Examples of pump sources include electrical discharges, flashlamps, arc lamps, light from another laser, chemical reactions and even explosive devices.
The gain medium is the major determining factor of the wavelength of operation, and other properties, of the laser.
The light may reflect from the mirrors and thus pass through the gain medium many hundreds of times before exiting the cavity.
The design and alignment of the mirrors with respect to the medium is crucial for determining the exact operating wavelength and other attributes of the laser system.
Other optical devices, such as spinning mirrors, modulators, filters, and absorbers, may be placed within the optical resonator to produce a variety of effects on the laser output, such as altering the wavelength of operation or the production of pulses of laser light.