We have fabricated ion-exchanged potassium titanyl phosphate (KTP) Mach Zehnder and phase modulators operating at X = 1.3um and 0.633um. These devices were designed for very high frequency operation with a 3-db modulation bandwidth of greater than 12GHz. Device insertion losses were between 1.5db and 5db with switching voltages (D.C. ) of 10V. Thick (- 3μm) electroplated gold was used to produce low-loss 50Q impedance coplanar strip electrodes. High optical power operation at 0.633um ( -100μW) produced no optical damage effects. Further results such as device stability will be presented at the conference.