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 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

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

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

On-chip wireless silicon photonics: From reconfigurable interconnects to lab-on-chip devices

[EN] Photonic integrated circuits are developing as key enabling components for high-performance computing and advanced network-on-chip, as well as other emerging technologies such as lab-on-chip sensors, with relevant applications in areas from medicine and biotechnology to aerospace. These demanding applications will require novel features, such as dynamically reconfigurable light pathways, obtained by properly harnessing on-chip optical radiation. In this paper, we introduce a broadband, high-directivity (>150), low-loss, and reconfigurable silicon photonics nanoantenna that fully enables on-chip radiation control. We propose the use of these nanoantennas as versatile building blocks to develop wireless (unguided) silicon photonic devices, which considerably enhance the range of achievable integrated photonic functionalities. As examples of applications, we demonstrate 160 Gbit·s-1 data transmission over mm-scale wireless interconnects, a compact low-crosstalk 12-port crossing, and electrically reconfigurable pathways via optical beam steering. Moreover, the realization of a flow micro-cytometer for particle characterization demonstrates the smart system integration potential of our approach as lab-on-chip devices.Funding from grant TEC2015-63838-C3-1-R OPTONANOSENS (MINECO/FEDER, UE) is acknowledged. This work was also supported by project TEC2015-73581-JIN (AEI/FEDER, UE), the EU-funded projects FP7-ICT PHOXTROT (No.318240) and H2020-, the EU-funded H2020-FET-HPC EXANEST (No.671553) and the Generalitat Valenciana's PROMETEO grant NANOMET PLUS (PROMETEO II/2014/34) CG-M acknowledges support from Generalitat Valenciana’s VALi+d postdoctoral program (exp. APOSTD/ 2014/044). We thank David Zurita for his help in the design of the data acquisition code for the sensing application.García Meca, C.; Lechago-Buendia, S.; Brimont, ACJ.; Griol Barres, A.; Mas Gómez, SM.; Sánchez Diana, LD.; Bellieres, LC.... (2017). On-chip wireless silicon photonics: From reconfigurable interconnects to lab-on-chip devices. Light: Science & Applications. 6:e17053-e17053. https://doi.org/10.1038/lsa.2017.53e17053e170536Kirchain R, Kimerling R . A roadmap for nanophotonics. Nat Photonics 2007; 1: 303–305.Fan XD, White IM . Optofluidic microsystems for chemical and biological analysis. Nat Photonics 2011; 5: 591–597.Zhuang LM, Roeloffzen CGH, Meijerink A, Burla M, Marpaung DAI et al. Novel ring resonator-based integrated photonic beamformer for broadband phased array receive antennas—part II: experimental prototype. J Lightw Technol 2010; 28: 19–31.Yu NF, Capasso F . Flat optics with designer metasurfaces. Nat Mater 2014; 13: 139–150.Condrat C, Kalla P, Blair S . Crossing-aware channel routing for integrated optics. IEEE Trans Comput-Aided Design Integr Circuits Syst 2014; 33: 814–825.Lee BG, Rylyakov AV, Green WMJ, Assefa S, Baks CW et al. Monolithic silicon integration of scaled photonic switch fabrics, CMOS logic, and device driver circuits. J Lightw Technol 2014; 32: 743–751.Robinson JP, Roederer M . Flow cytometry strikes gold. Science 2015; 350: 739–740.Mao XL, Nawaz AA, Lin SC, Lapsley MI, Zhao YH et al. An integrated, multiparametric flow cytometry chip using 'microfluidic drifting' based three-dimensional hydrodynamic focusing. Biomicrofluidics 2012; 6: 024113.Schurr JM . Dynamic light scattering of biopolymers and biocolloids. CRC Crit Rev Biochem 1977; 4: 371–431.Padgett M, Bowman R . Tweezers with a twist. Nat Photonics 2011; 5: 343–348.Haurylau M, Chen GQ, Chen H, Zhang JD, Nelson NA et al. On-chip optical interconnect roadmap: challenges and critical directions. 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Multimode interference devices for focusing in microfluidic channels. Opt Lett 2011; 36: 3067–3069

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

Limits to dark matter annihilation cross-section from a combined analysis of MAGIC and Fermi-LAT observations of dwarf satellite galaxies

We present the first joint analysis of gamma-ray data from the MAGIC Cherenkov telescopes and the Fermi Large Area Telescope (LAT) to search for gamma-ray signals from dark matter annihilation in dwarf satellite galaxies. We combine 158 hours of Segue 1 observations with MAGIC with 6-year observations of 15 dwarf satellite galaxies by the Fermi-LAT. We obtain limits on the annihilation cross-section for dark matter particle masses between 10 GeV and 100 TeV - the widest mass range ever explored by a single gamma-ray analysis. These limits improve on previously published Fermi-LAT and MAGIC results by up to a factor of two at certain masses. Our new inclusive analysis approach is completely generic and can be used to perform a global, sensitivity-optimized dark matter search by combining data from present and future gamma-ray and neutrino detectors.Comment: 19 pages, 3 figures. V2: Few typos corrected and references added. Matches published version JCAP 02 (2016) 03

All-sky Medium Energy Gamma-ray Observatory: Exploring the Extreme Multimessenger Universe

The All-sky Medium Energy Gamma-ray Observatory (AMEGO) is a probe class mission concept that will provide essential contributions to multimessenger astrophysics in the late 2020s and beyond. AMEGO combines high sensitivity in the 200 keV to 10 GeV energy range with a wide field of view, good spectral resolution, and polarization sensitivity. Therefore, AMEGO is key in the study of multimessenger astrophysical objects that have unique signatures in the gamma-ray regime, such as neutron star mergers, supernovae, and flaring active galactic nuclei. The order-of-magnitude improvement compared to previous MeV missions also enables discoveries of a wide range of phenomena whose energy output peaks in the relatively unexplored medium-energy gamma-ray band

GABAergic regulation of cerebellar NG2 cell development is altered in perinatal white matter injury.

Diffuse white matter injury (DWMI), a leading cause of neurodevelopmental disabilities in preterm infants, is characterized by reduced oligodendrocyte formation. NG2-expressing oligodendrocyte precursor cells (NG2 cells) are exposed to various extrinsic regulatory signals, including the neurotransmitter GABA. We investigated GABAergic signaling to cerebellar white matter NG2 cells in a mouse model of DWMI (chronic neonatal hypoxia). We found that hypoxia caused a loss of GABAA receptor-mediated synaptic input to NG2 cells, extensive proliferation of these cells and delayed oligodendrocyte maturation, leading to dysmyelination. Treatment of control mice with a GABAA receptor antagonist or deletion of the chloride-accumulating transporter NKCC1 mimicked the effects of hypoxia. Conversely, blockade of GABA catabolism or GABA uptake reduced NG2 cell numbers and increased the formation of mature oligodendrocytes both in control and hypoxic mice. Our results indicate that GABAergic signaling regulates NG2 cell differentiation and proliferation in vivo, and suggest that its perturbation is a key factor in DWMI