Reduction of optical insertion loss in traveling wave electroabsorption modulators by undercut-etching the active region

In this paper, an improved traveling wave electroabsorption modulators (TWEAM) waveguides with selectively undercut the active region is proposed and fabricated. Optical transmission on wavelength shows that the undercut-active-layer waveguide (UAW) structure has advantage over the conventional ridge-waveguide (CRW) due to the lower propagation loss and the difference (about 2 to 3 dB) between the UAW structures and CRW structures indicates that the optical insertion loss of UAW type is about 2 to 3 dB lower than the CRW. This kind of structure has high potential for the application of high-speed and lower optical insertion-loss EAMs.