Laser Datasheet Terminology

[tefeari]

Can anyone give me the definitions for the following laser terminology? These tend to be used on datasheets and I can't seem to find much discussion / use of them elsewhere:

- Parallel Beam Divergence
- Perpendicular Beam Divergence

I'm pretty sure these give some kind of half angle for the beam divergence straight out of the diode (without any collimation optics), but I'm not totally sure why there need to be two terms for it and why they are never the same (they must have slightly different geometric definitions and maybe someone can explain them?).

Then there's also:

- Parallel Deviation Angle
- Perpendicular Deviation Angle

Same as before. I assume these are maybe something like the angle variability of the laser beam itself coming out of the diode?

Then last there's:

- Emission Point Accuracy

Is this like the accuracy of the die inside the can relative to the center?

 

[Bluefan]

The beam divergence is the full angle a laser beam makes when it spreads out, it's usually give in milliradians (mrad) where 2 pi radians is a full circle. The parallel and perpendicular directions are probably the two axis. Lasers can have a different divergens in the horizontal and vertical direction. For diode lasers these two are nearly always different, gas lasers and DPSS lasers usually have a round dot and thus only one divergence value.

The deviation angle, again in the two directions, says how much the laser beam can point not straight out of the laser (or diode) but points somewhat to the side.

Emission point accuracy is not the uncertainty in angle as the previous term gives but the certainty of the location of the emitting area of the laser diode, it's not always guaranteed in the middle of the device.