Engineers at Ruhr-Universität Bochum have developed a novel concept for rapid data transfer via optical fibre cables. In current systems, a laser transmits light signals through the cables and information is coded in the modulation of light intensity. The new system, a semiconductor spin laser, is based on a modulation of light polarisation instead. Published on 3 April 2019 in the journal “Nature”, the study demonstrates that spin lasers have the capacity of working at least five times as fast as the best traditional systems, while consuming only a fraction of energy. Unlike other spin-based semiconductor systems, the technology potentially works at room temperature and doesn’t require any external magnetic fields. The Bochum team at the Chair of Photonics and Terahertz Technology implemented the system in collaboration with colleagues from Ulm University and the University at Buffalo.
Rapid data transfer is currently an energy guzzler
Due to physical limitations, data transfer that is based on a modulation of light intensity without utilizing complex modulation formats can only reach frequencies of around 40 to 50 gigahertz. In order to achieve this speed, high electrical currents are necessary. “It’s a bit like a Porsche where fuel consumption dramatically increases if the car is driven fast,” compares Professor Martin Hofmann, one of the engineers from Bochum. “Unless we upgrade the technology soon, data transfer and the Internet are going to consume more energy than we are currently producing on Earth.” Together with Dr. Nils Gerhardt and PhD student Markus Lindemann, Martin Hofmann is therefore researching into alternative technologies.
Circularly polarised light as information carrier
Provided by Ulm University, the lasers, which are just a few micrometres in size, were used by the researchers to generate a light wave whose oscillation direction changes periodically in a specific way. The result is circularly polarised light that is formed when two linear perpendicularly polarised light waves overlap.
In linear polarisation, the vector describing the light wave’s electric field oscillates in a fixed plane. In circular polarisation, the vector rotates around the direction of propagation. The trick: when two linearly polarised light waves have different frequencies, the process results in oscillating circular polarisation where the oscillation direction reverses periodically – at a user-defined frequency of over 200 gigahertz.
Speed limit as yet undetermined
“We have experimentally demonstrated that oscillation at 200 gigahertz is possible,” describes Hofmann. “But we don’t know how much faster it can become, as we haven’t found a theoretical limit yet.”
The oscillation alone does not transport any information; for this purpose, the polarisation has to be modulated, for example by eliminating individual peaks. Hofmann, Gerhardt and Lindemann have verified in experiments that this can be done in principle. In collaboration with the team of Professor Igor Žuti? and PhD student Gaofeng Xu from the University at Buffalo, they used numerical simulations to demonstrate that it is theoretically possible to modulate the polarisation and, consequently, the data transfer at a frequency of more than 200 gigahertz.
The generation of a modulated circular polarisation
Two factors are decisive in order to generate a modulated circular polarisation degree: the laser has to be operated in a way that it emits two perpendicular linearly polarised light waves simultaneously, the overlap of which results in circular polarisation. Moreover, the frequencies of the two emitted light waves have to differ enough to facilitate high-speed oscillation.
The laser light is generated in a semiconductor crystal, which is injected with electrons and electron holes. When they meet, light particles are released. The spin – an intrinsic form of angular momentum – of the injected electrons is indispensable in order to ensure the correct polarisation of light. Only if the electron spin is aligned in a certain way, the emitted light has the required polarisation – a challenge for the researchers, as spin alignment changes rapidly. This is why the researchers have to inject the electrons as closely as possible to the spot within the laser where the light particle is to be emitted. Hofmann’s team has already applied for a patent with their idea of how this can be accomplished using a ferromagnetic material.
Frequency difference through double refraction
The frequency difference in the two emitted light waves that is required for oscillation is generated using a technology provided by the Ulm-based team headed by Professor Rainer Michalzik. The semiconductor crystal used for this purpose is birefringent. Accordingly, the refractive indices in the two perpendicularly polarised light waves emitted by the crystal differ slightly. As a result, the waves have different frequencies. By bending the semiconductor crystal, the researchers are able to adjust the difference between the refractive indices and, consequently, the frequency difference. That difference determines the oscillation speed, which may eventually become the foundation of accelerated data transfer.
“The system is not ready for application yet,” concludes Martin Hofmann. “The technology has still to be optimised. By demonstrating the potential of spin lasers, we wish to open up a new area of research.”
Learn more: Spin lasers facilitate rapid data transfer
The Latest on: Spin lasers
[google_news title=”” keyword=”spin lasers” num_posts=”10″ blurb_length=”0″ show_thumb=”left”]
via Google News
The Latest on: Spin lasers
- Knuckles parents guide: The Sonic spin-off is LOL fun for the whole familyon April 26, 2024 at 10:00 am
Does Knuckles follow the same fun, PG-rated formula as the Sonic movies? Here's what parents need to know about the TV-PG age rating.
- Thom Yorke Keeps Exploring With Haunting Confidenza Soundtrackon April 26, 2024 at 9:16 am
Confidenza OST XL Recordings. Thom Yorke’s latest soundtrack opens with “The Big City,” an electro-symphonic slumber of synth bleeps and vocal blips. The albu ...
- Large Hadron Collider experiment zeroes in on magnetic monopoleson April 26, 2024 at 8:32 am
The late physicist Joseph Polchinski once said the existence of magnetic monopoles is "one of the safest bets that one can make about physics not yet seen." In its quest for these particles, which ...
- Laser light makes a material magneticon April 26, 2024 at 6:59 am
By applying laser light that is both circularly polarized – that is, its polarization traces out a corkscrew-like shape as it propagates – and resonant with the frequency of atomic oscillations within ...
- Shiny_Flakes: The Teenage Drug Lord Streaming: Watch & Stream Online via Netflixon April 26, 2024 at 6:31 am
Shiny_Flakes: The Teenage Drug Lord is a German documentary depicting the true story of Maximilian Schmidt, a young drug lord. It delves into the gritty world of cartels and gang conflicts, offering a ...
- Research investigates radio emission of the rotating radio transient RRAT J1854+0306on April 26, 2024 at 5:40 am
Using the Five-hundred-meter Aperture Spherical radio Telescope (FAST), Chinese astronomers have investigated radio emission from a rotating radio transient known as RRAT J1854+0306. Results of the ...
- Boeing’s Revival Roadmap Put to Test by Dwindling Time and Cashon April 24, 2024 at 1:01 pm
Boeing Co.’s assurance that it can pull itself together in the next three months is giving rise to two opposing questions: is that too little time to turn things around — or too long to withstand the ...
- The best deals from REI, Nike, Amazon and more ahead of Memorial Dayon April 24, 2024 at 9:03 am
One of our favorite Nike tennis shoes to date has to be the Air Max 90. Featuring plush cushioning, a foam midsole and a rubber waffle outsole, this tennis shoe provides support, comfort and just the ...
- A Paradigm Shift in RAM Is About to Make Computing Unstoppableon April 24, 2024 at 5:30 am
For more than two decades, the most advanced version of this technology—magnetoresistive RAM, or MRAM—has been the go-to tech for the kind of intense computing necessary in industrial, military, and ...
- How voxels, pink laser death and a shred of humanity made this breakneck arcade shooter an all-timeron April 22, 2024 at 2:00 am
Throughout PS3 and PS4’s lifespans, the Finnish studio established a reputation for reimagining all-action arcade classics with added depth and eye-melting visuals, culminating in 2017’s explosive Nex ...
via Bing News