Abstract
The development of advanced photonic devices requires precise control of the optical properties of semiconductors. Gallium phosphide (GaP) is a promising wide-band-gap semiconductor of fascinating nonlinear optical applications. Here, we present experimental evidence for the success in fine-tuning the optical band gap of GaP single crystals by irradiation with MeV--GeV heavy ions of a wide range of ion fluences. The large variety of ion parameters from different ion-beam facilities made it possible to distinguish between the effects caused by nuclear energy loss and electronic energy loss, demonstrating the ability of avoiding possible unwanted structural damage. The presented results are essential for the application of ion-beam technology in the fabrication of nanophotonic devices by providing unique active materials, exhibiting the potential of emitting light with various controlled wavelengths of high precision. Furthermore, our findings are of high necessity for monitoring and establishing precautions for radiation effects at aviation altitudes and in space systems.