The leftover fundamental, pump or other wavelength that a dichroic mirror, harmonic separator or filter fails to remove completely. Behind a doubler there is often still far more infrared than green, so even a fraction of a percent leaking through can be watts of invisible beam. It confuses power readings and is a real eye hazard because safety eyewear chosen for the visible color may not block it.
Power meter says 2.3 watts of green but half of that is IR bleed-through, put the second separator in before you trust it.
Also heard as
- leak-through
Related terms
Doubler
Lab slang for the frequency-doubling crystal or module that turns an infrared laser into its second harmonic.
Goggles
Lab shorthand for laser safety eyewear, the filtering glasses or goggles rated by optical density at specific wavelengths.
OD
Optical Density: a logarithmic measure of how strongly a filter or laser eyewear blocks light at a given wavelength.
SHG
Second Harmonic Generation: converting light to exactly double its frequency, half its wavelength, in a nonlinear crystal.