Photonic Integrated Circuitry

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


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!


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


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


Four Directional Couplers

Grating can couple in multiple directions– Input/output

– Mesh structure FIB nanostructure Holographic lithography

– Two step process

– Crossed Gratings


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


Mag

nit

ud

e

0 0.2 0.4 0.6 0.8 1-100

-50

0

50

100


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


Two Dimensional GSE Lattices

~60 um

Completely new filter structure solved by layer peeling with 2nx2n matrices … Research is benefiting fundamental DSP engineering


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


Frequency Selection

0 0.2 0.4 0.6 0.8 1-200

-100

0

100

200


Ph

ase

(deg

rees

)

0 0.2 0.4 0.6 0.8 10

50

100

150

200


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


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


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


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

Documents

Photonic Integrated Circuitry