Lavinia P. Rajahram 18 th 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 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 R 1 = 20.25nm R 2 = R nm N X = 231 N Y = 321 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