An image of a Laser where a series showing how a laser light is produced and used.

• Gas mixture: Helium and neon gases are held in a sealed glass tube. Additional tubes, containing electrodes, are attached at the sides.
• Electrode: An electric current passes between this electrode and its twin on the other side of the tube, raising gas atoms to an excited state. This causes the atoms to release photons.
• Photon multiplication: The photons began to bounce back and forth off the mirrors at either end. Some hit other excited atoms, stimulating the emission of additional photons.
• Semi reflective mirror: Because it is only semi-reflective, this mirror reflects most of the photons but lets a few of them through.
• Laser beam: A straight, narrow, intense beam of coherent light emerges at this end.

This image is also labeled as 'Fully reflective mirror: Photons bounce between this and a second, semi-reflective mirror." An illustration of a Laser beam showing neon atom, tube wall, mirror, coherent waves, helium atom, and mirror. Beside this illustration, the following text is written: Coherent light The waves in laser light all have the same wavelength and direction of travel, and their peaks coincide. Light with these properties is called coherent light. Another image shows a laser beam scanning the label of a bottle with the following text: Using lasers Hand-held devices incorporating lasers are used in stores for reading bar codes. In the home, they are at the heart of many devices such as DVD and CD players.