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The Erik Jonsson School of Engineering and Computer Science
Photonic Integrated Circuitry
Duncan MacFarlane
The University of Texas at Dallas
Gary Evans
Southern Methodist UniversityJack Kilby’s revolutionary integrated circuit
The Erik Jonsson School of Engineering and Computer Science
Introduction
Early electronic filters used only L, C and R’s – “Passive Filters”
Gain elements, first vacuum tubes, later transistors, allowed “Active Filters”
Current optical filters are purely passive It is time to develop optical filters with gain that are
higher performance, and adaptive
We are developing a manufacturable, programmable, Photonic Integrated Circuit!
The Erik Jonsson School of Engineering and Computer Science
Active Lattice Filters
Lattice Filters good for:– Linear Prediction– Frequency Discrimination– Robust wrt realization
limitations
+
+
+
+
Z-1/2
Z-1/2
G
G
Tk(z)
Rk(z) Rk+1(z)
Tk+1(z)tk
tktk-1
tk-1
-rkrkrk-1 -rk-1
An active optical filter has a gain element that allows the weights associated with the different poles and zeroes to be tuned.
Gain Block Delay Block
Gain allows:– Improved quality factors
– Adaptive filters
The Erik Jonsson School of Engineering and Computer Science
Surface Grating Photonic IC
We are using the GSE technology for integrated active optical filters
Grating
Gain Region
AlGaInAs/InP Material System w. MQW waveguide/active gain region
electrode electrodeelectrode electrodeInput
Reflected Output
Transmitted Output
SurfaceGrating
Gain AndDelay Stage
The Erik Jonsson School of Engineering and Computer Science
Four Directional Couplers
Grating can couple in multiple directions– Input/output
– Mesh structure FIB nanostructure Holographic lithography
– Two step process
– Crossed Gratings
The Erik Jonsson School of Engineering and Computer Science
2D GSE Lattices: “Thick Linear”
0 0.2 0.4 0.6 0.8 1-1000
-800
-600
-400
-200
0
Normalized Frequency ( rad/sample)
Ph
ase
(deg
rees
)
0 0.2 0.4 0.6 0.8 10
0.2
0.4
0.6
0.8
1
Normalized Frequency ( rad/sample)
Mag
nit
ud
e
0 0.2 0.4 0.6 0.8 1-100
-50
0
50
100
Normalized Frequency ( rad/sample)
Ph
ase
(deg
rees
)0 0.2 0.4 0.6 0.8 1
0
0.2
0.4
0.6
0.8
1
Normalized Frequency ( rad/sample)M
agn
itu
de
The Erik Jonsson School of Engineering and Computer Science
Two Dimensional GSE Lattices
~60 um
Completely new filter structure solved by layer peeling with 2nx2n matrices … Research is benefiting fundamental DSP engineering
The Erik Jonsson School of Engineering and Computer Science
Two Dimensional GSE Lattices
Multiple Input, Multiple Output Applications– Add/drop applications, dwdm, o-cdma on same chip– Cross correlators, decouplers, cross-talk cancelation – multi-trajectory tracking, joint process estimation
Fully Tunable … programmable Extends the palette of filter realizations for
optimal implementations
The Erik Jonsson School of Engineering and Computer Science
Frequency Selection
0 0.2 0.4 0.6 0.8 1-200
-100
0
100
200
Normalized Frequency ( rad/sample)
Ph
ase
(deg
rees
)
0 0.2 0.4 0.6 0.8 10
50
100
150
200
Normalized Frequency ( rad/sample)
Mag
nit
ud
e
OUTPUT II---coeffp10=0.7 coeffp01=0.7 Gx00=0.6 Gy00=0.6 Gx01= 1.291Gy10= 1.291
Stable operation withQ >75,000
The Erik Jonsson School of Engineering and Computer Science
Bandpass Frequency Tuning via Gain
0.40.5
0.60.7
0.80.9
0.4
0.6
0.8
10.26
0.27
0.28
0.29
0.3
Gx00
Peak Postion vs.Gx00&Gy00
Gy00
Pea
k P
osi
tio
n
The Erik Jonsson School of Engineering and Computer Science
Economically Viable Device
Structure is highly manufacturable– Standard Epitaxy– Photolithographic gratings
• Last step in process• No regrowth• Chip scale process (parallel)
– Being commercialized for lasers Basic structure can be standardized for fabrication
purposes– Individual users may then program them for a particular
application– Just like an FPGA or a DSP
The Erik Jonsson School of Engineering and Computer Science
Outcome of the Research Program
Standardized Photonics– Two dimensional lattice has wealth of transfer functions
supporting widespread applications– Programming determines application
Basic advances in DSP– Two dimensional structure is new– Highly appropriate for MIMO applications
100 GHz clock rates and GHz tuning rates will enable high volume information engineering applications