Infrared Optical Interference Filters
Long Wave Pass Filters
Long Wave Pass filters (also referred
to as edge filters) are constructed from stacks of thin
layers. They are distinguished by a sharp transition
from a zone of rejection to a zone of transmission. The
rejection region extends to below 0.3um and the
transmission region typically extends to greater than
twice the wavelength of the edge position.
When ordering it is necessary to
specify the required 5% or 50% cut on edge position (the
5% point is measured as an absolute value but the 50%
point is measured as 50% of peak transmittance).
Typical Performance

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Typical Characteristics
| Available wavelength range (edge
position) |
~1 to 20um |
| Edge tolerance |
To customers requirements, from +/-1% but
standard tolerance +/-4%
|
| Average transmittance |
Typically >75% (depending on wavelength) |
| Cut on slope |
Typically < 5% |
| Blocking (attenuation) |
Typically <0.1% to 0.3 micron |
|