O

Object

The subject matter or figure imaged by, or seen through, an optical system.

Opacity

The condition of being non-transparent.

Open installation

Any location in which lasers are used that will be open to operating personnel during laser operation and may or may not specifically restrict entry to observers.

Operation

The performance of the laser or laser system over the full range of its intended functions (normal operation). It does not include maintenance or services as defined in this glossary.

Optic disc

The portion of the optic nerve within the eye that is formed by the meeting of all the retinal nerve fibers at the level of the retina.

Optical cavity

Space between the laser mirrors where lasing action occurs.

Optical density

A logarithmic expression for the attenuation produced by an attenuating medium, such as an eye protection filter.

Optical fiber

A filament of quartz or other optical material capable of transmitting light along its length by multiple internal reflection and emitting it at the end.

Optical pumping

The excitation of the lasing medium by the application of light rather than electrical discharge.

Optical radiation

Ultraviolet, visible, and infrared radiation (0.35 to 1.4 æm) that falls in the region of transmittance of the human eye.

Optical resonator

See resonator.

Optically-pumped lasers

A type of laser that derives energy from another light source, such as a xenon or krypton flashlamp or other laser source.

Output coupler

Partially reflective mirror in a laser cavity that allows emission of laser light.

Output power

The energy per second measured in Watts emitted from the laser in the form of coherent light.