Tunable and sensitive biophotonic waveguides based on photonic-bandgap microcavities

This paper presents a theoretical study of active one-dimensional (1-D) silicon photonic bandgap waveguides. To the best of our knowledge, we provide for the first time, a systematic study of the various physical parameters that can affect the Q factor and transmission properties in such waveguides. In order to make this technology viable, the waveguides must be tunable, have low attenuation, possess high Q factor, and can be switched. Can these be achieved simultaneously without changing the device width and height dimensions? Furthermore, can we meet these aims without placing unrealistic demands in fabrication? The electrical switching of this device is implemented using a p-i-n optical diode. The diode is predicted to require a ON state power of 81 nW with rise and fall times of 0.2 ns and 0.043 ns respectively. The length of the microcavity and the diameter of the air holes are finely tuned with reference to the Q factor and transmission. It will be shown that for certain desired resonant wavelength, the Q factor and transmission properties can be optimized by tuning the length of the cavity and the diameter of the two inner most air holes. This method allows ease of fabrication by not having to vary the waveguide width and height to obtain the tuning effects. Optical simulation was performed using 3-D finite difference time domain (FDTD) simulation method.