Towards Compact and High Speed Silicon Modulators

Los moduladores son elementos claves para la transmisión de la señal y el procesamiento de la información. Las técnicas de fabricación avanzadas "complementary metal-oxide semiconductor" (CMOS) permiten reducir drásticamente las dimensiones de estos dispositivos de interés para la implementación a gran escala en un chip de silicito a bajo coste. El trabajo realizado en esta tesis se centra en el diseño, la fabricación y la caracterización de estructuras de onda lenta con el objetivo de realizar moduladores compactos y eficientes integrados en un chip de silicio. El trabajo se divide en cuatro capítulos y un capítulo de conclusión y perspectivas. El capítulo uno introduce los fundamentos de física del estado sólido y de los mecanismos básicos de propagación guiada de la luz por reflexión total interna. El capítulo dos presenta los parámetros importantes de los moduladroes electro-ópticos así como un trabajo de recopilación de todos los mecanismos físicos que pueden ser empleados para modular la luz en silicio. Además, se presenta el estado del arte de los moduladores basados en silicio. El capítulo tres presenta el diseño , fabricación y caracterización de un modulador electro-óptico en silicio compacto y eficiente basado en el efecto de onda lenta en una estructura periódica unidimensional integrada, cuya geometría, similar a la de una red de Bragg, permite reducir la velocidad de grupo de un paquetes de ondas. Dicho efecto, se emplea para incrementar la interacción luz-materia y por lo tanto la eficiencia del modulador electro-óptico. El capítulo cuatro demuestra experimentalmente que dicha guía unidimensional periódica puede ser mejorada a fin de conseguir que el efecto de baja velocidad de grupo suceda en un rango mayor de longitudes de onda para posibles aplicaciones como la multiplexación por división de longitudinal de onda. En el capítulo cinco, se proporcionan conclusiones y perspectivas sobre el trabajo realizado.Brimont ., ACJ. (2011). Towards Compact and High Speed Silicon Modulators [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/14345Palanci

Toward Nonvolatile Switching in Silicon Photonic Devices

[EN] Nonvolatile switching is still a missing functionality in current mainstream silicon photonics complementary metal-oxide-semiconductor platforms. Fundamentally, nonvolatile switching stands for the ability to switch between two or more photonic states reversibly without needing additional energy to hold each state. Therefore, such a feature may push one step further the potential of silicon photonics by offering new ways of achieving photonic reconfigurability with ultrasmall energy consumption. Here, a detailed review of current developments that enable nonvolatile switching in silicon photonic waveguide devices is provided. Nonvolatility is successfully demonstrated either based on device engineering or by hybrid integration of silicon waveguides with materials exhibiting unique optical properties. Furthermore, several approaches with high potential for evolving toward a nonvolatile behavior with enhanced performance are also being explored. In most cases, many development steps are still necessary to ensure reliable devices. However, this research field is expected to progress in the coming years boosted by current and emerging applications benefiting from such functionality, such as new paradigms for photonic computing or advanced reconfigurable circuits for programmable photonic systems.This work was supported by Ministerio de Economia y Competitividad (MINECO) (TEC2016-76849); Ministerio de Ciencia e Innovacion (PID2019-111460GB-I00, FPU17/04224); and Generalitat Valenciana (PROMETEO/2019/123).Parra Gómez, J.; Olivares-Sánchez-Mellado, I.; Brimont, ACJ.; Sanchis Kilders, P. (2021). Toward Nonvolatile Switching in Silicon Photonic Devices. Laser & Photonics Review. 15(6):1-18. https://doi.org/10.1002/lpor.20200050111815

Ultra-compact optical switches using slow light bimodal silicon waveguides

[EN] Switches are essential components in several optical applications, in which reduced footprints are highly desirable for mass production of densely integrated circuits at low cost. However, most conventional solutions rely on making long switching structures, thus increasing the final device size. Here, we propose and experimentally demonstrate an ultra-compact 2x2 optical switch based on slow-light-enhanced bimodal interferometry in one-dimensional silicon photonic crystals. By properly designing the band structure, the device exhibits a large group index contrast between the fundamental even mode and a higher order odd mode for TE polarization. Thereby, highly dispersive and broadband bimodal regions for high-performance operation are engineered by exploiting the different symmetry of the modes. Two configurations are considered in the experiments to analyze the dimensions influence on the switching efficiency. As a result, a photonic switch based on a bimodal single-channel interferometer with a footprint of only 63 mu m(2), a power consumption of 19.5 mW and a crosstalk of 15 dB is demonstrated for thermo-optic tunability.This work was supported in part by Generalitat Valenciana under Grants AVANTI/2019/123 and ACIF/2019/009, in part by the Spanish Ministerio de Ciencia e Innovacion through PID2019-106965RBC21 and PID2019-111460GB-I00 projects, and in part by the European Union through the operational program of the European Regional Development Fund (FEDER) of the Valencia Regional Government 2014-2020Torrijos-Morán, L.; Brimont, ACJ.; Griol Barres, A.; Sanchis Kilders, P.; García-Rupérez, J. (2021). Ultra-compact optical switches using slow light bimodal silicon waveguides. Journal of Lightwave Technology. 39(11):3495-3501. https://doi.org/10.1109/JLT.2021.3066479S34953501391

High-contrast 40 Gb/s operation of a 500 um long silicon carrier-depletion slow wave modulator

This paper was published in OPTICS LETTERS and is made available as an electronic reprint with the permission of OSA. The paper can be found at the following URL on the OSA website: http://dx.doi.org/10.1364/OL.37.003504. Systematic or multiple reproduction or distribution to multiple locations via electronic or other means is prohibited and is subject to penalties under law[EN] In this Letter, we demonstrate a highly efficient, compact, high-contrast and low-loss silicon slow wave modulator based on a traveling-wave Mach¿Zehnder interferometer with two 500 μm long slow wave phase shifters. 40 Gb ∕ s operation with 6.6 dB extinction ratio at quadrature and with an on-chip insertion loss of only 6 dB is shown. These results confirm the benefits of slow light as a means to enhance the performance of silicon modulators based on the plasma dispersion effect.Funding by the European Commission (EC) under project Photonics Electronics Functional Integration on CMOS (HELIOS) (FP7224312) and PROMETEO-2010- 087 R&D Excellency Program are acknowledged. F.Y.G, D.J.T. and G.T.R. acknowledge funding support from the United Kingdom Engineering and Physical Sciences Research Council (EPSRC) under the grant “UK Silicon Photonics”.Brimont, ACJ.; Thomson, DJ.; Gardes, FY.; Fedeli, JM.; Reed, GT.; Martí Sendra, J.; Sanchis Kilders, P. (2012). High-contrast 40 Gb/s operation of a 500 um long silicon carrier-depletion slow wave modulator. Optics Letters. 37(17):3504-3506. https://doi.org/10.1364/OL.37.003504S350435063717Liao, L., Liu, A., Rubin, D., Basak, J., Chetrit, Y., Nguyen, H., … Paniccia, M. (2007). 40 Gbit/s silicon optical modulator for high-speed applications. Electronics Letters, 43(22), 1196. doi:10.1049/el:20072253Gardes, F. Y., Thomson, D. J., Emerson, N. G., & Reed, G. T. (2011). 40 Gb/s silicon photonics modulator for TE and TM polarisations. Optics Express, 19(12), 11804. doi:10.1364/oe.19.011804Thomson, D. J., Gardes, F. Y., Hu, Y., Mashanovich, G., Fournier, M., Grosse, P., … Reed, G. T. (2011). High contrast 40Gbit/s optical modulation in silicon. Optics Express, 19(12), 11507. doi:10.1364/oe.19.011507Brimont, A., Thomson, D. J., Sanchis, P., Herrera, J., Gardes, F. Y., Fedeli, J. M., … Martí, J. (2011). High speed silicon electro-optical modulators enhanced via slow light propagation. Optics Express, 19(21), 20876. doi:10.1364/oe.19.020876Ziebell, M., Marris-Morini, D., Rasigade, G., Fédéli, J.-M., Crozat, P., Cassan, E., … Vivien, L. (2012). 40 Gbit/s low-loss silicon optical modulator based on a pipin diode. Optics Express, 20(10), 10591. doi:10.1364/oe.20.010591Dong, P., Chen, L., & Chen, Y. (2012). High-speed low-voltage single-drive push-pull silicon Mach-Zehnder modulators. Optics Express, 20(6), 6163. doi:10.1364/oe.20.006163Taylor, H. F. (1999). Enhanced electrooptic modulation efficiency utilizing slow-wave optical propagation. Journal of Lightwave Technology, 17(10), 1875-1883. doi:10.1109/50.793770O’Faolain, L., Beggs, D. M., White, T. P., Kampfrath, T., Kuipers, K., & Krauss, T. F. (2010). Compact Optical Switches and Modulators Based on Dispersion Engineered Photonic Crystals. IEEE Photonics Journal, 2(3), 404-414. doi:10.1109/jphot.2010.2047918Brimont, A., Vicente Galán, J., Maria Escalante, J., Martí, J., & Sanchis, P. (2010). Group-index engineering in silicon corrugated waveguides. Optics Letters, 35(16), 2708. doi:10.1364/ol.35.002708Soref, R., & Bennett, B. (1987). Electrooptical effects in silicon. IEEE Journal of Quantum Electronics, 23(1), 123-129. doi:10.1109/jqe.1987.1073206Nguyen, H. C., Sakai, Y., Shinkawa, M., Ishikura, N., & Baba, T. (2011). 10 Gb/s operation of photonic crystal silicon optical modulators. Optics Express, 19(14), 13000. doi:10.1364/oe.19.013000Dong, P., Liao, S., Liang, H., Qian, W., Wang, X., Shafiiha, R., … Asghari, M. (2010). High-speed and compact silicon modulator based on a racetrack resonator with a 1 V drive voltage. Optics Letters, 35(19), 3246. doi:10.1364/ol.35.00324

High performace silicon 2x2 optical switch based on a thermo-optically tunable multimode interference coupler and efficient electrodes

Optical switches based on tunable multimode interference (MMI) couplers can simultaneously reduce the footprint and increase the tolerance against fabrication deviations. Here, a compact 2x2 silicon switch based on a thermo-optically tunable MMI structure with a footprint of only 0.005mm2 is proposed and demonstrated. The MMI structure has been optimized using a silica trench acting as a thermal isolator without introducing any substantial loss penalty or crosstalk degradation. Furthermore, the electrodes performance have significantly been improved via engineering the heater geometry and using two metallization steps. Thereby, a drastic power consumption reduction of around 90% has been demonstrated yielding to values as low as 24.9 mW. Furthermore, very fast switching times of only 1.19 μs have also been achieved.Financial support from LEOMIS TEC2012-38540 and PROMETEOII/2014/034 projects is acknowledged. Alvaro Rosa also acknowledges the Spanish Ministry of Economy and Competitiveness for funding his grant. The authors also would like to thank the Electronic Microscopy Department at UPV for taking the SEM images.Rosa Escutia, Á.; Gutiérrez Campo, AM.; Brimont, ACJ.; Griol Barres, A.; Sanchis Kilders, P. (2016). High performace silicon 2x2 optical switch based on a thermo-optically tunable multimode interference coupler and efficient electrodes. Optics Express. 24(1):191-198. https://doi.org/10.1364/OE.24.000191S191198241Subbaraman, H., Xu, X., Hosseini, A., Zhang, X., Zhang, Y., Kwong, D., & Chen, R. T. (2015). Recent advances in silicon-based passive and active optical interconnects. Optics Express, 23(3), 2487. doi:10.1364/oe.23.002487Nikolova, D., Rumley, S., Calhoun, D., Li, Q., Hendry, R., Samadi, P., & Bergman, K. (2015). Scaling silicon photonic switch fabrics for data center interconnection networks. Optics Express, 23(2), 1159. doi:10.1364/oe.23.001159Dong, P., Preble, S. F., & Lipson, M. (2007). All-optical compact silicon comb switch. Optics Express, 15(15), 9600. doi:10.1364/oe.15.009600Biberman, A., Lira, H. L. R., Padmaraju, K., Ophir, N., Chan, J., Lipson, M., & Bergman, K. (2011). Broadband Silicon Photonic Electrooptic Switch for Photonic Interconnection Networks. IEEE Photonics Technology Letters, 23(8), 504-506. doi:10.1109/lpt.2011.2112763Li, G., Zheng, X., Yao, J., Thacker, H., Shubin, I., Luo, Y., … Krishnamoorthy, A. V. (2011). 25Gb/s 1V-driving CMOS ring modulator with integrated thermal tuning. Optics Express, 19(21), 20435. doi:10.1364/oe.19.020435Densmore, A., Janz, S., Ma, R., Schmid, J. H., Xu, D.-X., Delâge, A., … Cheben, P. (2009). Compact and low power thermo-optic switch using folded silicon waveguides. Optics Express, 17(13), 10457. doi:10.1364/oe.17.010457Van Campenhout, J., Green, W. M., Assefa, S., & Vlasov, Y. A. (2009). Low-power, 2×2 silicon electro-optic switch with 110-nm bandwidth for broadband reconfigurable optical networks. Optics Express, 17(26), 24020. doi:10.1364/oe.17.024020Dong, P., Liao, S., Liang, H., Shafiiha, R., Feng, D., Li, G., … Asghari, M. (2010). Submilliwatt, ultrafast and broadband electro-optic silicon switches. Optics Express, 18(24), 25225. doi:10.1364/oe.18.025225Sun, P., & Reano, R. M. (2010). Submilliwatt thermo-optic switches using free-standing silicon-on-insulator strip waveguides. Optics Express, 18(8), 8406. doi:10.1364/oe.18.008406Watts, M. R., Sun, J., DeRose, C., Trotter, D. C., Young, R. W., & Nielson, G. N. (2013). Adiabatic thermo-optic Mach–Zehnder switch. Optics Letters, 38(5), 733. doi:10.1364/ol.38.000733Harris, N. C., Ma, Y., Mower, J., Baehr-Jones, T., Englund, D., Hochberg, M., & Galland, C. (2014). Efficient, compact and low loss thermo-optic phase shifter in silicon. Optics Express, 22(9), 10487. doi:10.1364/oe.22.010487Suzuki, K., Cong, G., Tanizawa, K., Kim, S.-H., Ikeda, K., Namiki, S., & Kawashima, H. (2015). Ultra-high-extinction-ratio 2 × 2 silicon optical switch with variable splitter. Optics Express, 23(7), 9086. doi:10.1364/oe.23.009086Sanchez, L., Griol, A., Lechago, S., Brimont, A., & Sanchis, P. (2015). Low-Power Operation in a Silicon Switch Based on an Asymmetric Mach–Zehnder Interferometer. IEEE Photonics Journal, 7(2), 1-8. doi:10.1109/jphot.2015.2407317Besse, P. A., Bachmann, M., Melchior, H., Soldano, L. B., & Smit, M. K. (1994). Optical bandwidth and fabrication tolerances of multimode interference couplers. Journal of Lightwave Technology, 12(6), 1004-1009. doi:10.1109/50.296191Soldano, L. B., & Pennings, E. C. M. (1995). Optical multi-mode interference devices based on self-imaging: principles and applications. Journal of Lightwave Technology, 13(4), 615-627. doi:10.1109/50.372474Leuthold, J., & Joyner, C. W. (2001). Multimode interference couplers with tunable power splitting ratios. Journal of Lightwave Technology, 19(5), 700-707. doi:10.1109/50.923483Fan Wang, Jianyi Yang, Limei Chen, Xiaoqing Jiang, & Minghua Wang. (2006). Optical switch based on multimode interference coupler. IEEE Photonics Technology Letters, 18(2), 421-423. doi:10.1109/lpt.2005.86320

Compact and low-loss asymmetrical multimode interference splitter for power monitoring applications

[EN] This Letter presents a compact and low-loss 1 x 2 asymmetrical multimode interference (A-MMI) splitter in rib geometry for on-chip power monitoring at 1.55 mu m, where a given alteration of the component cavity determines arbitrary values of the output power splitting ratios. The device shows reduced losses (similar to 0.4-0.8 dB) and robustness across a 40 nm optical bandwidth (1540-1580 nm). (C) 2016 Optical Society of America7th European community Framework Programme (FP7-ICT-318240); Spanish Ministry of Science and Technology (TEC2012-38540).Zanzi, A.; Brimont, ACJ.; Griol Barres, A.; Sanchis Kilders, P.; Martí Sendra, J. (2016). Compact and low-loss asymmetrical multimode interference splitter for power monitoring applications. Optics Letters. 41(2):227-229. https://doi.org/10.1364/OL.41.000227S227229412Zang, Z., Minato, T., Navaretti, P., Hinokuma, Y., Duelk, M., Velez, C., & Hamamoto, K. (2010). High-Power ($> 110$ mW) Superluminescent Diodes by Using Active Multimode Interferometer. IEEE Photonics Technology Letters, 22(10), 721-723. doi:10.1109/lpt.2010.2044994Zang, Z., Mukai, K., Navaretti, P., Duelk, M., Velez, C., & Hamamoto, K. (2012). Thermal resistance reduction in high power superluminescent diodes by using active multi-mode interferometer. Applied Physics Letters, 100(3), 031108. doi:10.1063/1.3678188Soldano, L. B., & Pennings, E. C. M. (1995). Optical multi-mode interference devices based on self-imaging: principles and applications. Journal of Lightwave Technology, 13(4), 615-627. doi:10.1109/50.372474Bachmann, M., Besse, P. A., & Melchior, H. (1994). General self-imaging properties in N × N multimode interference couplers including phase relations. Applied Optics, 33(18), 3905. doi:10.1364/ao.33.003905Reed, G. T., Hu, Y., Thomson, D. J., Khokhar, A. Z., Stanković, S., Mitchell, C. J., … Mashanovich, G. Z. (2015). Fabrication error tolerant SOI WDM device using bidirectional angled multimode interferometers. Silicon Photonics X. doi:10.1117/12.2076824Halir, R., Molina-Fernandez, I., Ortega-Monux, A., Wanguemert-Perez, J. G., Xu, D.-X., Cheben, P., & Janz, S. (2008). A Design Procedure for High-Performance, Rib-Waveguide-Based Multimode Interference Couplers in Silicon-on-Insulator. Journal of Lightwave Technology, 26(16), 2928-2936. doi:10.1109/jlt.2007.914511Halir, R., Roelkens, G., Ortega-Moñux, A., & Wangüemert-Pérez, J. G. (2011). High-performance 90° hybrid based on a silicon-on-insulator multimode interference coupler. Optics Letters, 36(2), 178. doi:10.1364/ol.36.000178Zhen Sheng, Zhiqi Wang, Chao Qiu, Le Li, Pang, A., Aimin Wu, … Fuwan Gan. (2012). A Compact and Low-Loss MMI Coupler Fabricated With CMOS Technology. IEEE Photonics Journal, 4(6), 2272-2277. doi:10.1109/jphot.2012.2230320Yi-Ling, S., Xiao-Qing, J., Jian-Yi, Y., Yi, T., & Ming-Hua, W. (2003). Experimental Demonstration of Two-Dimensional Multimode-Interference Optical Power Splitter. Chinese Physics Letters, 20(12), 2182-2184. doi:10.1088/0256-307x/20/12/027Deng, Q., Liu, L., Li, X., & Zhou, Z. (2014). Arbitrary-ratio 1 × 2 power splitter based on asymmetric multimode interference. Optics Letters, 39(19), 5590. doi:10.1364/ol.39.00559

Low-Power Operation in a Silicon Switch Based on an Asymmetric Mach Zehnder Interferometer

[EN] Mach Zehnder interferometer (MZI) structures are widely used as optical switches in photonic integrated circuits. However, power consumption is still the key parameter to make such devices practical in the silicon platform, particularly for those based on the thermo-optic effect. A new approach to significantly decrease the power consumption of a silicon switch based on an asymmetric MZI, together with an optimum selection of the operation wavelengths, is proposed. A power consumption reduction up to 50% is experimentally demonstrated in agreement with simulation results.This work was supported by TEC2012-38540 LEOMIS and NANOMET PLUS-Conselleria d'Educacio, Cultura i EsportPROMETEOII/2014/034. The work of L. Sanchez was supported by Generalitat Valenciana in the context of the VALi+d program.Sánchez Diana, LD.; Griol Barres, A.; Lechago Buendía, S.; Brimont, ACJ.; Sanchis Kilders, P. (2015). Low-Power Operation in a Silicon Switch Based on an Asymmetric Mach Zehnder Interferometer. IEEE Photonics Journal. 7(2):1-8. https://doi.org/10.1109/JPHOT.2015.2407317S187

A CMOS Compatible Silicon-on-Insulator Polarization Rotator Based on Symmetry Breaking of the Waveguide Cross Section

[EN] A polarization rotator in silicon-on-insulator technology based on breaking the symmetry of the waveguide cross section is reported. The 25-mu m-long device is designed to be integrated with standard grating couplers without the need for extra fabrication steps. Hence, fabrication is carried out by a 2-etch-step complementary metal-oxide-semiconductor compatible process using 193-nm deep ultraviolet lithography. A polarization conversion efficiency of more than -0.85 dB with insertion losses ranging from -1 to -2.5 dB over a wavelength range of 30 nm is demonstrated. © 1989-2012 IEEEThis work was supported by the European Commission under Project HELIOS (pHotonics Electronics functional Integration on CMOS), FP7-224312, TEC2008-06333 SINADEC and PROMETEO-2010-087 R&D Excellency Program (NANOMET).Aamer, M.; Gutiérrez Campo, AM.; Brimont, ACJ.; Vermeulen, D.; Roelkens, G.; Fedeli, J.; Håkansson, OA.... (2012). A CMOS Compatible Silicon-on-Insulator Polarization Rotator Based on Symmetry Breaking of the Waveguide Cross Section. IEEE Photonics Technology Letters. 24(22):2031-2034. https://doi.org/10.1109/LPT.2012.2218593S20312034242

Low-Loss and Compact Silicon Rib Waveguide Bends

[EN] Waveguide bends support intrinsically leaky propagation modes due to unavoidable radiation losses. It is known that the losses of deep-etched/strip waveguide bends increase inevitably for decreasing radius. Here, we theoretically and experimentally demonstrate that this result is not directly applicable to shallow-etched/rib waveguide bends. Indeed, we show that the total losses caused by the bends reach a local minimum value for a certain range of compact radii and rib waveguide dimensions. Specifically, we predicted the minimum intrinsic losses < 0.1 dB/90 degrees turn within the range of 25-30 mu m bend radii in a 220 nm-thick and 400 nm-wide silicon rib waveguide with 70 nm etching depth. This unexpected outcome, confirmed by experimental evidence, is due to the opposite evolution of radiation (bending) losses and losses caused by the coupling to lateral slab modes (slab leakage) as a function of the bend radius, hence creating an optimum loss region. This result may have important implications for the design of compact and low-loss silicon nanophotonic devices.This work was supported in part by the European STREP Program under Grant FP7-ICT-2013-11-619456-SITOGA and Grant FP7-ICT-2012-10-318240 PhoxTroT and in part by LEOMIS under Grant TEC2012-38540. (Corresponding author: Regis Orobtchouk.)Brimont, ACJ.; Hu, X.; Cueff, S.; Rojo-Romeo, P.; Saint Girons, G.; Griol Barres, A.; Zanzi, A.... (2016). Low-Loss and Compact Silicon Rib Waveguide Bends. IEEE Photonics Technology Letters. 28(3):299-302. https://doi.org/10.1109/LPT.2015.2495230S29930228

Optical fiber-to-chip assembly process for ultra-low loss photonic devices based on silicon nitride for space applications

[EN] In this work, we demonstrate an efficient fiber array-to-chip assembly process with a high number of input/output ports. The proposed approach is based on using a pre-alignment coupling structure to separately align the input and output ports. The assembling process has been experimentally validated in photonic integrated circuits fabricated with an ultra-low-loss waveguide technology based on silicon nitride, which features propagation losses as low as 9.5 dB/m. The developed technology is expected to extend the use of integrated photonics for space applicationsThis work was supported by EU-funded H2020 project RETINA under grant agreement n° 821943Brimont, ACJ.; Zurita Herranz, D.; Duarte, VC.; Mengual, T.; Chmielak, B.; Suckow, S.; Giesecke, A.... (2020). Optical fiber-to-chip assembly process for ultra-low loss photonic devices based on silicon nitride for space applications. 1-3. http://hdl.handle.net/10251/1786581