Existing silicon-photonic devices rely on different physical mechanisms than the high-end optoelectronic components in telecommunications networks do. The telecom devices exploit so-called second-order nonlinearities, which make optical signal processing more efficient and reliable.
In the latest issue of Nature Photonics, MIT researchers present a practical way to introduce second-order nonlinearities into silicon photonics. They also report prototypes of two different silicon devices that exploit those nonlinearities: a modulator, which encodes data onto an optical beam, and a frequency doubler, a component vital to the development of lasers that can be precisely tuned to a range of different frequencies.
In optics, a linear system is one whose outputs are always at the same frequencies as its inputs. So a frequency doubler, for instance, is an inherently nonlinear device.
“We now have the ability to have a second-order nonlinearity in silicon, and this is the first real demonstration of that,” says Michael Watts, an associate professor of electrical engineering and computer science at MIT and senior author on the new paper.
“Now you can build a phase modulator that is not dependent on the free-carrier effect in silicon. The benefit there is that the free-carrier effect in silicon always has a phase and amplitude coupling. So whenever you change the carrier concentration, you’re changing both the phase and the amplitude of the wave that’s passing through it. With second-order nonlinearity, you break that coupling, so you can have a pure phase modulator. That’s important for a lot of applications. Certainly in the communications realm that’s important.”
The first author on the new paper is Erman Timurdogan, who completed his PhD at MIT last year and is now at the silicon-photonics company Analog Photonics. He and Watts are joined by Matthew Byrd, an MIT graduate student in electrical engineering and computer science, and Christopher Poulton, who did his master’s in Watts’s group and is also now at Analog Photonics.
Nature Photonics - Electric field-induced second-order nonlinear optical effects in silicon waveguides
Read more »
Reposted via Next Big Future
No comments:
Post a Comment