If I understand it correctly the light waves are standing within the laser cavity as they bounce off the walls. Does that mean they remain standing as they leave the cavity? There is nothing out there to introduce a time varying phase, right?
I don't know if it's obvious or even true but I could not find the answer.
Outside the cavity the laser is usually a traveling wave, not a standing wave.
A standing wave is a pair of traveling waves traveling in opposite directions. The walls of the cavity cause the wave to travel in both directions inside the cavity. Outside the cavity there is usually nothing to make it travel back.
Of course, it is possible to set up something outside the cavity to reflect the laser back along its original path. In that case it would be a standing wave outside too. That scenario would be unusual, but possible.
