Traveling Wave Electrodes for Substrate Removed Electro-Optic Modulators With Buried Doped Semiconductor Electrodes

This paper reports theoretical and experimental studies of traveling wave electrodes suitable for wide bandwidth operation of ultra-low voltage substrate removed compound semiconductor electro-optic modulators. These modulators use submicron epitaxial layers removed from their substrates and contain buried electrodes made out of doped semiconductors. This approach enables very uniform submicron electrode gap resulting in ultra-low voltage operation. Traveling wave electrodes suitable for wide bandwidth and low voltage operation are designed using loaded line approach. Electrode capacitance and resistance are reduced significantly using staircase waveguides and n-i-p-i-n epitaxial layer designs. A very accurate modeling of the electrode is introduced. Such electrodes are fabricated and characterized up to 35 GHz. Experimental and modeling results are found to agree very well, making the design of such electrodes possible. Theoretical and experimental results show that subvolt modulators with electrical to optical bandwidths in excess of 35 GHz are possible.