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Optical Control of Light on a Silicon Chip
An anonymous reader writes "Researchers at Cornell University have demonstrated a device that allows one low-powered beam of light to switch another on and off, on silicon, a key component for future "photonic" microcircuits in which light replaces electrons for propagating signals. It is highly desirable to use silicon--the dominant material in the microelectronic industry--as the platform for these photonic chips.
The approach developed confines the beam to be switched in a circular resonator, greatly reducing the footprint required on the chip and allowing a very small change in refractive index to shift the material from transparent to opaque."
I thought diffraction and interference was to be the answer to switching light. Does anybody know what happened to this technology?
Light travels about 10x faster than electrons in their optimal medium, so the potential processing speed limit is increased.
Also, light processing does not necessarily generate heat, so there is no cooling needed to preserve the hardware, unlike the electro solution.
"Think again" is right. The electrons are involved in propagating a wave of electromagnetic energy, in ways that are fun to examine. But what you are describing is the average rate of travel of an electron, much like the average rate of travel of a lake: only a little bit of water goes in and out of it, on the average, so the average speed is very slow.
The *wave* in the lake, however, is much faster, carried by particles that bounce around each other much faster. Typical propagation speeds of electrical signals in network cable is a significant fraction of the speed of light, roughly 75% of the speed of light for 75-Ohm coax cable as one example.
Optical propagation in fiber-optic cable, which is what this new technology will be used for, is also limited to less than the speed of light. There, you get interesting effects because it's being transmitted through glass (or plastic for short cables), but still a significant fraction of the speed of light in vacuum.