1.2W Class 4 Very High Power Blue Laser, Dark Background
This is a picture of my 1200mW 445nm vacuum wavelength semiconductor diode class 4 very high-power blue laser with no lenses attached (only the built-in focusing/collimating lens) lasing in the dark. The beam is extremely pronounced due to Rayleigh scattering and dust in the air (visible as streaks in the beam). Aside from the red light used to provide a counterbalance to the blue light of the laser, the laser was the only active light source in my room when I took this photo. All the blue light visible is due to reflective scatter from the wall the (focused) laser beam was striking.
Fun fact: By my calculations, this laser emits about 2.69e18 (that's 2,690,000,000,000,000,000) photons per second.
Now, for the obligatory "DANGER BIG SCARY LASER" warning:
DANGER: The laser shown here is a class 4 laser device. Class 4 lasers are NOT laser pointers, and should never be used for that purpose. Despite the fact that I took the picture with the laser sitting on my desk, and despite the fact that I seem to have fun when using my lasers (I do), I took proper safety precautions to ensure that myself and others do not get injured; for example, I wore ANSI Z87.1-standard blue laser safety goggles at all times when the laser was operating.
CLASS 4 LASERS ARE THE MOST DANGEROUS KIND OF LASER. All exposure (especially direct contact with skin) to the beam should be avoided, and these lasers are a fire hazard. Proper precautions must be taken to ensure the safety of people and property.
In other words, unless you know what you're doing, DO NOT TRY THIS AT HOME. You could inadvertently blind yourself or someone else. And, of course, high power laser devices should NEVER be pointed at other people, and lasers of any kind should NEVER be pointed at aircraft, especially those in flight. High-power lasers like this one should be treated with the same respect as you would treat a loaded gun.
Please be aware that high power laser devices may be restricted by laws in your area.
HIGH-ENERGY VISIBLE LIGHT WARNING: Lasers emitting in the blue and violet parts of the visible light spectrum (high-energy visible light, HEV light) present an additional hazard to eyes. Prolonged exposure to HEV light, even at relatively low power levels, can cause permanent damage to eyesight. Please see here for more information.