Mixing light in plasmonic circuits for all optical modulation and

Mixing light in plasmonic circuits for all optical modulation and switching
Tim Davis†‡, Daniel Gomez†‡ and Fatima Eftekhari‡
†CSIRO Manufacturing Flagship, Private Bag 10, Clayton South, Victoria, Australia 3169
‡Melbourne Centre for Nanofabrication, ANFF, 151 Wellington Road, Clayton, Victoria, Australia 3168
LSPs as optical circuits
Incident light field
Light incident on a metal nanoparticle excites coherent oscillations of the electric charge at the metal surface –
this is a localised surface plasmon (LSP)
Circuit – a closed path around which flows electrical current
For LSPs it is the displacement current which flows
More complex circuits are made by coupling LSPs. These can be used to mix optical signals together
Electric charge excitation
Coupling of plasmonic particles
Plasmon hybridization
Fano resonances
Dark modes
Induced transparency …
Isolated particles
Plasmon coupling alters the
excitations of the particles
Davis et al. PRB (79), 155423 (2009)
Davis et al. Nano Letters (10) 2618 (2010)
Plasmonic circuits for mixing optical signals
Input optical signals
Inputs via free‐space coupling, dielectric or metal waveguides, optical antennas …
Processed optical signal
Plasmon coupling leading to filtering and mixing
Davis et al. PRB (79), 155423 (2009)
Davis et al. Nano Letters (10) 2618 (2010)
Eftekhari et al. Optics Letters (39) 2994 (2014)
Plasmonic difference circuit
200 nm
Plasmonic circuit (Wheatstone bridge)
20 nm
Input 1
metal rods
Output related to differences at the inputs
Davis et al: J. Appl. Phys. (106), 043502 (2009); Eftekhari et al. Optics Letters (39) 2994 (2014)
Input 2
All‐optical modulation
Output related to phase difference of input
Input generating phase difference at output
“Control” beam
“Signal” beam
“Signal” beam
The “control” beam is used to modulate the Modulate the interference of light at the “inputs” “signal” beam
by driving the “output”
All‐optical modulation
100% modulation
“control” beam
“signal” beam
Incidence angle 25 degrees to surface normal
680 nm light
For 100% modulation only 8% of the control beam is mixed with the signal beam!
Davis, Gómez, Eftekhari, Optics Letters (39), 4938‐4941 (2014)
All‐optical modulation
Modulation depends on:
1) the amplitude ratio C/S
2) the relative phase
3) Incidence angle
All‐optical switch
Plasmonic switching effect by interference
‐ all‐optical control of the blaze of the grating
Diffraction grating of optical circuits
Davis et al, Optics Letters (39), 4938‐4941 (2014)
• Discussed the idea of localised surface plasmons
as forming part of optical circuits
• Used an electrical systems analogy to describe coupled LSPs
• Demonstrated a plasmonic circuit that detects optical phase differences • Showed an array of plasmonic circuits that mix optical signals together to induce modulation by interference
• Demonstrated all‐optical switching or a diffraction grating with an optically controlled blaze Acknowledgements
Fatima Eftekhari
Daniel Gomez
CSIRO Office of the Chief Executive
Melbourne Centre for Nanofabrication
Australian National Fabrication Facility
Thank you
Manufacturing Flagship
Dr. Tim Davis
t +61 3 9545 2881
e [email protected]
w www.csiro.au
CSIRO Nanophysics