Temperature insensitive waveguide interferometer based on subwavelength gratings

We present a design for a temperature insensitive Mach-Zehnder interferometer in which temperature compensating segment is achieved through tailored subwavelength gratings. By engineering the thermal response and the relative length of this segment, an overall temperature insensitivity below ±4pm/ºK is predicted for 100nm bandwidth around 1550nm

Designing polarization management devices by tilting subwavelength grating structures

Subwavelength gratings (SWG) are periodic structures which behave as controllable homogeneous metamaterials. SWGs are extremely interesting when they are used in platforms with a limited choice of material refractive indices, enabling the design of a myriad of high-performance devices. Here we present a novel technique to gain control over the intrinsic anisotropy of the synthesized metamaterial. We show that tilting the silicon segments in a SWG structure mainly affects the in-plane (TE) modes, with little impact on the out-of-plane (TM) modes. Moreover, we present a methodology to quickly but accurately calculate the modes of a tilted periodic structure modeling the structure as a rotated uniaxial crystal which can be solved with an anisotropic mode solver. Measurements on a set of fabricated tilted SWG waveguides validate our simulation results. By using the presented technique, we design a polarization beam splitter based on a 2x2 multimode interferometer. The design is based on the optimization of the tilting angle to tone the beat length of the TE modes to be a half of the beat length of the TM modes.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech; Ministerio de Economía y Competitividad (MINECO) (IJCI-2016-30484, TEC2015-71127-C2-R, TEC2016-80718-R); Ministerio de Educación, Cultura y Deporte (MECD) (FPU16/06762); European Regional Development Fund (ERDF); Comunidad de Madrid (SINFOTON-CM S2013/MIT-2790); European Association of National Metrology Institutes (EURAMET) (H2020-MSCA-RISE-2015:SENSIBLE, JRP-i22 14IND13 Photind)

Polarization and wavelength agnostic nanophotonic beam splitter

High-performance optical beam splitters are of fundamental importance for the development of advanced silicon photonics integrated circuits. However, due to the high refractive index contrast of the silicon-on-insulator platform, state of the art Si splitters are hampered by trade-offs in bandwidth, polarization dependence and sensitivity to fabrication errors. Here, we present a new strategy that exploits modal engineering in slotted waveguides to overcome these limitations, enabling ultra-wideband polarization-insensitive optical power splitters, with relaxed fabrication tolerances. The proposed splitter relies on a single-mode slot waveguide which is transformed into two strip waveguides by a symmetric taper, yielding equal power splitting. Based on this concept, we experimentally demonstrate -3$\pm$0.5 dB polarization-independent transmission in an unprecedented 390 nm bandwidth (1260 - 1650 nm), even in the presence of waveguide width deviations as large as $\pm$25 nm

A broadband polarization splitter directional coupler based on tilted subwavelengh grating metamaterials

Tilted subwavelength gratings (SWG) allows anisotropy tailorable metamaterials with applications in polarization management. Based on this concept, here we experimentally demonstrate a broadband directional-couplerbased polarization beam splitter with sub-decibel insertion loss in a 100 nm bandwidth.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Broadband Fourier-transform silicon nitride spectrometer with wide-area multiaperture input

4 pags., 5 figs.Integrated microspectrometers implemented in silicon photonic chips have gathered a great interest for diverse applications such as biological analysis, environmental monitoring, and remote sensing. These applications often demand high spectral resolution, broad operational bandwidth, and large optical throughput. Spatial heterodyne Fourier-transform (SHFT) spectrometers have been proposed to overcome the limited optical throughput of dispersive and speckle-based on-chip spectrometers. However, state-of-the-art SHFT spectrometers in near-infrared achieve large optical throughput only within a narrow operational bandwidth. Here we demonstrate for the first time, to the best of our knowledge, a broadband silicon nitride SHFT spectrometer with the largest light collecting multiaperture input (320 × 410 µm) ever implemented in an SHFT on-chip spectrometer. The device was fabricated using 248 nm deep-ultraviolet lithography, exhibiting over 13 dB of optical throughput improvement compared to a single-aperture device. The measured resolution varies between 29 and 49 pm within the 1260-1600 nm wavelength range.Spanish Ministry of Science and Innovation (MICINN) (RED2018-102768-T, RTI2018-097957-B-C33, TEC2015-71127-C2-1-R (FPI Scholarship BES-2016-077798)); Community of Madrid-FEDER funds (S2018/NMT-4326); Horizon 2020 Research and Innovation Program (Marie Sklodowska-Curie 734331); H2020 European Research Council (ERC POPSTAR 647342); European Commission (H2020- ICT-26127-2017 COSMICC 688516); French Industry Ministry (Nano2022 project under IPCEI program); Agence Nationale de la Recherche (ANR-MIRSPEC-17-CE09-004

Mode Converter and Multiplexer with a Subwavelength Phase Shifter for Extended Broadband Operation

4 pags., 3 figs., 1 tab.On-chip mode converters and multiplexers are fundamental components to scale the capacity of silicon optical interconnects by using different spatial modes of waveguides. Recently, we proposed a low loss and compact mode converter and multiplexer consisting of a subwavelength-engineered multimode interference coupler, tapered waveguides as phase shifter and a symmetric Y-junction. However, the narrow spectral response of the tapered phase shifter limited the device crosstalk performance. In this work, we demonstrate that the use of a subwavelength grating phase shifter with low phase-shift errors substantially reduces the crosstalk and expands the operational bandwidth. A complete multiplexer-demultiplexer link consisting of two devices in back-to-back configuration was fabricated in a 220-nm silicon-on-insulator platform. Experimental measurements of the complete link show insertion loss below 2 dB and crosstalk less than -17 dB over a bandwidth of 245 nm (1427 - 1672 nm).is work was supported in part by the Spanish Ministry of Science and Innovation (MICINN) under grants RTI2018- 097957-B-C33, RED2018-102768-T, TEC2015-71127-C2-1-R (FPI BES- 2016-077798) and NEOTEC-CDTI-SNEO20181232 (Alcyon Photonics S.L.); and the Community of Madrid – FEDER funds (S2018/NMT-4326). This project has received funding from the Horizon 2020 research and innovation program under Marie Sklodowska-Curie grant No. 73433

Silicon high performance devices using subwavelength structures

Ministerio de Economía y Competitividad, Programa Estatal de Investigación, Desarrollo e Innovación Orientada a los Retos de la Sociedad (cofinanciado FEDER), Proyecto TEC2016-80718-R Universidad de MälagaSilicon photonics is poised to solve challenges in areas such as datacom, environmental monitoring and diagnostics, by leveraging the economies of scale afforded by CMOS manufacturing. This requires a wide variety of integrated silicon devices, including fiber-to-chip couplers, polarization splitters and waveguide couplers, operating both in the near-infrared and the mid-infrared wavelength range. However, the reduced set of materials available in this platform can often limit the performance of these devices. Subwavelength structures enable the synthesis of optical metamaterials, with properties than can be tuned to enhance device performance, by using fully etched silicon structures with a periodicity smaller than the wavelength of light. Here we review the basic operating principles of these structures, discuss how to efficiently model them, and report on the latest advances in this rapidly growing field.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Separador de polarización integrado de altas prestaciones basado en estructuras sub-longitud de onda

Polarization management is a key factor in photonics integration platforms with high birefringence such as Silicon-On- Insulator. Here we design a directional coupler polarization beam splitter composed of two subwavelength waveguides, which only differ in the tilt angle of the silicon segments. Our simulations predict an extinction ratio higher than 20 dB over an 86 nm bandwidth with negligible losses. The fabricated device is only 14 μm long, covers a 72 nm bandwidth with sub-decibel insertion losses and exhibits an extinction ratio in excess of 15 dB.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Subwavelength silicon photonics: keynote presentation

2020 Photonics North (PN), Niagara Falls, ON, Canada, 26-28 May 2020Subwavelength structures are enabling a host of high-performances devices in the silicon photonic platform. Here we review our progress in the field, with an emphasis on the auspicious anisotropic properties of these structures for applications ranging from broadband on-chip GRIN-lenses, to zero-birefringence waveguides and polarization splitters