MATTER LogoIntroduction to Electrons in Crystals

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Lasers > Basic Principles

Description of Flash Animation.

This simulation models the excitation and decay of an electron.

This resource requires Flash Player 9 or above available to download from http://www.adobe.com/go/getflash

To understand the laser we need to consider the relaxation of electrons in excited states. In any system containing two energy levels (see box) an electron can be excited from the lower to the higher energy state by the absorption of a photon.

If the downward jump is permitted, the electron will spontaneously decay from the higher to the lower energy level. The energy difference between the excited and lower energy states can be emitted as a photon. The photon may be in the range of wavelengths we call light.

We call this process spontaneous emission. It is exploited most notably in the LED. The alternative process which occurs in a laser is called stimulated emission.

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