Low-threshold power and tunable integrated optical limiter based on an ultracompact VO2/Si waveguide

[EN] Optical limiters are nonlinear devices that encompass applications from device protection to activation functionalities in neural networks. In this work, we report an optical limiter on silicon photonics based on an ultracompact VO2/Si waveguide. Our 20-¿m-long experimental device features a thermal tunable threshold power of only ~3.5 mW while being spectrally broadband. Our work provides a new pathway to achieve integrated optical limiters for dense and low-power photonic integrated circuits.This study was supported by Grant Nos. PID2019- 111460GB-I00 and FPU17/04224 funded by MCIN/AEI/ 10.13039/501100011033 and, by ESF Investing in your future; Grant funded by FEDER/Ministerio de Ciencia e InnovaciónAgencia Estatal de Investigación/Ref.ICTS-2017-28-UPV-9; PROMETEO Program (Ref.2019/123)-Generalitat Valenciana; and Action co-financed by the European Union through the European Regional Development Fund (ERDF) operational program for the Valencian Community 2014-2020. The authors also thank David Zurita for his help with the experimental setup and Pía Homm for the sample preparation.Parra Gómez, J.; Navarro-Arenas, J.; Menghini, M.; Recaman, M.; Pierre-Locquet, J.; Sanchis Kilders, P. (2021). Low-threshold power and tunable integrated optical limiter based on an ultracompact VO2/Si waveguide. APL Photonics. 6(12):1-6. https://doi.org/10.1063/5.0071395S1661

All-Optical Hybrid VO2/Si Waveguide Absorption Switch at Telecommunication Wavelengths

[EN] Vanadium dioxide (VO2) is one of the most promising materials for developing hybrid photonic integrated circuits (PICs). At telecommunication wavelengths, VO2 exhibits a large change on the refractive index (¿n ~ 1 and ¿¿ ~ 2.5) between its insulating and metallic state. Such insulating-to-metal transition (IMT) can be triggered by light, which could enable all-optical hybridVO2-waveguide devices. Here, we experimentally demonstrate an all-optical absorption switch using a hybridVO2/Si waveguide fully compatible with the silicon photonics platform. All-optical characterization was carried out for TE polarization and at telecommunication wavelengths using an in-plane approach. The temporal dynamics were retrieved by means of pump-probe measurements. Our results show an extinction ratio of 0.7 dB/¿m with a maximum switchable length of 15 ¿m, a switching speed as low as 318 ns, and an energy per switch of 15.8 nJ. The inherit large optical bandwith of a non-resonant waveguide poses this device as a promising candidate for developing all-optical and broadband silicon PICs.This work was supported by Ministerio de Economia y Competitividad (MINECO) under Grant TEC2016-76849; in part by Ministerio de Ciencia e Innovacion underGrant PID2019-111460GB-I00 and Grant FPU17/04224; and in part by Generalitat Valenciana under Grant PROMETEO/2019/123.Parra Gómez, J.; Ivanova-Angelova, T.; Menghini, M.; Homm, P.; Locquet, J.; Sanchis Kilders, P. (2021). All-Optical Hybrid VO2/Si Waveguide Absorption Switch at Telecommunication Wavelengths. Journal of Lightwave Technology. 39(9):2888-2894. https://doi.org/10.1109/JLT.2021.30549422888289439

Two-dimensional honeycomb-kagome V2O3: a robust room-temperature magnetic Chern insulator interfaced with graphene

The possibility of dissipationless chiral edge states without the need of an external magnetic field in the quantum anomalous Hall effect (QAHE) offers a great potential in electronic/spintronic applications. The biggest hurdle for the realization of a room-temperature magnetic Chern insulator is to find a structurally stable material with a sufficiently large energy gap and Curie temperature that can be easily implemented in electronic devices. This work based on first-principle methods shows that a single atomic layer of V2O3 with honeycomb-kagome (HK) lattice is structurally stable with a spin-polarized Dirac cone which gives rise to a room-temperature QAHE by the existence of an atomic on-site spin-orbit coupling (SOC). Moreover, by a strain and substrate study, it was found that the quantum anomalous Hall system is robust against small deformations and can be supported by a graphene substrate.Comment: Accepted at NPJ 2D Materials & Application

Comparison of the Transport Mechanism in Underdoped High Temperature Superconductors and in Spin Ladders

Recently, the normal state resistivity of high temperature superconductors (in particular in La2-xSrxCuO4 single crystals) has been studied extensively in the region below Tc by suppressing the superconducting state in high magnetic fields. In the present work we report on the normal state resistance of underdoped La2-xSrxCuO4 thin films under epitaxial strain, measured far below Tc by applying pulsed fields up to 60 T. We will compare the transport measurements on these high temperature superconductors with transport data reported for the Sr2.5Ca11.5Cu24O41 spin ladder compound. This comparison leads to an interpretation of the data in terms of the recently proposed 1D quantum transport model and the charge-stripe models.Comment: 5 pages, PDF fil

Ultrathin GeSn p-channel MOSFETs grown directly on Si(111) substrate using solid phase epitaxy

Ultrathin GeSn layers with a thickness of 5.5 nm are fabricated on a Si(111) substrate by solid phase epitaxy (SPE) of amorphous GeSn layers with Sn concentrations up to 6.7%. We demonstrate well-behaved depletion-mode operation of GeSn p-channel metal–oxide–semiconductor field-effect transistors (pMOSFETs) with an on/off ratio of more than 1000 owing to the ultrathin GeSn channel layer (5.5 nm). It is found that the on current increases significantly with increasing Sn concentration at the same gate overdrive, attributed to an increasing substitutional Sn incorporation in Ge. The GeSn (6.7%) layer sample shows approximately 90% enhancement in hole mobility in comparison with a pure Ge channel on Si.status: publishe