[Skripsi ini membahas tentang disain 3 dB Y-junction Power Splitter berbasisGaN/Al2O3 (Sapphire) untuk konfigurasi rib dan ridge waveguide. Disain dilakukanmenggunakan perangkat lunak OptiBPM 12 free trial. Dari hasil simulasi dengankriteria single mode ditunjukan bahwa Y-junction Power Splitter terbaik, yaitu low lossdan distribusi medan optik yang uniform, diperoleh saat sudut antara dua cabang 0,1o,pada posisi pandu gelombang 0,8 μm di atas sapphire (untuk rib waveguide) dan 0,55μm di atas sapphire (untuk ridge waveguide), untuk lebar dan ketebalan pandugelombang berturut-turut 3,1 μm dan >0,8 μm, ketebalan buffer layer 0,55 μm, sertaindeks bias dan ketebalan material cladding sebesar 2,12 dan 8,8 μm., In this final project, I’m designing GaN/Al2O3 (Sapphire) based 3 dB Y-junction PowerSplitter. There are two configurations used in the simulation, which are rib waveguideand ridge waveguide. Based on the data acquired for single mode criteria, the optimaldesign, which is low loss and uniform optical distribution, is achieved by adjusting theangle of Y-junction to 0.1o with the position of waveguide is 0.8 μm above the sapphire(rib waveguide) and 0.55 μm above the sapphire (ridge waveguide) for the width andthickness of waveguide consecutively are 3.1 μm and more than 0.8 μm, the thicknessof buffer layer used is 0.55 μm while the refractive index and the thickness of claddingused are 2.12 and 8.8 μm.]