispersive Metasurfaces Excited at Oblique Incidence.

Ultrathin metasurfaces supporting transverse surface currents provide extreme electromagnetic wave front and polarization control. Here, it is shown that adding longitudinal (normal) surface currents significantly expands the scope of electromagnetic phenomena that can be engineered with reciprocal materials. In particular, these metasurfaces are inherently spatially dispersive, which allows them to emulate nonreciprocal phenomena. It is analytically shown that spatially dispersive metasurfaces are effectively self-biased by the transverse momentum of the incident wave front. Long-standing notions of what makes a metasurface reciprocal are reinvestigated, and generalized reciprocity relations are derived. Several metasurfaces are designed that imitate Faraday rotation and optical isolation when illuminated with obliquely incident plane waves and normally incident vortex beams. These new surfaces break the inherent symmetry of previous metasurface designs, enabling low-profile devices with unprecedented functionality.

High performance bianisotropic metasurfaces: asymmetric transmission of light.

It is experimentally shown that bianisotropic metasurfaces allow for extreme polarization control of light with high performance. A metasurface providing asymmetric transmission (i.e., polarization conversion) of circularly polarized light is reported at a wavelength of 1.5 µm. The experimental transmittance and extinction ratio are 50% and 20:1, which represents an order of magnitude improvement over previous optical structures exhibiting asymmetric transmission. The metasurface consists of patterned gold sheets that are spaced at a subwavelength distance from each other. The same design and fabrication processes can be used in the future to completely control the phase, amplitude, and polarization of light.

Efficient light bending with isotropic metamaterial Huygens' surfaces.

Metamaterial Huygens' surfaces manipulate electromagnetic wavefronts without reflection. A broadband Huygens' surface that efficiently refracts normally incident light at the telecommunication wavelength of 1.5 µm is reported. The electric and magnetic responses of the surface are independently controlled by cascading three patterned, metallic sheets with a subwavelength overall thickness of 430 nm. The peak efficiency of the device is significantly enhanced by reducing the polarization and reflection losses that are inherent to earlier single-layer designs.

Metamaterial Huygens' surfaces: tailoring wave fronts with reflectionless sheets.

Huygens' principle is a well-known concept in electromagnetics that dates back to 1690. Here, it is applied to develop designer surfaces that provide extreme control of electromagnetic wave fronts across electrically thin layers. These reflectionless surfaces, referred to as metamaterial Huygens' surfaces, provide new beam shaping, steering, and focusing capabilities. The metamaterial Huygens' surfaces are realized with two-dimensional arrays of polarizable particles that provide both electric and magnetic polarization currents to generate prescribed wave fronts. A straightforward design methodology is demonstrated and applied to develop a beam-refracting surface and a Gaussian-to-Bessel beam transformer. Metamaterial Huygens' surfaces could find a wide range of applications over the entire electromagnetic spectrum including single-surface lenses, polarization controlling devices, stealth technologies, and perfect absorbers.

Direct transfer patterning of electrically small antennas onto three-dimensionally contoured substrates.

A direct transfer patterning process is presented that allows metallic patterns to be stamped onto a contoured substrate. This process was used to make some of the most efficient electrically small antennas to date, while maintaining bandwidths approaching the physical limit.

Nucleotide sequence of the p53 cDNA of beluga whale (Delphinapterus leucas).

The cDNA (DNA complementary to RNA) of the p53 gene of the beluga whale (Delphinapterus leucas) was sequenced by the method of 5'- and 3'-rapid amplification of cDNA ends (RACE) with the cDNA made for the RNA obtained from fresh peripheral blood leukocytes isolated from two animals. Primers for the RACE method were synthesized based on the sequence of the DNA of beluga whale corresponding to exon 5 of the human p53 gene, which was determined after amplification of the DNA isolated from the liver from a beluga whale by using a pair of primers for the human sequence. The sequenced cDNA had a 2150-nucleotide length and contained the whole region corresponding to human exons 1 through 11. The reading frame was 1164 bp (base pair) long and began in exon 2 and ended in exon 11, coding for a 387-amino acid protein. The nucleotide sequence of the reading frame showed high similarity over 85% with pig, sheep, cow, and human genes. The similarities with the former two animals at the amino acid level were also more than 85%. Lower similarity of the beluga whale p53 gene was also found with those of lower tetrapods, fish and invertebrates.