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Opacity
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The
reciprocal of transmittance, 1/T.
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Open
Installation
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Any
location where lasers are used which will be open to operating
personnel during laser operation and may or may not specifically
restrict entry to observers.
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Operation
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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.
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Optic
Axis
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A
birefringent crystal, such as calcite, will divide an entering
beam of monochromatic light into two beams having opposite
polarization. The beams usually propagate in different directions
and have different speeds. There will be only one or two directions
within the crystal in which the beam will remain collinear
and both polarizations will propagate at the same speed. These
directions are referred to as optic axes (not to be confused
with optical axes). A uniaxial birefringent crystal has a
single optic axis; a biaxial birefringent crystal has two
optic axes.
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Optical
Axis
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The
optical axis is the line passing through the centers of curvature
of a lens. For a train of lenses or optical components, it
is the optical centerline for all the centers of the optical
components. Note: This is not the same as the optic axis.
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Optical
Cavity (Resonator)
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Space
between the laser mirrors where lasing action occurs.
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Optical
Density
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A
logarithmic expression for the attenuation produced by an
attenuating medium, such as an eye protection filter.
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Optical
Fiber
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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.
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Optical
Flats
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Precision
ground and polished, clear disks ranging from about 1 inch
in diameter to over 14 inches in diameter. They are used for
measuring shape and the flatness optical parts.
To determining
the flatness of a part, the optical flat is placed on the
part to be measured. The two parts are examined, through the
optical flat, under a monochromatic light. Interference fringes
are generated at the surfaces. The pattern of the fringes
indicated the shape of the part. The wavelength of the light
and the number, or straightness of light bands, determine
the flatness for the part.
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Optical
Pumping
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The
excitation of the lasing medium by the application of light
rather than electrical discharge.
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Optical
Radiation
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Ultraviolet,
visible and infrared radiation (0.35-1.4 nm) that falls in
the region of transmittance of the human eye.
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Optically
Pumped Lasers
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A
type of laser that derives energy from another light source
such as a xenon or krypton flashlamp or other laser source.
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Output
Coupler
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Partially
reflective mirror in laser cavity which allows emission of
laser light.
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Output
Power
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The
energy per second measured in watts emitted from the laser
in the form of coherent light.
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