A method of manufacturing a polymer optical waveguide which is capable of efficiently manufacturing a polymer optical waveguide with a low optical loss by using a photosensitive resin of the type hardenable by a photo-cationic polymerization reaction is provided. The input power sources may have different voltage, frequency, and phase characteristics, and may be DC voltages. Baffles obstruct upward flow to effect mixing of regenerated and carbonized catalyst to obtain a more uniform temperature and catalyst mixture before contacting the feed. A phosphor for a display, which emits red light, comprises a yttrium oxysulfide phosphor or a yttrium oxide phosphor and has an average particle diameter in a range of \xb120%\u03bcm. The manufacturing method of the flexible display prevents the problem of low yield rate caused by the damage to the plastic substrate in the separation process.