Wavelength and composition dependence of the thermo-optic coefficient for InGaAsP-based integrated waveguides

A method to take into account the wavelength, composition, and temperature dependencies in the calculation of the refractive index and linear thermo-optic coefficient of In1−xGaxAsyP1−y alloys is presented. The method, based on the modified single oscillator model, shows a good agreement with experimental data for InP reported in literature at different wavelength and temperature ranges. Further, we exploit this approach with a Film-Mode Matching solver to calculate the linear thermo-optic coefficients of both phase and group effective indices of an InGaAsP-based waveguide. The same waveguide structure is also experimentally investigated through a reflectometric technique and results are found to be in accordance with the simulations performed exploiting the proposed method. In both cases, a dependence of the group index on temperature, almost twice that of the phase index, is observed. These results provide a deeper understanding on the influence of the temperature on the behaviour of optical waveguides and devices, making possible an accurate and realistic modelling of integrated circuits

Waveguiding light into silicon oxycarbide

In this work, we demonstrate the fabrication of single mode optical waveguides in silicon oxycarbide (SiOC) with a high refractive index n = 1.578 on silica (SiO2), exhibiting an index contrast of δn = 8.2%. Silicon oxycarbide layers were deposited by reactive RF magnetron sputtering of a SiC target in a controlled process of argon and oxygen gases. The optical properties of SiOC film were measured with spectroscopic ellipsometry in the near-infrared range and the acquired refractive indices of the film exhibit anisotropy on the order of 10-2. The structure of the SiOC films is investigated with atomic force microscopy (AFM) and scanning electron microscopy (SEM). The channel waveguides in SiOC are buried in SiO2 (n = 1.444) and defined with UV photolithography and reactive ion etching techniques. Propagation losses of about 4 dB/cm for both TE and TM polarizations at telecommunication wavelength 1550 nm are estimated with cut-back technique. Results indicate the potential of silicon oxycarbide for guided wave applications

Automatic configuration and wavelength locking of coupled micro ring resonators in presence of thermal cross-talk.

Thermal cross-talk can impair the efficiency of tuning algorithms employed for the control, calibration and reconfiguration of photonic integrated circuits (PICs). For example, in coupled microring resonator (MRRs) architectures, thermal crosstalk is responsible for an unwanted coupling among the round trip phases of the resonators, thus affecting their resonance frequencies. Here we propose a novel approach, named Transform Coordinate method (TCM), enabling thermal cross-talk cancellation in PICs. In the TCM, instead of controlling the phase shift of each photonic element individually, the eigensolutions of the thermally coupled system are calculated and employed as control variables. The effectiveness of the TCM is demonstrated by implementing a feedback control system providing automatic resonance tuning of 3rd order coupled MRR filters. Numerical simulations, confirmed by experimental results achieved on a high-index-contrast silicon oxynitride (SiON) platform, demonstrate that the TCM enables a tuning process that is faster, more accurate and more robust with respect to conventional methods based on individual tuning of each MRR. Further, the TCM can be used as a wavelength locking algorithm to maintain the tuned condition in the presence of temperature drift as well as random fluctuations of the wavelength and of the power of the input signal. Finally, the TCM can be applied to generic PIC architectures based on arbitrary combinations of MRRs and other integrated interferometric devices

Automatic Hitless Tuning of Third Order Micro-Ring Resonator Add-Drop Filters

The tuning and locking of a silicon photonics third order microring based filter suitable for hitless operation is presented. The filter has 8 nm Free Spectral Range (FSR) and operates in L band with a bandwidth of 42.5 GHz and isolation better than 20 dB. A novel channel

An introduction to InP-based generic integration technology

Photonic integrated circuits (PICs) are considered as the way to make photonic systems or subsystems cheap and ubiquitous. PICs still are several orders of magnitude more expensive than their microelectronic counterparts, which has restricted their application to a few niche markets. Recently, a novel approach in photonic integration is emerging which will reduce the R&D and prototyping costs and the throughput time of PICs by more than an order of magnitude. It will bring the application of PICs that integrate complex and advanced photonic functionality on a single chip within reach for a large number of small and larger companies and initiate a breakthrough in the application of Photonic ICs. The paper explains the concept of generic photonic integration technology using the technology developed by the COBRA research institute of TU Eindhoven as an example, and it describes the current status and prospects of generic InP-based integration technology

A unified approach for radiative losses and backscattering in optical waveguides

Sidewall 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

The long march of slow photonics

Correspondance con Nature Photonic

Design of a hybrid silicon-plasmonic co-propagating coupler operating close to coherent perfect absorption

By hybrid integration of plasmonic and dielectric waveguide concepts, it is shown that nearly perfect coherent absorption can be achieved in a co-propagating coupler geometry. First, the operating principle of the proposed device is detailed in the context of a more general 2 × 2 lossy coupler formalism. Then, it is shown how to tune the device in a wide region of possible working points, its broadband operation, and the tolerance to fabrication uncertainties. Finally, a complete picture of the electromagnetic modes inside the hybrid structure is analyzed, shining light onto the potentials which the proposed device holds in view of classical and quantum signal processing, nonlinear optics, polarization control, and sensing

An optical device based on a three arm Mach-Zehnder interferometer

Brevetto Pirelli/Coreeco

Statistical Process Design Kits: analysis of fabrication tolerances in integrated photonic circuits

Process Design Kits including statistical data are used to study the effects of production process fluctuations on the response of photonic circuits. Sobol indices allow to measure the impact of random parameters on the transfer function variability