Abstract
A new off-on switching scheme is introduced which blocks a waveguide path in the passive off-state and transmits the signal in the active on-state. The operating principle is based on the self-diffraction of a narrow guided beam when it escapes from a waveguide with two dimensional confinement into a region of appropriate length with at most one dimensional confinement. In particular a remaining interface of the initial waveguide superimposes reflection, which in sum results in a very efficient asymmetrical blow out of the guided power. In the active on-state, low-loss waveguiding is sustained when an electrode causes an appropriate refractive index change, e.g. due to the thermo-optical effect. Thus the signal is received in the output waveguide, an identical pendant of the input guide. The switching behavior is almost digital, and the wavelength dependence is minimal only. This makes the device useful for switching and modulation in a multi-wavelength optical network. Calculations sh ow on-off signal ratios of better than 30 dB e.g. in a polymeric waveguide configuration of 3 min length. This is nicely adapted to the demands of crosstalk reduction in switching networks. Experimental results from a thermo-optic polymer waveguide device with 32 dB off-state attenuation and 0.8 dB on-state excess loss fit well to the data obtained from the numerical modeling.