Dan's Biz Bookshelf: 'Getting Naked: A Business Fable'
The Chemical Connection: Common Misconceptions in Wet Processing
It’s Only Common Sense: Selling to Engineers
Nanoscale One-Way-Street for Light
December 16, 2015 | Technische Universität WienEstimated reading time: 3 minutes
If light is able to propagate from left to right, the opposite direction is usually allowed as well. A beam of light can normally be sent back to its point of origin, just by reflecting it on a mirror. Researchers at TU Wien have developed a new device for breaking this rule. Just like in an electrical diode, which allows current to pass only in one direction, this glass fibre-based device transmits light only in one direction. The one-way-rule holds even if the pulse of light that passes through the fibre consists of only a few photons. Such a one-way-street for light can now be used for optical chips and may thus become important for optical signal processing.
Optical Signal Processing Instead of Electronics
Elements which allow light to pass in only one direction are called “optical isolators”. “In principle, such components have been around for a long time”, says Arno Rauschenbeutel, from the Vienna Center for Quantum Science and Technology at the Atominstitut at TU Wien. “Most optical isolators, however, are based on the Faraday effect: A strong magnetic field is applied to a transparent material between two crossed polarization filters. The direction of the magnetic field then determines the direction in which light is allowed to pass.”
For technical reasons, devices using the Faraday effect cannot be constructed at the nanoscale – an unfortunate fact, because this would have many interesting applications. “Today, researchers seek to build optical integrated circuits, similar to their electronic counterparts”, says Rauschenbeutel. Other methods for breaking this symmetry only work at very high intensities. But in nanotechnology, an ultimate goal is to work with extremely faint light signals, which may even consist of individual photons.
Glass Fibres and Atoms
Arno Rauschenbeutel’s team chose a completely different approach: Alkali atoms were coupled to the light field of an ultrathin glass fibre. In a glass fibre, the light can propagate forwards or backwards. There is, however, another property of light which has to be taken into account: the direction of oscillation of the light wave, also called the polarization.
The interaction of light and the glass fibre modifies the oscillation state of the light. “The polarization rotates, much like a helicopter’s rotor”, says Arno Rauschenbeutel. The sense of rotation depends on whether the light travels forwards or backwards. In one case, the light wave oscillates clockwise and in the other, counterclockwise. The direction of propagation and the state of oscillation of the light wave are locked to each other.
If the alkali atoms are prepared in the right quantum state and coupled to the light in the ultrathin glass fibre, it is possible to make them react differently to the two senses of light rotation. “The light in the forward direction is not affected by the atoms. However, light which travels backwards and consequently rotates the other way around, couples to the alkali atoms and is scattered out of the glass fibre”, says Arno Rauschenbeutel.
Page 1 of 2
Share on:
Suggested Items
Rules of Thumb: Design007 Magazine, November 2024
11/11/2024 | I-Connect007 Editorial TeamRules of thumb are everywhere, but there may be hundreds of rules of thumb for PCB design. They’re built on design formulas, fabricators’ limitations, and tribal knowledge. And unfortunately, some longtime rules of thumb should be avoided at all costs. How do we separate the wheat from the chaff, so to speak?
Connect the Dots: Best Practices for Prototyping
09/21/2023 | Matt Stevenson -- Column: Connect the DotsPCB prototyping is a critical juncture during an electronic device’s journey from concept to reality. Regardless of a project’s complexity, the process of transforming a design into a working board is often enlightening in terms of how a design can be improved before a PCB is ready for full production.
The Drive Toward UHDI and Substrates
09/20/2023 | I-Connect007 Editorial TeamPanasonic’s Darren Hitchcock spoke with the I-Connect007 Editorial Team on the complexities of moving toward ultra HDI manufacturing. As we learn in this conversation, the number of shifting constraints relative to traditional PCB fabrication is quite large and can sometimes conflict with each other.
Asia/Pacific AI Spending Surge to Reach a Projected $78 Billion by 2027
09/19/2023 | IDCAsia/Pacific spending on Artificial Intelligence (AI) ), including software, services, and hardware for AI-centric systems will grow to $78.4 billion in 2027, according to International Data Corporation's latest Worldwide Artificial Intelligence Spending Guide.
Intel to Sell Minority Stake in IMS Nanofabrication Business to TSMC
09/13/2023 | IntelIntel Corporation announced that it has agreed to sell an approximately 10% stake in the IMS Nanofabrication business to TSMC. TSMC’s investment values IMS at approximately $4.3 billion, consistent with the valuation of the recent stake sale to Bain Capital Special Situations.