Active laser medium
Videos
The active laser medium is the source of optical gain within a laser. The gain results from the stimulated emission of photons through electronic or molecular transitions to a lower energy state from
Laser rods (from left to right): Ruby, alexandrite, Er:YAG, Nd:YAG
Laser diode
Videos
A laser diode is a semiconductor device similar to a light-emitting diode in which a diode pumped directly with electrical current can create lasing conditions at the diode's junction.
Active laser medium
…with electrical currents (e.g. semiconductors, or gases via high-voltage discharges) or with light, generated by discharge lamps or by other lasers (semiconductor lasers). More exotic gain media can be pumped by chemical reactions, nuclear fission, or with high-energy electron beams. The simplest model of optical gain…
A packaged laser diode shown with a penny for scale: a 488 nm InGaN green-blue laser, which became widely available in mid-2018.
The laser diode chip removed and placed on the eye of a needle for scale
A laser diode with the case cut away. The laser diode chip is the small black chip at the front; a photodiode at the back is used to control output power.
SEM (scanning electron microscope) image of a commercial laser diode with its case and window cut away. The anode connection on the right has been accidentally broken by the case cut process.