An integrated demultiplexer/photoreceiver (IDP) for optical networks and optical interconnection devices has a common substrate which supports three sequentially arranged basic components: a waveguide grating router, an array of photodetectors, and an array of heterojunction transistors. Basic layers of all three components are grown together in a common epitaxial process, and then each of the components is individually patterned in accordance with its function. Such structure of IDP makes it possible to reduce the cost, simplify the design, improve conditions for optical alignment, and reduce optical losses. In accordance with one embodiment of the invention, transparency of the optical signal transmission layer of the WGR is controlled by selectively doping the layers of the multiple-layer waveguide structure, while in another embodiment such control is achieved by changing the width of the energy gap in the optical signal transmission layer of the WGR. Such a change is achieved by utilizing electrical bias and optical pumping from an external light source operating on a predetermined wavelength. The invention also provides a method for controlling transparency of the layer that transmits optical signals through the waveguide units in optoelectronic devices, such as an integrated demultiplexer/photoreceiver for optical network, by utilizing optical pumping and electrical bias.