Spectral Broadening due to Self Phase Modulation.

1. a) University of Twente, Faculty of Electrical Engineering, Mathematics and Computer Science, Integrated Optical Micro Systems, P.O.Box 217, 7500 AE Enschede, The Netherlands. Phone: +31-53-489 4440; E-mail: R.Dekker@utwente.nl b) RWTH Aachen, Institut für Halbleitertechnik, Sommerfeldstrasse 24, 52074 Aachen, Germany. c) IREE, Department of Guided Wave Photonics, Chaberska 57, 182 51 Prague, Czech Republic. d)The Institute of Optics, University of Rochester, Rochester New York 14627. “Self Phase Modulation and Stimulated Raman Scattering due to High Power Femtosecond Pulse Propagation in Silicon-on-Insulator Waveguides.” R.Dekkera), E.J.Kleina), J.Niehusmannb), M.Förstb), F.Ondracekc), J.Ctyrokyc), N.Usechakd), and A.Driessena). Spectral Broadening due to Self Phase Modulation. Laserpulses (tFWHM=200fs, frep=80MHz, Pavg=75mW) with a center wavelength of 1550nm were coupled into 400x400nm straight SOI waveguides while the output spectra were recorded at increasing input power. Spectral broadening due to Self Phase Modulation (SPM), caused by the Kerr nonlinearity, has been observed as shown in the graphs on the left. The asymmetry in the peak heights after broadening is caused by higher order dispersion, which is confirmed by simulations. Intrapulse Stimulated Raman Scattering can be excluded as the cause for this, since the input spectrum does not overlap with the Raman gain spectrum, which is 520cm-1 shifted and extremely narrow (0.9nm). Broadband Raman amplification in Silicon. Because of the crystalline structure of silicon, the bandwidth of the Raman phonon spans only 105GHz. This is small compared to the relatively large Raman bandwidth of ~6THz that is present in silica fibers. The result of this small bandwidth is that the Raman gain spectrum is only 0.9nm in width. However, when the silicon lattice is pumped with a high power broadband signal, for instance the SPM broadened signal discussed above, this small gain bandwidth limitation can be overcome. Below, a clear enhancement of the laser idler signal around 1650nm is observed. The pink dotted line indicates the broad Raman gain curve with a 520cm-1 shift relative to the pump. Power fractions of spectral components: Solving the NLSE using the Split Step Fourier method. In order to analyze our experimental results,a simulation tool has been developed to solve the nonlinear Schrödinger equation (NLSE) using the Split Step Fourier Method (SSFM). A lot of effort has been put in the use of ‘real world parameters’ as opposed to standard methods that use normalized time- and frequency scales. Various effects like dispersion (i), linear absorption (0), two-photon absorption (2), Kerr nonlinearities (), intrapulse Raman scattering (TR) and self-steepening (/0) are taken into account.