iiiv/siliconphotonicsfor+microwave+photonics · photonicsr esearchg roup) 1 photonics research...

PHOTONICS  RESEARCH  GROUP   1  

PHOTONICS RESEARCH GROUP

III-­‐V/silicon  photonics  for  microwave  photonics  

The  case  of  an  electro-­‐photonic  frequency  converter  

G.  Roelkens1,  W.  Bogaerts1,  D.  Van  Thourhout1,  G.  MorCer1,  R.  Baets1,  E.  Bente2,  L.  Thomassen3  

1  Photonics  Research  Group,  Ghent  University  –  imec  

2  Eindhoven  University  of  Technology,  Netherlands  

3  Antwerp  Space,  Belgium  

2  PHOTONICS  RESEARCH  GROUP  

Outline  

•  Silicon  photonics  

•  III-­‐V/Silicon  photonics  

•  Electro-­‐photonic  frequency  converter  as  case  for  MWP  applicaCons  

3  PHOTONICS  RESEARCH  GROUP  

Silicon photonics

High index contrast waveguide structures • Size reduction of photonic integrated circuits • CMOS fabrication technology (200mm/300mm) • High performance passive devices • High performance Ge photodetectors • High performance electro-optic devices

PHOTONICS  RESEARCH  GROUP   4  PHOTONICS  RESEARCH  GROUP  

Silicon  wire  waveguides  

220nm

460nm

5  PHOTONICS  RESEARCH  GROUP  

Mach-Zehnders

Ring resonators

Arrayed waveguide gratings

Bragg reflectors

Echelle gratings

Spectral  filters  

6  PHOTONICS  RESEARCH  GROUP  

-10 -5 0 5 10

-15

-10

-5

0

1.85pm

Data ring 1 Data ring 2 Lorentzian fit ring 1 Lorentzian fit ring 2

Nor

mal

ized

resp

onse

(dB

)

Wavelenght (pm)

3.05pm

Example:  ring  resonators  with  intrinsic  Q  of  8*105  

700nm

150nm 70nm

Results: Ring 1: Q = 508k, Finesse = 1340 Ring 2: Q = 831k, Finesse = 1067

(R=25µm) (R=50µm)

Linewidth: 200-300MHz

Microwave photonics filtering

7  PHOTONICS  RESEARCH  GROUP  

High  speed  opIcal  modulators  

Based  on  carrier  depleCon  in  a  lateral  p-­‐i-­‐n  diode  =>  phase  change  

P++ P N N++

V

P N P+ N+ N+ P+ N

cathode anode -- ++ -- ++ -- ++

- + - + - +

Vertical PN junction Interdigitated PN junction

Doping patterns to enhance the modulation efficiency, linearity,…

8  PHOTONICS  RESEARCH  GROUP  

High  speed  opIcal  modulators    

5 10 15 20 25 30 35 40-9

-6

-3

0

f (GHz)

Freq

uenc

y re

spon

se (d

B)

measurementtheory

•  f3dB of |S21| is 15 GHz for 3 mm traveling wave electrode; •  f3dB of |S21| is 5.5 GHz for 1.5 mm lumped electrode.

R L

Cair Cbox

Csub

Gsub

CssubCsub1

Cdep

ZSi

Cvia Cmetal

Air Sub BoxPMD_right Wg_rightWg_left

RSi

Csslab

Cslab GslabCslab1CPMD_r

•  conformal mapping •  partial capacitance technique

Air

Air

SiO 2

Si Sub

PMD

W G G W g W g

n ++ Si p Si n Si i Si W via

p + W dep

H metal

p ++ Si H via

H box

H sub

H slab W rib  

Signal Ground Ground

n +

h 1

h 4 h 3

h 2

Bandwidth  of  the  traveling  wave  design    is  determined  by:  •     impedance  match；  •     RF  aLenuaIon;  •     velocity  match  between  RF  and  lightwave.  

Reverse bias= -4 V

9  PHOTONICS  RESEARCH  GROUP  

High  speed  opIcal  modulators  

•  Currently  most  focus  is  on  digital  applicaCons  

•  Literature  on  linear  modulaCon  in  silicon  is  emerging  [1]  [2]  

[1]  A  Silicon  modulator  enabling  RF  over  fiber  for  802.11  OFDM  signals,  JSTQE  16(1),  p.  141  (2010)    [2]  Broadband  linearized  silicon  modulator,  Opt.  Expr.    19(5),  p.  4485  (2011)  (figure  b)  

PHOTONICS  RESEARCH  GROUP   10  PHOTONICS  RESEARCH  GROUP  

Ge  photodetectors  

Process is currently being developed in imec •  First results: 10Gbit/s operation •  100GHz bandwidth in a single PD and 10Gb/s operation

in a balanced configuration has been shown (process: CEA-LETI)

[1]  Zero-­‐bias  40Gbps  Ge  waveguide  photodetector  on  Si  Opt  Expr  20(2),  p.1096-­‐1103  

!

PHOTONICS  RESEARCH  GROUP   11  PHOTONICS  RESEARCH  GROUP  

High-­‐efficiency  fiber-­‐to-­‐chip  graIng  couplers  

-­‐5.0

-­‐4.5

-­‐4.0

-­‐3.5

-­‐3.0

-­‐2.5

-­‐2.0

-­‐1.5

-­‐1.0

-­‐0.5

0.0

1510 1520 1530 1540 1550 1560 1570

Insertion  loss  fo

r  1  cou

pler  [d

B]

Wavelength  [nm]2µm SiO2

silicon substrate

220nm Si

Thicker teeth: poly-Si overlay

-1.6dB coupling efficiency

12  PHOTONICS  RESEARCH  GROUP  

Automated  wafer-­‐scale  measurement  set-­‐up  

GraCng  couplers  enable  wafer-­‐scale  tesCng  of  the  photonic  integrated  circuits  

13  PHOTONICS  RESEARCH  GROUP  

Outline  

•  Silicon  photonics  

•  III-­‐V/Silicon  photonics  

•  Electro-­‐photonic  frequency  converter  as  case  for  MWP  applicaCons  

14  PHOTONICS  RESEARCH  GROUP  

Silicon ++ photonics

Integration of light sources and optical amplifiers • Completes the set of building blocks • Heterogeneous integration of III-V semiconductors

•  state-of-the art electrically injected light sources •  Large design space and many technological choices

15  PHOTONICS  RESEARCH  GROUP  

III-­‐V  integraIon  on  SOI  

Song e.a. OE 17, 14063-14068 (2009)

Hybrid / flip chip integration

Junesand e.a., IPRM 2009 pp. 59

III-V on Si heteroepitaxy Wafer bonding

Roelkens e.a., LPR 2010

16  PHOTONICS  RESEARCH  GROUP  

III-­‐V  integraIon  on  SOI  

An  adhesive  bonding  layer  (DVS-­‐BCB  polymer)  is  used  

   -­‐  Large  range  of  bonding  layer  thicknesses  (20nm  to  2µm)      -­‐  Requirements  on  wafer  quality  are  relaxed  

(a) (b)

(e) (f)

(c)

(d)

SOI-wafer Planarization Bonding

Substrate Removal Pattern definition III-V processing

17  PHOTONICS  RESEARCH  GROUP  

III-­‐V  integraIon  on  SOI  Both  mulCple  die-­‐to-­‐wafer  bonding  and  full  wafer  bonding  (2inch)  

30+/-5nm bonding layer

18  PHOTONICS  RESEARCH  GROUP  

Example:  III-­‐V/Si  extended  cavity  laser  

From  full  confinement  in  III-­‐V  to  full  confinement  in  SOI  

I II III IV

Fundamental mode in different cross-sections (BCB thickness=80nm)

19  PHOTONICS  RESEARCH  GROUP  

Example:  opIcal  amplifier  based  on  same  technology  

!

20  PHOTONICS  RESEARCH  GROUP  

Example:  integraIon  of  tunable  laser  with  modulator  

 III-­‐V/silicon  tunable  laser  realized,  co-­‐integrated  with  silicon  electro-­‐opCc  modulator,  based  on  ring  resonator  feedback  

21  PHOTONICS  RESEARCH  GROUP  

 Y.  Tang,  J.  Peters,  J.  Bowers,  Over  67GHz  bandwidth  hybrid  silicon  electroabsorpCon  modulator,  Opt.  Expr.  20(10),  p.  11529  (2012)  

DemonstraIons  from  other  labs:  hybrid  EA  modulators  

22  PHOTONICS  RESEARCH  GROUP  

Outline  

•  Silicon  photonics  

•  III-­‐V/Silicon  photonics  

•  Electro-­‐photonic  frequency  converter  as  case  for  MWP  applicaIons  

23  PHOTONICS  RESEARCH  GROUP  

Concept of the electro-photonic frequency converter (EPFC) Implement functionality on III-V on silicon platform:

•  III-V on silicon modelocked laser •  Silicon EO modulator or III-V EA modulator •  Silicon or III-V balanced detector pair

Proposed  implementaIon  

24  PHOTONICS  RESEARCH  GROUP  

Proposed  implementaIon  

Fundamental rep rate or higher harmonic

Push pull operation to avoid IMD2

External reference necessary to reach phase-noise specs

25  PHOTONICS  RESEARCH  GROUP  

Proposed  implementaIon:  Mode-­‐locked  laser  

Sat. Abs. Gain region

Long delay in low loss silicon WG: improved phase

noise

26  PHOTONICS  RESEARCH  GROUP  

Value  of  integraIon  for  frequency  downconverter  

Electro-­‐photonic  frequency  conversion  allows  for:  –  Broad  bandwidth  –  Flexibility  –  Re-­‐configurability  

But  also  increased  scalability  at  lower  mass,  volume  and  power  consumpCon.