The Pleasure of Finding Things Out

Deborah Berebichez, Ph.D.

Optical Society of America

July, 2009

"An honest man, the outstanding intuitionist of our age, and a prime example of what may lie in store for anyone who dares to follow the beat of a different drum" - Dr. Julian Schwinger

The ideal physics professor. Utterly brilliant and engaging, he was an inspiration.

Feynman, Photonics and Communications

“I find it odd when an introduction mentions that I

play the bongo drums it rarely finds it necessary to

mention that I also do theoretical physics. It shows that we have more respect

for the arts than for science.” Richard Feynman

Problem with science is that a lot of people don’t find it interesting or relevant

“Don't blindly accept the word of authority. Test it for yourself! And this is what science does. It tests and it tests again, and it doubts and it doubts—always.”

Feynman

Feynman’s Open Questions

“There is Plenty of Room at the Bottom” 1959 Feynman challenged physicists to write the entire Encyclopedia Brittanica on the head of a pin

He was predicting nanotechnology

Feynman examines Bill McLellan’s motor, 1960

Charles Dickens’ A Tale of Two Cities:12 characters per micron. (Stanford University)

We actually did it!

And the Story Continues…

The S U Hologram

Fabricating these tiny objects is not easy…

•Photonic crystals are periodic optical nanostructures that are designed to affect the motion of photons

•They work by affecting the propagation of electromagnetic waves (EM)

•Photons (waves) propagate through the structure - or not - depending on their wavelength. Wavelengths of light that are allowed to travel are known as models

What are Photonic Crystals?

•The repeating regions of high and low dielectric constants have to be of ~200 nm (blue) to 350 nm (red) . This makes the fabrication of optical photonic crystals cumbersome and complex.

•By making point defects in a photonic crystal, light can be localized, trapped in the defect.

Trapping Light in Photonic Crystals

Let me tell you why it matters…

Quantum computers will harness the power of atoms and molecules to perform memory and processing tasks 10X faster than silicon based ones

Recent research shows promise in trapping light in crystals to build waveguides, or to replace electron storage for computer logic

Modeling the trapping of light in crystals

Courant Institute, NYU and Department of Applied Physics and Applied Mathematics,

Columbia University

Let me tell you how we helped…

Optimization of Scattering ResonancesJournal of Mathematical OptimizationP. Heider D. Berebichez R.V. Kohn M.I. Weinstein

Simulating Physics with Computers

Physics is the act of modeling the world

Waves are everywhere!

More Waves: Communications

Wireless communications with desired usersStanford University

Time-Reversal for Focusing Waves

It is reversing the order in which a series of waves arrive at a defined position

It can compress signals and focus them on a desired target, ex: lithotripsy, targeted ads,

secure communications

WHAT IS TIME-REVERSAL?

WHY IS IT IMPORTANT?

Conventional waves disperse when traveling through a medium

Focusing waves has applications in several areas such as secure wireless communications

Communicating with time reversal

IMAGINE THE FOLLOWING SCENARIO…

Using time-reversal, when sending a secret message, the sender could ensure that only one location would receive the message. Interceptors at other locations would only pick up noise due to unfocused waves.

source

detector2.59m

2.4m

2.8m

Time Reversal explained

t0 T

T – t0

FWD phas

e

BWD phas

e

1 2

3 4

A picture of what happens in space

Spatial Focusing to within /2

Temporal Compressionof the Acoustic Waveto the Initial Pulse

The Two Main Results of TR

1.29 cmred: original

blue: after TR

From original =2.6 cm

From a State of Multiple Scattering…From Long Time-Dispersion…

With TR The Bit Stream is Recovered

We Recover the Bit Stream: { 0, 1, 1 }

-1 +1

+1

Recompressed signal after TR obtained at Rx

1.Spatial Focusing Only the Intended Receiver Gets the Message

2.Temporal Compression Bit Streams can be Recovered with Fidelity and Relatively Low Interference

Conclusions on TR Communications

Rx

Tx

TR works without line of sight

Message focuses at desired location

Experimental TR: Measurement locations

LOCATION A

LOCATION B

LOCATION C

1.2km

2.6km

2km

29 floors (5, 19, 28)

Balconies SW & NE

28 floors (19, 29)

7 floors (roof)

SECURE WIRELESS COMMUNICATIONS THAT REACH ONLY THE INTENDED RECEIVER AND CANNOT BE INTERCEPTED

COMMUNICATIONS IN INDOOR BUILDINGS (UWB)

Antisubmarine warfare and underwater communications that benefit from targeted signaling

UNDERWATER ACOUSTIC COMMUNICATIONS

IN THE BATTLEFIELD: LOCATING SOLDIERS AND FINDING TANKS IN

COMPLICATED FOLIAGE SCENARIOS

•Since spatial focusing can deliver focused energy at the intended receiver it can have applications also in homeland security and military communications. SPONSORS: NSF, ONR, DOE, DARPA, Intel UWB

But: People get discouraged at a young age to be analytical, scientific or

technologically oriented

Science is fun!

We can change that!

Why Now?

• We’re not growing enough scientists, especially compared to India and China

• The Problems that need solving need science: Energy, Climate, Genetics, Medicine, IT

• Good Citizens need to understand scientific issues to be informed, good voters

•Kid’s should be excited about science!

The Science of Everyday Life

It’s good to see a

coolWoman doing science

I want to study science and biology

-Ana, age 14

I enjoy being in the lab

thank you for showing me that A Woman

Can do Science

Ximena, age 16

Thank You for your Attention