Researchers from Applied Analysis and Stochastics with the Max Born Institute in Berlin are chasing after the ever elusive optical transistor. Their goal is to use light to switch intensities, or frequencies, if another light source. In other words, create an optical circuit. In prior cases, when two optical pulse collide nothing that noticeable changes. A more intense pulse in needed to have an effect on another. This could be a rapidly escalating intensity battle. The researchers came up with an method to use far weaker pulses to manipulate a main signal pulse.
From the view point of the control pulse, the signal pulse acts as an optical event horizon. The researchers liken the idea to a "while hole," when nothing can enter it but light can escape. The control pulse rides alone the event horizon long enough to influence the signal pulse's intensity, frequency, speed, shape, etc. In other words the control pulse acts like a switch on the signal, a transistor of sorts. Since the strong signal pulse does not change much, it could then be used on the next pulse and so one. A cascading and fan-out result is then possible. Fan-out lets multiple inputs create an output. Photons move faster than electrons, faster switching speeds compared to anything at present is possible.
No optical transistor up to this point has the ability to cascade, so this is a highly potential option.