Absil, P

Bogaerts, Wim

Lepage, G

Moelants, M

Pantouvaki, M

Radisic, D

Van Campenhout, J

Vandervorst, A

Verheyen, P

Wouters, J

Yu, Hui

English

Ghent University Academic Bibliography

Lateral versus Interdigitated Voltage LowM. Pantouvaki, H. Yu1, P. Verheyen, G. Lepage, W. BogaertsVandervorst, P. Absil 1Photonics Research Group, Dept. of Information Technology, Ghent University  Abstract:  Silicon ring modulators with interdigitated diodes loss for 1 Vpp, a 4.5 dB improvement over the lateral diode dSilicon ring optical modulators are attracting increasing interest co-integrated with CMOS electronicsloss, high modulation efficiency, multimodulation has been reported in carrier[1, 2]. However, the obtained extinction ratios were limited to 5dB for imodulators are typically designed with the depletion area Modulators with junctions perpendicular to the waveguide (increase the modulation efficiency and extinction ratio, however incompatible with CMOS [3, 4]. differing only in the diode design. We fachieving a 7.5 dB extinction ratio for 3the lateral diode design. Open eye diagrams The silicon ring modulators were fabricated crystalline silicon on 2 µm thick buried oxideetching of 70 nm Si. 248 nm lithography was subsequently used to define the Figure 1(a). Conventional back-end-Figure 1: a) Lateral versus interdigitatedwith lateral and c) interdigitated diode designFigure 1(a) shows the two diode designs that were investigated on ring modulators 450 nm waveguide width, 570 nm 0.8e18cm-3 for both p and n dopants. are parallel to the ring waveguide, and the second was the periodically interleaved perpendicularly to the ring. The widtn-doping, while the interaction length was of ~380 fF at 0 V for rings with the longitudinal resistance of ~20 Ohm for both. Transmission spectra for different bias conditions of the lateral and designs are shown in Figures 1(b) and 1(c)and interdigitated designs respectively. Consequently, the calculated 312.5 GHz for the lateral design, limited by the cavity photon lifetime, and 6by the RC time constant when driven from a 50 Ohm transmission lineFigure 2 shows the static extinction lateral and interdigitated modulator Diode Design for -Loss Silicon Ring Modulators 1, M. Moelants, J. Wouters, D. Radisic, A. and J. Van Campenhout  imec, Kapeldreef 75, 3001, Leuven, Belgium – imec, Center of Nano- and Biophotonics (NB Photonics),Pietersnieuwstraat 41, 9000 Ghent, Belgium Author e-mail address:pantouvm@imec.be demonstrate 7.5 dB extinction ratios esign, and can operate up to 10 Gb/sfor low energy, small footprint . Key requirements for such devices are high extinction ratio, low insertion -Gb/s speed and low energy per bit. Recently, 10-depletion ring modulators using a 1 V peak-to-nsertion losses lower than 3dB.parallel to the waveguideinterdigitated diode designso far they required high In this work we compare the performance of two ind that the interdigitated design results in higher modulation efficiency,  dB insertion loss using 1 Vpp, as opposed to only 3were obtained at 10 Gb/s for both modulator on 200 mm Silicon-On-Insulator (SOI) wafers with 220 nm . Rings of 40 µm radius were defined by 193p- and n-doping patterns as shown in of line W contacts and Cu metal interconnects were used for wiring diode design. b) Transmitted power versus wavelength of silicon ring modulators , for different applied bias.   wgap between the ring and the bus waveguide, and nominal The first was the typical lateral diode design, where the pinterdigitated pattern, where the ph of the fingers in this case was 300d1 = 1.8 µm for each finger. This resulted in a lowdesign as opposed to 97 fF for the lateral . The experimental quality factors Q were 15400 and 18700 for the dB cut-off frequency for the GHz for the longitudinal design.  ratio at1 Vpp and the corresponding insertion loss design. While both modulators are capable of high extinction ratios10 Gb/s Low- St. at 3 dB insertion . optical interconnects  Gb/s and 25 Gb/s optical peak driving voltage (Vpp)  Such  (lateral diode design). ) have been proposed to voltage swings Vpp, identical ring modulators,  dB extinction ratio with types.  thick  nm lithography and dry .  ith identical dimensions of doping densities of - and n- doped areas - and n-doped areas are  nm for both p- and -frequency capacitance design, and a series interdigitated  lateral se devices was  limited versus wavelength for  at resonance, the interdigitated diode design results in smaller losses for higher extinction ratios. In particular, extinction ratios of 18.5 dB and 29insertion losses of 7.9 dB and 4.8 dBratios for the lateral and interdigitated patterns werewavelength shift of the two designs with applied bias. design, this was increased to 30 pm/V for the interdigitatedEye diagrams from both devices sequence (PRBS) of 215-1 are shown in Figure energy consumption of about 31 fJ/bit and are open with dynamic extinctioninterdigitated modulator is suffering improved by reducing the interaction lwaveguide area, a reduction in capacitancesubstantial penalty on the extinction ratio and insertion loss. In athe power consumption in future devices.Figure 2: Extinction ratio and insertion loss versus wavelengthextinction ratios corresponding to 3 dB insertion loss are indicated by the shadowed areas in each plot. resonance wavelength shift with applied voltage for Figure 3: 10 Gb/s optical eye diagrams In conclusion, a comparison of silicon ring modulators differing only in the diode design was made. Extinction ratios of 3 dB and 7.5 dB for an insertion loss of 3the interdigitated diode design respectively. Both devices generatedmodulation speed is close to the RC limit for The authors acknowledge the efforts of imec’s 200work was supported by imec’s Core Partner ProgramReferences    [1] G. Li, X. Zheng, J. Yao, H. Thacker, I. Shubin, Y. Luo, K. Raj, J. E. Curing modulator with integrated thermal tuning[2] P. Dong, Sh. Liao, H. Liang, W. Qian, X. Wang, R. Shafiiha, D. Feng, G. Li, X. Zheng, A. V. Krishnamoorand compact silicon modulator based on a racetrack resonator with a 1V drive voltage,” Optics Letters [3] M. Ziebell, D. Marris-Morini, Gilles Rasigade, P. Crozat, J.modulator based on interdigitated PN junctions,” Optics Express 19, 14690[4] H. Yu, W. Bogaerts, K. Komorowska, R. Baets, D. Korn, L. Alloatti, D. Hillerkuss, C. Koos, W. Freude, J. LeutholVerheyen and P. Absil, “Comparison between carrierCommunication Conference 2012.   dB were measured for lateral and interdigitated modulators respectively. More specifically, for an insertion loss  3 dB and 7.5 dB respectively. Figure While the modulation efficiency was 2 design.  generated at 10 Gb/s using 1.2 Vpp at -1 V DC bias 3. Considering the capacitance of each device, this corresponds to an 117 fJ/bit for the lateral and interdigitated device ratios in excess of 10 dB. However, the horizontal eye opening of the from the RC frequency limitation of this device. Thength of the diode fingers (d1). If the interaction length is limited to the  and power consumption by a factor of up to ddition, shrinking the ring radius will help to lower    at 1 Vpp for a) lateral and b) interdigitatedlateral and interdigitated diode design. at 1.2 Vpp of ring modulators with (a) lateral and (b) interdigitated dB and driving voltage 1 Vpp were obtained  open-eye diagrams at 10the current interdigitated-diode design.  -mm pline for their contributions to the device fabrication. This. nningham, and A. V. Krishnamoorthy,” Optics Express 19(21), 20435-443 (2011). 35(19), 3246-M. Fedeli, P. Grosse, E. Cassan, and L Vivien, “Ten Gbit/s ring resonator silicon -695 (2011).  -depletion-based silicon modulators with different doping patterns,” Omaximum , corresponding to of 3 dB, the extinction 2(c) shows the resonance 2 pm/V for the lateral and a pseudo-random bit s respectively. Both eyes is speed limitation can be 3 is expected, without a   diode design. The c) Comparison of   diode design. with the lateral and  Gb/s, although this  , “25Gb/s 1V-driving CMOS thy, and M. Asghari, “High-speed -3248, (2010). d, J. Van Campenhout, P. ptical Fiber 

Lateral versus interdigitated diode design for 10 Gb/s low-voltage low-loss silicon ring modulators

https://biblio.ugent.be/publication/2996842/file/2996855

Lateral versus interdigitated diode design for 10 Gb/s low-voltage low-loss silicon ring modulators

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