An　ultra-compact　three-port　photonic　coupler　is　proposed　on　a　glass　substrate　based　upon　a　principle　of　frustrated　total　internal　reflection.　A　single　slash　shape　narrow　trench　at　the　＂T＂　intersection　of　two　ion-exchanged　waveguides　forms　the　coupler　and　is　aligned　45　degrees　to　the　waveguides.　The　three-dimensional　finite　difference　time　domain　(FDTD)　theory　is　used　to　simulate　the　parameterization　of　the　coupler,　such　as　splitting　ratios　and　efficiency　versus　trench　widths,　trench　lengths,　trench　locations,　and　trench　angles.　The　waveguide　model　used　in　FDTD　is　based　on　an　experimental　condition　of　the　K+-Na+　ion-exchange　process.　A　single-mode　6　mu　m　wide　glass　waveguide　at　1550　nm　wavelength　is　fabricated　through　the　analysis　of　the　effective　index　method.　The　numerical　results　show　that　the　arbitrary　splitting　ratios　may　be　controlled　by　trench　widths　and　trench　angles.　Comparing　to　Si,　InP　and　GaAs　materials,　trench-based　coupler　on　glasses　may　readily　achieve　the　manufacturability　since　the　low　index　of　glass　waveguides　results　in　a　wider　trench　opening.　Taking　advantage　of　low　loss　ion-exchanged　waveguides,　the　high　efficiency　and　short　interaction　length　photonic　couplers　have　a　great　potential　to　be　integrated　for　large　scale　glass-based　photonic　circuits.　(C)　2013　The　Authors.　Published　by　Elsevier　B.V.　All　rights　reserved.