A New Integrated All-Optical Switch Based on a Micro-Cavity - Lasers and Electro-optics Europe, 1996. CLEO/Europe., Conference on

Integrated all-optical switches [I] can be of great importance for optical transparent telecommunication network All-optical switching is based on the phase change of the light due to the intensity in nonlinear optical (NLO) materials The materials investigated up to now exhibit NLO coefficients which are still too low for realistic high speed devices performance at low optical power A possible way to improve the NLO is enhancement of the electric field inside the material using micro-cavities Recently rotationally symmetric dielectric micro-cavities with radii larger than the wavelength are modelled theoretically for linear and NLO materials These micro cavities can confine large electromagnetic fields in small volumes and act as optical cavities with high quality factors (Q s >IO4 (21) Examples of these micro-cavities are semiconductor microdisk lasers and Nd YAG spherical lasers All kind of NLO processes, such as stimulated Raman scattering and sum-frequency generation have already been reported for liquid droplets however in integrated optic devices micro-cavities have not yet been used The spatial distribution of the internal field in the cavity is in general dominated by the near resonance-mode the whispering gallery mode, when the incident frequency is near one of the high-Q modes (o, The switching speed of these high-Q micro-cavities is usually limited by the cavity lifetime r where T is Q/o, When Q is about I O 3 the cavity lifetime is in the case of cavities with radii of about 8 micron smaller than nanoseconds The proposed all optical switching device is presented in figure 1 The device consists of a micro-cavity surrounded by a NLO material and sandwiched between two waveguides (see figure 1) NLO switching can be expected if the cavity is close to resonance Then by increasing the intensity of the incident light. the high Q-resonance frequency will shift towards the incident frequency due to the refractive index change in the NLO material In this way most of the power