1,721,005 research outputs found
NH<sub>3</sub>-free PECVD silicon nitride for photonic applications
No full textSilicon Photonics has open the possibility of developing multilayer platforms based on complementary metal-oxide semiconductors compatible materials that have the potential to provide the density of integration required to fabricate complex photonic circuits. Amongst these materials, silicon nitride (SiN) has drawn attention due to its fabrication flexibility and advantageous intrinsic properties that can be tailored to fulfil the requirements of different linear and non-linear photonic applications covering the ultra-violet to mid-infrared wavelengths. Yet, the fabrication techniques typically used to grow SiN layers rely on processing temperatures > 400 C to obtain low propagation losses, which deem them inappropriate for multilayer integration. This thesis presents a systematic investigation that provided a comprehensive knowledge of a deposition method based on an NH3-free plasma enhanced chemical vapour deposition recipe that allows the fabrication of low-loss silicon nitride layers at temperatures < 400 C. The results of this study showed that the properties of the studied SiN layers depend mostly on their N/Si ratio, which is in fact one of the only properties that can be directly tuned with the deposition parameters. These observations provided a framework to optimise the propagation losses and optical properties of the layers in order to develop three platforms intended for specific photonic applications. The first one comprises 300nm stoichiometric SiN layers with refractive index (n) of 2 that enable the fabrication of photonic devices with propagation losses < 1 dB/cm at l = 1310nm and < 1:5 dB/cm at l = 1550 nm, which are good for applications that require efficient routing of optical signals. The second one consists on 600nm N-rich layers (n = 1.92) that allow fabricating both devices with propagation losses < 1 dB/cm at l = 1310 nm, apt for polarisation independent operation and coarse wavelength division multiplexing devices with cross-talk < 20 dB and low insertion losses. Finally, the last platform consisted of suspended Si-rich layers (n = 2.54) that permits the demonstration of photonic crystal cavities with Q factors as high as 122 000 and photonic crystal waveguides capable of operating in the slow-light regime. Hopefully, the demonstration of these platforms will stimulate the development of more complex SiN devices for multilayer routing, wavelength division multiplexing applications and non-linear integrated photonics in the future
Athermal silicon nitride angled MMI wavelength division (de)multiplexers for the near-infrared
No full textWDM components fabricated on the silicon-on-insulator platform have transmission characteristics that are sensitive to dimensional errors and temperature variations due to the high refractive index and thermo-optic coefficient of Si, respectively. We propose the use of NH3-free SiNx layers to fabricate athermal (de)multiplexers based on angled multimode interferometers (AMMI) in order to achieve good spectral responses with high tolerance to dimensional errors. With this approach we have shown that stoichiometric and N-rich SiNx layers can be used to fabricate AMMIs with cross-talk<30dB, insertion loss <2.5dB, sensitivity to dimensional errors <120pm/nm, and wavelength shift <10pm/°C
Fully Integrated SiN/SOI (De)Multiplexer for the O-band
No full textWe present the experimental demonstration of a silicon nitride (de)multiplexer fully integrated with a thick silicon-on-insulator platform for coarse wavelength division multiplexing applications in the O-band
Coupling strategy between high-index and mid-index micro-metric waveguides for O-band applications
No full textThe integration of fast and power efficient electro-absorption modulators on silicon is of utmost importance for a wide range of applications. To date, Franz-Keldysh modulators formed of bulk Ge or GeSi have been widely adopted due to the simplicity of integration required by the modulation scheme. Nevertheless, to obtain operation for a wider range of wavelengths (O to C band) a thick stack of Ge/GeSi layers forming quantum wells is required, leading to a dramatic increase in the complexity linked to sub-micron waveguide coupling. In this work, we present a proof-of-concept integration between micro-metric waveguides, through the butt-coupling of a [Formula: see text] thick N-rich silicon nitride (SiN) waveguide with a [Formula: see text] thick silicon waveguide for O-band operation. A numerical analysis is conducted for the design of the waveguide-to-waveguide interface, with the aim to minimize the power coupling loss and back-reflection levels. The theoretical results are compared to the measured data, demonstrating a coupling loss level of [Formula: see text] for TE and TM polarisation. Based on the SiN-SOI interconnection simulation strategy, the simulation results of a quantum-confined Stark effect (QCSE) stack waveguide coupled to a SiN waveguide are then presented
Hot-wire chemical vapour deposition for silicon nitride waveguides
No full textIn this work, we demonstrate the use of HWCVD as an alternative technique to grow SiN layers for photonic waveguides at temperatures <400ºC. In particular, the effect of the ammonia flow and the filament temperature on the material structure, optical properties and propagation losses of the deposited films was investigated. SiN layers with good thickness uniformity, roughness as low as 0.61nm and H concentration as low as 10.4×1021 atoms/cm3 were obtained. Waveguides fabricated on the studied materials exhibited losses as low as 7.1 and 12.3 dB/cm at 1310 and 1550nm respectively
SiN/SOI sub-dB butt-coupling scheme in the O-band
No full textThe monolithic integration of micro-metric silicon nitride and silicon-on-insulator platforms is presented. We demonstrate an interconnection of sub-dB coupling loss and less than -16dB back-reflection for operation in the O-band
Low temperature silicon nitride waveguides for multilayer platforms
Full text linkSeveral 3D multilayer silicon photonics platforms have been proposed to provide densely integrated structures for complex integrated circuits. Amongst these platforms, great interest has been given to the inclusion of silicon nitride layers to achieve low propagation losses due to their capacity of providing tight optical confinement with low scattering losses in a wide spectral range. However, none of the proposed platforms have demonstrated the integration of active devices. The problem is that typically low loss silicon nitride layers have been fabricated with LPCVD which involves high processing temperatures (<1000 ºC) that affect metallisation and doping processes that are sensitive to temperatures above 400ºC. As a result, we have investigated ammonia-free PECVD and HWCVD processes to obtain high quality silicon nitride films with reduced hydrogen content at low temperatures. Several deposition recipes were defined through a design of experiments methodology in which different combinations of deposition parameters were tested to optimise the quality and the losses of the deposited layers. The physical, chemical and optical properties of the deposited materials were characterised using different techniques including ellipsometry, SEM, FTIR, AFM and the waveguide loss cut-back method. Silicon nitride layers with hydrogen content between 10-20%, losses below 10dB/cm and high material quality were obtained with the ammonia-free recipe. Similarly, it was demonstrated that HWCVD has the potential to fabricate waveguides with low losses due to its capacity of yielding hydrogen contents <10% and roughness <1.5nm
Group IV functionalization of low index waveguides
No full textLow fabrication error sensitivity, integration density, channel scalability, low switching energy and low insertion loss are the major prerequisites for future on-chip WDM systems and interfacing with optical fibres. A number of device geometries have already been demonstrated that fulfil these criteria, at least in part, but combining all of the requirements is still a difficult challenge.Two contenders that could fulfil these criteria are the low loss nitride waveguiding platform and the high index group IV compounds for active photonic devices. Silicon Oxynitride (SiON) and Silicon Nitride (SiN) based waveguides are extremely powerful and central to today’s optical communications networks. The intermediate refractive index provides low footprint devices but eases the fabrication demands that can result in phase errors and repeatability problems in the all silicon approach. This enables multiplexers and demultiplexers with very low crosstalk and insertion loss and extremely low loss long range waveguides, making them very attractive for the optical backplanes and rack to rack links inside supercomputers and data centers. Group IV Photonics GeSi has a number of attractive optical characteristics for modulation, absorption and detection in a small volume area enabling low power and high density integration.Here, we propose and demonstrate a novel architecture consisting of the interfacing of a range of deposition method using low temperature PECVD and HWCVD nitride waveguides, Photonic crystal modulators [1] but also detectors [2] connected by a silicon nitride bus waveguide. The architecture features very high scalability due to the small size of the devices (~100 micrometre square) and the modulators operate with an AC energy consumption of less than 1fJ/bit
SiGe bandgap tuning for high speed Eam
No full textWe report bandgap engineering of Ge rich SiGe rib waveguides between 1550 nm and 1580 nm through an annealing process. The insertion loss of the material (transmission spectrum) is analysed between 1520 nm and 1600 nm. The experimental data are elaborated by implementing the Tauc Method analysis, and the material bandgap estimation is calculated. A maximum blue shift of 38 nm, with an overall reduction of Si content, suggests that the diffusion of Si in the Ge seed layer during anneal improves the homogeneity of the growth layer. The proposed technique provides a path for tailoring the operational wavelength of devices such as electro-absorption modulators, realized on an SOI platform
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