In this paper we experimentally demonstrate the use of near-ultraviolet steady state illumination to increase the spectral sensitivity of a double a-SiC/Si pi’n/pin photodiode beyond the visible spectrum (400 nm-880 nm). The concept is extended to implement a one by four wavelength division multiplexer with channel separation in the visible/near infrared range. Optoelectronic characterization of the device is presented and shows the feasibility of tailoring the wavelength and bandwidth of a polychromatic mixture. Several monochromatic pulsed lights in the VIS/NIR range, separately or in a polychromatic mixture illuminated the device. Independent tuning of the wavelengths is performed by steady state 390 nm optical bias superimposed from front and back sides. Results show that, front background enhances the light-to-dark sensitivity of the medium, long and infrared wavelength channels, and quench strongly the shorter wavelengths. Back background has the opposite effect; it only enhances the channel magnitude in short wavelength range and strongly reduces it in the long ones. This nonlinearity provides the possibility for selective tuning a specific wavelength. A capacitive optoelectronic model supports the experimental results. A numerical simulation is presented.