Visible　emissions　in　microresonators　by　high-harmonic　generation　with　input　at　telecom　wavelengths　have　been　demonstrated　in　a　number　of　platforms,　such　as　silica　[1],　silicon　photonic-crystal　[2],　and　silicon　nitride　[3].　In　this　work,　we　report　the　first　observation　of　green　emission　by　third-harmonic　generation　(THG)　in　a　highly　doped　glass　micro　ring-resonator　and　show　that　the　measured　pump　and　emission　dependence　agrees　with　the　theoretical　prediction　of　the　THG　process.　The　ring　resonator　used　in　the　experiment　is　composed　of　highly-doped　silica　glass　with　core　refractive　index　of　1.7　and　a　radius　of　135　μm.　With　waveguide　dimensions　of　2μm　×　1μm,　it　corresponds　to　a　free-spectral　range　(FSR)　of　201.5　GHz.　Fig.　1(a)　shows　the　effective　index　mismatch　between　the　pump　mode　and　the　various　THG　modes.　With　a　measured　Q　factor　of　~5.5×105　at　1550　nm　and　small　mode　volume,　it　contributes　to　the　high　conversion　efficiency　of　the　THG　where　the　threshold　pump　power　for　THG　is　approximately　2.4　mW.　The　captured　green　emission　from　directly　above　the　ring　resonator　(insert　of　Fig.　1(b))　when　pumped　with　a　continuous-wave　(CW)　laser　at　1550　nm　centred　at　516.7　nm　demonstrates　that　the　green　light　is　attributed　to　the　THG　process.　©　2019　IEEE