Laser beam powered optical transistor may lead to ultrafast light-based computers

LONDON - Swiss researchers have made an optical transistor that uses one laser beam to control another, an instrument that could form the heart of a future generation of ultrafast light-based computers.

Conventional computers are based on transistors, which allow one electrode to control the current moving through the device and are combined to form logic gates and processors.

According to a report in New Scientist, the new component achieves the same thing, but for laser beams, not electric currents.

A green laser beam is used to control the power of an orange laser beam passing through the device.

This offers another possible route to light-based rather than electronic, computing.

Such “photonic” computing is desirable because components using optical fibres carrying light could be much faster than those using wires to carry electricity.

However, previous attempts to make optical transistors for such circuits only produced very weak effects.

The new device could change that.

To make their device, Vahid Sandoghdar and colleagues at the Swiss Federal Institute of Technology in Zurich, suspended tetradecane, a hydrocarbon dye, in an organic liquid.

They then froze the suspension to -272 degrees Celsius using liquid helium - creating a crystalline matrix in which individual dye molecules could be targeted with lasers.

When a finely tuned orange laser beam is trained on a dye molecule, it efficiently soaks up most of it up - leaving a much weaker “output” beam to continue beyond the dye.

But when the molecule is also targeted with a green laser beam, it starts to produce strong orange light of its own and so boosts the power of the orange output beam.

This effect is down to the hydrocarbon molecule absorbing the green light, only to lose the equivalent energy in the form of orange light.

“That light constructively interferes with the incoming orange beam and makes it brighter,” said Sandoghar’s colleague Jaesuk Hwang.

Using the green beam to switch the orange output beam from weak to strong is analogous to the way a transistor’s control electrode switches a current between “on” and “off” voltages, and hence the 0s and 1s of digital data.

Doing it with a single molecule means billions could be packed into future photonic chips. (ANI)