Analysis and design of traveling-wave photodetectors for RF optical link communication using the finite-difference time-domain method

We invetigate the microwave characteristics of traveling-wave photodetector using the finite-difference time-domain method. This method enables us to consider the full configuration of the device to be studied with no assumption. Therefore we obtain accurate simulation results, though the geometry of ridge-type coplanar waveguide photodetector is complicated. Physical phenomena such as attenuation and dispersion are shown in time domain. We offer two design parameters, the width of PIN region and the thickness of i-layer, and analyze TWPD's property in frequency domain. Microwave loss, characteristic impedance, and RF refractive index are shown and we find out that there exists a tradeoff condition for design.