A semiconductor-based optical amplifier/attenuator is disclosed. An apparatus according to aspects of the present invention includes an optical waveguide disposed in semiconductor material. A first optical beam having a first wavelength is to be directed through the optical waveguide. The optical waveguide is optically coupled to receive a pump optical beam having a pump wavelength. The pump optical beam also has a power level sufficient to amplify the first optical beam via stimulated Raman scattering (SRS) in the optical waveguide. A diode structure is disposed in the optical waveguide. The diode structure coupled is to be selectively biased to selectively control free carrier lifetimes of the free carriers in the optical waveguide. This enables to selective amplification or attenuation of the first optical beam output from the optical waveguide.