ABSTRACT
Indium-tin-oxide nanowhiskers were employed as transparent electrodes in a liquid-crystal terahertz phase shifter. Transmittance of the device was as high as â¼75%. Phase shift exceeding π/2 at 1.0 THz is achieved in a â¼500 µm-thick cell. The driving voltage required for the device operating as a quarter-wave plate was as low as 17.68 V (rms), an improvement of nearly an order of magnitude over previous work.
Subject(s)
Metal Nanoparticles/chemistry , Tin Compounds/chemistry , Electricity , Electrodes , Liquid Crystals , Optical Devices , Optical PhenomenaABSTRACT
This paper reports the implementation and integration of a self-assembled nanoporous anodic aluminum oxide (np-AAO) film and liquid crystal (LC) on an ITO-glass substrate for liquid crystal display (LCD) panel applications. An np-AAO layer with a nanopore array acts as the vertical alignment layer to easily and uniformly align the LC molecules. Moreover, the np-AAO nanoalignment layer provides outstanding material properties, such as being inorganic with good transmittance, and colorless on ITO-glass substrates. In this application, an LCD panel, with the LC on the np-AAO nanoalignment layer, is successfully implemented on an ITO-glass substrate, and its performance is demonstrated. The measurements show that the LCD panel, consisting of an ITO-glass substrate and an np-AAO layer, has a transmittance of 60-80%. In addition, the LCD panel switches from a black state to a bright state at 3 V(rms), with a response time of 62.5 ms. In summary, this paper demonstrates the alignment of LC on an np-AAO layer for LCD applications.
ABSTRACT
Fano resonances are features in absorption, scattering or transport spectra resulting from the interaction of discrete and continuum states. They have been observed in a variety of systems. Here, we report a many-body Fano resonance in bilayer graphene that is continuously tunable by means of electrical gating. Discrete phonons and continuous exciton (electron-hole pair) transitions are coupled by electron-phonon interactions, yielding a new hybrid phonon-exciton excited state. It may also be possible to control the phonon-exciton coupling with an optical field. This tunable phonon-exciton system could allow novel applications such as phonon lasers.
ABSTRACT
The electronic bandgap is an intrinsic property of semiconductors and insulators that largely determines their transport and optical properties. As such, it has a central role in modern device physics and technology and governs the operation of semiconductor devices such as p-n junctions, transistors, photodiodes and lasers. A tunable bandgap would be highly desirable because it would allow great flexibility in design and optimization of such devices, in particular if it could be tuned by applying a variable external electric field. However, in conventional materials, the bandgap is fixed by their crystalline structure, preventing such bandgap control. Here we demonstrate the realization of a widely tunable electronic bandgap in electrically gated bilayer graphene. Using a dual-gate bilayer graphene field-effect transistor (FET) and infrared microspectroscopy, we demonstrate a gate-controlled, continuously tunable bandgap of up to 250 meV. Our technique avoids uncontrolled chemical doping and provides direct evidence of a widely tunable bandgap-spanning a spectral range from zero to mid-infrared-that has eluded previous attempts. Combined with the remarkable electrical transport properties of such systems, this electrostatic bandgap control suggests novel nanoelectronic and nanophotonic device applications based on graphene.
ABSTRACT
We describe the synthesis of periodic waveforms consisting of a train of pulses that are 0.83 cycles long and have an electric field pulse width of 0.44 fs using 7 Raman sidebands generated by molecular modulation in H2. We verify by optical correlation that the carrier-envelope phase is constant in these waveforms when they are synthesized from commensurate sidebands. The estimated overall shift of the carrier-envelope phase is less than 0.18 cycles from the first to the last pulse of nearly 10(6) pulses in the pulse train.
ABSTRACT
Phase shift exceeding tau/2 at 1 THz is demonstrated by using electrically controlled birefringence in a homeotropically aligned nematic liquid crystal (E7) cell, 570 microm in thickness. The driving voltage required for a phase shift of 90 degrees is 125 V (rms). We demonstrate that the phase shifter works as an electrically switchable quarter-wave plate at 1 THz. The device can also be used as an electrically tuned phase compensator around the quarter-wave point near 1 THz.
