1,721,061 research outputs found
Towards VLSI photonics with PDK: tolerances, sensitivity, yield
No full textProcess Design Kits are enabling the access to generic photonic foundries according to the scheme of multiple projects wafer. Here we show the importance to include also statistical data to evaluate the effects of production process fluctuations on the response of photonic integrated circuits. Sensitivity analysis by M and Sobol indices allow to measure the impact of random parameters on the transfer function variability, estimate the yield and achieve a robust and reliable design
Waveguide-based technique for wafer-level measurement of phase and group effective refractive indices
No full textA novel optical technique for multipoint on-wafer testing is reported. The technique exploits an integrated optical waveguide named point reflector optical waveguide (PROW) carrying multiple sensing probes based on lumped reflectors. PROW can be placed on the wafer along the desired paths, is compatible with chips tiling, requires a very small dedicated area and is here exploited to map the on-wafer distribution of the phase and group effective indices with an accuracy down to 10-3. The technique is useful to retrieve and map the variations of the physical and geometrical properties of the waveguides (e.g., width and core material composition) on the investigated wafer area. The potential of the PROW is here demonstrated on a InP wafer but can be readily extended to other platforms
A unified approach for radiative losses and backscattering in optical waveguides
Full text linkSidewall roughness in optical waveguides represents a severe impairment for the proper functionality of photonic integrated circuits. The interaction between the propagating mode and the roughness is responsible for both radiative losses and distributed backscattering. In this paper, a unified vision on these extrinsic loss phenomena is discussed, highlighting the fundamental role played by the sensitivity of the effective index n eff of the optical mode to waveguide width variations. The n w model presented applies to both 2D slab waveguides and 3D laterally confined waveguides and is in very good agreement with existing models that individually describe radiative loss or backscattering only. Experimental results are presented, demonstrating the validity of the n w model for arbitrary waveguide geometries and technologies. This approach enables an accurate description of realistic optical waveguides and provides simple design rules for optimization of the waveguide geometry in order to reduce the propagation losses generated by sidewall roughness
Real photonic waveguides: guiding light through imperfections
Full text linkReal photonic waveguides are affected by structural imperfections due to fabrication tolerances that cause scattering phenomena when the light propagates through. These effects result in extrinsic propagation losses associated with the excitation of radiation and backscattering modes. In this work, we present a comprehensive review on the extrinsic loss mechanisms occurring in optical waveguides, identifying the main origins of scattering loss and pointing out the relationships between the loss and the geometrical and physical parameters of the waveguides. Theoretical models and experimental results, supported by statistical analysis, are presented for two widespread classes of waveguides: waveguides based on total internal reflection (TIR) affected by surface roughness, and disordered photonic crystal slab waveguides (PhCWs). In both structures extrinsic losses are strongly related to the waveguide group index, but the mode shape and its interaction with waveguide imperfections must also be considered to accurately model the scattering loss process. It is shown that as long as the group index of PhCWs is relatively low (ng\<30), many analogies exist in the radiation and backscattering loss mechanisms with TIR waveguides; conversely, in the high ng regime, multiple scattering and localization effects arise in PhCWs that dramatically modify the waveguide behavior. The presented results enable the development of reliable circuit models of photonic waveguides, which can be used for a realistic performance evaluation of optical circuits
Scattering in optical waveguides: a comprehensive model for radiative losses and backreflections
No full textA unified model to describe both radiative losses and distributed backscattering generated by sidewall roughness is presented. The model is in very good agreement with experimental results obtained on different types of optical waveguides, demonstrating its validity for arbitrary waveguide geometries and technologies
Modeling reflections induced by waveguide transitions
No full textReflections generated along optical waveguidesmay result in detrimental effects
and deterioration of the circuit performances. In this work we propose a fast and accurate
circuit model to predict the reflection induced by a waveguide discontinuity. The model is
based on a variational approach of the Fresnel expression of the reflectivity. After theoretical
description, the model is applied to two different interfaces: a waveguide transition inducing
very low reflections and a reflective chip facet. A comparison with experimental results and
electromagnetic simulations is shown, demonstrating the accuracy of the proposed method
Modelling and circuit simulation of distributed reflections in integrated optical waveguides and circuits
No full textReconfigurable photonic integrated mode (de)multiplexer for SDM fiber transmission
Full text linkSpatial division multiplexing in multi-mode fibers allows to largely enhance transmission capacity compared to single-mode links. Photonic integrated circuits can provide solutions for mode multiplexing at the transmitter and demultiplexing at the receiver but have to generally face high losses and inter-modal cross-talk issues. Here a photonic circuit for efficient mode multiplexing and demultiplexing in few-mode fibers is presented and demonstrated. Two 10 Gbit/s channels at the same wavelength and polarization are simultaneously transmitted over modes LP01 and LP11a of a few-mode fiber relying only on integrated mode MUX and DEMUX. The proposed Indium-Phosphide-based circuits have a good coupling efficiency with fiber modes and mode-dependant loss smaller than 1 dB. Measured mode excitation cross-talk is as low as -20 dB and a channel cross-talk after propagation and demultiplexing of -15 dB is achieved. An operational bandwidth of the full transmission system of at least 10 nm is demonstrated. Both mode MUX and DEMUX are fully reconfigurable and allow a dynamic switch of channel routing in the transmission system. These results enable fully-integrated fiber mode handling for high-bandwidth flexible optical networks
Toward building-block-based approach for generic integration photonic technologies
No full textIn the last years the concept of building-block approach and circuit-model simulation in photonics has been thoroughly developed and is now becoming a pervasive methodology for Silicon, Indium Phosphide and dielectric based generic integration technologies. The current status and prospects of the BB approach, the concept, the potential and the limits are discussed focusing on materials, technologies, software tools and characterization techniques. Statistical analysis, yield and tolerance aspect are addressed too. The effort of introducing Photonics Design Kits is described and a comparison between the various technologies is presented. Successful examples based on our experience are presented and discussed and a tentative roadmap proposed
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