High-efficiency Si optical modulator using Cu travelling ...€¦ · material in silicon optical modulators [6–14]. For example, one kind of silicon slot photonic crystal modulator

High-efficiency Si optical modulator using Cu travelling-wave electrode

Yan Yang123 Qing Fang1 Mingbin Yu1 Xiaoguang Tu1 Rusli Rusli2 and Guo-Qiang Lo1 1Institute of Microelectronics ASTAR (Agency for Science Technology and Research) 11 Science Park Road

Science Park II 117685 Singapore 2Novitas Nanoelectronics Centre of Excellence School of Electrical and Electronic Engineering Nanyang

Technological University 639798 Singapore 3CINTRA CNRSNTUTHALES UMI 3288 Research Techno Plaza 50 Nanyang Drive Border X Block Level 6

637553 Singapore yyang10entuedusg

Abstract We demonstrate a high-efficiency and CMOS-compatible silicon Mach-Zehnder Interferometer (MZI) optical modulator with Cu traveling-wave electrode and doping compensation The measured electro-optic bandwidth at Vbias = minus5 V is above 30 GHz when it is operated at 1550 nm At a data rate of 50 Gbps the dynamic extinction ratio is more than 7 dB The phase shifter is composed of a 3 mm-long reverse-biased PN junction with modulation efficiency (VπLπ) of ~185 Vmm Such a Cu-photonics technology provides an attractive potentiality for integration development of silicon photonics and CMOS circuits on SOI wafer in the future

copy2014 Optical Society of America

OCIS codes (1303120) Integrated optics devices (2304000) Microstructure fabrication (2507360) Waveguide modulators (2303990) Micro-optical devices

References and links

1 M Paniccia ldquoIntegrating silicon photonicsrdquo Nat Photonics 4(8) 498ndash499 (2010) 2 L Tsybeskov D J Lockwood and M Ichikawa ldquoSilicon photonics CMOS going opticalrdquo Proc IEEE 97(7)

1161ndash1165 (2009) 3 Y H D Lee and M Lipson ldquoBack-end deposited silicon photonics for monolithic integration on CMOSrdquo IEEE

J Sel Top Quantum Electron 19(2) 8200207 (2013)4 Q Fang T Y Liow J F Song K W Ang M B Yu G Q Lo and D L Kwong ldquoWDM multi-channel

silicon photonic receiver with 320 Gbps data transmission capabilityrdquo Opt Express 18(5) 5106ndash5113 (2010) 5 D J Thomson F Y Gardes J M Fedeli S Zlatanovic Y F Hu B P P Kuo E Myslivets N Alic S Radic

G Z Mashanovich and G T Reed ldquo50-Gbs silicon optical modulatorrdquo IEEE Photon Technol Lett 24(4)234ndash236 (2012)

6 X N Chen Y S Chen Y Zhao W Jiang and R T Chen ldquoCapacitor-embedded 054 pJbit silicon-slot photonic crystal waveguide modulatorrdquo Opt Lett 34(5) 602ndash604 (2009)

7 K Ogawa K Goi Y T Tan T Y Liow X G Tu Q Fang G Q Lo and D L Kwong ldquoSilicon Mach-Zehnder modulator of extinction ratio beyond 10 dB at 100-125 Gbpsrdquo Opt Express 19(26) B26ndashB31 (2011)

8 J F Ding H T Chen L Yang L Zhang R Q Ji Y H Tian W W Zhu Y Y Lu P Zhou and R Min ldquoLow-voltage high-extinction-ratio Mach-Zehnder silicon optical modulator for CMOS-compatibleintegrationrdquo Opt Express 20(3) 3209ndash3218 (2012)

9 P Dong L Chen and Y-K Chen ldquoHigh-speed low-voltage single-drive push-pull silicon Mach-Zehnder modulatorsrdquo Opt Express 20(6) 6163ndash6169 (2012)

10 X G Tu T Y Liow J F Song X S Luo Q Fang M B Yu and G Q Lo ldquo50-Gbs silicon optical modulator with traveling-wave electrodesrdquo Opt Express 21(10) 12776ndash12782 (2013)

11 X G Tu T Y Liow J F Song M B Yu and G Q Lo ldquoFabrication of low loss and high speed silicon optical modulator using doping compensation methodrdquo Opt Express 19(19) 18029ndash18035 (2011)

12 L Yang and J F Ding ldquoHigh-speed silicon Mach-Zehnder optical modulator with large optical bandwidthrdquo J Lightwave Technol 32(5) 966ndash970 (2014)

13 H Xu X Y Li X Xiao Z Y Li Y D Yu and J Z Yu ldquoDemonstration and characterization of high-speed silicon depletion-mode MachndashZehnder modulatorsrdquo IEEE J Sel Top Quantum Electron 20(4) 3400110(2013)

14 M Streshinsky R Ding Y Liu A Novack Y S Yang Y J Ma X G Tu E K S Chee A E-J Lim P G-Q Lo T Baehr-Jones and M Hochberg ldquoLow power 50 Gbs silicon traveling wave Mach-Zehnder modulator near 1300 nmrdquo Opt Express 21(25) 30350 (2013)

15 M Ziebell D Marris-Morini G Rasigade J M Feacutedeacuteli P Crozat E Cassan D Bouville and L Vivien ldquo40 Gbits low-loss silicon optical modulator based on a pipin dioderdquo Opt Express 20(10) 10591ndash10596 (2012)

221387 - $1500 USD Received 20 Aug 2014 revised 20 Oct 2014 accepted 28 Oct 2014 published 21 Nov 2014(C) 2014 OSA 1 December 2014 | Vol 22 No 24 | DOI101364OE22029978 | OPTICS EXPRESS 29978

16 D J Thomson F Y Gardes Y Hu G Mashanovich M Fournier P Grosse J-M Fedeli and G T Reed ldquoHigh contrast 40Gbits optical modulation in siliconrdquo Opt Express 19(12) 11507ndash11516 (2011)

17 H Yu M Pantouvaki J Van Campenhout D Korn K Komorowska P Dumon Y Li P Verheyen P Absil L Alloatti D Hillerkuss J Leuthold R Baets and W Bogaerts ldquoPerformance tradeoff between lateral and interdigitated doping patterns for high speed carrier-depletion based silicon modulatorsrdquo Opt Express 20(12) 12926ndash12938 (2012)

18 J C Rosenberg W M J Green S Assefa D M Gill T Barwicz M Yang S M Shank and Y A Vlasov ldquoA 25 Gbps silicon microring modulator based on an interleaved junctionrdquo Opt Express 20(24) 26411ndash26423 (2012)

19 D Edelstein J Heidenreich R Goldblatt W Cote C Uzoh N Lustig P Roper T Mcdevitt W Motsiff A Simon J Dukovic R Wachnik H Rathore R Schulz L Su S Luce and J Slattery ldquoFull copper wiring in a sub-025um CMOS ULSI technologyrdquo Proceedings of IEEE International Electron Devices Meeting (IEEE 1997) pp 773ndash776

20 X Zhu S Santhanam H Lakdawala H Luo and G K Fedder ldquoCopper interconnect low-K dielectric post-CMOS micromachiningrdquo Proceedings of 11th International Conference on Solid-State Sensors and Actuators (Munich Germany 2001) pp 1548ndash1551

21 Q Jiang Y F Zhu and M Zhao ldquoCopper metallization for current very large scale integrationrdquo Recent Pat Nanotechnol 5(2) 106ndash137 (2011)

22 S Assefa S Shank W Green M Khater E Kiewra C Reinholm S Kamlapurkar A Rylyakov C Schow F Horst H Pan T Topuria P Rice D M Gill J Rosenberg T Barwicz M Yang J Proesel J Hofrichter B Offrein X Gu W Haensch J Ellis-Monaghan and Y Vlasov rdquo A 90nm CMOS integrated nano-photonics technology for 25Gbps WDM optical communications applicationsrdquo Proceedings of IEEE International Electron Devices Meeting (IEEE 2012) postdeadline session 338 pp 809ndash811

23 J E Cunningham I Shubin H D Thacker L Jin-Hyoung L Guoliang Z Xuezhe J Lexau R Ho J G Mitchell L Ying Y Jin K Raj and A V Krishnamoorthy ldquoScaling hybrid-integration of silicon photonics in Freescale 130nm to TSMC 40nm-CMOS VLSI drivers for low power communicationsrdquo Electronic Components and Technology Conference (ECTC) (IEEE 62nd 2012) pp 1518ndash1525

24 T Pinguet P M D Dobbelaere D Foltz S Gloeckner S Hovey Y Liang M Mack G Masini A Mekis M Peterson T Pinguet S Sahni J Schramm M Sharp L Verslegers B P Welch K Yokoyama and S H Yu ldquo25 Gbs silicon photonic transceiversrdquo 2012 IEEE 9th International Conference on Group IV Photonics (GFP) (IEEE 2012) pp189ndash191

25 R H Havemann and J A Hutchby ldquoHigh-performance interconnects an integration overviewrdquo Proc IEEE 89(5) 586ndash601 (2001)

26 M Matsumoto K Suzuki T Sakamoto and A Kamisawa ldquoTechnology challenges for advanced Cu CMP using a new slurry free processrdquo Proceedings of IEEE international conference on interconnect technology (IEEE 1999) pp 92ndash94

27 R Chang and C J Spanos ldquoDishing-radius model of copper CMP dishing effectsrdquo IEEE Trans Semicond Manuf 18(2) 297ndash303 (2005)

28 S Lakshminarayanan P J Wright and J Pallinti ldquoElectrical characterization of the copper CMP process and derivation of metal layout rulesrdquo IEEE Trans Semicond Manuf 16(4) 668ndash676 (2003)

29 R Ding Y Liu Q Li Y S Yang Y J Ma K Padmaraju A E J Lim G Q Lo K Bergman T B Jones and M Hochberg ldquoDesign and characterization of a 30-GHz bandwidth low-power silicon traveling-wave modulatorrdquo Opt Commun 321 124ndash133 (2014)

30 J M Liu Photonic Devices (Cambridge University 2005) Chap 6

1 Introduction

Silicon photonics devices have a promising future in the application of optical communications due to their low cost high performances and compatibility with the existing complementary metal-oxide-semiconductor (CMOS) technology [1ndash4] Silicon optical modulator is one key component for data communication related application and significant progress has been achieved in the field of silicon photonics modulator over the past decade [5ndash18] Among all kinds of silicon optical modulators silicon carrier-depletion-based modulator has proven itself to be the most prevailing solution for optical modulation on silicon because of its high performances such as high speed and low power consumptions

In most reported papers aluminum is usually adopted as electrodes and contactvia plugs material in silicon optical modulators [6ndash14] For example one kind of silicon slot photonic crystal modulator with 054 pJbit power consumption was formed with Al metal electrode [6] In 2011 one group from Fujikura achieved a silicon Mach-Zehnder Interferometer (MZI) modulator of extinction ratio beyond 10 dB at 100-125 Gbps [7] Also a silicon MZI modulator with low power and data rate of 125 Gbps was reported [8] and Bell Labs demonstrated a single-drive push-pull silicon MZI modulator with data rate up to 50 Gbps in 2012 [9] Our group also presented a 50 Gbps silicon MZI modulator last year in which Al was also used as the metal electrode [10] These silicon modulators with high data rate and


low power consumption based on Al electrode have been achieved in the past few years However Al material has its shortcomings such as nano-pores-induced low density and high resistivity which result in large delay Large delay impedes further improvement of high speed devices A good alternative to be used as electrode is Cu which can replace Al in silicon photonics devices in the future because it has lower resistivity higher conductivity and lower activation energy than Al [19ndash21] In principle these advantages of Cu contribute to higher speed and lower power consumption for silicon photonics active devices and higher integration intensity for circuits Currently few silicon photonics devices with Cu electrode have been reported IMEC reported one modulator with Cu traveling-wave electrode and contact filling material of W in 2012 which has a data rate up to 40 Gbps [17] IBM reported a 25 Gbps microring modulator using Cu electrode [18] and a 90 nm CMOS-photonics technology node for 25 Gbps transceiver [22] in 2012 Oracle labs reported hybrid-integration of silicon photonics using Cu electrode in 2012 [23] Luxtera reported a 4 times 25 Gbps transceiver [24] The stacked TiTiNAlCuTiTiN material utilized as electrodes are also reported to reduce the RF loss [15 16]

In this paper we demonstrate a high efficiency PN junction silicon optical modulator with Cu traveling-wave electrode on silicon-on-insulator (SOI) wafer with 220 nm-thick top Si layer The phase shifter length is 3 mm To reduce the optical transmission loss of phase shifter caused by ion implantation while keeping the modulation efficiency and switching speed at a high level a doping compensation method is utilized to optimize the doping level on the depletion region of the phase shift [11] Since it is difficult to delineate Cu by subtractive etch due to the limited number of volatile Cu compounds dual-damascene process was utilized to form the Cu traveling-wave electrode and the contact plugs [25] Cu deposition and chemical-mechanical polishing (CMP) process are included in dual-damascene process To avoid the dishing caused by CMP process [26] on Cu surface a latticed Cu surface pattern is designed The simulated results show this kind of latticed Cu pattern does not degrade the speed of the modulator in the bandwidth range of 40 GHz The measured results show the bandwidth of our modulator reaches above 30 GHz Its modulation efficiency (VπLπ) is ~185 Vmm and the implantation-induced optical loss is ~13 dBmm The dynamic extinction ratio is 708 dB at a bias of minus5 V and at a data rate of 50 Gbps which is also close to the limit of our eye diagram measurement equipment Cu application can further improve the integration of silicon photonics devices and CMOS circuits in the future

2 Design and fabrication

21 Modulator design

Figure 1 shows the microscope image of the modulator The silicon MZI modulator is based on a 3 mm-long PN junction phase shifter on a SOI wafer with 220 nm-thick top Si and 2 microm-thick buried oxide (BOX) The waveguide width is 500 nm and the slab height of the ridge waveguide of the phase shifter is 100 nm A 1 times 2 multimode interference (MMI) structure is used as the splitter and the combiner It is an asymmetrical MZI structure and the arm length difference ∆L is 300 microm The inset (a) of Fig 1 shows the pattern of implantations The implantation compensations are designed on both areas of the ridge corners for lower implantation-induced optical loss and higher modulation speed The implantation compensation design is similar to our reported modulator [11]


Phase shifter length

Phase shifter Cu travelling wave electrode

G

S

G

S

G

1times2 MMI

out

in

Cudielectric

N++P++ NP

Compensation doping

Inset (a) BOX

SiO2

N++

Cu electrodeContact plugs

SiO2

Inset (b)

Fig 1 Microscope image of the MZI silicon optical modulator Inset (a) implantation schematic diagram of the phase shifter (not to scale) Inset (b) latticed Cu surface pattern

0 10 20 30 40

-6

-4

-2

0 (a)

EE S

21 a

mpl

itude

(dB

)

Frequency (GHz)

normal Cu_1mm normal Cu_3mm normal Cu_5mm latticed Cu_1mm latticed Cu_3mm latticed Cu_5mm normal Al_1mm normal Al_3mm normal Al_5mm -64 dB marker

0 10 20 30 40-60

-50

-40

-30

-20

-10

EE S

11 a

mpl

itude

(dB

)Frequency (GHz)

normal Cu_1mm normal Cu_3mm normal Cu_5mm latticed Cu_1mm latticed Cu_3mm latticed Cu_5mm normal Al_1mm normal Al_3mm normal Al_5mm

(b)

Fig 2 Simulated insertion loss S21 (a) and return loss S11 (b) of the normal Cu traveling-wave electrode the latticed Cu traveling-wave electrode and the normal Al traveling-wave electrode

In our design the Cu thickness is 2 microm In order to reduce the dishing on Cu surface caused by CMP process [26ndash28] a latticed Cu pattern was used as Cu traveling-wave electrode of our silicon modulator HFSS a commercial simulation software was used to evaluate the RF loss of the latticed Cu electrode The inset (b) of Fig 1 shows the latticed Cu pattern The size of each dielectric slot pattern is 3 microm times 8 microm The maximum Cu unit size in the electrode is 15 microm times 15 microm which can effectively reduce the Cu dishing Three kinds of metal electrodes are simulated including the normal Al electrode the normal Cu electrode and the latticed Cu electrode Coplanar waveguide (CPW) models were adopted in this simulation All models are with a Si substrate which has permittivity of εr = 119 and resistivity of ρ = 1000 Ωcm Between the Si substrate and the CPW layer there was an oxide layer with 4 microm-thick The thickness of the CPW layer is 2 microm To obtain a 50-Ω impedance match the width of the central signal CPW was set to be 10 microm and the gap between the signal and ground was set to be 64 microm Assuming that both materials do not have any defects and the simulated result of insertion loss S21 and return loss S11 are shown in Fig 2 The insertion loss and the return loss of the electrical signal in the latticed Cu pattern are quite close to that in the normal Cu electrode at 40GHz which are both smaller than that in the normal Al electrode for different electrode lengths These are caused by the lower resistivity of Cu (ρCu = 172e-6 Ωcm) than Al (ρAl = 263e-6 Ωcm) The RF 64-dB bandwidth is related to the electro-optic (EO) 3-dB bandwidth [29 30] The insertion loss of the latticed Cu electrode is less than 64 dB and the return loss is less than minus10 dB within 40 GHz when the electrode length is no more than 5 mm which is longer than the length of latticed Cu electrode of our modulator Therefore this kind of latticed Cu electrode does not degrade the speed of our modulator within the range of 40 GHz

22 Modulator fabrication

This silicon modulator was fabricated on an 8-inch SOI wafer with top Si layer of 220 nm and BOX of 2 μm After P and N compensation implantations were done the waveguide was


formed by double silicon dry etching processes Figure 3 shows the scanning electron microscope (SEM) images of the silicon waveguide Four more implantations and a rapid thermal annealing were performed for the formation of PN junction Based on the actual implantation condition the P and N doping levels in the PN junctions are estimated as ~4e17 cmminus3 And the P and N doping levels in both compensation areas are estimated as ~3e16 cmminus3 Dual-damascene process was utilized to form the Cu traveling-wave electrode and the contact connection After SiO2 dielectric layer was deposited and polished the trench of Cu electrode and the contact hole were formed in sequence

50microm 4microm 1microm

(a) (b) (c)

Fig 3 SEM images of modulator waveguide Output part of the modulator (a) Ridge waveguide of the phase shifter (b) 1 times 2 MMI combinersplitter (c)

SiO2

WG

WG

Cu electrode

A

A

Cu contact plugsCu electrode

BOX

WGSiO2

Si

BOX

SiO2

Inset

50microm

(a) (b)

Fig 4 Images of Cu electrode SEM image of the top view of the Cu electrode (a) TEM image of the phase shifter at the A-A line (b) Inset TEM image of the silicon ridge waveguide

To avoid the diffusion of Cu into the SiSiO2 layer a 250 Aring-thick TaN barrier layer was deposited first A 1500 Aring-thick Cu seed layer was next deposited by physical vapor deposition (PVD) followed by 6 microm-thick Cu layer by electrochemical-plating (ECP) After removing the excess Cu by CMP the Cu electrode and contact plugs were finally formed after annealing The structures of the Cu electrode are presented in Fig 4 with Fig 4(a) showing the image of the Cu electrode surface after Cu CMP A 5000 Aring-thick SiO2 was deposited as a dielectric layer over the Cu electrode subsequently After the opening of the bond-pad a thin Al layer was formed on the bond-pad pattern to avoid the oxidation of Cu electrode Finally more than 100 μm-deep Si trench was etched to hold optical lensed fiber for coupling with the nano-taper of Si waveguide Figure 4(b) shows the transmission electron microscope (TEM) image of the phase shifter cross-section with Cu electrode and contact plugs The inset shows the cross-section of the silicon ridge waveguide and the silicon slab height is ~100 nm

3 Characterization results and discussion

31 Cu contact and Cu traveling-wave electrode characterization

Small signal microwave performance in the latticed Cu electrode with 3 mm-long phase shifter was measured through Agilent N4373C Lightwave Component Analyzer (LCA) which has a maximum bandwidth of 40 GHz The signal is dependent on the PN junction of phase


shifter by which the ground and signal Cu electrodes are connected After the EE calibration of measurement setup EE S21 signals of Cu electrode are measured with different DC biases which are used to avoid the PN junction effect shown in Fig 5(a) The EE bandwidth increases with the bias This is caused by the carrier depletion out of the PN junction area under a reversed bias voltage and the effect of PN junction on the Cu electrode reduces with increasing bias The 64-dB bandwidth is more than 40 GHz when the bias is minus18 V or more This result proves that this latticed Cu electrode transmission speed is beyond 40 GHz and it does not degrade the speed of modulator within the range of 40 GHz The Al traveling-wave electrode which is laid over the same implanted 3 mm-long phase shifter is also characterized to compare the bandwidth The 64-dB bandwidth of microwave transmission in the Al electrode increases from 97 GHz at Vbias = 0 V to 211 GHz at Vbias = minus18 V It is verified that the Cu traveling-wave electrode can provide a higher bandwidth than Al

0 5 10 15 20 25 30 35 40

-36

-30

-24

-18

-12

-6

0

260

GH

z

-10

V23

9 G

Hz

-8

V

211

GH

z

-5 V

178

GH

z

-3 V

116

GH

z

0 V

Cu

EE S

21 (d

B)

Frequency (GHz)

0V -3V -5V -8V -10V -12V -15V -18V -20V

-64 dB marker

310

GH

z

-15

V

~40

GH

z gt

-18

V

281

GH

z

-12

V

(a)

04 05 06 07 08 09 10 11 12 13 14 15 16-05

00

05

10

15

20

25

30

35

40

45

Cu-

indu

ced

WG

pro

paga

tion

loss

(dB

cm

)

Cu-to-WG distance (um)

(b)

Fig 5 EE S21 of the latticed Cu traveling-wave electrode (a) Cu-induced waveguide propagation loss (b)

Table 1 Sheet Resistance of Cu and Al and Cu-to-Si Contact Resistivity

Sheet resistance (mΩsquare)with 2 microm-depth and 5 microm-width

Cu-to-Si contact resistivity (Ωmicrom2)

Cu Al N-contact P-contact 183 plusmn 03 253 plusmn 04 1784 plusmn 33 2329 plusmn 45

Two lensed fibers with 25 microm focal-length were used to characterize the optical

performance of the modulator Figure 5(b) shows the result of the Cu-induced propagation loss of silicon waveguide When the Cu-to-waveguide distance is more than 1 microm the Cu-induced optical loss is less than 025 dBcm In our design the Cu-to-waveguide distance is 4 microm as seen in Fig 4(b) Therefore the Cu-induced propagation loss in our modulator is negligible The 2 microm-thick Cu sheet resistance is shown in Table 1 (left) It is 183 plusmn 03 mΩsquare lower than Al sheet resistance of 253 plusmn 04 mΩsquare It also reveals that Cu is better than Al as the electrode and contact material of silicon modulator for higher modulation speed The Cu-to-Si contact resistivity was also measured and shown in Table 1 (right) The contact size of our modulator is 4 times 3000 microm2 for both N- and P-contact Based on the Cu-to-Si contact resistivity the contact resistances of the modulator for both N- and P-contact are 15 mΩ and 19 mΩ respectively

32 DC measurement of silicon optical modulator

The measured output spectra of the silicon optical modulator under different reversed bias voltages are shown in Fig 6(a) The bias is applied on one arm of the modulator The free spectrum range (FSR) of the asymmetric MZI is 185 nm which is dependent on ∆L Without any bias the optical extinction ratio of this modualtor is ~28 dB With the reversed bias the carrier is pumped out of the waveguide and the optical loss reduces Thus the optical extinction ratio decreases due to the unbalance of optical power in two modulatorrsquos arms with


the increase of the reversed bias The measured insertion loss of the modulator is ~9 dB as shown in Fig 6(a) while the dynamic loss is shown in the inset of Fig 6(a) which is the average measurement result Based on the waveguide loss of 12 dB (undoped waveguide propagation loss ~02 dBmm) 2 MMI loss of 06 dB and double fiber-to-waveguide coupling loss of 32 dB the optical loss caused by implantation is 13 dBmm In Fig 6(b) a π-phase shift can be realized under 60 V reversed voltage for a 3 mm-long phase shifter which corresponds to a modulation efficiency (VπmiddotLπ) = 185 Vmiddotmm With an increase in the applied reversed voltage from minus2 V to minus10 V the efficiency is reduced from 111 Vmiddotmm to 215 Vmiddotmm which is caused by the depletion of free carriers in the PN junction In the deep depletion region the modulation efficiency becomes lower because there are fewer free carriers left in the depletion region The efficiency is improved compared with our previous Al-modulator [10] mainly due to the sheet resistance of Cu is 28 smaller than Al as shown in Table 1 Under the same DC bias measurement condition the Cu-modulator PN junction experiences a higher DC voltage compared with the Al-modulator therefore Cu-modulator has a larger phase shift

1545 1546 1547 1548 1549-44

-40

-36

-32

-28

-24

-20

-16

-12

-8

Inse

rtio

n lo

ss (d

B)

Wavelength (nm)

0V -2V -4V -6V -8V -10V

Di

0 2 4 6 8 1088

90

92

94

96

Dyn

amic

in

sert

ion

loss

(dB

)

Applied Reversed Voltage (V)

0 2 4 6 8 10

0

60

120

180

240

300


Phas

e sh

ift (d

egre

e)

10

12

14

16

18

20

22

Efficiency Vπ Lπ(Vmiddotm

m)

(b)

Fig 6 Output spectra of silicon modulator with 3 mm-long phase shifter (a) Inset dynamic insertion loss Phase shift and efficiency VπLπ of the phase shifter under different applied reversed voltages of the 3 mm-long phase shifter (b)

33 AC measurement of silicon optical modulator

0 5 10 15 20 25 30 35 40-12

-9

-6

-3

0 (a)

EO S

21 (d

B)

Frequency (GHz)

98

GH

z

0 V

173

GH

z

-1

V

236

GH

z

-2

V

287

GH

z

-3

V

333

GH

z

-4

V

370

GH

z

-5

V

505Gbs ER=708dB (b)

Fig 7 The EO bandwidth of the silicon modulator (a) and eye diagram of the silicon modulator (b)

The small signal response of the silicon optical modulator with 3 mm-long phase shifter was measured using Agilent N4373C LCA The input signal was adopted by a 67 G probe which was pinned on one end of Cu electrode The 50-Ω matching impedance as a terminator was connected on the other end of Cu electrode by another 67 G probe to reduce the signal reflection The measured EO bandwidth of silicon modulator is shown in Fig 7(a) Under a


Vbias of minus5 V the 3-dB bandwidth of this modulator is up to 37 GHz In order to get the eye diagram results a high speed electrical signal coming from a 5056-Gbps Anritsu Pattern Generator MP1822A was firstly amplified through a 67 G high speed driver It was applied to the modulator through a 60 G DC bias tee and the input 67 G probe A continuous-wave light coming from the 1550 nm tunable laser was firstly amplified through an erbium doped fibre amplifier (EDFA) and then it was modulated by adding a non-return-zero pseudorandom binary sequence (PRBS) 231minus1 signal under Vbias = minus50 V with Vpp = 35 V The output optical signal was amplified again and collected by an Agilent Digital Communications Analyzer (DCA) after the optical filter The data rate of the eye diagram reaches 50 Gbps with a dynamic extinction ratio of 708 dB as shown in Fig 7(b) A performance comparison of this work to other MZI modulators is shown in Table 2

Table 2 Comparison to Other MZI Modulators with Traveling-wave Electrode

PN junction type

wavelength

Electrodes material

Phase shifter length (mm)

Driving voltage and

bias (V)

Efficiency (Vmm)

EO bandwidth

(GHz)

Data rate

(Gbps)

Extinction ratio (dB)

Lateral PN 1550 nm [5] NA 1

65 V Vpp -4 V bias 28 NA 50 31

Lateral PN 1550 nm [10] Al 4

7 V Vpp -5 V bias 267 256 50 556

Lateral PN 1529-1565 nm

[12] Al 2

6 V Vpp -3 V bias NA NA 40 49-64

Lateral PN 1550 nm [13] Al 1 2

35 V Vpp -3 V bias 31 30 20 40 41 47


15 V Vpp 0 V bias 243 264 30 50 34

pipin diode 1550 nm [15]

TiTiNAlCuTiTiN 47 095

7 V Vpp Bias NA 35 20 40 40 66 32

Lateral PN 1530 nm [16]

TiTiNAlCuTiTiN 35 1

65 V Vpp Bias NA 27 NA 40 10 35

This work Lateral PN

1550 nm Cu 3

35 V Vpp -5 V bias 185 gt 30 505 708

4 Conclusion

We have demonstrated a CMOS-compatible silicon MZI optical modulator enabled by Cu traveling-wave electrode and doping compensation Cu electrode with low resistance provides higher bandwidth than Al electrode and does not show any undesirable influence on the EO performance of silicon modulator within the range of 40 GHz The phase shifter of the modulator is composed of a 3 mm-long reverse-biased PN junction with modulation efficiency (VπLπ) of ~185 Vmm The eye diagram of 50 Gbps data rate with dynamic extinction ratio of 708 dB is reached under Vbias = minus50 V with Vpp = 35 V The measured EO bandwidth is up to above 30 GHz at Vbias = minus50 V when it is operated at 1550 nm Such a Cu-photonics application can further improve the integration of silicon photonics devices and CMOS circuits in the future


16 D J Thomson F Y Gardes Y Hu G Mashanovich M Fournier P Grosse J-M Fedeli and G T Reed ldquoHigh contrast 40Gbits optical modulation in siliconrdquo Opt Express 19(12) 11507ndash11516 (2011)

17 H Yu M Pantouvaki J Van Campenhout D Korn K Komorowska P Dumon Y Li P Verheyen P Absil L Alloatti D Hillerkuss J Leuthold R Baets and W Bogaerts ldquoPerformance tradeoff between lateral and interdigitated doping patterns for high speed carrier-depletion based silicon modulatorsrdquo Opt Express 20(12) 12926ndash12938 (2012)

18 J C Rosenberg W M J Green S Assefa D M Gill T Barwicz M Yang S M Shank and Y A Vlasov ldquoA 25 Gbps silicon microring modulator based on an interleaved junctionrdquo Opt Express 20(24) 26411ndash26423 (2012)

19 D Edelstein J Heidenreich R Goldblatt W Cote C Uzoh N Lustig P Roper T Mcdevitt W Motsiff A Simon J Dukovic R Wachnik H Rathore R Schulz L Su S Luce and J Slattery ldquoFull copper wiring in a sub-025um CMOS ULSI technologyrdquo Proceedings of IEEE International Electron Devices Meeting (IEEE 1997) pp 773ndash776

20 X Zhu S Santhanam H Lakdawala H Luo and G K Fedder ldquoCopper interconnect low-K dielectric post-CMOS micromachiningrdquo Proceedings of 11th International Conference on Solid-State Sensors and Actuators (Munich Germany 2001) pp 1548ndash1551

21 Q Jiang Y F Zhu and M Zhao ldquoCopper metallization for current very large scale integrationrdquo Recent Pat Nanotechnol 5(2) 106ndash137 (2011)

22 S Assefa S Shank W Green M Khater E Kiewra C Reinholm S Kamlapurkar A Rylyakov C Schow F Horst H Pan T Topuria P Rice D M Gill J Rosenberg T Barwicz M Yang J Proesel J Hofrichter B Offrein X Gu W Haensch J Ellis-Monaghan and Y Vlasov rdquo A 90nm CMOS integrated nano-photonics technology for 25Gbps WDM optical communications applicationsrdquo Proceedings of IEEE International Electron Devices Meeting (IEEE 2012) postdeadline session 338 pp 809ndash811

23 J E Cunningham I Shubin H D Thacker L Jin-Hyoung L Guoliang Z Xuezhe J Lexau R Ho J G Mitchell L Ying Y Jin K Raj and A V Krishnamoorthy ldquoScaling hybrid-integration of silicon photonics in Freescale 130nm to TSMC 40nm-CMOS VLSI drivers for low power communicationsrdquo Electronic Components and Technology Conference (ECTC) (IEEE 62nd 2012) pp 1518ndash1525

24 T Pinguet P M D Dobbelaere D Foltz S Gloeckner S Hovey Y Liang M Mack G Masini A Mekis M Peterson T Pinguet S Sahni J Schramm M Sharp L Verslegers B P Welch K Yokoyama and S H Yu ldquo25 Gbs silicon photonic transceiversrdquo 2012 IEEE 9th International Conference on Group IV Photonics (GFP) (IEEE 2012) pp189ndash191

25 R H Havemann and J A Hutchby ldquoHigh-performance interconnects an integration overviewrdquo Proc IEEE 89(5) 586ndash601 (2001)

26 M Matsumoto K Suzuki T Sakamoto and A Kamisawa ldquoTechnology challenges for advanced Cu CMP using a new slurry free processrdquo Proceedings of IEEE international conference on interconnect technology (IEEE 1999) pp 92ndash94

27 R Chang and C J Spanos ldquoDishing-radius model of copper CMP dishing effectsrdquo IEEE Trans Semicond Manuf 18(2) 297ndash303 (2005)

28 S Lakshminarayanan P J Wright and J Pallinti ldquoElectrical characterization of the copper CMP process and derivation of metal layout rulesrdquo IEEE Trans Semicond Manuf 16(4) 668ndash676 (2003)

29 R Ding Y Liu Q Li Y S Yang Y J Ma K Padmaraju A E J Lim G Q Lo K Bergman T B Jones and M Hochberg ldquoDesign and characterization of a 30-GHz bandwidth low-power silicon traveling-wave modulatorrdquo Opt Commun 321 124ndash133 (2014)

30 J M Liu Photonic Devices (Cambridge University 2005) Chap 6

1 Introduction

Silicon photonics devices have a promising future in the application of optical communications due to their low cost high performances and compatibility with the existing complementary metal-oxide-semiconductor (CMOS) technology [1ndash4] Silicon optical modulator is one key component for data communication related application and significant progress has been achieved in the field of silicon photonics modulator over the past decade [5ndash18] Among all kinds of silicon optical modulators silicon carrier-depletion-based modulator has proven itself to be the most prevailing solution for optical modulation on silicon because of its high performances such as high speed and low power consumptions

In most reported papers aluminum is usually adopted as electrodes and contactvia plugs material in silicon optical modulators [6ndash14] For example one kind of silicon slot photonic crystal modulator with 054 pJbit power consumption was formed with Al metal electrode [6] In 2011 one group from Fujikura achieved a silicon Mach-Zehnder Interferometer (MZI) modulator of extinction ratio beyond 10 dB at 100-125 Gbps [7] Also a silicon MZI modulator with low power and data rate of 125 Gbps was reported [8] and Bell Labs demonstrated a single-drive push-pull silicon MZI modulator with data rate up to 50 Gbps in 2012 [9] Our group also presented a 50 Gbps silicon MZI modulator last year in which Al was also used as the metal electrode [10] These silicon modulators with high data rate and





21 Modulator design





G

S

G

S

G

1times2 MMI

out

in

Cudielectric

N++P++ NP

Compensation doping

Inset (a) BOX

SiO2

N++


SiO2

Inset (b)


0 10 20 30 40

-6

-4

-2

0 (a)

EE S

21 a

mpl

itude

(dB

)

Frequency (GHz)


0 10 20 30 40-60

-50

-40

-30

-20

-10

EE S

11 a

mpl

itude

(dB

)Frequency (GHz)


(b)








(a) (b) (c)


SiO2

WG

WG

Cu electrode

A

A


BOX

WGSiO2

Si

BOX

SiO2

Inset

50microm

(a) (b)








0 5 10 15 20 25 30 35 40

-36

-30

-24

-18

-12

-6

0

260

GH

z

-10

V23

9 G

Hz

-8

V

211

GH

z

-5 V

178

GH

z

-3 V

116

GH

z

0 V

Cu

EE S

21 (d

B)

Frequency (GHz)

0V -3V -5V -8V -10V -12V -15V -18V -20V

-64 dB marker

310

GH

z

-15

V

~40

GH

z gt

-18

V

281

GH

z

-12

V

(a)

04 05 06 07 08 09 10 11 12 13 14 15 16-05

00

05

10

15

20

25

30

35

40

45

Cu-

indu

ced

WG

pro

paga

tion

loss

(dB

cm

)


(b)












1545 1546 1547 1548 1549-44

-40

-36

-32

-28

-24

-20

-16

-12

-8

Inse

rtio

n lo

ss (d

B)

Wavelength (nm)

0V -2V -4V -6V -8V -10V

Di

0 2 4 6 8 1088

90

92

94

96

Dyn

amic

in

sert

ion

loss

(dB

)


0 2 4 6 8 10

0

60

120

180

240

300


Phas

e sh

ift (d

egre

e)

10

12

14

16

18

20

22


m)

(b)



0 5 10 15 20 25 30 35 40-12

-9

-6

-3

0 (a)

EO S

21 (d

B)

Frequency (GHz)

98

GH

z

0 V

173

GH

z

-1

V

236

GH

z

-2

V

287

GH

z

-3

V

333

GH

z

-4

V

370

GH

z

-5

V

505Gbs ER=708dB (b)






PN junction type

wavelength

Electrodes material


Driving voltage and

bias (V)

Efficiency (Vmm)

EO bandwidth

(GHz)

Data rate

(Gbps)



65 V Vpp -4 V bias 28 NA 50 31


7 V Vpp -5 V bias 267 256 50 556


[12] Al 2



35 V Vpp -3 V bias 31 30 20 40 41 47


15 V Vpp 0 V bias 243 264 30 50 34



7 V Vpp Bias NA 35 20 40 40 66 32


TiTiNAlCuTiTiN 35 1

65 V Vpp Bias NA 27 NA 40 10 35


1550 nm Cu 3

35 V Vpp -5 V bias 185 gt 30 505 708

4 Conclusion






21 Modulator design





G

S

G

S

G

1times2 MMI

out

in

Cudielectric

N++P++ NP

Compensation doping

Inset (a) BOX

SiO2

N++


SiO2

Inset (b)


0 10 20 30 40

-6

-4

-2

0 (a)

EE S

21 a

mpl

itude

(dB

)

Frequency (GHz)


0 10 20 30 40-60

-50

-40

-30

-20

-10

EE S

11 a

mpl

itude

(dB

)Frequency (GHz)


(b)








(a) (b) (c)


SiO2

WG

WG

Cu electrode

A

A


BOX

WGSiO2

Si

BOX

SiO2

Inset

50microm

(a) (b)








0 5 10 15 20 25 30 35 40

-36

-30

-24

-18

-12

-6

0

260

GH

z

-10

V23

9 G

Hz

-8

V

211

GH

z

-5 V

178

GH

z

-3 V

116

GH

z

0 V

Cu

EE S

21 (d

B)

Frequency (GHz)

0V -3V -5V -8V -10V -12V -15V -18V -20V

-64 dB marker

310

GH

z

-15

V

~40

GH

z gt

-18

V

281

GH

z

-12

V

(a)

04 05 06 07 08 09 10 11 12 13 14 15 16-05

00

05

10

15

20

25

30

35

40

45

Cu-

indu

ced

WG

pro

paga

tion

loss

(dB

cm

)


(b)












1545 1546 1547 1548 1549-44

-40

-36

-32

-28

-24

-20

-16

-12

-8

Inse

rtio

n lo

ss (d

B)

Wavelength (nm)

0V -2V -4V -6V -8V -10V

Di

0 2 4 6 8 1088

90

92

94

96

Dyn

amic

in

sert

ion

loss

(dB

)


0 2 4 6 8 10

0

60

120

180

240

300


Phas

e sh

ift (d

egre

e)

10

12

14

16

18

20

22


m)

(b)



0 5 10 15 20 25 30 35 40-12

-9

-6

-3

0 (a)

EO S

21 (d

B)

Frequency (GHz)

98

GH

z

0 V

173

GH

z

-1

V

236

GH

z

-2

V

287

GH

z

-3

V

333

GH

z

-4

V

370

GH

z

-5

V

505Gbs ER=708dB (b)






PN junction type

wavelength

Electrodes material


Driving voltage and

bias (V)

Efficiency (Vmm)

EO bandwidth

(GHz)

Data rate

(Gbps)



65 V Vpp -4 V bias 28 NA 50 31


7 V Vpp -5 V bias 267 256 50 556


[12] Al 2



35 V Vpp -3 V bias 31 30 20 40 41 47


15 V Vpp 0 V bias 243 264 30 50 34



7 V Vpp Bias NA 35 20 40 40 66 32


TiTiNAlCuTiTiN 35 1

65 V Vpp Bias NA 27 NA 40 10 35


1550 nm Cu 3

35 V Vpp -5 V bias 185 gt 30 505 708

4 Conclusion





G

S

G

S

G

1times2 MMI

out

in

Cudielectric

N++P++ NP

Compensation doping

Inset (a) BOX

SiO2

N++


SiO2

Inset (b)


0 10 20 30 40

-6

-4

-2

0 (a)

EE S

21 a

mpl

itude

(dB

)

Frequency (GHz)


0 10 20 30 40-60

-50

-40

-30

-20

-10

EE S

11 a

mpl

itude

(dB

)Frequency (GHz)


(b)








(a) (b) (c)


SiO2

WG

WG

Cu electrode

A

A


BOX

WGSiO2

Si

BOX

SiO2

Inset

50microm

(a) (b)








0 5 10 15 20 25 30 35 40

-36

-30

-24

-18

-12

-6

0

260

GH

z

-10

V23

9 G

Hz

-8

V

211

GH

z

-5 V

178

GH

z

-3 V

116

GH

z

0 V

Cu

EE S

21 (d

B)

Frequency (GHz)

0V -3V -5V -8V -10V -12V -15V -18V -20V

-64 dB marker

310

GH

z

-15

V

~40

GH

z gt

-18

V

281

GH

z

-12

V

(a)

04 05 06 07 08 09 10 11 12 13 14 15 16-05

00

05

10

15

20

25

30

35

40

45

Cu-

indu

ced

WG

pro

paga

tion

loss

(dB

cm

)


(b)












1545 1546 1547 1548 1549-44

-40

-36

-32

-28

-24

-20

-16

-12

-8

Inse

rtio

n lo

ss (d

B)

Wavelength (nm)

0V -2V -4V -6V -8V -10V

Di

0 2 4 6 8 1088

90

92

94

96

Dyn

amic

in

sert

ion

loss

(dB

)


0 2 4 6 8 10

0

60

120

180

240

300


Phas

e sh

ift (d

egre

e)

10

12

14

16

18

20

22


m)

(b)



0 5 10 15 20 25 30 35 40-12

-9

-6

-3

0 (a)

EO S

21 (d

B)

Frequency (GHz)

98

GH

z

0 V

173

GH

z

-1

V

236

GH

z

-2

V

287

GH

z

-3

V

333

GH

z

-4

V

370

GH

z

-5

V

505Gbs ER=708dB (b)






PN junction type

wavelength

Electrodes material


Driving voltage and

bias (V)

Efficiency (Vmm)

EO bandwidth

(GHz)

Data rate

(Gbps)



65 V Vpp -4 V bias 28 NA 50 31


7 V Vpp -5 V bias 267 256 50 556


[12] Al 2



35 V Vpp -3 V bias 31 30 20 40 41 47


15 V Vpp 0 V bias 243 264 30 50 34



7 V Vpp Bias NA 35 20 40 40 66 32


TiTiNAlCuTiTiN 35 1

65 V Vpp Bias NA 27 NA 40 10 35


1550 nm Cu 3

35 V Vpp -5 V bias 185 gt 30 505 708

4 Conclusion





(a) (b) (c)


SiO2

WG

WG

Cu electrode

A

A


BOX

WGSiO2

Si

BOX

SiO2

Inset

50microm

(a) (b)








0 5 10 15 20 25 30 35 40

-36

-30

-24

-18

-12

-6

0

260

GH

z

-10

V23

9 G

Hz

-8

V

211

GH

z

-5 V

178

GH

z

-3 V

116

GH

z

0 V

Cu

EE S

21 (d

B)

Frequency (GHz)

0V -3V -5V -8V -10V -12V -15V -18V -20V

-64 dB marker

310

GH

z

-15

V

~40

GH

z gt

-18

V

281

GH

z

-12

V

(a)

04 05 06 07 08 09 10 11 12 13 14 15 16-05

00

05

10

15

20

25

30

35

40

45

Cu-

indu

ced

WG

pro

paga

tion

loss

(dB

cm

)


(b)












1545 1546 1547 1548 1549-44

-40

-36

-32

-28

-24

-20

-16

-12

-8

Inse

rtio

n lo

ss (d

B)

Wavelength (nm)

0V -2V -4V -6V -8V -10V

Di

0 2 4 6 8 1088

90

92

94

96

Dyn

amic

in

sert

ion

loss

(dB

)


0 2 4 6 8 10

0

60

120

180

240

300


Phas

e sh

ift (d

egre

e)

10

12

14

16

18

20

22


m)

(b)



0 5 10 15 20 25 30 35 40-12

-9

-6

-3

0 (a)

EO S

21 (d

B)

Frequency (GHz)

98

GH

z

0 V

173

GH

z

-1

V

236

GH

z

-2

V

287

GH

z

-3

V

333

GH

z

-4

V

370

GH

z

-5

V

505Gbs ER=708dB (b)






PN junction type

wavelength

Electrodes material


Driving voltage and

bias (V)

Efficiency (Vmm)

EO bandwidth

(GHz)

Data rate

(Gbps)



65 V Vpp -4 V bias 28 NA 50 31


7 V Vpp -5 V bias 267 256 50 556


[12] Al 2



35 V Vpp -3 V bias 31 30 20 40 41 47


15 V Vpp 0 V bias 243 264 30 50 34



7 V Vpp Bias NA 35 20 40 40 66 32


TiTiNAlCuTiTiN 35 1

65 V Vpp Bias NA 27 NA 40 10 35


1550 nm Cu 3

35 V Vpp -5 V bias 185 gt 30 505 708

4 Conclusion




0 5 10 15 20 25 30 35 40

-36

-30

-24

-18

-12

-6

0

260

GH

z

-10

V23

9 G

Hz

-8

V

211

GH

z

-5 V

178

GH

z

-3 V

116

GH

z

0 V

Cu

EE S

21 (d

B)

Frequency (GHz)

0V -3V -5V -8V -10V -12V -15V -18V -20V

-64 dB marker

310

GH

z

-15

V

~40

GH

z gt

-18

V

281

GH

z

-12

V

(a)

04 05 06 07 08 09 10 11 12 13 14 15 16-05

00

05

10

15

20

25

30

35

40

45

Cu-

indu

ced

WG

pro

paga

tion

loss

(dB

cm

)


(b)












1545 1546 1547 1548 1549-44

-40

-36

-32

-28

-24

-20

-16

-12

-8

Inse

rtio

n lo

ss (d

B)

Wavelength (nm)

0V -2V -4V -6V -8V -10V

Di

0 2 4 6 8 1088

90

92

94

96

Dyn

amic

in

sert

ion

loss

(dB

)


0 2 4 6 8 10

0

60

120

180

240

300


Phas

e sh

ift (d

egre

e)

10

12

14

16

18

20

22


m)

(b)



0 5 10 15 20 25 30 35 40-12

-9

-6

-3

0 (a)

EO S

21 (d

B)

Frequency (GHz)

98

GH

z

0 V

173

GH

z

-1

V

236

GH

z

-2

V

287

GH

z

-3

V

333

GH

z

-4

V

370

GH

z

-5

V

505Gbs ER=708dB (b)






PN junction type

wavelength

Electrodes material


Driving voltage and

bias (V)

Efficiency (Vmm)

EO bandwidth

(GHz)

Data rate

(Gbps)



65 V Vpp -4 V bias 28 NA 50 31


7 V Vpp -5 V bias 267 256 50 556


[12] Al 2



35 V Vpp -3 V bias 31 30 20 40 41 47


15 V Vpp 0 V bias 243 264 30 50 34



7 V Vpp Bias NA 35 20 40 40 66 32


TiTiNAlCuTiTiN 35 1

65 V Vpp Bias NA 27 NA 40 10 35


1550 nm Cu 3

35 V Vpp -5 V bias 185 gt 30 505 708

4 Conclusion




1545 1546 1547 1548 1549-44

-40

-36

-32

-28

-24

-20

-16

-12

-8

Inse

rtio

n lo

ss (d

B)

Wavelength (nm)

0V -2V -4V -6V -8V -10V

Di

0 2 4 6 8 1088

90

92

94

96

Dyn

amic

in

sert

ion

loss

(dB

)


0 2 4 6 8 10

0

60

120

180

240

300


Phas

e sh

ift (d

egre

e)

10

12

14

16

18

20

22


m)

(b)



0 5 10 15 20 25 30 35 40-12

-9

-6

-3

0 (a)

EO S

21 (d

B)

Frequency (GHz)

98

GH

z

0 V

173

GH

z

-1

V

236

GH

z

-2

V

287

GH

z

-3

V

333

GH

z

-4

V

370

GH

z

-5

V

505Gbs ER=708dB (b)






PN junction type

wavelength

Electrodes material


Driving voltage and

bias (V)

Efficiency (Vmm)

EO bandwidth

(GHz)

Data rate

(Gbps)



65 V Vpp -4 V bias 28 NA 50 31


7 V Vpp -5 V bias 267 256 50 556


[12] Al 2



35 V Vpp -3 V bias 31 30 20 40 41 47


15 V Vpp 0 V bias 243 264 30 50 34



7 V Vpp Bias NA 35 20 40 40 66 32


TiTiNAlCuTiTiN 35 1

65 V Vpp Bias NA 27 NA 40 10 35


1550 nm Cu 3

35 V Vpp -5 V bias 185 gt 30 505 708

4 Conclusion





PN junction type

wavelength

Electrodes material


Driving voltage and

bias (V)

Efficiency (Vmm)

EO bandwidth

(GHz)

Data rate

(Gbps)



65 V Vpp -4 V bias 28 NA 50 31


7 V Vpp -5 V bias 267 256 50 556


[12] Al 2



35 V Vpp -3 V bias 31 30 20 40 41 47


15 V Vpp 0 V bias 243 264 30 50 34



7 V Vpp Bias NA 35 20 40 40 66 32


TiTiNAlCuTiTiN 35 1

65 V Vpp Bias NA 27 NA 40 10 35


1550 nm Cu 3

35 V Vpp -5 V bias 185 gt 30 505 708

4 Conclusion



Documents

High-efficiency Si optical modulator using Cu travelling ...€¦ · material in silicon optical modulators [6–14]. For example, one kind of silicon slot photonic crystal modulator