POLARIZATION-INSENSITIVE AND WAVELENGTH-INSENSITIVE GUIDED-WAVE OPTICAL SWITCH WITH SEMICONDUCTOR Y-JUNCTION

A polarization- and wavelength - insenstive semiconductor guided-wave optical switch with a Yjunction is proposed. In this switch, an injected current at the p-n junction induces polarization-independent refractive index decrease through the plasma dispersion and band-filling effects. The index change, in turn, introduces asymmetry to a symmetric Y junction waveguide, and a local mode of one of the branches becomes cut off, when the induced index change is sufficiently large to cancel out the built-in index difference of the waveguide. Therefore, this switch exhibits a so-called digital response with respect to current, and thus it can be used as a wavelength-insensitive 1 × 2 optical switch. The polarization- and wavelength-insensitive switching operation was confirmed with a fabricated GaAs/GaAlAs switch at wavelengths of 1.3 and 1.55 μm and the on/off ratio exceeded 20 dB at an injection current of 250 mA at these wavelengths. © 1990, IEEE.