Shallow etch electrical isolation in capacitively loaded Mach-Zehnder modulators

To compensate for velocity mismatch in travelling wave opto-electronic devices, the microwave velocity of the propagating RF signal is reduced by introducing capacitively loaded elements. For high speed operation, these elements must be electrically isolated from one another, which is typically achieved by using ion-implantation to render the p-doped material non-conducting. We propose and demonstrate through optical and electrical simulations that ion-implantation can be avoided by using a quasi-shallow etch to electrically isolate the capacitive elements. High isolation can be achieved using such an etch without introducing additional losses to the propagating optical signal.