Embed Size (px)
Citation preview
Doing the Work: Linyou Cao, Majid Esfandyarpour, Erik C. Garnett, Soo-JinPengyu Fan Soo-Jin Kim, Dianmin Lin, Juhyung Kang, Jung Hyun Park, Isabell Thomann.
Speaking: Mark Brongersma @ Stanford University
Funding: AFOSR, DOE EFRC, Samsung
Semiconductor Nanowire Nanophotonics and Optoelectronics
Thank you: Mike McGehee group (Stanford) Yi Cui group (Stanford)Pieter Kik (CREOL)Nader Engheta (Upenn)Erez Hasman (Technion)
Reflection Absorption/Emission Transmission
P <<
Optoelectronic Devices are Everywhere…
Flexible displaySamsung
LasersSolar cells, SunPower
Image sensors
Most Optoelectronic Devices Rely on Planar Device Technologies
http://spie.org/Images/Graphics/Newsroom/Imported‐2012/004167/004167_10_fig3.jpg
www.olympusmicro.com
CMOS Image sensors (Sony)
Keisuke Nakayama H.A. Atwater et al., Appl. Phys. Lett. 93, 121904 (2008)
Can metamaterials have an impact on these technologies ??..Lower power, higher speed, thinner..
Enhanced Light-Matter Interaction Comes For Free at the Nanoscale
Electronics1st transistor and IC
Current technology
Linyou Cao et al., Nano Lett., 2649, 10 (2010)
Semiconductor nanostructures
Semiconductor wafersOptical Properties Semiconductors
30 nm 185 nm
Noble metal and high-index semiconductor nanostructures exhibit strong, tunable optical resonances
Development of Metafilms and Metasurfaces from Resonant Nanostructures
L. Cao, M.L. Brongersma et al., Nano Lett., 2649, 10 (2010)
Semiconductor nanostructures
30 nm 185 nm
Assembly nanostructures into metasurfaces and metafilms
Absorption/Emission Transmission
P <<
Short History of Resonant High-index Nanostructures
2000 Kuester & Holloway Artificial dielectrics materials in RF range 2003 – Visible & Near IR: Pendry, Joannopoulos, Kuznetsov, Luk’yanchuk, Evlyukhin,
Polman, Novotny, Kivshar, Chang-Hasnein, Brener, Brongersma, Valentine, Zheludev, Rockstuhl, Cui, Seo, etc.
– IR: Brener, Brongersma, Hasman, Schuler , Zheludev, etc..– RF: Cummer, Gopinath, Lippens, Kuester & Holloway, etc.
1908 Gustav Mie: Light scattering from a dielectric sphere
1947 L. Lewin Medium with spheresL. Lewin, Inst. Electr. Eng. III Radio Commun. Eng. 94, 65–68. 1947,
Gustav Mie, Ann. Phys. 25, 377–445 (1908)
1980 Long, McAllister, and Shen Dielectric Resonator AntennasS. A. Long, M. W. McAllister, and L. C. Shen, "The Resonant Cylindrical Dielectric Cavity Antenna," IEEE Transactions on Antennas and Propagation, 31, 406, 1983.
Engineering optical resonance frequency with size
Beneficial Properties of Resonant Semiconductor Nanostructures
Effective light concentration to the deep subwavelength scales
|E|2
x
y
E
d =100nm
d
d
SiO2 (n = 1.45)
Air
g = 10 nm
= 550 nm
Si
Engineering optical resonance frequency with shape
Cao, Brongersma et al., Nano Lett., 2649, 10, 2010.
30 nm 180 nmDiameter
Length
D
Ho-Seok Ee et al., Nano Letters, 15, 1759 (2015).
Wide range of resonances in simple structures
Mature processing semiconductor fabrication techniques
Doping and band engineering to realize devices (e.g. pn junctions, transistors, Q‐wells..)
Electrical doping can be used to tune carrier density and thus the optical properties
Mobile carrier densities and thus optical properties are low enough to impact them by gating
Beneficial Properties of Resonant Semiconductor Nanostructures
Interaction of multiple Mie resonances
Light can generate long‐lived carriers and vice versa (detectors, sources,…)
Ohmic loss can be “zero” (h < Egap) or loss can be useful (photocarrier generation!)
Person et al., Nano Lett. 13, 1367‐1868 (2013).Y.H. Fu et al., Nature Comm. 4, 1527 (2013).
Quantifying Light Scattering from Nanowires
Microscope for performing darkfield light scattering measurements
Linyou Cao et al., Nano Lett., 2649–2654, 10, 2010.
Iscatter
I scat
ter(
a.u.
)
Quantification of the Color Tuning
Scattering spectra show a redshift and multiple peaks emergence for large wiresdiameter in nm
Wavelength (nm)
Linyou Cao et al., Nano Lett., 2649–2654, 10, 2010.
Sca
ttere
d lig
ht in
tens
ity (a
.u.)
Polarization‐dependence of Light Scattering from SiNWs
Observed color under white light illumination can change with illumination conditions
I sca
tter(
a.u.
)
Linyou Cao et al., Nano Lett., 2649–2654, 10, 2010.
Example: Optical properties of high index nanowires
Optical Properties of Dielectric/Semiconductor Structures
Free space photons can couple to Mie or leaky mode resonances
Intuitive resonance condition: mλeff = 2πr
TMml
For top-illumination resonances split in TM and TE modes
m: # wavelengths l : # radial maxima
Nomenclature
|H|2
Example: Optical interconnection schemes require ultrafast, low noise photodetectors
Device Applications of Semiconductor Nanowires
Speed typically scales with a linear size of the detector
Power and noise scale typically scale with capacitance/area Small detectors are good
Example of a fabricated Ge nanowire detector structure
Challenge: Wires are small compared to the diffraction limit……
L. Cao, J.S. White, J-S Park, J.A. Schuller, B.M. Clemens, and M.L. Brongersma, Nature Mat. 8, 643-647 (2009).
Solution: Light absorption in designed semiconductor nanostructures is naturally enhanced
Pho
tocu
rrent
(a.
u.)
Wavelength (nm)
Photocurrent shows strong enhancements at some s
Spectral Photocurrent Response of Ge nanowires
Spectral photocurrent measurements on Ge nanowires of different radius
L. Cao, J.S. White, J-S Park, J.A. Schuller, B.M. Clemens, and M.L. Brongersma, Nature Mat. 8, 643-647 (2009).
R=10 nm R=25 nm R=110 nm
Qabs = σabs/σgeom
= optical size/physical size
σgeom
σabs
Simple optimization procedure
Engineering Better NW Photodetectors and Solar Cells
10 nm radius
25 nm radius
110 nm radius
SimulatedExperiment
Can We Build NW Molecules and Materials ?Optical coupling of closely-spaced nanowires
Wire stateAnti-bonding
Bonding state
E = ħωState of individual nanowires States of coupled nanowires
The science of coupling nanowires
Linyou Cao, Pengyu Fan, and Mark L. Brongersma, Nano Letters 11, 1463-1468, (2011).
50nm
A.E. Krasnok et al, Opt. Express 20, 20599 (2012)
Dielectric Yagi Uda antenna
R.M. Bakker et al., Nano Letters 15, 2137 (2015).
Electric and Magnetic hotspots
Dielectric Antennas of more Complex Architecture
A.M. Miroshnichenko, et al., Nano Letters 12, 6459 (2012).
Fano Resonance in dielectric oligomers Reflective dielectric metasurfaces
S. Liu et al. Optica 1, 320 (2014).
Lenses are everywhere
18 Photo credit: google images
iPhone’s Protruding Camera
Professional Camera Microscope Drone
Solar concentrator Optical Communication
3 um
100nm Si
Pancharatnam-Berry phase
Optical Antennas+
“Dielectric Gradient Metasurface Optical Elements,” Dianmin Lin, Science, 298 ‐302, 345 (2014).
DGMOE of Axicon and Generated Bessel beam
5 μm
0 50 100-50 z (μm)
x (μ
m)
0
10
-10
I (a.
u.)
1.0
0
x (μm)0 10-10
0.5
λ=550nmRCP
Experimentally measured intensity profile of Bessel beam
y
x
Semiconductors offer: low optical loss, facile integration with electronics, easy patterning, .. New opportunities to construct low-loss gradient metasurface optical elements
Experiment on DGMOE Axicon based on Si nanobeams
Enhancing Light Absorption in a Ge Metafilm on Metal Substrate
SEM image of fabricated sample Optical reflection image A 50-nm-thick Ge film is patterned into a metafilm consisting of many subwavelength Ge beams
Patterning the Ge film at subwavelength scale enhances the broadband light absorption
Soo Jin Kim et al., Nature Communications 6, 7591 (2015).
Power flow ( = 800 nm)
The flow light (Poynting vector) shows an antenna effect that ‘funnels’ light into the beams
Optical, Mie-like resonances in the Ge beams are at the origin of the strong light absorption
The continuous film look grey and patterned Ge film look black !
500 550 600 650 700 750 800 850 9000
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
w = 60 nm w500 600 700 800 900
0
0.2
0.4
Abs
orpt
ivity 0.6
0.8
1
Wavelength (nm)
Absorptivity ( 1 – Reflectivity)
Reflection measurement from Ge nanobeams on Au
Example: Array with 60 nm beams illuminated 800 nm, TM polarized light Strong absorption is observed at the nanobeam resonance wavelength
Individu
al beam
Soo Jin Kim et al., Nature Communications 6, 7591 (2015).
500 550 600 650 700 750 800 850 900 9500
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
w500 550 600 650 700 750 800 850 900
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
500 600 700 800 9000
0.2
0.4
Abs
orpt
ivity 0.6
0.8
1
Wavelength (nm)
Absorptivity ( 1 – Reflectivity)
w = 60 nm
Tuning of the absorption spectrum by changing the beam width
Resonance wavelength is tunable with the beam width Reflection spectra Ge metafilms with constant duty cycle of 1:3 (beam width : period) First-order effective medium theory predicts that optical properties are independent of period
εeff = fGe εGe + (1‐fGe)εairFor TM polarization:
30 45 60
w = 30 nmw = 45 nm
Soo Jin Kim et al., Nature Communications 6, 7591 (2015).
Broadband Absorption Can be Achieved with Big and Small Beams
Just 120 nm beams Just 30 nm beams 120 nm and 30 nm beam
800 nm
Experiment simulation
Metafilms with wide (120 nm) and narrow (30 nm) beams were created SEM images of the subwavelength nanobeam arrays
Reflection measurements show strong absorption at resonance wavelength beams
Sample with wide and narrow beams show strong absorption at short and long
Metafilms Offering Lateral Spectral Splitting Capabilities
Goal: Demonstrate ability to collect different s into spatially separated regionsSchematic showing the concept TEM & SEM images first batch of devices
Si
Device with narrow and wide Si beams spectrally splits light of different s into differently-sized beams
Beams of different width resonate and collect light at different wavelengths
Photocurrent from differently-sized beams can be collected separately
Metafilms offer new ways to perform spectral photon sorting at the nanoscale !
Lateral spectral splitting of light at sub scale
Goal: Demonstrate ability to collect different s into spatially separated regions
Absorption spectra small and BIG beams Power flow at short and LONG wavelengths
Peak absorbtion (on resonance) in small (blue curve) and BIG (red curve) beams is well over 50% Total absorption close to unity (black dashed curve)
Si
= 595nm = 625nm
Si
Spectral splitting without color filters has application in image sensors and biosensors
Many Optoelectronic Devices Rely on Planar Device Technologies
http://spie.org/Images/Graphics/Newsroom/Imported‐2012/004167/004167_10_fig3.jpg
www.olympusmicro.com
CMOS Image sensors (Sony)
Keisuke Nakayama H.A. Atwater et al., Appl. Phys. Lett. 93, 121904 (2008)
Can metamaterials have an impact on these technologies ?? !!
