A novel Zn-indiffused mode converter has been proposed and experimentally studied in an x-cut/z-propagation lithium niobate at a wavelength of 0.632 mum for the first time. The optimized phase-matching and mode-conversion voltages for maximum conversion are 12 V and -?5 V, respectively. The results show that the proposed mode converter can operate with a stable conversion efficiency of about 99.5% between TM and TE polarizations at a throughput power of 25 muW in a period of 60 min. Moreover, a comparison of optical power-handling stability between the Ti-indiffused and the Zn-indiffused channel waveguides, was explored. The encouraging results indicate that the Zn-indiffused waveguide has better power stability than the Ti-indiffused waveguide. Thus, it is expected that the proposed mode converter will have better stability than the conventional Ti-indiffused ones, especially in the visible wavelength region.