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
- When injecting pure spin into chiral materials, direction matterson May 4, 2024 at 1:31 am
Researchers from North Carolina State University and the University of Pittsburgh studied how the spin information of an electron, called a pure spin current, moves through chiral materials. They ...
- Amazon's bestselling electric spin scrubber sold 20,000 times recently and is 68% offon May 3, 2024 at 1:00 pm
"It has made my life so much easier." ...
- Quantum breakthrough: MIT physicists achieve record-breaking proximity of atomson May 3, 2024 at 12:53 am
However, researchers at MIT have shattered this barrier, developing a groundbreaking technique that positions atoms a staggering ten times closer – a mere 50 nanometers apart. To put this in ...
- New sensor detects errors in MRI scanson May 2, 2024 at 3:33 pm
A new prototype sensor is capable of detecting errors in MRI scans using laser light and gas. The new sensor can thereby do what is impossible for current electrical sensors -- and hopefully pave the ...
- Good vibrations: Low-energy lasers induce atomic excitation in semiconductor materialson May 2, 2024 at 9:22 am
Semiconductors are a cornerstone of next-generation technology, so a new method to excite atoms in semiconductor materials is likely to excite a broad range of researchers and industries as well.
- Physicists arrange atoms in extremely close proximityon May 1, 2024 at 5:00 pm
When the two beams travel through a super-cooled cloud of atoms, the atoms can orient their spin in opposite directions, following either of the two lasers' polarization. The result is that the beams ...
- Iron & Wine Find Hope in Despair in Hope in Despairon May 1, 2024 at 9:37 am
“There’s a wealth of opportunity clinging to the world,” Beam sings on “Bag of Cats.” “You’ll never find a better place to die.” More from Spin: The 50 Best Songs of 2002 Modest Mouse: Our 2004 ...
- BREAKTHROUGH : Lightsolver Makes Ultrafast Laser Based Computerson April 27, 2024 at 5:00 pm
LightSolver, creator of a new laser-based computing paradigm, announced a breakthrough in quantum-inspired high-performance computing. Its LPU100 system unleashes the power of 100 lasers to solve the ...
- 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 ...
- Florida man arrested for allegedly pointing lasers at passenger aircraft at international airport: policeon April 25, 2024 at 8:55 pm
A Florida man's hobby of allegedly pointing lasers directly at incoming aircraft was recently caught after a Jet Blue pilot experienced the blinding rays of a laser. The Tampa Police Department ...
via Bing News