Semiconductor lasers are widely used in modern life. In telecommunications they send signals for thousands of kilometres along optical fibres. In consumer electronics, semiconductor lasers are used to read the data on compact disks and CD-ROMs. Other applications include laser printers and laser pointers. Although they are just the size of a grain of salt, typically a few microns in cross-section and a few hundred microns long, semiconductor lasers are an integral part of the modern world.