Development of Photonic Devices Based on the Strained Silicon Technology

[ES] En la última década, la plataforma de silicio ha emergido como la plataforma por excelencia para desarrollar circuitos fotónicos integrados debido a su versatilidad, la posibilidad de miniaturización y de una producción de bajo coste y a gran escala compatible con los sistemas CMOS ("complementary metal-oxide semiconductor"). La conversión de señales eléctricas a alta velocidad en señales ópticas es una función crítica hoy en día tanto para el procesamiento de datos como en el ámbito de las telecomunicaciones. La forma más eficaz de implementar actualementeuna ,modulación electro-óptica ultra-rápida se basa en el efecto Pockels que, de hecho,se encuentra en el corazón de los moduladores comerciales basados en niobato de litio y polímeros. Sin embargo, la implementación de esta funcionalidad se ve impedida en la plataforma de silicio debido a la simetría de inversión de la red cristalina del silicio. En este contexto, el silicio deformado surgió hace más de un decenio como una solución revolucionaria para romper esa centrosimetría y, de ese modo, hacer emerger no-linealidades de segundo orden en el propio silicio. Sin embargo, y a pesar de los alentadores resultados iniciales, estudios posteriores cuestionaron el origen de las respuestas obtenidas, achacando dichos resultados principalmente al efecto de dispersión de plasma. De hecho, más tarde se puso de manifiesto la presencia de varios factores limitantes y, más recientemente, se estimó que el valor del coeficiente χ(2) debía encontrarse en torno a varios pm/V. El trabajo desarrollado en esta tesis tiene como objetivo contribuir a impulsar el campo de silicio deformado mediante la investigación y el abordaje de dichos factores limitantes para, de esta fora, conseguir un efecto Pockels eficiente. Además, las características de captura de carga libre observadas en las estructuras de silicio deformado se han explotado para desarrollar un dispositivo fotónico no volátil.[CA] En l'última dècada, la plataforma de silici ha emergit com la plataforma per excelència per a desenvolupar circuits fotònics integrats a causa de la seua versatilitat i la possibilitat de miniaturització i d'una producció de baix cost i a gran escala compatible amb els sistemes CMOS ("complementary metall-oxide semiconductor"). La conversió de senyals elèctrics a alta velocitat en senyals òptics és una funció crítica hui dia tant per al processament de dades com en l'àmbit de les telecomunicacions. La forma més eficaç d'implementar una modulació electro-òptica ultra-ràpida actualemente es basa en l'efecte *Pockels, que de fet,es troba en el cor dels moduladors comercials basats en el niobato de liti i polímers. No obstant això, la implementació d'aquesta funcionalitat es veu impedida en la plataforma de silici degut a la simetria d'inversió de la xarxa cristal·lina del silici. En aquest context, el silici deformat va sorgir fa més d'un decenni com una solució revolucionària per a trencar aqueixa centrosimetría i, d'aqueixa manera, fer emergir no-linealitats de segon ordre en el propi silici. No obstant això, malgrat els encoratjadors resultats inicials, estudis posteriors van qüestionar l'origen de la resposta obtinguda, atribuint-la principalment a aquest efecte de dispersió de plasma. De fet, més tard es va posar en relleu la presència de diversos factors limitants i, més recentment, es va estimar un valor de χ(2) en el rang de diversos pm/V. El treball desenvolupat en aquesta tesi té com a objectiu contribuir a impulsar el camp de silici deformat mitjançant la investigació i l'abordatge d'aquests factors limitants per a aconseguir un efecte Pockels eficient. A més, les característiques de captura de càrrega lliure observades en les estructures de silici deformat s'han explotat per a desenvolupar un dispositiu fotònic no volàtil.[EN] In the last decade, silicon has emerged as the platform of choice for developing photonic integrated circuits due to its versatility, small footprint and the possibility of a low cost, large-scale CMOS compatible production. The conversion of high-speed electrical signals into optical digital data is a critical function for modern data communication technology. The most effective way for enabling ultra-fast electro-optical modulation is currently based on the Pockels effect, which is the basis of commercial modulators based on lithium niobate and polymers. However, the implementation of such functionality is prevented in the silicon platform due to the inversion symmetry of the silicon lattice. In this context, strained silicon emerged more than a decade ago as a revolutionary solution for breaking that centrosymmetry and, thus, allowing Pockels effect in the silicon material itself. However, despite the encouraging results from initial findings, following studies questioned the origin of the measured electro-optic response. In fact, the presence of several limiting factors was also later highlighted and a rather low strain induced χ(2) in the range of several pm/V was more recently estimated. The work developed on this thesis aims at contributing to push forward the strained silicon field by investigating and tackling such limiting factors to enable an efficient Pockels effect. Furthermore, the trapping properties observed in strained silicon structures have been exploited to develop a non-volatile photonic device.Olivares Sánchez-Mellado, I. (2021). Development of Photonic Devices Based on the Strained Silicon Technology [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/167055TESI

A SiGe Slot Approach for Enhancing Strain Induced Pockels Effect in the Mid-IR Range

[EN] Strained silicon was proposed more than a decade ago promising to revolutionize the silicon photonics field by allowing efficient modulation in this platform. Despite all the efforts, still rather low chi(2) values have been measured in strained silicon devices. In addition, the way of applying strain has not barely changed since the concept was proposed, usually consisting on a silicon waveguide covered by a stressor material such as silicon nitride. In this letter, a SiGe slot approach is explored as a different route to enhance the strain induced Pockels effect in the mid-IR range. Such approach would allow effective index change values which are near to 10(-4) and improve the values expected for the most common silicon - silicon nitride structure by more than three orders of magnitude.This work was supported in part by the Ministerio de Ciencia e Innovacion under Grant TEC2016-76849 and Grant PID2019-111460GB-I00 and in part by the Generalitat Valenciana under Grant PROMETEO/2019/123.Olivares-Sánchez-Mellado, I.; Sanchis Kilders, P. (2021). A SiGe Slot Approach for Enhancing Strain Induced Pockels Effect in the Mid-IR Range. IEEE Photonics Technology Letters. 33(16):848-851. https://doi.org/10.1109/LPT.2021.3075753848851331

Enhanced Pockels effect in strained silicon by means of a SiGe/Si/SiGe slot structure

[EN] A slot waveguide structure made of a SiGe/Si/SiGe heterojunction is proposed to enhance Pockels effect in strained silicon. The strain is applied via lattice mismatch between layers, while the slot configuration optimizes the overlap between the optical and electric field inside the strained silicon.Funding from projects TEC2016-76849 (MINECO/FEDER, UE) and PROMETEO/2019/123 (Generalitat Valenciana) is acknowledged. Irene Olivares acknowledges the UPV for funding her research staff training (FPI) grant.Olivares-Sánchez-Mellado, I.; Sanchis Kilders, P. (2020). Enhanced Pockels effect in strained silicon by means of a SiGe/Si/SiGe slot structure. IEEE. 1-2. https://doi.org/10.1109/IPC47351.2020.9252351S1

Non-Volatile Photonic Memory Based on a SAHAS Configuration

[EN] The non-volatile memory is a crucial functionality for a wide range of applications in photonic integrated circuits, however, it still poses a challenge in silicon photonic technology. This problem has been overcome in the microelectronic industry by using SONOS (silicon-oxide-nitride-oxide-silicon) memory cells, in which the non-volatility is enabled by a dielectric trapping layer such as silicon nitride. Analogously, in this work, a similar approach in which the nitride has been replaced by a hafnium oxide layer, named as SAHAS configuration, is proposed for enabling a programmable erasable photonic memory fully compatible with the silicon platform. The structure features an efficient performance with writing and erasing times of 100 mu s, retention times over 10 years and energy consumption in the pJ range, which improve the current SONOS or floating gate based photonic approaches that exploit the plasma dispersion effect in silicon. The proposed non-volatile photonic memory device shows an extinction ratio above 12 dB and insertion losses below 1 dB in a compact footprint. In addition, because the memory is optically read, ultrafast access times in the picosecond range are also achieved.This work was supported in part by Ministerio de Economia y Competitividad (MINECO/FEDER, UE) (TEC2016-76849), in part by Generalitat Valenciana (PROMETEO/2019/123), in part by Ministerio de Ciencia e Innovacion (MINECO/FEDER, UE) (PID2019-111460GB-I00, FPU17/04224), and in part by Universitat Politecnica de Valencia (FPI Grant).Olivares-Sánchez-Mellado, I.; Parra Gómez, J.; Sanchis Kilders, P. (2021). Non-Volatile Photonic Memory Based on a SAHAS Configuration. IEEE Photonics Journal. 13(2):1-9. https://doi.org/10.1109/JPHOT.2021.3060144S1913

On the influence of interface charging dynamics and stressing conditions in strained silicon devices

[EN] The performance of strained silicon devices based on the deposition of a top silicon nitride layer with high stress have been thoroughly analyzed by means of simulations and experimental results. Results clearly indicate that the electro-optic static response is basically governed by carrier efects. A frst evidence is the appearance of a variable optical absorption with the applied voltage that should not occur in case of having a purely electro-optic Pockels efect. However, hysteresis and saturation efects are also observed. We demonstrate that such efects are mainly due to the carrier trapping dynamics at the interface between the silicon and the silicon nitride and their infuence on the silicon nitride charge. This theory is further confrmed by analyzing identical devices but with the silicon nitride cladding layer optimized to have intrinsic stresses of opposite sign and magnitude. The latter is achieved by a post annealing process which produces a defect healing and consequently a reduction of the silicon nitride charge. Raman measurements are also carried out to confrm the obtained results.Funding from projects TEC2016-76849-C2-2-R (MINECO/FEDER, UE) and NANOMET PLUS-Conselleria d'EducaciA3, Cultura i Esport - PROMETEOII/2014/034 is acknowledged. Irene Olivares also acknowledges the Universitat Politecnica de Valencia for funding his research staff training (FPI) grant. The authors would also like to thank Steven Van Roye from Ghent University for participating in the measurements of the annealed samples.Olivares-Sánchez-Mellado, I.; Ivanova-Angelova, T.; Sanchis Kilders, P. (2017). On the influence of interface charging dynamics and stressing conditions in strained silicon devices. Scientific Reports. 7(7241):1-8. https://doi.org/10.1038/s41598-017-05067-91877241Reed, G. T., Mashanovich, G., Gardes, F. Y. & Thomson, D. J. Silicon optical modulators. 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Phase-matched sum frequency generation in strained silicon waveguides using their second-order nonlinear optical susceptibility. Optics Express 19, 21707–21716 (2011).Schriever, C., Bohley, C., Schilling, J. & Wehrspohn, R. B. Strained Silicon Photonics. Materials 5, 889–908 (2012).Bianco, F. et al. Two-dimensional micro-Raman mapping of stress and strain distributions in strained silicon waveguides. Semiconductor Science and Technology 27, 085009 (2012).Chmielak, B. et al. Investigation of local strain distribution and linear electro-optic effect in strained silicon waveguides. Optics Express 21, 25324–25332 (2013).Aleali, A., Xu, D., Schmid, J. H., Cheben, P. & Winnie, N. Y. Optimization of stress-induced pockels effect in silicon waveguides for optical modulators. In Group IV Photonics (GFP), 2013 IEEE 10th International Conference on, 109–110 (IEEE, 2013).Puckett, M. W., Smalley, J. S., Abashin, M., Grieco, A. & Fainman, Y. Tensor of the second-order nonlinear susceptibility in asymmetrically strained silicon waveguides: analysis and experimental validation. Optics Letters 39, 1693–1696 (2014).Damas, P. et al. Wavelength dependence of pockels effect in strained silicon waveguides. Optics Express 22, 22095–22100 (2014).Khurgin, J. B., Stievater, T. H., Pruessner, M. W. & Rabinovich, W. S. On the origin of the second-order nonlinearity in strained Si-SiN structures. JOSA B 32, 2494–2499 (2015).Manganelli, C. L., Pintus, P. & Bonati, C. Modeling of strain-induced Pockels effect in Silicon. Optics Express 23, 28649–28666 (2015).Damas, P., Marris-Morini, D., Cassan, E. & Vivien, L. Bond orbital description of the strain-induced second-order optical susceptibility in silicon. Physical Review B 93, 165208 (2016).Cazzanelli, M. et al. Second-harmonic generation in silicon waveguides strained by silicon nitride. Nature Materials 11, 148–154 (2012).Schriever, C. et al. Second-Order Optical Nonlinearity in Silicon Waveguides: Inhomogeneous Stress and Interfaces. Advanced Optical Materials 3, 129–136 (2015).Borghi, M. B. et al. High-frequency electro-optic measurement of strained silicon racetrack resonators. Optics Letters 40, 5287–5290 (2015).Azadeh, S. S., Merget, F., Nezhad, M. & Witzens, J. On the measurement of the Pockels effect in strained silicon. Optics Letters 40, 1877–1880 (2015).Sharma, R. et al. Effect of dielectric claddings on the electro-optic behavior of silicon waveguides. Optics Letters 41, 1185–1188 (2016).Borghi, M. et al. Homodyne Detection of Free Carrier Induced Electro-Optic Modulation in Strained Silicon Resonators. Journal of Lightwave Technology 34, 5657–5668 (2016).Olivares, I., Ivanova, T., Pinilla-Cienfuegos, E. & Sanchis, P. A systematic optimization of design parameters in strained silicon waveguides to further enhance the linear electro-optic effect. 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Ultra-compact non-volatile Mach-Zehnder switch enabled by a high-mobility transparent conducting oxide

[EN] Compact and broadband non-volatile silicon devices are mainly absorption based. Hence, access to low-loss non-volatile phase shifters is still a challenge. Here, this problem is addressed by using a high-mobility transparent conducting oxide such as cadmium oxide as a floating gate in a flash-like structure. This structure is integrated in a Mach¿Zehnder interferometer switch. Results show an active length of only 30 µm to achieve a ¿¿ phase shift. Furthermore, an extinction ratio of 20 dB and insertion loss as low as 1 dB may be attained. The device shows an optical broadband response and can be controlled with low-power pulses in the nanosecond range. These results open a new, to the best of our knowledge, way for enabling compact silicon-based phase shifters with non-volatile performance.Ministerio de Economia y Competitividad (TEC2016-76849); Generalitat Valenciana (PROMETEO/2019/123); Ministerio de Ciencia, Innovacion y Universidades (FPU17/04224).Parra Gómez, J.; Olivares-Sánchez-Mellado, I.; Ramos, F.; Sanchis Kilders, P. (2020). Ultra-compact non-volatile Mach-Zehnder switch enabled by a high-mobility transparent conducting oxide. Optics Letters. 45(6):1503-1506. https://doi.org/10.1364/OL.388363S1503150645

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

Experimental demonstration of a tunable transverse electric pass polarizer based on hybrid VO2/silicon technology

[EN] A tunable transverse electric (TE) pass polarizer is demonstrated based on hybrid vanadium dioxide/silicon (VO2/Si) technology. The 20-mu m-long TE pass polarizer exploits the phase transition of the active VO2 material to control the rejection of the unwanted transverse magnetic (TM) polarization. The device features insertion losses below 1 dB at static conditions and insertion losses of 5.5 dB and an attenuation of TM polarization of 19 dB in the active state for a wavelength range between 1540 nm and 1570 nm. To the best of our knowledge, this is the first time that tunable polarizers compatible with Si photonics are demonstrated. (C) 2018 Optical Society of AmericaMinisterio de Economia y Competitividad (MINECO) (TEC2016-76849); European Commission (EC) [PHRESCO (688579), SITOGA (619456)]; Universitat Politecnica de Valencia; Comision Nacional de Investigacion Cientifica y Tecnologica (CONICYT).Sánchez Diana, LD.; Olivares-Sánchez-Mellado, I.; Parra Gómez, J.; Menghini, M.; Homm, P.; Locquet, J.; Sanchis Kilders, P. (2018). Experimental demonstration of a tunable transverse electric pass polarizer based on hybrid VO2/silicon technology. Optics Letters. 43(15):3650-3653. https://doi.org/10.1364/OL.43.003650S365036534315Liu, L., Ding, Y., Yvind, K., & Hvam, J. M. (2011). Efficient and compact TE–TM polarization converter built on silicon-on-insulator platform with a simple fabrication process. Optics Letters, 36(7), 1059. doi:10.1364/ol.36.001059Alonso-Ramos, C., Halir, R., Ortega-Moñux, A., Cheben, P., Vivien, L., Molina-Fernández, Í., … Schmid, J. (2012). Highly tolerant tunable waveguide polarization rotator scheme. Optics Letters, 37(17), 3534. doi:10.1364/ol.37.003534Zhang, H., Das, S., Zhang, J., Huang, Y., Li, C., Chen, S., … Thong, J. T. L. (2012). Efficient and broadband polarization rotator using horizontal slot waveguide for silicon photonics. Applied Physics Letters, 101(2), 021105. doi:10.1063/1.4734640Azzam, S. I. H., Hameed, M. F. O., Areed, N. F. F., Abd-Elrazzak, M. M., El-Mikaty, H. A., & Obayya, S. S. A. (2014). Proposal of an Ultracompact CMOS-Compatible TE-/TM-Pass Polarizer Based on SoI Platform. IEEE Photonics Technology Letters, 26(16), 1633-1636. doi:10.1109/lpt.2014.2329416Dai, D., Wang, Z., Julian, N., & Bowers, J. E. (2010). Compact broadband polarizer based on shallowly-etched silicon-on-insulator ridge optical waveguides. Optics Express, 18(26), 27404. doi:10.1364/oe.18.027404Aamer, M., Gutierrez, A. M., Brimont, A., Vermeulen, D., Roelkens, G., Fedeli, J.-M., … Sanchis, P. (2012). 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Compact silicon photonic waveguide modulator based on the vanadium dioxide metal-insulator phase transition. Optics Express, 18(11), 11192. doi:10.1364/oe.18.011192Ryckman, J. D., Hallman, K. A., Marvel, R. E., Haglund, R. F., & Weiss, S. M. (2013). Ultra-compact silicon photonic devices reconfigured by an optically induced semiconductor-to-metal transition. Optics Express, 21(9), 10753. doi:10.1364/oe.21.010753Markov, P., Marvel, R. E., Conley, H. J., Miller, K. J., Haglund, R. F., & Weiss, S. M. (2015). Optically Monitored Electrical Switching in VO2. ACS Photonics, 2(8), 1175-1182. doi:10.1021/acsphotonics.5b00244Joushaghani, A., Jeong, J., Paradis, S., Alain, D., Stewart Aitchison, J., & Poon, J. K. S. (2015). Wavelength-size hybrid Si-VO_2 waveguide electroabsorption optical switches and photodetectors. Optics Express, 23(3), 3657. doi:10.1364/oe.23.003657Sánchez, L., Lechago, S., & Sanchis, P. (2015). Ultra-compact TE and TM pass polarizers based on vanadium dioxide on silicon. Optics Letters, 40(7), 1452. doi:10.1364/ol.40.001452Sanchez, L., Lechago, S., Gutierrez, A., & Sanchis, P. (2016). Analysis and Design Optimization of a Hybrid VO2/Silicon2 $\times$ 2 Microring Switch. IEEE Photonics Journal, 8(2), 1-9. doi:10.1109/jphot.2016.2551463Miller, K. J., Hallman, K. A., Haglund, R. F., & Weiss, S. M. (2017). Silicon waveguide optical switch with embedded phase change material. Optics Express, 25(22), 26527. doi:10.1364/oe.25.026527Clark, J. K., Ho, Y.-L., Matsui, H., & Delaunay, J.-J. (2018). Optically Pumped Hybrid Plasmonic-Photonic Waveguide Modulator Using the VO2 Metal-Insulator Phase Transition. IEEE Photonics Journal, 10(1), 1-9. doi:10.1109/jphot.2017.2784429Ko, C., & Ramanathan, S. (2008). Observation of electric field-assisted phase transition in thin film vanadium oxide in a metal-oxide-semiconductor device geometry. Applied Physics Letters, 93(25), 252101. doi:10.1063/1.3050464Zimmers, A., Aigouy, L., Mortier, M., Sharoni, A., Wang, S., West, K. G., … Schuller, I. K. (2013). Role of Thermal Heating on the Voltage Induced Insulator-Metal Transition inVO2. Physical Review Letters, 110(5). doi:10.1103/physrevlett.110.056601Kats, M. A., Blanchard, R., Genevet, P., Yang, Z., Qazilbash, M. M., Basov, D. N., … Capasso, F. (2013). Thermal tuning of mid-infrared plasmonic antenna arrays using a phase change material. Optics Letters, 38(3), 368. doi:10.1364/ol.38.000368Chae, B.-G., Kim, H.-T., Youn, D.-H., & Kang, K.-Y. (2005). Abrupt metal–insulator transition observed in VO2 thin films induced by a switching voltage pulse. Physica B: Condensed Matter, 369(1-4), 76-80. doi:10.1016/j.physb.2005.07.032Ruzmetov, D., Gopalakrishnan, G., Deng, J., Narayanamurti, V., & Ramanathan, S. (2009). Electrical triggering of metal-insulator transition in nanoscale vanadium oxide junctions. Journal of Applied Physics, 106(8), 083702. doi:10.1063/1.3245338Lee, S. B., Kim, K., Oh, J. S., Kahng, B., & Lee, J. S. (2013). Origin of variation in switching voltages in threshold-switching phenomena of VO2 thin films. Applied Physics Letters, 102(6), 063501. doi:10.1063/1.4790842Joushaghani, A., Jeong, J., Paradis, S., Alain, D., Stewart Aitchison, J., & Poon, J. K. S. (2014). Voltage-controlled switching and thermal effects in VO2 nano-gap junctions. Applied Physics Letters, 104(22), 221904. doi:10.1063/1.4881155Yang, Z., Hart, S., Ko, C., Yacoby, A., & Ramanathan, S. (2011). Studies on electric triggering of the metal-insulator transition in VO2thin films between 77 K and 300 K. Journal of Applied Physics, 110(3), 033725. doi:10.1063/1.3619806Yoon, J., Lee, G., Park, C., Mun, B. S., & Ju, H. (2014). Investigation of length-dependent characteristics of the voltage-induced metal insulator transition in VO2 film devices. Applied Physics Letters, 105(8), 083503. doi:10.1063/1.4893783Sánchez, L., Rosa, A., Griol, A., Gutierrez, A., Homm, P., Van Bilzen, B., … Sanchis, P. (2017). Impact of the external resistance on the switching power consumption in VO2 nano gap junctions. Applied Physics Letters, 111(3), 031904. doi:10.1063/1.4994326Ryckman, J. D., Diez-Blanco, V., Nag, J., Marvel, R. E., Choi, B. K., Haglund, R. F., & Weiss, S. M. (2012). Photothermal optical modulation of ultra-compact hybrid Si-VO_2 ring resonators. Optics Express, 20(12), 13215. doi:10.1364/oe.20.013215Abreu, E., Gilbert Corder, S. N., Yun, S. J., Wang, S., Ramírez, J. G., West, K., … Averitt, R. D. (2017). Ultrafast electron-lattice coupling dynamics in VO2 and V2O3 thin films. Physical Review B, 96(9). doi:10.1103/physrevb.96.094309Van Bilzen, B., Homm, P., Dillemans, L., Su, C.-Y., Menghini, M., Sousa, M., … Locquet, J.-P. (2015). Production of VO2 thin films through post-deposition annealing of V2O3 and VOx films. Thin Solid Films, 591, 143-148. doi:10.1016/j.tsf.2015.08.036Olivares, I., Sánchez, L., Parra, J., Larrea, R., Griol, A., Menghini, M., … Sanchis, P. (2018). Optical switching in hybrid VO2/Si waveguides thermally triggered by lateral microheaters. Optics Express, 26(10), 12387. doi:10.1364/oe.26.012387Rosa, Á., Gutiérrez, A., Brimont, A., Griol, A., & Sanchis, 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. doi:10.1364/oe.24.000191Shibuya, K., Kawasaki, M., & Tokura, Y. (2010). Metal-insulator transition in epitaxial V1−xWxO2(0≤x≤0.33) thin films. Applied Physics Letters, 96(2), 022102. doi:10.1063/1.3291053Ahuja, R., Granqvist, C. G., Hermansson, K., Niklasson, G. A., & Scheicher, R. H. (2012). Optical properties of Mg-doped VO2: Absorption measurements and hybrid functional calculations. Applied Physics Letters, 101(20), 201902. doi:10.1063/1.4766167Miyazaki, K., Shibuya, K., Suzuki, M., Wado, H., & Sawa, A. (2014). Correlation between thermal hysteresis width and broadening of metal–insulator transition in Cr- and Nb-doped VO2films. Japanese Journal of Applied Physics, 53(7), 071102. doi:10.7567/jjap.53.071102Niklasson, G. A., Granqvist, C. G., & Hunderi, O. (1981). Effective medium models for the optical properties of inhomogeneous materials. Applied Optics, 20(1), 26. doi:10.1364/ao.20.000026Jepsen, P. U., Fischer, B. M., Thoman, A., Helm, H., Suh, J. Y., Lopez, R., & Haglund, R. F. (2006). Metal-insulator phase transition in aVO2thin film observed with terahertz spectroscopy. Physical Review B, 74(20). doi:10.1103/physrevb.74.205103Fang, X., & Yang, L. (2017). Thermal effect analysis of silicon microring optical switch for on-chip interconnect. Journal of Semiconductors, 38(10), 104004. doi:10.1088/1674-4926/38/10/10400

Optical switching in hybrid VO2/Si waveguides thermally triggered by lateral microheaters

© 2018 Optical Society of America. One print or electronic copy may be made for personal use only. Systematic reproduction and distribution, duplication of any material in this paper for a fee or for commercial purposes, or modifications of the content of this paper are prohibited"[EN] The performance of optical devices relying in vanadium dioxide (VO2) technology compatible with the silicon platform depends on the polarization of light and VO2 properties. In this work, optical switching in hybrid VO2/Si waveguides thermally triggered by lateral microheaters is achieved with insertion losses below 1 dB and extinction ratios above 20 dB in a broad bandwidth larger than 30 nm. The optical switching response has been optimized for TE and TM polarizations by using a homogeneous and a granular VO2 layer, respectively, with a small impact on the electrical power consumption. The stability and reversibility between switching states showing the possibility of bistable performance is also demonstrated. (C) 2018 Optical Society of America under the terms of the OSA Open Access Publishing Agreement.Funding from project TEC2016-76849 (MINECO/FEDER, UE) is acknowledged. The SOI samples were fabricated at IHP (we acknowledge Lars Zimmermann) in the framework of FP7-ICT-2013-11-619456 SITOGA project. Irene Olivares and Roberto Larrea also acknowledge respectively the Universitat Politecnica de Valencia and the Ecuadorian Government for funding their grant. P.H. acknowledges support from Becas Chile-CONICYT.Olivares-Sánchez-Mellado, I.; Sánchez Diana, LD.; Parra Gómez, J.; Larrea-Luzuriaga, RA.; Griol Barres, A.; Menghini, M.; Homm, P.... (2018). Optical switching in hybrid VO2/Si waveguides thermally triggered by lateral microheaters. Optics Express. 26(10):12387-12395. https://doi.org/10.1364/OE.26.012387S12387123952610Sorger, V. J., Lanzillotti-Kimura, N. D., Ma, R.-M., & Zhang, X. (2012). Ultra-compact silicon nanophotonic modulator with broadband response. Nanophotonics, 1(1), 17-22. doi:10.1515/nanoph-2012-0009Liang, H., Soref, R., Mu, J., Majumdar, A., Li, X., & Huang, W.-P. (2015). Simulations of Silicon-on-Insulator Channel-Waveguide Electrooptical 2 × 2 Switches and 1 × 1 Modulators Using a ${\bf Ge_2}{\bf Sb_2}{\bf Te_5}$ Self-Holding Layer. Journal of Lightwave Technology, 33(9), 1805-1813. doi:10.1109/jlt.2015.2393293Seo, G., Kim, B.-J., Ko, C., Cui, Y., Lee, Y. W., Shin, J.-H., … Kim, H.-T. (2011). Voltage-Pulse-Induced Switching Dynamics in $\hbox{VO}_{2}$ Thin-Film Devices on Silicon. IEEE Electron Device Letters, 32(11), 1582-1584. doi:10.1109/led.2011.2163922Yang, Z., Ko, C., & Ramanathan, S. (2011). Oxide Electronics Utilizing Ultrafast Metal-Insulator Transitions. Annual Review of Materials Research, 41(1), 337-367. doi:10.1146/annurev-matsci-062910-100347Vitale, W. A., Casu, E. A., Biswas, A., Rosca, T., Alper, C., Krammer, A., … Ionescu, A. M. (2017). A Steep-Slope Transistor Combining Phase-Change and Band-to-Band-Tunneling to Achieve a sub-Unity Body Factor. Scientific Reports, 7(1). doi:10.1038/s41598-017-00359-6Zimmers, A., Aigouy, L., Mortier, M., Sharoni, A., Wang, S., West, K. G., … Schuller, I. K. (2013). Role of Thermal Heating on the Voltage Induced Insulator-Metal Transition inVO2. Physical Review Letters, 110(5). doi:10.1103/physrevlett.110.056601Kats, M. A., Blanchard, R., Genevet, P., Yang, Z., Qazilbash, M. M., Basov, D. N., … Capasso, F. (2013). Thermal tuning of mid-infrared plasmonic antenna arrays using a phase change material. Optics Letters, 38(3), 368. doi:10.1364/ol.38.000368Chae, B.-G., Kim, H.-T., Youn, D.-H., & Kang, K.-Y. (2005). Abrupt metal–insulator transition observed in VO2 thin films induced by a switching voltage pulse. Physica B: Condensed Matter, 369(1-4), 76-80. doi:10.1016/j.physb.2005.07.032Ruzmetov, D., Gopalakrishnan, G., Deng, J., Narayanamurti, V., & Ramanathan, S. (2009). Electrical triggering of metal-insulator transition in nanoscale vanadium oxide junctions. Journal of Applied Physics, 106(8), 083702. doi:10.1063/1.3245338Joushaghani, A., Jeong, J., Paradis, S., Alain, D., Stewart Aitchison, J., & Poon, J. K. S. (2014). Voltage-controlled switching and thermal effects in VO2 nano-gap junctions. Applied Physics Letters, 104(22), 221904. doi:10.1063/1.4881155Markov, P., Marvel, R. E., Conley, H. J., Miller, K. J., Haglund, R. F., & Weiss, S. M. (2015). Optically Monitored Electrical Switching in VO2. ACS Photonics, 2(8), 1175-1182. doi:10.1021/acsphotonics.5b00244Yang, Z., Hart, S., Ko, C., Yacoby, A., & Ramanathan, S. (2011). Studies on electric triggering of the metal-insulator transition in VO2thin films between 77 K and 300 K. Journal of Applied Physics, 110(3), 033725. doi:10.1063/1.3619806Yoon, J., Lee, G., Park, C., Mun, B. S., & Ju, H. (2014). Investigation of length-dependent characteristics of the voltage-induced metal insulator transition in VO2 film devices. Applied Physics Letters, 105(8), 083503. doi:10.1063/1.4893783Sánchez, L., Rosa, A., Griol, A., Gutierrez, A., Homm, P., Van Bilzen, B., … Sanchis, P. (2017). Impact of the external resistance on the switching power consumption in VO2 nano gap junctions. Applied Physics Letters, 111(3), 031904. doi:10.1063/1.4994326Ryckman, J. D., Diez-Blanco, V., Nag, J., Marvel, R. E., Choi, B. K., Haglund, R. F., & Weiss, S. M. (2012). Photothermal optical modulation of ultra-compact hybrid Si-VO_2 ring resonators. Optics Express, 20(12), 13215. doi:10.1364/oe.20.013215Ryckman, J. D., Hallman, K. A., Marvel, R. E., Haglund, R. F., & Weiss, S. M. (2013). Ultra-compact silicon photonic devices reconfigured by an optically induced semiconductor-to-metal transition. Optics Express, 21(9), 10753. doi:10.1364/oe.21.010753Abreu, E., Gilbert Corder, S. N., Yun, S. J., Wang, S., Ramírez, J. G., West, K., … Averitt, R. D. (2017). Ultrafast electron-lattice coupling dynamics in VO2 and V2O3 thin films. Physical Review B, 96(9). doi:10.1103/physrevb.96.094309Sánchez, L., Lechago, S., & Sanchis, P. (2015). Ultra-compact TE and TM pass polarizers based on vanadium dioxide on silicon. Optics Letters, 40(7), 1452. doi:10.1364/ol.40.001452Joushaghani, A., Jeong, J., Paradis, S., Alain, D., Stewart Aitchison, J., & Poon, J. K. S. (2015). Wavelength-size hybrid Si-VO_2 waveguide electroabsorption optical switches and photodetectors. Optics Express, 23(3), 3657. doi:10.1364/oe.23.003657Diana, L. D. S., Juan, F. C., Escutia, A. R., & Kilders, P. S. (2017). Ultra-compact electro-absorption VO2–Si modulator with TM to TE conversion. 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High-speed metal-insulator transition in vanadium dioxide films induced by an electrical pulsed voltage over nano-gap electrodes. Applied Physics Letters, 100(21), 213507. doi:10.1063/1.4721520Xu, X., He, X., Wang, H., Gu, Q., Shi, S., Xing, H., … Chu, J. (2012). The extremely narrow hysteresis width of phase transition in nanocrystalline VO2 thin films with the flake grain structures. Applied Surface Science, 261, 83-87. doi:10.1016/j.apsusc.2012.07.098Kumar, S., Lenoble, D., Maury, F., & Bahlawane, N. (2015). Synthesis of vanadium oxide films with controlled morphologies: Impact on the metal-insulator transition behaviour. physica status solidi (a), 212(7), 1582-1587. doi:10.1002/pssa.201532325Guzman, G., Morineau, R., & Livage, J. (1994). Synthesis of vanadium dioxide thin films from vanadium alkoxides. Materials Research Bulletin, 29(5), 509-515. doi:10.1016/0025-5408(94)90039-6Gao, W., Wang, C. M., Wang, H. Q., Henrich, V. E., & Altman, E. I. (2004). 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Association Between Preexisting Versus Newly Identified Atrial Fibrillation and Outcomes of Patients With Acute Pulmonary Embolism

Background Atrial fibrillation (AF) may exist before or occur early in the course of pulmonary embolism (PE). We determined the PE outcomes based on the presence and timing of AF. Methods and Results Using the data from a multicenter PE registry, we identified 3 groups: (1) those with preexisting AF, (2) patients with new AF within 2 days from acute PE (incident AF), and (3) patients without AF. We assessed the 90-day and 1-year risk of mortality and stroke in patients with AF, compared with those without AF (reference group). Among 16 497 patients with PE, 792 had preexisting AF. These patients had increased odds of 90-day all-cause (odds ratio [OR], 2.81; 95% CI, 2.33-3.38) and PE-related mortality (OR, 2.38; 95% CI, 1.37-4.14) and increased 1-year hazard for ischemic stroke (hazard ratio, 5.48; 95% CI, 3.10-9.69) compared with those without AF. After multivariable adjustment, preexisting AF was associated with significantly increased odds of all-cause mortality (OR, 1.91; 95% CI, 1.57-2.32) but not PE-related mortality (OR, 1.50; 95% CI, 0.85-2.66). Among 16 497 patients with PE, 445 developed new incident AF within 2 days of acute PE. Incident AF was associated with increased odds of 90-day all-cause (OR, 2.28; 95% CI, 1.75-2.97) and PE-related (OR, 3.64; 95% CI, 2.01-6.59) mortality but not stroke. Findings were similar in multivariable analyses. Conclusions In patients with acute symptomatic PE, both preexisting AF and incident AF predict adverse clinical outcomes. The type of adverse outcomes may differ depending on the timing of AF onset.info:eu-repo/semantics/publishedVersio