The ‘spin lasers’ have the potential to achieve modulation frequencies of above 100GHz, the researchers at the Ruhr University Bochum (RUB) in Germany claim.
Optical data transmission using semiconductor lasers underpins the globally networked world and today’s information society.
However, the ever-increasing degree of networking and the desire to exchange larger amounts of data require the development of ever-faster optical data transmission systems.
The maximum speed of conventional semiconductor lasers has long been a limiting factor — typical modulation frequencies are currently at levels well below 50GHz.
Researchers at RUB were able to overcome this by making use of the intrinsic angular momentum of electrons, called spin.
Whereas in conventional lasers the spin of the electrons injected is entirely arbitrary, in spin lasers only electrons with a previously determined spin state are used. By injecting these spin-polarised electrons, the laser is forced to work simultaneously on two laser modes with different frequencies.
‘This frequency difference can easily be tuned using the so-called birefringence in the resonator, for example, by simply bending the microlaser,’ said project collaborator Dr Nils Gerhardt of RUB.
By coupling the two laser modes in the microresonator, oscillation with a new frequency occurs, which can theoretically reach more than 100GHz.