One of the commenters has an interesting suggestion:

you should also have dry ice covering all sides.. the top was not cooled at all …. ( the thermal conductivity of the material surrounding the diode is not good. nex time submerge it in dry ice and just leave enough space for the beam. or add some water … ( wont hurt the diode ) …

Also in the video his partner says DO NOT have the propane tank in the site of the laser.  He agrees

Here is more about general laser properties from wikipedia:

Lasers are distinguished from other light sources by their coherence. Spatial coherence is typically expressed through the output being a narrow beam, which is diffraction-limited. Laser beams can be focused to very tiny spots, achieving a very high irradiance, or they can have very low divergence in order to concentrate their power at a great distance.

We hope you enjoy the video and are inspired to be scientific and ask questions as well es experiment safely!