Download - Optoelectronics & Photonics
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Air Force Research Laboratory
Integrity Service Excellence
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Optoelectronics &
Photonics
Gernot S. Pomrenke, PhD
Program Manager
AFOSR/RTD
Air Force Research Laboratory
MARCH 2014
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2014 AFOSR SPRING REVIEW
BRIEF DESCRIPTION OF PORTFOLIO (3001C): Explore light-matter interactions at the subwavelength- and nano-scale between
metals, semiconductors, & insulators.
Explore optoelectronic information processing, integrated photonics, and
associated optical & photonic device components for air and space platforms to
transform AF capabilities in computing, communications, storage, sensing and
surveillance … with focus on nanotechnology approaches. Explore chip-scale
optical networks, signal processing, and novel-sensing .
LIST SUB-AREAS IN PORTFOLIO: - Nanophotonics & Plasmonics: Plasmonics, Photonic Crystals, Metamaterials,
Nano-materials & 2D materials, Opto-mechanics, & Novel Sensing
- Integrated Photonics & Silicon Photonics: Optical Components, Silicon
Photonics, Hybrid Photonics
- Reconfigurable Photonics and Electronics
- Nanofabrication for Photonics: (3-D Assembly, Print, Model & Simulation Tools)
- Quantum Computing w/ Optical Methods (NV diamond, Q-dots in PCs, etc)
- Terahertz Sources & Detectors Exploring light/matter physics, materials, structures, devices, architectures, integration & processing
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Focus & Scientific Challenges
--Explore light-matter interactions at the
subwavelength- and nano-scale between
metals, semiconductors, & insulators
--Radiative lifetimes and gain dynamics
--E&M fields & strong nonlinearities
--Efficiently convert optical radiation into
localized energy, and vice versa.
--Enhancing local photo-physical
processes
--Integrating plasmonics with
nanostructured semiconductor devices
(enhance radiative recombination,
generation processes, & understand
loss)
--Growth/fab and placement of nanowires,
quantum dots, 2D materials
--Fundamental building block of info-
processing in the post-CMOS era
--Si Laser & Photonics Simulation Tools
SCIENTIFIC CHALLENGES
--Adding the power and speed of light
waves to traditional electronics could
achieve system performance
inconceivable by electronic means alone.
--By confining light to sub-micron
dimensions, optical nonlinearities can be
enhanced by many orders of magnitude
over free space:
--New class of optical nanostructures –
'photonic bandgap materials' -- that guide
and store light in ways similar to the
processing of electrons in
semiconductors, at fraction of the
wavelength in free space;
--Quantum behavior of light in optical
nanostructures to study information
processing at the fundamental level
FOCUS
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PHOTONICS - MOTIVATION
• Significant advances in Photonics & Optoelectronics over the past 15 years and
strong drive for continued growth & innovation
• Robust international commercial markets for Photonics and world-wide R&D for
creating new capabilities:
– US focus to maintain a significant share of Long-Haul (telecom) and Data-Center) (inter-
machine ) interconnect applications
– US continues research lead in intra-machine (Supercomputer) interconnects,
– Existing and planned European Framework and East Asia Programs are strong and
China is moving to close the gap
– Past national initiatives and renewed interest in the USA (NPI)
– Innovations at the component level suggest expanding potential for applications in
embedded supercomputing, quantum computing and all-optical signal processing
• Photonics appears to also offer significant advantages for RF and avionic
systems
• SOI silicon is emerging as a single platform that can provide all optical functions
except laser (3 decades after Si:Er results by Ennen & Pomrenke, APL 43 (10) 15 Nov 83 p.943)
• Opportunities from CMOS electronics - successful scaling of photonics will enable
devices & circuits that offer lower power operation, higher speed, new functionalities,
denser integration
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Portfolio Decision
Mission Need:
Advanced Components for EW
ACE Report
ASD(R&E), formerly Mr
Lemnios
AFRL, AF, DOD interactions
Other agencies
Principle Investigators
Reviewer / Evaluator
National & International Colleagues
Economic & DoD System drivers
Workshop Involvement
Workshop – Conference Planning
Review Meetings – AFOSR & other
agencies
Example workshops: Microphotonics –
Boston, NATO – Plasmonics,
Trieste Nanophotonics, Purdue Nanophotonics
Optics Report
National Academies:
Optics and Photonics: Essential
Technologies for Our Nation
ISBN 978-0-309-26377-1
Trends:
Tre
nd
s T
ren
ds
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1-Medium term integrated photonics (12 + years):
OpSIS – toward complex systems – Hochberg U DE
Reconfigurable Optical Directed-Logic Circuits – Xu Rice U
Integrated Optoelectronic Networks for Application-Driven
Multicore Computing – Pasricha CSU
New silicon photonics materials: SiGeSn – Kolodzey U DE,
Kouvetakis ASU, Claflin AFRL/RY
Hetero and Monolithic Integration-integration, nano lasers
[III-V & Si] – Huffaker UCLA & Ning ASU
2-Long term integrated photonics (25 + years):
Electrically Pumped Plasmonic Nano-Laser – Zhang UC Berkeley
Hybrid Nanophotonics – Brongersma Stanford U Cavity-Free, Matrix-Addressable Quantum Dot Architecture for On-Chip Optical Switching – Zia Brown U
OUTLINE Integrated Photonics & Nanophotonics
Subareas: Integrated Photonics & Silicon Photonics;
Nanophotonics & Plasmonics
Silicon Photonics
Hybrid Si & III-V
Nano-sized, nano-
structured photonics
Plasmonics Photonics
Q-dot & Q-bit
Photonics
Quantum
Metaphotonics
Now
Future
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60
Years
Why did silicon win for electronics?
It was the best platform for integrated systems!
An
opportunity
to support
shared
fabrication
for silicon
photonics
Optoelectronic Systems Integration in Silicon
Prof Michael Hochberg, Univ of Delaware, OpSIS Foundry
opsisfoundry.org/
http
://n
an
op
ho
ton
ics.e
ce
.ud
el.ed
u/a
bo
ut_
the
_la
b.h
tml
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OpSIS - Scaling toward complex systems
• We’re seeing a Moore’s Law-like growth in
system complexity
• Doubling time is around a year
• Filling a reticle with photonic devices of
~500 square microns gets us to ~1.7M
devices
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OpSIS Institute at UD An opportunity to support shared fabrication for silicon photonics
OpSIS Objective:
•Make integrated photonic fabrication flows easily and cheaply accessible to the research and development community through MPW shared-shuttle processes
•Drive process and tool development and standardization
•Provide educational resources and support to the community
•Develop an ecosystem of service and equipment providers to help move the silicon photonics community forward
~150 users around the world
Half corporate, half academic
0
50
100
150
2011 2012 2013 2014(est)
pre-run 001 002,3,4 005,6,7,8
Active OpSIS Users
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OpSIS Research Activities
• Development of design tools & design elements
• Demonstrations of complex systems
• Development of methodology & measurement tools/techniques
• Design automation
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Recent results in the OpSIS platform
• Working on run 4 now.
• Runs 1, 2 delivered to ~70 users
• 50 Gbit/second platform – modulators, detectors, low-loss waveguides
• High-efficiency waveguide-coupled photodiodes at 1.2 A/W (not yet published)
• World-record low-loss silicon modulators at 30 GHz (MZI) and 45 GHz (ring)
• Ultra-low loss passives library – crossings, couplers, junctions, etc at both 1550 and 1310 nm
• Hybridized lasers at 200 kHz linewidths
• World-record bipolar amplifiers at 80+ GHz for electronic-photonic integration
OpSIS
320 Gbit/second (40Gx8) Over 1 fiber with WDM
2 km reach <10 mm2 silicon
World record transmitter (with Bergman Group, Columbia)
2.4 Tbit/second
transceiver
demonstration
in progress now
86 GHz amplifier
Telecom-grade laser
40G data
8 channel
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Qianfan Xu, Rice University
Reconfigurable Optical Directed-Logic Circuits
Objective:
• Develop a scalable and reconfigurable directed
logic architecture for low-latency optical
computing.
• Demonstrate a direct logic circuit with the highly
integrated silicon photonic technology.
• Demonstrate a reconfigurable optical switch with
high speed, high extinction ratio and low
insertion loss as the basic building block.
• Develop a complete circuit simulation tool.
Approach:
• A cellular geometry with a regular row-column layout of
reconfigurable optical switches.
• Each switch has three distinctive operation modes.
• Direct mapping the truth table of an arbitrary logic function
to the operation modes of the optical switches.
• Double-ring based optical switches as the unit cell.
• A multi-spectral implementation will be realized.
• Both electro-optic and all-optical logic will be investigated.
Impact:
• Overcome the limitation of
conventional optical logic.
• Boost the performance of digital
systems for real-time applications
such as video analysis, object
recognition, missile guidance,
visualization and battle management.
• Enable highly efficient packet-switched
optical networks on chip.
• Provide a scalable platform for various
applications and for future expansion.
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Experimental Demonstration
Circuits based on the multi-spectral
implementation are fabricated in CMOS
photonics foundry at IME Singapore.
Each switch has an embedded p-i-n
junction for logic input and a micro-heater
for reconfiguration.
y
l1
l2
l1
l
x1 x2
l1& l2
A 2×2 switch array can
calculate any logic function
between two logic inputs.
0 1
0 X X
1 X X
A B
Q. Xu and R. Soref, Opt. Express 19, 5244-5259 (2011) [email protected] http://www.ece.rice.edu/ece/xugroup/
fiber
ring
optical logic circuits fabricated through OPSIS program
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Objective:
•Investigate the best architectural modalities to insert silicon photonic interconnect technology into systems of interest to the DOD to overcome performance and energy bottlenecks in emerging SoCs
Impact:
•This research will aim to meet aggressive ITRS data rates of multiple TB/s and a power goal of less than 1pJ/bit in multi-core SoCs, far exceeding what is possible with conventional electronics today
Approach:
•Design innovative heterogeneous network topologies and protocols that effectively combine multiple stacked layers of optical links with electrical wires
•Create new techniques for enhancing memory-access performance with optically connected DRAM and mechanisms for energy-efficient reconfiguration of opto-electronic components at run-time
Integrated Optoelectronic Networks for
Application-Driven Multicore Computing
PI: Sudeep Pasricha, Colorado State University
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SiGeSn: Basic Features and Properties
• CMOS - compatible (with SiGe); strain control,
stressors for high velocity MOSFET channels
• Variable bandgap of SiGeSn: ≈ 1.1 to 0.11 eV; (1.1 to
11 μm)
• Lattice/ strain control (aSn = 6.5 Å; aGe = 5.6 Å: aSi =
5.43 Å) (strain engineering)
• SiGeSn: highly conductive; covalent bonds; no
scattering by polar optical phonons, or Reststrahlen
absorption (limitation of III-V’s); direct bandgap (from
0.2 to 0.6 eV); enhanced luminescence; high optical
absorption; high speed (small effective mass)
Group IV
elements
Beyond Silicon Photonics - SiGeSn: a promising material system
The first group-IV material with a widely tunable 2D
compositional space, SiGeSn makes it possible to
decouple band gap and lattice constant, enabling
wide-range applications from thermal imaging to
photovoltaics to lasers
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-Integrated circuits are moving to Ge-rich SiGe
materials; this requires the larger lattice constant of
GeSn for stressor layers to increase active channel
carrier mobility
-Experiments and theory suggest that Ge1-ySny has
a direct bandgap for Sn contents above 6 %
(wavelengths above 2 μm) for efficient detectors
and emitters in the mid-IR region, and compatibility
with SiGe integrated circuits. (Beyond Si Photonics)
-Mid-IR devices: GeSn provides excellent mid-IR
performance (beyond 1.8 μm limit of Ge) with possibility of
multi-pixel arrays compatible with integrated circuits and
lasers
Three prime motivators for
SixGeySn1-x-y Research
Wide Area
Motion
Imagery
Full
Motion
Video
Hyperspectral
Imagery
Enhanced
Resolution at
Range
Higher Altitude
and
Greater Standoff
Day and NIGHT
TRADITIONAL
ASYMMETRIC
HME/IED/CBRNE
Missile Warning
Active Sensor/Seeker
Detection
Pre-LaunchSensor/SeekerCountermeasure
Expendable
Post-Launch Laser
Countermeasure
Counter EO/IR Adjuncts on AAA, RF SAM, LBR, DE Weapons…
RF/EO/IR Threat Warning
and ProtectionPassive EO/IR Sensing in
Contested Environments
Laser Radar Sensing in Contested Environments
Phenomenology and
Innovative Concepts
Modeling and
Analysis
Laser Source
Research
Detector/FPA
Research
Optics/Aperture
Research
Cross-Range [m]
Ran
ge [m
]
F-4 1D Ladar Back-Projection Reconstrunction
-8 -6 -4 -2 0 2 4 6 8 10
-8
-6
-4
-2
0
2
4
6
8
10
0
20
40
60
80
100
120
140
160
180
80 100 120 140 160 180 200 220
NET
D a
t R
ange
(m
K)
Detector Operating Temperature (K)
nBn
XBn
MCT Rule 7
BLIP
InSb, 10 mm
NS4 InSb, 20 mm, 7500 ft AGL
NS25 InSb, 20 mm, 7500 ft AGL
NS25, InSb, 20 mm, 20000 ft AGL
MCT/Si
NETD Goal: 75 mK
Long Term
Concepts
[note that previous detector
arrays using III-V’s such as
InGaAs are incompatible with
SiGe circuits]
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Challenges of SiGeSn
• Increase Sn content in GeSn above 14 atomic %, to study the
direct bandgap compositions, and for mid-IR operation
(present reported devices use about 4 % Sn, ~45% Sn in SiSn)
• Improve thermal stability (above 400 °C) of high Sn content
alloys for subsequent device processing (contacts, etching,
annealing)
• Identify a robust Sn source for CVD: Sn hydrides are unstable
after weeks: SnCl4 is more stable, but needs study
• Investigate fundamental properties of SiGeSn (bandgap,
mobility, carrier lifetime, electrooptic coefficients)
• World-wide, no dedicated device quality material growth
facilities available (home build CVD systems, too simple; ASM &
Applied Materials UHV-CVD, too expensive; MBE, difficult to achieve high
Sn and high quality)
• Building research teams with sufficient resources and
expertise (Kolodzey Univ of DE, Kouvetakis ASU, & Dr Bruce
Claflin WPAFB AFRL/RY developing remote-plasma-
enhanced-CVD (RPECVD) for IR application
Group IV
atoms
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Results: SiGeSn Photodiode & Emitter Kolodzey Group; Univ of Delaware
• MBE growth of GeSn – up to 14.5 % Sn –
world record Sn composition in Ge lattice
• fabricated p-n GeSn/Ge heterojunctions with
good rectifying characteristics
• GeSn/Ge heterojunction photodiodes with
direct bandgap behavior for Sn above 6 %;
responsivity = 0.13 A/W for 10% Sn device
• Ge1-xSnx light emitting diode: 216 μW power;
peak emission at 2.2 μm, at T=100K with 8 %
Sn; direct bandgap behavior – (note: other
groups report uncalibrated output power)
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From molecules …….
Edirect
Eindirect
Ge1-ySixSny alloys with tunable band gaps
above and below Ge
and the direct-indirect gap crossover
Below: crossover from
indirect to direct gap
semiconductor for 1st time
Left: Si4H10 (tetrasilane)
and Ge4H10
(tetragremane) molecular
sources are combined
with SnD4 to produce light
emitting direct gap
SiGeSn alloys (the
equilibrium mixture of
Si4H10 and Ge4H10
isomers are shown by the
models at left)
……to direct gap materials
Below: ASU chemical process was featured
Top: Calculated representative SiGeSn alloy
Kouvetakis, ASU
Above: first example of GeSiSn
diodes with low dark currents and
collection efficiencies up to ~80%
(better than the best GaInAsN
analogs) have been fabricated on
Ge and Si wafers.
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Integrated Nanopillar Lasers and APDs for
Ultra-High-Density Optical Interconnects
• Silicon photonic systems can be densely integrated due to
tight optical confinement in silicon waveguides and mature
process technology
Problem Statement
The reduction of process complexity, improved device
performance, and device footprint can bring silicon
photonic interconnects to maximum integration density.
Relevance
Approach
• Nanopillar lasers on SOI will be:
• Electrically driven at room temperature on SOI
• Greater than 10 µW output power @ 50 µA
• Nanopillar APDs on SOI will be:
• -30 dBm sensitivity @ >10 Gb/s
Metrics / Deliverables
Device Innovations
• Integrating lasers and
detectors requires extensive
and complicated processing
• Scaling conventional planar
grown material is limited by
surface effects and cavity
geometry.
• Electrically driven micro/nano
lasers do not provide sufficient
output power to drive state-of-
the-art Ge-on-Si APDs.
• Patterned Ga(In)As(P) nanopillars grown on silicon will
simultaneously form nanopillar lasers and avalanche
photodiodes coupled to a silicon waveguides on SOI
• Difference between laser and APD is doping in silicon
• Single crystal growth step for both devices
• Fast, simple device processing after growth for rapid feedback
|E| 2 Mode:
Luxtera’s packaged
transceiver chip [1]
Bonded
InP lasers
Ge
detectors
n-Si
SOI
p-Si
Laser Detector
Nanopillars
GaP passivation InGaAs active
P+/n Si multiplier N+ Si injector
Waveguide
Output
Waveguide
Input
Prof Diane Huffaker, UCLA
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1.3 µm Nanopillar LEDs
Axial/core-shell nanopillar LEDs exhibit record low leakage current
SiNx
mask
GaAs
pillar
InGaAs
insert
InGaP
shell
100 nm
p
i
n
Shapiro et al, APL 97(1), 2010. Scofield et al, Nano Lett., 2011
•IV/CV measurements show low leakage of 12 nA at -5 V
and high rectification ratios of > 10^6
•Axial InGaAs inserts are strain relaxed, emitting at 1.3 µm
Axial current injdection
with Zn and Sn doping
during growth
IV-CV measurements
on NP-LEDs Electroluminescence
at 1.3 µm
Nanopillar photonic crystal lasers are promising for high-
efficiency, high-bandwidth transceivers on silicon:
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NP Arrays for Waveguides
CYTOP n = 1.34
Polyimide n = 1.7
CYTOP n = 1.34
NPs
Top-view Side-view
Design concept: “Beam” array of NPs
NP Beam arrays:
•Light is confined by NPs and polymers
•No need for precision alignment
•Can be engineered for high-Q cavities
Beam array growth:
Tilted SEM view of
4x150 NP array
Pitch = 400nm
Height = 2400 nm
10 µm
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Electrical Injection Nanolaser at Room Temperature
Challenges in Nanophotonics & Miniaturization of
Semiconductor Lasers - Ning, ASU
Background
• Making a laser smaller with a total volume smaller than wavelength cubed has
been a worldwide goal for the last 5-6 years & initially thought impossible
• Other small lasers such as microcavity or photonic crystal lasers have a much
larger total volume
• Nanolasers with small total volume are expected to play an important role in
chip-scale nanophotonic integrated systems for future IT and other sensing or
detection applications
Nanolaser milestones by the Prof Ning, ASU Team: 2013- Demonstration of CW
room temperature operation with linewidth at 0.5 nm.
Silver
n-contact
n-InGaAs n-InP
InGaAs
SiN
p-InP
p-contact
p-InGaAsP
InP substrate (SEM image of etched pillar) 1500 1600 17000
10
20
30
40
92uA
316uA
618uA
1036uA
320X
80X
40X
8X
Inte
ns
ity
(a
.u.)
Wavelength (nm)
1652uA
B
B-Right: Spectra of laser output at
various injection current level under
the same conditions as in the left.
Laser intensity
in a nanolaser
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Electrically Pumped Plasmonic
Nano-Laser
Program Goal:
To develop nano-scale plasmon laser
by direct electrical pumping.
Approach: Designed a waveguide
embedded (WEB) Plasmon Laser that
allows carriers to be transported in and
out-of the cavity without disturbing the well
confined plasmon modes.
Key Features
• Direct electrical modulation
• First directionally emitted plasmon laser
• Enhanced extrinsic efficiency
• Wavelength multiplexing
Motivation: enhanced light-matter interaction in nanoscale systems will enable
both ultra-small & fast laser devices at nanometer scale. Electrical operation is
vital step toward realizing practical implementation of nanoscale lasers & devices.
X. Zhang, UC Berkeley
X. Zhang, UC Berkeley
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Electrical Interfaces and Modulation for
Plasmon Laser (optically pumped)
WEB plasmon laser :
• Constructed by crossing semiconductor
nanostrips over metal nanostrips with an 5-
10nm insulator gap layer
• A square shaped plasmon laser cavity at each
intersection
• Both metal and semiconductor strips can be
used as electrical contacts
Direct laser amplitude modulation with low
power consumption:
•16 dB modulation depth for a peak bias of 4V
•Opposite operation - injecting electrons and
holes into the active cavity region - can lead
to an electrically pumped semiconductor
plasmon laser
2 mm
Future: develop efficient electrical injection strategies and materials & Multiple WEB plasmon lasers at different wavelengths
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FY11 MURI: Hybrid Nanophotonics
Team: Prof Mark Brongersma, Stanford Univ, PI & team lead; Zhang – UCBerkeley; Miller
& Fan – Stanford; Shalaev - Purdue; Atwater & Painter – CalTech; Lukin & Park - Harvard
Objective: Explore the full potential of hybrid nanophotonic components for on
chip optical communication by combining the best aspects of metal and
semiconductor photonics
- a suite of high performance hybrid
nanophotonic devices and systems
- new simulation tools that can deal
with the hybrid/quantum nature of the
components
- new materials and “meta” building
blocks for hybrid devices and systems
-new optical characterization tools to
analyze hybrid devices with nano-
scale resolution
-new fabrication techniques that
enable scalable fabrication of
complex hybrid devices
- Plasmonics for extremely light concentration and
enhancing light matter-interaction at nanoscale
- Semiconductors for active functions, quantum
behavior
scaling of photonics will enable devices and circuits that offer lower power operation, higher speed,, denser integration
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Objective: Electrically-driven plasmon source
Objective – explore & develop electrically-
driven plasmon sources that via short
plasmonic waveguides can be coupled to
low loss dielectric waveguides
Key findings/Implications
Technical Approach
Embed p-GaAs /InGaAs/n-GaAs quantum well source
(lem = 970 nm) at in a plasmonic slot waveguide
Use same metals for waveguide as for electrical contacts
Exploit Purcell effect to enable effective coupling to the
emission to a single plasmonic mode
Optical simulations show possibility to effectively
couple QW emission into a plasmon slot
waveguide (>80%) Using e-beam lithography, plasmonic QW sources
coupled to plasmonic slot waveguides have been
realized
(a)
Basic, ultra-compact circuit elements have been
implemented
Brongersma Group, Stanford
(b)
(d) (e) ENZ modulator
Electrically-driven plasmon source
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Objective: Hybrid Nanophotonic Photodetectors
demonstrate efficient photodetection into
subwavelength structures compatible with CMOS
processing techniques
Technical Approach
Embed a semiconductor detector in a nanometallic slit
Use same metals for contacts and optical confinement
Exploit resonances in the combined metal/dielectric
resonance to enhance absorption efficiency and allow
tunability of spectral response
Silicon fin detectors showing strong absorption near 850 nm
Good quantum efficiency in only 170 nm Si thickness
Key findings
Germanium fin detectors extend absorption beyond 1550 nm
Silicon two-fin detectors for simultaneous two color detection
David Miller Group, Stanford
1.5mm
v1
v2
Hybrid Nanophotonic
Photodetectors
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Cavity-Free, Matrix-Addressable Quantum Dot Architecture for On-Chip Optical Switching
-- Rashid Zia and Arto V. Nurmikko, Brown University
Device integration enabled by the precise placement of Quantum Dots in Waveguide-Addressable Matrix.
Schematic Design of
Colloidal Quantum Dot
Optical Circuit
Architecture exploits strong localized fields from plasmonic & nanophotonic waveguides to:
(1)Direct quantum dot emission for scalable on-chip single photon sources, and
(2) Mediate strong interaction between quantum dots for low-photon number optical switches
Objective: Develop a cavity-free architecture for waveguide-integrated single
photon sources and optical signal processing at the few to single photon level.
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The Scalable Approach builds on the recent development of highly-ordered colloidal quantum dot arrays in Nurmikko Lab through a two-step process of dielectric encapsulation and electrostatic self assembly.
50 nm
TEM Image of Silica-clad QD
Process allows one to exploit precision of E-Beam Lithography to position single QDs in large-scale arrays
Cavity-Free, Matrix-Addressable Quantum Dot Architecture for On-Chip Optical Switching
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Cuong Dang et al., Nature Nanotechnology, Vol: 7, 335–339, (2012)
DBRs, R>99%
Threshold ~
60µJ/cm2 <N> ~
0.53 exciton
• First colloidal QD-based vertical-cavity surface-emitting laser (VCSEL)
• Very low threshold, well defined coherent beam at R,G, & B wavelengths
Demonstration of Colloidial
QD-VCSEL
Development of high-quality colloidal QDs enables new applications for these scalable materials in photonic devices.
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LDOS Engineering in 1-D
Waveguides
1D waveguide thickness allows the direct emission into a desired mode.
Theory
Experiment
Pol
TE mode TM mode TE mode
Fabrication: electrostatic deposition and e-beam evaporation
Randomly oriented QDs present challenge for directing light emission.
Demonstrated that engineering the local optical environment can preferentially couple QD emission into specific modes.
Optimized a fabrication technique to safely embed QDs within high index dielectric layers for 1-D waveguides.
DISTRIBUTION STATEMENT A – Unclassified, Unlimited Distribution
Robust (Statistical) Nanophotonics
by Repeatable, Scalable Emitter Integration
• Waveguide-Integrated Single Photon Sources
• Demonstrating a scalable process for embedding colloidal QDs in dielectric
waveguides
Method easily integrated with any nanofab process.
Reusable templates allow for repeated study of the same resonant nanostructure with different single emitters -- i.e. building statistical data sets without variations of fabrication errors or irregularities.
SEM images of QD integrated with gold rods
Scanning image of QD embedded waveguide
DISTRIBUTION STATEMENT A – Unclassified, Unlimited Distribution
Impact and Implication for Future Work
Quantum Emitter Substrate
Silica-clad Quantum dots: 1.7-3.5 NV center nano-diamond: ~3 Defects in ZnO nano-crystal: 8.7-10.3 Transition metal ions doped MgO nano-cube: 12-13
VO2: 1-2
Quartz(SiO2): 1.7-3.5 SiC: 2-3.5 ITO: ~6 Sapphire(Al2O3): 7~9 Y2O3: 7~9 Si3N4: ~9 MgO: 12-13
Isoeletric Point (IEP) of different materials
The electrostatic self-assembly technique can be easily extended to other quantum emitters and material systems. By choosing proper materials for the patterns and substrates, one can precisely place various single quantum emitters.
DISTRIBUTION STATEMENT A – Unclassified, Unlimited Distribution 35
Technology Transitions
Technology Transitions
• Students to Intel, Professor to Max Planck Institute
• Nanomembranes: MURIs ended late 2013
– Flexible Electronics – electronic tattoos, nano-printing tech:
Other AF interest (Air Combat Command, SMC)
– USDA Forest Products Laboratory - High-speed flexible
electronics on nanofibrillated cellulose (NCF) substrate
– STTRs: SysteMech, Omega, Semerane
• EM Photonics: Scalable Reconfigurable Chip-Scale Routing
Architecture to spin-off Lumilant, with subsequent transition to
JSF-F35 components
• Capasso, Harvard – Brucker - Fourier Transform Spectrometers
Utilizing Mid-Infrared Quantum Cascade Lasers
• Abeam Technologies - Spectrometer –digital planar holography
http://abeamtech.com/
DISTRIBUTION STATEMENT A – Unclassified, Unlimited Distribution 36
- Nanophotonics more
---- Plasmonics, Nonlinear, MetaPhotonics
---- Chip-scale, 3D, computation
---- 2D materials
- Integrated Photonics, Silicon Photonics more
- Reconfigurable Elec/Photonics lower
- Quantum Computing w/ Optical Methods (QIS) const
- Nanofabrication (MURI, OSD & AFOSR STTR) lower
- Terahertz Sources & Detectors zero out
- Microwave/Millimeter Wave photonics change
Interactions - Program Trends
AFRL – RY, RI, RX, RV, RW, 475th/RH
AFRL – HPC Resources
EOARD – Gonglewski & LtCol Pollak
AOARD – Mah, Caster, Hong, LtCol
Low
SOARD – Fillerup, Pokines
ONR, ARO – MURI etc eval team
AFOSR POs
RTX: Weinstock, Curcic, Nachman,
Parra, Schlossberg, C. Lee,
Harrison, Bonneau, DeLong, Sayir
RT Special Programs: Lawal, E.
Lee, Marshall
Fed Agencies: NSF, DOE, NASA etc
DISTRIBUTION STATEMENT A – Unclassified, Unlimited Distribution
DISTRIBUTION STATEMENT A – Unclassified, Unlimited Distribution 37
Conclusion & Future
Key Program ideas, thrusts, and challenges: Plasmonics & Metamaterials/ Metasurfaces/ Meta Photonics
Bandgap engineering, Strain engineering, Index of refraction eng.
Subwavelength - Operating beyond the diffraction limit; hole transmission
Optomechanics; Single photon device concepts; quantum dot devices and
architecture; Optoelectronics of 2D materials beyond graphene
Integrated photonics & establishing a shared, rapid, stable shuttle process
for high-complexity silicon electronic-photonic systems (MOSIS model)
STTR Need: Integrated Silicon Photonics, Photonics Fabrication &
Packaging, SiGeSn material development
Transformational Opportunities Reconfigurable chip-scale photonic; mmW & RF photonics;
Integrated photonics circuits
Integrated Photonics: Engine for 21st Century Innovation –
foundation for new IT disruptive technologies
Future: Metasurfaces/ Meta Photonics, Quantum Integrated
Nanophotonics, Ultra Low Power, Graphene & 2D Beyond graphene
Optoelectronics, 3D Photonics
DISTRIBUTION STATEMENT A – Unclassified, Unlimited Distribution 38 DISTRIBUTION STATEMENT A – Unclassified, Unlimited Distribution
Close coordination within AFRL, DoD, and 26 federal agencies as NSET
member to the National Nanotechnology Initiative (NNI)
http://www.nano.gov/partners
http://www.nano.gov/initiatives/government/signature
Close coordination with the National Photonics Initiative NPI
http://lightourfuture.org/
AFOSR is the scientific leader in Silicon Photonics, nanophotonics,
nanoelectronics, nanomaterials and nanoenergetics – one of the lead
agencies to the current OSTP Signature Initiatives “Nanoelectronics
for 2020 and Beyond” and coordinating member to “Sustainable
Nanomanufacturing”
Optoelectronics & Photonics Nanophotonics, Plasmonics, Integrated & Silicon Photonics
Demo’d first plasmonic all-optical modulator, plasmon enhanced semiconductor
photodetector, plasmon laser, superlens, hyperlens, plasmonic solitons, slot
waveguide, “Metasurface” collimator etc
Conclusion & Future (cont.)
DISTRIBUTION STATEMENT A – Unclassified, Unlimited Distribution 39 DISTRIBUTION STATEMENT A – Unclassified, Unlimited Distribution 20 February 2014
1 DISTRIBUTION A: Approved for public release; distribution is unlimited. 20 February 2014
Integrity Service Excellence
Gernot Pomrenke
Program Officer - Caretaker
AFOSR/RTD
Air Force Research Laboratory
GHz-THz Electronics
March 2014
2 DISTRIBUTION A: Approved for public release; distribution is unlimited.
2014 AFOSR SPRING REVIEW
NAME: Gernot Pomrenke / Jim Hwang/ Kitt Reinhardt
BRIEF DESCRIPTION OF PORTFOLIO: GHz-THz Electronics
LIST SUB-AREAS IN PORTFOLIO:
I. THz Electronics – Material and device breakthroughs for transistors based on conventional
semiconductors (e.g., group IV elements or group III-V compounds with covalent bonds) to
operate at THz frequencies with adequate power. Challenges exist mainly in perfecting
crystalline structure and interfaces.
II. Novel GHz Electronics – Material and device breakthroughs for transistors based on novel
semiconductors (e.g., transition-metal oxides with ionic bonds) to operate at GHz
frequencies with high power. Challenges exist mainly in controlling purity and stoichiometry,
as well as in understanding doping/transport.
III. Reconfigurable Electronics – Material and device breakthroughs for meta-materials,
artificial dielectrics, ferrites, multi-ferroics, nano-magnetics, and micro/nano
electromechanical systems to perform multiple electronic, magnetic and optical functions.
Challenges exist mainly in understanding the interaction between electromagnetic waves,
electrons, plasmons and phonons on nanometer scale.
3 DISTRIBUTION A: Approved for public release; distribution is unlimited.
I. THz Electronics
DARPA
DARPA
ONR III-N THz
ONR DEFINE
AFOSR
X’tal
Reliability
•Sub-millimeter-wave radar & imaging
•Space situation awareness
•Chemical/biological/nuclear sensing
•Ultra-wideband communications
•Ultra-high-speed on-board and
front-end data processing
Intel
IBM
Cutoff Frequency
(Po
wer)
THz
4 DISTRIBUTION A: Approved for public release; distribution is unlimited.
Intel’s High-k FinFETs
Pro
du
cti
on
De
ve
lop
me
nt
Channel
Source Drain
Gate
Stack
e
S
d
k
V
QC 0
5 DISTRIBUTION A: Approved for public release; distribution is unlimited.
Challenges for THz Electronics
•Highly strained
growth
•Single-phase
ternary
•P doping
6 DISTRIBUTION A: Approved for public release; distribution is unlimited.
Covalent Semiconductors
Covalent Semiconductors
7 DISTRIBUTION A: Approved for public release; distribution is unlimited.
InAlN Molecular Beam Epitaxy Jim Speck, UC Santa Barbara
X-ray diffraction confirms lattice match Cross-sectional transmission electron
microscopy reveals columnar structure
17% In mole fract.
140nm thickness
Scanning transmission electron
microscopy shows nano-network
Atomic probe confirms
composition variation
GaN
peak
•First extensive study of phase
separation in nitrides
•Nano-network may be useful for
thermoelectrics
•Homogeneous InAlN grown by
NH3 MBE and MOCVD perhaps by
suppressing In ad-layer at higher
growth temperatures
8 DISTRIBUTION A: Approved for public release; distribution is unlimited.
P-Doped InGaN Alan Doolittle, Georgia Tech
GaN:Mg Constant resistivity when
doped 1019/cm3
GaN
GaN
GaN
GaN
GaN
In0.4Ga0.6N
In0.2Ga0.8N
Objective: P-type GaN or InGaN for HBT
Approach: Optimize MBE temperature and flux to prevent surface
segregation/decomposition & to provide optimum Mg substitutional sites
Results: Breakthrough in single-phase, high-quality InGaN doped with
1020/cm3 Mg and >50% temperature-independent activation
Plan: Mitigate electrical leakage via metal-decorated dislocations
9 DISTRIBUTION A: Approved for public release; distribution is unlimited.
Hot Electrons/Phonons in GaN Hadis Morkoc, Virginia Commonwealth
Pla
sm
on
Reso
nan
ce
P
eak
Ve
locit
y I ~ nv
Optimum electron
concentration for
plasmon resonance
and optical-acoustic
phonon decay
2700K Electrons
Acoustic
phonons
2400K
optical
phonons
Power Supply
300K heat sink
Objective: Optimize electron density
Approach: Understand interaction of hot
electrons and phonons
Result: Explained limits of many GaN devices
Plan: Dual-well channel
10 DISTRIBUTION A: Approved for public release; distribution is unlimited.
Limit of AlN/GaN HEMTs Grace Xing & Debdeep Jena, Notre Dame
Regrown contact with Rs<0.1Ω-mm
Reduce
gate length Control
surface
states
Increase 2DEG mobility
Add AlN back barrier
Year
Speed (GHz)
400
600
‘11 ‘10 2007
200
‘09
NiCT
HRL MIT
Notre Dame
‘12
Objective: THz AlN/GaN HEMTs
Approach: Outlined below
Results: 370GHz cutoff frequency
Plan: Verify/improve phonon-
limited velocity model
11 DISTRIBUTION A: Approved for public release; distribution is unlimited.
II. Novel GHz Electronics
DARPA
DARPA
ONR III-N THz
ONR DEFINE
ZnO MOSFET
AFOSR
Nano-Oxide
DARPA
MESO
ONR
Extreme E
ARO
Interact TI
ONR
Coupled Φ
NSF
DMR
DTRA
Rad-Hard E
Industry
Thin-Film E
AFOSR
X’tal
Reliability
IBM
Intel
Breakdown,
Power
Cutoff Frequency
12 DISTRIBUTION A: Approved for public release; distribution is unlimited.
Ionic vs. Covalent Semiconductors
Covalent Semiconductors •Transparent Electronics: ZnO, MgO, InGa3Zn5O5
•Heterojunctions: MgZnO/ZnO, LaAlO3/SrTiO3
•Multiferroics: BiFeO3, EuO,
•Metal-Insulator Transition: VO2, SmNiO3, NdNiO3,
•Topological Insulators: Bi2Se3, Bi2Te3, Bi1-xSex,
•Other Chalcogenides: sulfides, selenides, tellurides
13 DISTRIBUTION A: Approved for public release; distribution is unlimited.
Challenges for THz Electronics
•Highly strained
growth
•Single-phase
ternary
•P doping
14 DISTRIBUTION A: Approved for public release; distribution is unlimited.
Merits of Ionic Semiconductors
Covalent Semiconductor
Ionic Semiconductor
Mo
bilit
y
Ionicity
Ionic Covalent
•Less demanding on crystalline perfectness
•Deposition on almost any substrate at low temp.
•Radiation hard, fault tolerant, self healing
•High electron concentration with correlated transport
•Metal-insulator transition with high on-off ratio
•Wide bandgap for high power and transparency
•Topological effects
•SWAP-C and conforming
Challenges
•Composition and
purity control
•Transport not well
understood
15 DISTRIBUTION A: Approved for public release; distribution is unlimited.
Transport in ZnO Dave Look, Wright State
24
26
28
30
32
0 100 200 300
m*0.30
0.34
0.40
Fitting parameters:
ND = 1.45 x 10
21 cm
-3
NA = 1.71 x 10
20 cm
-3
m* = 0.34m0
T (K)
(
cm
2/V
s)
Pulse Laser
Deposition
in Ar
SIMS
Positron
Kane model
•[VZn ] = 1.7x1020
cm-3 gives
E(formation) =
0.2 eV; provides
accurate check
on theory (DFT)
•Reduced [VZn ]
with Zn anneals:
got = 1.4x10-4
-cm, 3rd best in
world
•Future: create
GaZn donors by
filling VZn with Ga
•Future: apply
methods to other
TMOs
µ (ND, NA, m*, T)
Mobili
ty
16 DISTRIBUTION A: Approved for public release; distribution is unlimited.
LG=1.2m
Grain
Boundaries
Nanocrystalline
ZnO
PLD
World’s 1st microwave thin-film transistor
ZnO Thin-Film Transistors Burhan Bayraktaroglu, AFRL/RYDD
Record Performance
150°C deposition
110 cm2/V.s electron mobility
875mA/mm current density
9.5W/mm dc power density
1012 on/off ratio
60mV/dec sub-threshold slope
10 GHz cut-off frequency
Plan
•Room-temp.
deposition
•High-k gate
insulator
•MgZnO/ZnO
hetero-
junction
Objective: Exploit unique electronic
properties of nanocrystalline ZnO films
Approach:
•Theoretical doping & mobility models
• Pulsed laser deposition (PLD)
• Ga doping in Ar at low temperatures
17 DISTRIBUTION A: Approved for public release; distribution is unlimited.
Correlated Oxide Field-Effect Devices Shriram Ramanathan, Harvard
Estimated
power-delay
product
VO2 Mott FET
vs. Si MOSFET
MBE
SmNiO3
LaAlO3
Temperature (°C)
Objective: Fundamental understanding of field-effect
switches utilizing ultra-fast (ps) reversible metal-
insulator (Mott) transition in correlated oxides
Approach: Fabricate field-effect transistors with oxide
channels and investigate device characteristics
Result: High-quality SmNiO3 grown by molecular-
beam epitaxy on LaAlO3 for room-temperature
transition
Plan: Electronic transport measurement on thin-film
hetero-junctions of different oxides
18 DISTRIBUTION A: Approved for public release; distribution is unlimited.
III. Reconfigurable Electronics
Challenges: Understand
interaction between
electromagnetic waves,
electrons, plasmons and
phonons on nm scale
•Multiple electronic, magnetic and optical functions for UAV/MAV
•Meta-materials, artificial dielectrics, ferrites, multi-ferroics, nano-magnetics, MEMS/NEMS
19 DISTRIBUTION A: Approved for public release; distribution is unlimited.
EuO-Based Multiferroics Darrell Schlom, Cornell
= 0.6eV
Andreev reflection of
>96% spin-polarized
carriers from EuO to Nb
0
0.5
1
20 40 60 80 100 120 140
No
rma
lize
d M
ag
ne
tizati
on
(a.u
.)
Temperature (K)
5% La-doped
5% Lu-doped
5% Gd-doped
Insulator
Metal
Fe
rro
ma
gn
eti
c
Pa
ram
ag
ne
tic
Objective: Enhance and
exploit exceptional
spintronic, optical, and
magnetic properties of
EuO, including highest
∆R/R of any metal-insulator
transition, greatest spin-
splitting of any
semiconductor, and 2nd
highest of spin
polarization.
Approach: Reduce defects
in EuO films to enable
controlled doping.
Combine strain and doping
to boost Curie temperature.
Results: Demonstrated
controlled rare-earth
doping of EuO.
Plan: Apply misfit strain to
boost Curie temperature
20 DISTRIBUTION A: Approved for public release; distribution is unlimited.
Topological Insulators Yoichi Ando, Osaka U.
Unexpected
mass
acquisition of
Dirac fermions
on TlBi(S,Se)2
Phenomena:
• Insulating bulk with metallic surface
•Massless Dirac fermions
high-mobility transistor
•Dissipationless spin current
Low-loss spintronics
Objectives:
•To explore novel physics
•To minimize bulk current
•To discover better TI materials
•To detect surface spin currents
Approaches:
•Explore ternary chalcogenides
•Fabricate TI-ferromagnet devices
•Precise transport measurements
21 DISTRIBUTION A: Approved for public release; distribution is unlimited.
Collaboration
• AFOSR
• Gernot Pomrenke – THz optics, microwave photonics, reconfigurable electronics &
photonics (ex. TMO)
• Harold Weinstock – Nanoscale oxides
• AOARD - Seng Hong – Osaka U., Ken Caster & Misoon Mah – 2D materials
• EOARD – SPI Lithuania
• ONR
• Paul Maki – GaN
• ARO
• Marc Ulrich – Physics of topological insulators
• DARPA
• Dan Green – high overlap of interest (NEXT)
• Bill Chappell – Adaptive RF technology, RF-FPGA
• DTRA
• Tony Esposito & Kiki Ikossi – THz applications
• NSF
• Samir El-Ghazaly – THz electronics
• Anu Kaul – 2D materials & devices beyond graphene (Joint Program Initiated)
22 DISTRIBUTION A: Approved for public release; distribution is unlimited.
I. Covalent Semiconductors • Transition bulk growth and reliability projects via STTRs
• Push to THz via highly-strained thin-film growth, surface
passivation, and high-k gate stack
II. Ionic Semiconductors • Push oxide electronics to high GHz range
• Emphasize thin-film heterostructures
• Explore extreme carrier concentration
• Understand and overcome mobility limitation
• Explore metal-insulator transition & topological insulators
III. Reconfigurable Electronics • Plans for buildup program
Take Away Messages
High-k Gate
Multi-Ferroics
Complex
Oxides
Oxide Electronics
IV. Opportunities: 2D electronics, SiGeSn electronics