The electronic diode is a device that allows current to travel in one direction but not the other. That makes them handy things to have around. So handy, in fact, that you'd be hard pressed to find an electronic device that doesn't contain one. It's no exaggeration to say they have become one of the fundamental building blocks of the modern world.
Physicists have known for some time that it is possible to make diode-like devices for electromagnetic waves. The mathematics of electromagnetic wave propagation suggests that certain types of material should allow polarized waves to pass in one direction but not the other when bathed in a magnetic field. Engineers can readily build such a device but its effect is what physicists call linear, meaning that the amount of light you get out is proportional to the mount you put in.
That's not really how an electronic diode acts. Its behaviour is nonlinear meaning that a small change in the input can have a mssive change in the output. For example, a small change in the electronic current can make the output current fall to zero. This highly nonlinear behaviour is what makes electronic diodes so useful.
So it's no wonder that physicists have searched for ways to do something similar with electromagnetic waves. They know for example, that lithium iodate crystals behave like this, except that the effect is tiny. Before the invention of the laser, physicists thought the light intensity necessary to see the effect could only exist inside stars.
Today, Ilya Shadrivov at the Australian National University in Canberra and buddies say it is possible to do much better than this thanks to the nonlinear magic of matematerials, stuff that has been engineered to manipulate the behaviour of light travelling through it.
This metamaterial breakthrough will have important ramifications for the development of new, advanced ground to orbit and beyond rocket propulsion systems. To read the rest of the article, click here.