Journal of Optics Volume 16 Number 8, 2014.
F De Leonardis, B Troia, C E Campanella and V M N Passaro.
Photonics Research Group, Dipartimento di Ingegneria Elettrica e dell’Informazione, Politecnico di Bari, via Edoardo Orabona n. 4, 70125 Bari, Italy
In this paper, the detailed modeling of Raman lasers in silicon-on-insulator guided-wave racetrack resonant microcavities is developed. Modeling based on full-vectorial equations, including thermal and stress effects, is presented for the first time. Simulation results are compared with experimental and theoretical results in the literature, demonstrating very good agreement. Moreover, parametric investigations, including waveguide sizes, pump and Stokes coupling factors, cavity shape, polarization states, and waveguide orientation are presented; and the effects of these characteristics in conjunction with thermal and stress influence on laser features are discussed.
The physical principles of the Raman amplification in micrometer waveguides fabricated on the Silicon-on-Insulator (SOI) technology platform was experimentally proved in 2002 for the first time. Consequently, nonlinear effects in SOI photonic integrated devices have been massively investigated since the first demonstration, focusing on Stokes and anti-Stokes Raman conversion, stimulated Raman scattering (SRS), Kerr effect and induced self-phase modulation (SPM) or cross-phase modulation (XPM), two photon absorption (TPA) with the consequent free carrier absorption (FCA), and free carrier dispersion (FCD). The excitation of these nonlinear physical principles in SOI optical resonant cavities has been experimentally demonstrated to be particularly suitable for the fabrication of low threshold integrated Raman laser sources. Since 2006, the Photonics Research Group at Politecnico di Bari (URL: http://dee.poliba.it/photonicsgroup ) has developed several contributions on nonlinear effects in SOI, defining the theoretical design guidelines for active SOI optical cavities based on the SRS effect. Then, we have investigated the temperature and the stress effects affecting the performance of the SOI racetrack resonator Raman lasers. In particular, we have developed a general and self-consistent physical model, which allows to evaluate how the temperature and the stress in silicon can affect the performance of SRS-based SOI racetrack resonator lasers focusing on Raman gain variation, Stokes and anti-Stokes wavelength shifts and polarization state coupling. This investigation represents a crucial approach for exploring and valuating applications of innovative photonic integrated circuits mainly in aerospace and aeronautics, where device performance can be dramatically influenced by stress, temperature and radiation effects.
In addition to the investigation of nonlinearities in photonic devices based on group IV materials, the research activities carried out by the Photonics Research Group are also focused on the theoretical and experimental investigation of advanced photonic sensors in integrated optics and fiber optic systems. In fact, novel ultra-high performance SOI chemical sensors operating in the near- and mid-infrared as well as ultra-high resolution fiber optic resonant sensors designed for measuring physical and chemical parameters, have been proposed, modeled and experimentally tested.
Schematic architecture of a SOI racetrack resonator based on a SOI rib waveguide for the excitation of co-propagating and counter-propagating Stokes signals generated by Stimulated Raman Scattering in the near-infrared.