The laser flash that escapes through the partially reflecting mirror lasts for only about 300 millionths of a second-but very intense. Early lasers could produce peak powers of some ten thousand watts. Modern lasers can produce pulses that are billions of times more powerful. Another characteristic of laser light is that it is coherent. That is, the emitted light waves are in phase with one another and are so nearly parallel that they can travel for long distances without spreading.
Coherence means that laser light can be focused with great precision.
Many different materials can be used as lasers. Some, like the ruby laser, emit short pulses of laser light. Others, like helium-neon gas lasers or liquid dye lasers emit a continuous beam of light. Our ICF lasers, like the ruby laser, are solid-state, pulsed lasers. In contrast to an ordinary light source, a laser produces a narrow beam of very bright light.