How Do Laser Diodes Work?

Conductors and Semiconductors

A semiconductor can be made by adding a small amount of impurity when forming a silicon matrix. This is called doping. Different impurities create a matrix which is either positive or negative.

The negative N-type semiconductor has a free electron that can move around. The positive P-type has "holes." These electron holes will accept an electron. N and P semiconductors are put together for a laser diode.

Light Production

A small voltage is used to start the hole-electron process going at the junction. The positive-charged holes on the p-doped material move to combine with the negatively charged electrons on the n-doped material releasing energy to produce light in the form of photons.

The release of the energy is located in a channel in the laser diode. It has mirrored ends. The light moves back and forth between the ends. It is amplified as it goes by other energized electrons. The light then passes out of one end of the channel and spreads into cone shaped beam. This is due to diffraction. A lens turns this laser diode light into a round beam.

Resources

• U.S. Department of Energy