Shouldn't the shape of a semiconductor laser be planar instead of conical?

[Ted goldmund lee]

TL;DR Summary

It feels like the shape of the blasting laser have to be planar because the gain medium itself looks like rectangular.

I read about semiconductor laser and its beam shape is conical with 50' of dispersion angle.

But for me, it is hard to accept that it is conical because every single drawing I see is rectangular and the plan that laser going out is also a plain, not a hole.

And this is the picture I saw earlier.

Please help me..

 

[Lord Jestocost]

See Fig. 6 in https://pe2bz.philpem.me.uk/Lights/.../C04-M06-DiodeLaserPowerSupplies/mod04_06.htm

"The beam emitted from a semiconductor laser typically has an elliptical spatial profile, as illustrated in Figure 6. The profile is caused by diffraction. In the direction perpendicular to the junction, the beam is confined by the narrow junction, typically of width around one micrometer. The beam in that direction is spread by diffraction to an angle often as large as several tens of degrees. In the direction parallel to the junction, the beam is not confined so stringently and spreads less, perhaps to around ten degrees or so. The result is a fan-shaped beam, as indicated in the figure. The beam is said to be astigmatic. "