Polarizing glass and optical isolator

A process of producing a polarizing glass containing anisotropically shaped metal particles oriented and dispersed in a glass substrate by stretching a glass preform, the process comprising:

• melting raw materials of the glass substrate in an airtight melting furnace;
• and
• replacing at least one of the alkali oxide components in the raw materials of the glass substrate with an alkali chloride component, wherein
• the glass substrate is a glass selected from the group consisting of silicate glass, borate glass, and borosilicate glass;
• the glass substrate contains at least one component selected from the group consisting of Y2O3, La2O3, V2O5, Ta2O5, WO3, and Nb2O5;
• the content of each of the selected components ranges from 0.05 to 4 mole percent, or the total content of the components is 6 mole percent or less if a plurality of components are selected;
• and
• the Cl content in the glass substrate ranges from 0.47 to 0.58 wt % relative to the entire glass substrate.