American scientists have created a non-magnetic, fully passive isolator that provides excellent signal integrity ensuring top notch wave transmission.
Modern-day technology demands efficient signal transmission that prevent interference and are more efficient in their use of the scarcely available frequency spectrum.
These requirements are however constrained by a law of physics called ‘reciprocity’ that forces the transmission of light to be identical in opposite directions.
Scientists and engineers have been trying to address these challenges with the creation of isolators – devices that use an external magnetic field to force light waves to travel in a single direction. But this form of wave isolation is costly, and it requires the use of large, heavy magnets.
An additional drawback is that they cannot be integrated into silicon-based circuits and systems.
Now researchers at the Advanced Science Research Center (ASRC) at the Graduate Center of the City University of New York (CUNY), and at the University of Texas at Austin, have detailed the development of a new light wave-isolation method that may overcome these challenges:
“We have been working on overcoming reciprocity without magnets for a few years,” said professor Andrea Alù, director of the ASRC’s Photonics Initiative. “In the past we have explored using devices with moving or time-changing elements, but these approaches pose other technological challenges. In this paper, we show that a non-magnetic device free of an external power source – thanks to suitably tailored nonlinearities – can dramatically break transmission symmetry and realize efficient broadband isolation.”
Any system based on a single nonlinear resonator to isolate waves is inherently limited by a quality trade-off between level of isolation, bandwidth, and insertion loss, making any such device poorly performing and impractical.
The team has thus used two judiciously designed nonlinear resonators connected through a delay line, showing that this is the minimal configuration for enabling low-loss one-way transmission over a broad bandwidth.
The combined components, which were printed on a circuit board, formed a highly effective, fully passive isolator that provides excellent signal integrity.
The team anticipates the findings may find use in a variety of technologies, including consumer electronics, surgical lasers, automotive radar and lidar systems and nanophotonic circuits and systems.
Image credits and content: Andrea Alu/City University of New York