55 research outputs found
Full-range Gate-controlled Terahertz Phase Modulations with Graphene Metasurfaces
Local phase control of electromagnetic wave, the basis of a diverse set of
applications such as hologram imaging, polarization and wave-front
manipulation, is of fundamental importance in photonic research. However, the
bulky, passive phase modulators currently available remain a hurdle for
photonic integration. Here we demonstrate full-range active phase modulations
in the Tera-Hertz (THz) regime, realized by gate-tuned ultra-thin reflective
metasurfaces based on graphene. A one-port resonator model, backed by our
full-wave simulations, reveals the underlying mechanism of our extreme phase
modulations, and points to general strategies for the design of tunable
photonic devices. As a particular example, we demonstrate a gate-tunable THz
polarization modulator based on our graphene metasurface. Our findings pave the
road towards exciting photonic applications based on active phase
manipulations
The fast light of CsI(Na) crystals
The responds of different common alkali halide crystals to alpha-rays and
gamma-rays are tested in our research. It is found that only CsI(Na) crystals
have significantly different waveforms between alpha and gamma scintillations,
while others have not this phenomena. It is suggested that the fast light of
CsI(Na) crystals arises from the recombination of free electrons with
self-trapped holes of the host crystal CsI. Self-absorption limits the emission
of fast light of CsI(Tl) and NaI(Tl) crystals.Comment: 5 pages, 11 figures Submit to Chinese Physics
The Intelligent Transportation System Using the Infrared Sensors Based on the ZigBee Protocol and Eclipse
There are more and more cars. The traffic jam cost people a lot of time on the road. This system got the number of the cars in waiting on every crossroad by the infrared sensors in the CC2530. Based on the Zigbee protocol, the routers embedded in the infrared sensors sent the information of cars in waiting to the coordinator wirelessly. Then the coordinator sent the information to the website which is developed on the Eclipse platform through the serial port. People can check the designated crossroad whether there is the traffic jam by smart telephone or the web browser. This system can release the newest information. It can be widely applied in the transportation system
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