In which portions of the electromagnetic spectrum do diode lasers operate?

Diode lasers primarily operate in the visible and near-infrared portions of the electromagnetic spectrum. This range is significant because diode lasers are known for their efficiency in these areas, often emitting light at wavelengths between approximately 400 nm (visible violet light) to 1600 nm (near-infrared).

The technology behind diode lasers, which typically involves semiconductor materials, allows them to generate coherent light effectively within this spectrum. This capability makes them suitable for a variety of applications, including telecommunications, barcode scanners, and laser pointers.

The other ranges mentioned in the options do not correspond to the operational wavelengths of diode lasers, as they either fall into much higher energy levels (like X-rays and gamma rays) or much lower energy levels (like microwaves and radio waves), where different laser technologies are utilized.