The present invention provides methods of drying radiofrequency-activatable inkjet inks, methods for customizing the radiofrequency parameters of an RF source based on pre-selected printing conditions, and methods for selecting or formulating an RF inkjet ink composition based on pre-selected printing conditions andor printing equipment. A first active layer for forming a first semiconductor optical device is provided on the first cladding layer in a first area of a principal surface of a substrate. When the relative movement speed has not reached the reference speed, the frequency of the drive signal is lowered at a second change rate that is smaller than the first change rate.