Hexbyte Glen Cove Thin is now in to turn terahertz polarization thumbnail

Hexbyte Glen Cove Thin is now in to turn terahertz polarization

Hexbyte Glen Cove

Ultrathin, broadband polarization rotators are made possible by ultrathin carbon nanotube films developed at Rice University in 2016. The films of highly aligned single-walled nanotubes were first made in 2016. Credit: Kono Laboratory/Rice University

It’s always good when your hard work reflects well on you.

With the discovery of the giant rotation of light, that is literally so.

The ultrathin, highly aligned carbon nanotube films first made by Rice University physicist Junichiro Kono and his students a few years ago turned out to have a surprising phenomenon waiting within: An ability to make highly capable terahertz polarization rotation possible.

This rotation doesn’t mean the films are spinning. It does mean that polarized light from a laser or other source can now be manipulated in ways that were previously out of reach, making it completely visible or completely opaque with a device that’s extremely thin.

The unique optical rotation happens when linearly polarized pulses of light pass through the 45-nanometer film and hit the silicon surface on which it sits. The light bounces between the substrate and film before finally reflecting back, but with its polarization turned by 90 degrees.

This only occurs, Kono said, when the input light’s polarization is at a specific angle with respect to the nanotube alignment direction: the “magic angle.”

The discovery by lead author Andrey Baydin, a postdoctoral researcher in Kono’s lab, is detailed in Optica. The phenomenon, which can be tuned by changing the refractive index of the substrate and the film thickness, could lead to robust, flexible devices that manipulate .

Rice University physicists have made unique broadband polarization rotators with ultrathin carbon nanotube films. The films optically rotate polarized light output by 90 degrees, but only when the input light’s polarization is at a specific angle with respect to the nanotube alignment direction: the “magic angle.” Credit: Kono Laboratory/Rice University

Kono said easy-to-fabricate, ultrathin broadband polarization rotators that stand up to high temperatures will address a fundamental challenge in the development of terahertz optical devices. The bulky devices available until now only enable limited polarization angles, so compact devices with more capability are highly desirable.

Because easily passes through materials like plastics and cardboard, they could be particularly useful in manufacturing, quality control and process monitoring. They could also be handy in and for security screening, because many materials have unique spectral signatures in the terahertz range, he said.

“The discovery opens up new possibilities for waveplates,” Baydin said. A waveplate alters the polarization of light that travels through it. In devices like terahertz spectrometers used to analyze the molecular composition of materials, being able to adjust polarization up to a full 90 degrees would allow for data gathering at a much finer resolution.

“We found that specifically at far-—in other words, in the terahertz frequency range—this anisotropy is nearly perfect,” Baydin said. “Basically, there’s no attenuation in the perpendicular polarization, and then significant attenuation in the parallel direction.

“We did not look for this,” he said. “It was completely a surprise.”

He said showed the effect is entirely due to the nature of the highly aligned nanotube , which were vanishingly thin but about 2 inches in diameter. The researchers both observed and confirmed this giant polarization rotation with experiments and computer models.

“Usually, people have to use millimeter-thick quartz waveplates in order to rotate polarization,” said Baydin, who joined the Kono lab in late 2019 and found the phenomenon soon after that. “But in our case, the film is just nanometers thick.”

“Big and bulky waveplates are fine if you’re just using them in a laboratory setting, but for applications, you want a compact device,” Kono said. “What Andrey has found makes it possible.”



More information:
Andrey Baydin et al, Giant terahertz polarization rotation in ultrathin films of aligned carbon nanotubes, Optica (2021). DOI: 10.1364/OPTICA.422826

Citation:
Thin is now in to turn terahertz polarization (2021, May 20)
retrieved 21 May 2021
from https://phys.org/news/2021-05-thin-terahertz-polarization.html

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part may be reproduced without the written permission. The content is provided for information purposes only.

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Hexbyte Glen Cove Polarization increases with economic decline, becoming cripplingly contagious thumbnail

Hexbyte Glen Cove Polarization increases with economic decline, becoming cripplingly contagious

Hexbyte Glen Cove

Credit: Pixabay/CC0 Public Domain

The rise of populist movements is changing political systems around the world. As support for these “anti-elite” movements intensifies, many are scrambling to understand whether economic decline and intensifying inter-group conflict are playing a role.

A model developed by a team of researchers—including Nolan McCarty of Princeton University—shows how group polarization, rising inequality, and economic decline may be strongly connected.

The model develops a theory that group polarization tends to soar in times of economic duress and rising inequality. Yet, even after financial conditions improve, these divisions may remain deeply rooted.

This is why strengthened social safety nets are needed to help minimize conflict across social, ethnic, and , the researchers argue in Science Advances.

“Times arise when national unity is needed, like we’re seeing now with COVID-19, but we shouldn’t wait for a or war to bring people together. Policymakers and those in government should act now by investing in and protecting social safety nets that can prevent widening social and political divisions,” said McCarty, who is the Susan Dod Brown Professor of Politics and Public Affairs at the Princeton School of Public and International Affairs.

The authors’ model provides a theory to understand the root causes of the political polarization we see in the world today and what we can do to bring societies back together. Credit: Hertie School

McCarty worked on the model with Alexander Stewart of the University of Houston and Joanna Bryson of the Hertie School in Berlin, Germany. Using models of cultural evolution and , the team designed their model to examine people’s willingness to interact with people outside their own social group.

The model is based on a few assumptions—the first being that an individual’s economic success is tied to interactions with others and the performance of the underlying economy. They also assume that people tend to mimic the behavior of seemingly “successful” people so that social behaviors can spread through the public.

Lastly they assume that interactions within social in-group behavior is generally less risky with lower rewards while interactions with out-group members are more risky, but entail greater upside. This means that when economic conditions become more challenging, people will tend to prefer the safe bet of interacting with their own kind and avoid interactions with outsiders. As such behavior is mimicked, the interactions across groups declines precipitously.

Is it possible to predict when political polarization might lead to major social and civil conflicts? Credit: Hertie School

The model may be helpful in explaining political trends seen around the world. First, the model supports theories arguing that economic shocks embolden those far-right movements predicated vilifying social out-groups. For example, the Great Depression and Global Financial Crisis both led to increased support for right-wing populists in a number of countries including the United States, and the United Kingdom.

When it comes to inequality, most models suggest that a significant wealth gap tends to empower those on the left, as they will seek income redistribution. The researchers’ new model doesn’t necessarily show such a shift, but instead a general move away from interactions across social identity groups. Since cross-group interactions are economically valuable, society gets poorer.

Why is it hard to rid a society of polarization once it exists, even after economic conditions improve? Credit: Hertie School

“Rather than continue the unproductive debate over whether ‘economic anxiety’ or is most responsible for our deeply divided politics, scholars should spend more effort considering the debilitating feedback between economics and identity,” said McCarty.

The paper, “Polarization under rising inequality and ,” first appeared online in Science Advances on Dec. 11, 2020.



More information:
A.J. Stewart at University of Houston in Houston, TX el al., “Polarization under rising inequality and economic decline,” Science Advances (2020). advances.sciencemag.org/lookup … .1126/sciadv.abd4201

Citation:
Polarization increases with economic decline, becoming cripplingly contagious (2020, December 11)
retrieved 12 December 2020
from https://phys.org/news/2020-12-polarization-economic-decline-cripplingly-contagious.html

This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no
part may be reproduced without the written permission. The content is provided for information purposes only.

Read More Hexbyte Glen Cove Educational Blog Repost With Backlinks —