New technique could enable next-generation photonic chips

Photonic chips made from silicon will play a major role in future optical networks for worldwide data traffic.

The high refractive index of silicon makes optical structures the size of a fraction of the diameter of a human hair possible and by squeezing more and more optical structures for light distribution, modulation, detection and routing into smaller chip areas allows for higher data rates at lower fabrication costs.

As the complexity of optical chips increases, testing and characterising such chips becomes more difficult. Light traveling in the chip is confined in the silicon, that is, it cannot be ‘seen’ or measured from the outside.

Southampton researchers are now said to have now developed a new method, which will help solve this problem, to find out at which time the light in the chip is at which position.

The technique - Ultrafast photomodulation spectroscopy (UPMS) - uses ultraviolet laser pulses of femtosecond duration to change the refractive index of silicon in a minute area on the photonic chip.