World record optical switch
Scientists from the University of Twente, the FOM Institute AMOLF in Amsterdam and the Institute for Nanoscience and Cryogenics (CEA/INAC) in Grenoble have managed to make an ultrafast optical switch with a microcavity. It can switch on and off in a world record short time of less than 1 picosecond, or one millionth of a millionth second. This is very promising for optical data communication. The leading American journal Applied Physics Letters published the results yesterday.
Switches are devices that are omnipresent in computers, as they are vital for manipulating information encoded as bits. To greatly improve the speed with which information is processed, much work is being done worldwide to realise optical switches that control information encoded as light pulses.
Microcavities
The speed of optical switches is limited by the properties of the underlying materials. In modern science and technology, cavities fabricated from semiconductor materials such as GaAs and AlAs have become highly popular. The reason is that these cavities can be made very small with lengths of the order of microns (only 1/100th of the thickness of a human hair). These 'microcavities' can therefore be integrated on chips. They are also used to transmit e-mail, Internet, and TV messages as optical signals.
New design
The Dutch-French team employed a control laser pulse, which instantaneously changes the properties of the microcavity (by using the so-called electronic Kerr effect). This allows them to take advantage of the extremely fast motion of electrons in a semiconductor which 'dance to the beat of the laser light'. This makes the switch extremely fast. The hurdle that the team overcame was to tune the colour of the control laser in such a way as to avoid the absorption of light. As a result, the properties of the cavity are only switched when both the signal and the control pulses are present.
Beyond terahertz rates
The new switch is a major step forward: it is not restricted to a particular kind of semiconductor material or cavity design and it allows much flexibility in the colour of the control light. With this switch, information could be steered faster than 1000 GHz - several hundreds times faster than the clock speed of a fast personal computer. Future research will concentrate on the miniaturisation of the process to boost on-chip applications. Since computer speed is continuously raised by parallel processing, the new switch promises beyond terahertz rates for data communication.
Reference
'Ultimate fast optical switching of a planar microcavity in the telecom wavelength range'.
The team
MESA+ Institute for Nanotechnology, Enschede: Dr Georgios Ctistis, Emre Yuce MSc, Dr Alex Hartsuiker and Prof. Willem Vos from Complex Photonic Systems (COPS).
(Emre Yuce and Alex Hartsuiker were also affiliated with the FOM Institute AMOLF)
Institute for Nanoscience and Cryogenics, Grenoble: Julien Claudon, Maela Bazin and Prof. Jean-Michel Gérard.