A polymer optical fiber amplifier (POFA) of the graded-index (GI) type
, with gain in the visible region, was successfully prepared for the f
irst time, to our knowledge, with the interfacial-gel polymerization t
echnique. An input signal of 0.85 W at 591 nm was amplified to 420 W (
27-dB gain) by injection of 690 Tv of pump power at 532 nm into a GI P
OFA with a 0.5-m length. The efficiency of conversion of pump energy t
o signal amplification was more than 60%.