A diode bar carries dozens of emitters in a 10 mm row, and mounting stress or solder can bend that row into a gentle curve of a micron or more. Because the fast-axis collimating lens is a single cylinder lens, emitters off the line are aimed slightly up or down, smearing the collimated beam and lowering brightness and fiber coupling. Bar suppliers specify smile in microns.
Coupling efficiency is stuck at 70 percent and the near field looks curved, that bar has a smile of at least two microns.
Also heard as
- bar smile
Related terms
Laser diode
A semiconductor laser driven by electric current, used as a light source in its own right and to pump other lasers.
Pump
The energy source that excites a gain medium, or the act of supplying it, usually with diodes, flashlamps or current.
M-squared
The beam quality factor: how many times worse a beam focuses and diverges than an ideal Gaussian of the same wavelength.