Abstract
Recently, two photon absorption (TPA) in semiconductor materials has been found to impose a serious limitation on the amount of ultrafast optically induced phase modulation available for use in all-optical switching elements1. The limit arises because nonlinear absorption reduces the effective available nonlinear length of an element so that it is not possible to obtain large, ultrafast, all-optical phase modulation at a given switching power by merely increasing the device length. To date the magnitude of ultrafast all-optical phase modulation in semiconductor materials operating relatively close to the bandgap has proved insufficient for their use in all all-optical switching structures2,3, although it has been possible to obtain sufficient phase modulation by using the relatively slow (>50ps recovery time) refractive index change from photogenerated carriers4. In this paper we demonstrate that it is possible to work beyond the TPA limit by operating close to the half bandgap wavelength where TPA is minimal. We have observed over π radians ultrafast all-optical phase modulation in a GaAs/AlGaAs multi-quantum well (MQW) waveguide and have characterised the field and polarization dependences of the nonlinear absorption near half bandgap. These measurements show that GaAs/AIGaAs MQW waveguides can be successfully used for ultrafast all-optical switching in the 1.55μm optical fiber communications band.
© 1991 Optical Society of America
PDF ArticleMore Like This
M.N. Islam, C.E. Soccolich, R.E. Slusher, A. F. J. Levi, W. S. Hobson, and M.G. Young
PD3 Nonlinear Guided-Wave Phenomena (NP) 1991
D. J. Goodwill, J. E. Ehrlich, and A. C. Walker
CTuW54 Conference on Lasers and Electro-Optics (CLEO:S&I) 1991
F.R. Laughton, J.H. Marsh, and J.S. Roberts
MF4 Integrated Photonics Research (IPR) 1992