Lavinia P. Rajahram

18th April 2014

NANO LASER

SHRINKING THE LASER!

A BRIEF OVERVIEW

An oscillator comprises:• Amplifier with gain-saturation mechanism• A feedback system• A frequency-selection mechanism• Output coupling scheme

SUB-WAVELENGTH DIMENSIONS!

NANO LASER - BACKGROUND• Concept developed by Mark Stockman in 2003 at Georgia State University. Theory is

based on electron vibration rather than the traditional electron excitation

• These vibrating electrons (called nanopendulums or plasmons) were not seen as of 2003.

• In 2009, after almost 50 years of laser invention, Surface Plasmon Amplification by Stimulated Emission of Radiation(SPASER) was achieved.

• To act like lasers a feedback system was required for the Surface Plasmon to oscillate back and forth so that they gain power and can be emitted as light

SPASER (2009)

• Photons replaced by Surface Plasmon

• Resonant cavity replaced by Nanoparticles

• Energy source active gain medium excited externally

PHOTON SURFACE PLASMON

• 44nm nanoparticle with gold core and dye doped silica shell

• Surface plasmon resonance capable of squeezing optical frequency

SPASER BASED NANOLASER

Nature, 27 August 2009

Induced Radiation Rate or Excitation Rate depending on its

sign!

LASING IN METAMATERIAL NANOSTRUCTURES

• Gain described by generic 4 level atomic system• Critical pumping rate to compensate losses in

nanostructure

Journal of Optic, Jan 2010

LASING IN METAMATERIAL NANOSTRUCTURE

MY CURRENT RESEARCH

• To understand fundamental properties of spontaneous emission altered by metamaterial

• To understand the coupled nanostructure gain system (dealing with time dependent wave equations in metamaterial)

• Coupling Maxwell’s equation with the Rate equation of electron populations

• Starting with a 3 level atomic system code with FDTD formalization

• Understanding parallel simulations

3 LEVEL SYSTEM

• Maxwell + Rate Equation• Atomic transition dipole• Forth order Runge - Kutta Method• Finite – Difference Time Domain Method

(FDTD)

PARALLEL COMPUTATION

R1 = 20.25nm

R2 = R1 + 10.25nm

NX = 231

N Y = 3

21

• Each rank has 20 grid• No of processor 16• Scattered field zone at Rank 12

REMOVING THE METAL LAYER

REMOVING DYE/MOLECULES LAYER

COMPLETE MODEL

VARYING THE THICKNESS OF METAL