Slow light: The route to faster communications Professor Benjamin J. Eggleton CUDOS Research Director ARC Federation Fellow School of Physics, University of Sydney Slow light: The route to faster communications

Hunger for more bandwidth : Internet and Cellular Network 2

Electromagnetic spectrum

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Underwater Optical Fibre Network Each point on this diagram where two lines intersect represents a point where cables join. This is much the same as merging major roads. And as with merging traffic, it’s not good if things merge into each other.

Photonic chip – Photonic integrated circuit

Underwater Optical Fibre Network Each point on this diagram where two lines intersect represents a point where cables join. This is much the same as merging major roads. And as with merging traffic, it’s not good if things merge into each other.

Merging traffic Each junction looks like this. If two signals interact, they interfere and the message is lost.

What & Why? Slow light is … Fundamental interest Device applications: pulse propagation at velocity << c, or optical delay comparable to pulse duration Fundamental interest phase velocity (c/n): little control group velocity (c/ng): enormous control [e.g. L. V. Hau, Nature (1999): vg = 17 m/s] Device applications: enhance nonlinear effects optical delay lines / optical buffers TIME

Slow light: Atomic vs Photonic Atomic resonance “Cycling at the speed of light” in cold atoms 17 m/s (Hau et al., Nature 1999) Narrowband (<MHz) 1. Slow light has been demonstrated using either atomic or photonic resonances. 2.1999, there was a demostration of light travelling at 17 m/s in a cloud of ultracold Na vapor. 2 yrs after that, the same group stopped light. 3. These are impressive results, HOWEVER, atomic resoanaces are narrow band, therefore not particularly useful for high bandwidth applications, for exmaple. 4.Instead in this work we try to slow light using a photonic resonance, which is comparatively broadband. Exmaples of such resonant structres include Bragg grating and photonic crystal

Slow light in photonic resonance Bragg grating, photonic crystal Broadband (>GHz) Compatible with telecom!

Problem Problem: Our solution: dispersive broadening length-limited  delay-limited (fractional delay ~ 0.1 to 3) Our solution: Balance dispersion with nonlinearity  Soliton! here a gap soliton [Winful, Chen and Mills (1980’s)] eliminate dispersion to all orders  no length/delay limitation

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World leading research! NSW, February 2008 Funding: 2003-2008, renewed 2008-2010 12 Chief Investigators, 50 researchers, 50 students, >20 international partners Fundamental science, Strong collaboration, Major international programs, Strong IP, End-user engagement and commercialization path, Outreach, E&T etc 15