Difference between radio waves and other electromagnetic waves? Yes radio waves have different frequency and wavelength than others but it seems that radio waves are produced by sinusoidal current while other electromagnetic waves do not need need sinusoidal current to be produced. Is that true ?
 A: The question appears to be about approaches to generate em radiation: For radio waves making electrons accelerate and de-accelerate in resonant circuits is fine, though by the time you get to microwaves you start to have to look at vacuum tube technology (for example, the klystron and its variants, the magnetron and the travelling wave tube) which is well advanced and still has important uses, particularly for those applications requiring power levels more than about 100 W. For lower power levels solid-state devices are desirable. Devices that are available include the Gunn diode (or transferred-electron device, TED), the impact-avalanche-transit-time (IMPATT) device and the metal-semiconductor field effect transistor (MESFET). More recently you will come across names like the modulation-doped field effect transistor (MODFET) (also referred to as the high electron mobility transistor (HEMT), the two-dimensional electron gas field effect transistor (TEGFET) or the selectively doped heterostructure transistor, (SDHT)). However, all of these devices generate em radiation by making electrons oscillate.
A quite different approach has been adopted for the generation of radiation by solid-state devices for the near-infrared (NIR) and optical frequencies, and is based on the quantum mechanical transitions of particles between discrete energy levels. For example, light emitting diodes (LEDs) and laser diodes both make use of the recombination of electrons and holes that have discrete energy levels in the conduction and valence bands respectively.
Most practical semiconductor lasers are based on the double heterostructure designs that have been successfully developed for wavelengths ranging from blue to the NIR, i.e. up to about 1.6 μm.
However, it is possible to generate light using nano antenna's, see Can I use an antenna as a light source? and the answer from Robert Filter.
