waveguide 2 from top and bottom sides in fig4 b other surface light emission source for pumpings 3 are installed also on the right and left sides of the optical waveguide 2 in addition to the constitution of fig1 to 3 to allow optical coupling with the optical waveguide 2 from top right and left sides in fig4 c a further other surface light emission source for pumping 3 is installed also on the back side of the substrate 4 in addition to the constitution of b to allow light coupling with the optical waveguide 2 from four sides if surface light emission sources for pumping 3 are installed on the respective sides of the optical waveguide 2 as shown in the respective examples of fig4 to increase the quantity of light coupled with the optical waveguide 2 the light emitting species in the optical waveguide 2 can be more highly efficiently excited to allow optical signal amplification fig5 shows an example of the optical amplifier of this invention in which plural identical components are arrayed since the respective components are identical with those of fig1 to 4 the corresponding components are given the same symbols to avoid double explanation in this example plural optical waveguides 2 are arrayed on.