Abstract-The effect of infrared plasmon on the performance of Si-based THz detectors

He Zhu, Jintao Xu, Jiaqi Zhu, Miao Wang, Huizhen Wu, Ning Li, Ning Dai

http://link.springer.com/article/10.1007/s10854-016-5598-7

Plasmons in metals have great impact on light emission, propagation, and detection in visible and infrared light wave frequencies. To explore plasmonic effect on the THz detection, both a backside-illuminated and a topside-illuminated blocking impurity band (BIB) THz detectors are developed and significant influence of plasmonic effect on the performance of BIB THz detectors is observed. The plasmonic effect in the heavily doped semiconductor layer of BIB THz detectors causes high reflectance of THz radiation which curtails the detection frequencies of the backside-illuminated BIB detectors. However, due to the advantages of flip-chip package and high quantum efficiency, the dark current, the responsivity, and the detectivity of the backside-illuminated detector shows superior characteristics to the topside-illuminated detector. The performance of the THz detector could be further improved with the suppression of the plasmonic effect.

Using plasmonics to transmit more data

http://phys.org/news/2016-02-plasmonics-transmit.html

Merely a decade ago, people were amazed that their cellular phones could send a simple text message. Now smartphones send and receive high-resolution photographs, videos, emails with large attachments, and much more. The desire for endless data has become insatiable.

"The ability to deliver information from one location to another has played a very important role in advancing human civilization," said Robert P.H. Chang, professor of materials science and engineering at Northwestern Engineering. "Today, we live in a digital world where the demand for the ability to transmit large amounts of data is growing exponentially."

To meet this high demand, Chang and his team developed a means to modulate light signals in the near-infrared wavelength region. Their work demonstrates a new scheme to control infrared plasmons, opening a new door for transmitting massive amounts of information.

The research appeared online on Monday, Feb. 22, 2016 in the Nature Photonics. Peijun Guo, a senior PhD student in Chang's laboratory, is the paper's first author.

A plasmon is a quantum particle that arises from collective oscillations of free electrons. By controlling the plasmons, researchers can enable optical switches, potentially permitting signals in optical fibers to be switched from one circuit to another—with ultimate high speeds in the terahertz.

Researchers have demonstrated active plasmonics in the ultraviolet to visible wavelength range using noble metals, such as gold. But controlling plasmons in the near- to mid-infrared spectral range—where noble materials suffer from excessive optical losses—is largely unexplored. Research in this area has recently attracted significant attention for its importance in telecommunications, thermal engineering, infrared sensing, light emission and imaging.

Chang's team successfully controlled plasmons in this technologically important range by using indium-tin-oxide (ITO) nanorod arrays. The low electron density of ITO enables a substantial redistribution of electron energies, which results in light signal modulation with very large absolute amplitude. By tailoring the geometry of the ITO nanorod arrays, researchers could further tune the spectral range of the signal modulation at will, which opens the door for improved telecommunications and molecular sensing.

"Our results pave the way for robust manipulation of the infrared spectrum," Chang said.

 Explore further: Theoretical calculations show graphene's potential for controlling nanoscale light propagation on a chip

More information: Ultrafast switching of tunable infrared plasmons in indium tin oxide nanorod arrays with large absolute amplitude, Nature Photonics, DOI: 10.1038/nphoton.2016.14

Read more at: http://phys.org/news/2016-02-plasmonics-transmit.html#jCp