Simplified colorless characterization scheme for coherent receivers in DWDM scenarios using a single interferer

Intradyne coherent receivers, capable of detecting an individual wavelength-division multiplexed channel just by tuning the local oscillator frequency, is of great interest for the development of high-capacity flexible optical networks. Nevertheless, the unavoidable amplitude imbalances inherent to any realistic coherent receiver induce an interference contribution from the self-beating of the coincident channels present at its input. The charac- terization of this degraded colorless reception operation is of fundamental importance, but it usually requires the use of rather complex experimental setups, especially when the effects of tens of interference channels should be evaluated. In this work we propose a novel experimental setup that only requires the use of a single intense interferer to emulate those coincident channels, thus drastically simplifying the characterization process. In addition, we develop a general expression for the signal-to-noise ratio of the system that theoretically justifies the intended setup and demonstrate by massive numerical simulations its accuracy in different scenarios. We believe that the proposed approach may contribute to facilitate the experimental characterization of high-performance colorless coherent receiversFunding for open access charge: Universidad de Málaga / CBU

Towards Simultaneous Absorption and Refractive Index Sensing using Integrated Photonics.

Photonic integrated sensors traditionally detect changes either in optical amplitude or phase. Here we experimentally demonstrate a sensing architecture which measures both amplitude and phase, enabling simultaneous detection of changes in absorption and refractive index.This work has received funding from the Ministerio de Ciencia, Innovación y Universidades (FPU19/03330, PID2019-106747RB-I00) and the Junta de Andalucía (Agencia Andaluza del Conocimiento PY18-793). We would also like to acknowledge the Universidad de Málaga, Campus de Excelencia Internacional Andalucía Tech

Efficient fiber-to-chip grating coupler for micrometric SOI rib waveguides

Grating couplers are an efficient means for fiber to chip coupling, as they require no facet preparation and enable wafer scale testing. While grating couplers are commonly used in silicon wire waveguides, their application to micrometric silicon-on-insulator rib waveguides is complicated due to the presence of high-order Bloch modes. We study the Bloch modes behavior and their excitation determined by access waveguide design. The latter is implemented to enable single Bloch mode excitation. The use of a design process based on modal analysis is proposed. A grating coupler is proposed in silicon-on-insulator with 1.5 microm thick silicon layer that achieves a coupling efficiency of 65.6% at 1.55 microm. The structure, including interconnection waveguides, access waveguide and grating can be fabricated using a single lithography step

High-Performance Bimodal Evanescent-Field Sensor with Coherent Phase Readout

By comparing optical signals travelling through a sensing and a reference arm, interferometric photonic sensors achieve remarkable sensitivities and detection limits using sim- ple single-wavelength laser sources. Sensors based on bimodal waveguides can, in principle, provide the same advantages without requiring a reference arm, by comparing the propagation of two modes travelling through a single sensing waveguide. However, typical implementations of bimodal sensors face two challenges: (i) the abrupt mode excitation and recombination at the sensor input and output is inefficient, unbalanced in power and produces spurious reflections that can mask small sensing signals, (ii) the sinusoidal nature of the output signal can lead to ambiguities in the readout. Here we present a spiralled bimodal refractive index sensor with full mode conversion, multiplexing and demultiplexing and a coherent phase detection, providing an unambiguous linear phase readout with a compact and robust layout. Our sensors have been designed for a 1550 nm central wavelength, fabricated on a silicon nitride platform and validated with bulk sensing experiments, achieving a limit of detection of 1.67 · 10^−7 RIU.This work has received funding from the Ministerio de Universidades, Ciencia e Innovacio ́n (FPU19/03330, PID2019- 106747RB-I00, PID2020-115204RB-I00), the Junta de An- daluc ́ıa (Agencia Andaluza del Conocimiento PY18-793, Consejer ́ıa de salud y familia PIN-0113-2020), and project TED2021-130400B-I00/ AEI/10.13039/501100011033/ Unio ́n Europea NextGenerationEU/PRTR

Performance of Bragg grating assisted multi-band add-drop filters on the silicon-on-insulator platform.

In this work, we designed multi-band add-drop filters based on Bragg grating assisted Mach-Zehnder interferometers for the LAN wavelength division multiplexing standard. We experimentally assessed their behaviors on the silicon-on-insulator commercial platform. We experimentally report insertion losses of less than 1 dB and a mean interchannel crosstalk of -20 dB for a channel separation of 9 nm and a channel width of 3 nmUniversidad de Málaga. Campus de Excelencia Internacional Andalucía Tec

High performance TM-pass polarizer via subwavelength grating bandgap engineering

Silicon photonics systems exhibit a strong birefrin- gence which makes polarization management critical. Here we demonstrate, with full 3D-FDTD simulations, a low-loss and high- extinction ratio TM-pass polarizer based on tilted subwavelength gratings that reflects the TE0 mode into the TE1 mode, with a 150 nm bandwidth.Junta de Andalucía (P18-RT-793 and P18-RT-1453); Universidad de Málaga (UMA20-FEDERJA-158); Ministerio de Economía y Competitividad (PID2019-106747RB-I00); Ministerio de Ciencia e Innovación (TED2021- 130400B-I00); Ministerio de Universidades (FPU19/02408); Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Optimizing the limit of detection of waveguide-based interferometric biosensor devices

Waveguide-based photonic sensors provide a unique combination of high sensitivity, compact size and label-free, multiplexed operation. Interferometric configurations furthermore enable a simple, fixed-wavelength read-out making them particularly suitable for low-cost diagnostic and monitoring devices. Their limit of detection, i.e., the lowest analyte concentration that can be reliably observed, mainly depends on the sensors response to small refractive index changes, and the noise in the read-out system. While enhancements in the sensors response have been extensively studied, noise optimization has received much less attention. Here we show that order-of-magnitude enhancements in the limit of detection can be achieved through systematic noise reduction, and demonstrate a limit of detection of ~10 RIU with a silicon nitride sensor operating at telecom wavelengths

Low-loss curved waveguide grating wavelength demultiplexer

We demonstrate a compact wavelength demultiplexer for the silicon on insulator platform based on the curved waveguide grating (CWG) architecture. We mitigate off-chip radiation loss by enforcing the single beam condition by using metamaterial index engineering. The fabricated device exhibits insertion loss as low as 1dB and crosstalk lower than -25 dB