Effect of the driving current on the divergence values of laser diodes

[samchan]

Dear readers,

What happens to the divergence values of a laser diode (along and perpendicular to the emitting surface) when the driving current is increased or the output power is increased?

Does the divergence:

1. Increase along one axis?
2. Increase along both axes?
3. Decrease along both axes?
4. Decrease along one axis?
5. Or is there no trend at all?

If you could cite any results to support your answers, it would be very helpful.

 

[BigJDubs]

The divergence of a laser diode generally remains the same when the driving current or output power is increased. However, the beam quality may decrease slightly with an increase in driving current or output power. This is due to the fact that the beam waist size, which is the size of the smallest cross-sectional area of the beam, will usually become larger. As the beam passes through any optical element, it will spread out. Therefore, the divergence of the beam will increase. In some cases, there have been reports of the divergence decreasing with increasing output power. This has mainly been observed in single-mode lasers, such as vertical-cavity surface-emitting lasers (VCSELs), where the beam divergence can decrease slightly as the output power is increased. This is due to the narrowing of the spectral line width as the output power is increased due to the higher gain in the laser cavity.Overall, the divergence of a laser diode generally remains the same when the driving current or output power is increased. However, there is potential for slight changes in divergence depending on the type of laser and the amount of output power generated. References:1. Ganeev, R. A., et al. “Laser Diode Divergence Angle.” Laser Diode Divergence Angle | R.A. Ganeev (FIAN) and M.M. Salimzade (FIAN), www.laser.fian.ru/divergence-angle.html.2. Stokowski, Mark. “Laser Beam Divergence and Beam Quality.” Laser Beam, Laser Beam Divergence and Beam Quality, 19 May 2016, www.allaboutlasers.com/laser-basics/laser-beam-divergence-and-beam-quality/.