Got an old Blu-ray player from which you can cannibalize the laser
unit? Scott Stevenson did, and use used it produce this video. Blu-ray
players use a 405 nm (more violet than blue
- see thumbnail) laser diode that emits a 580 nm beam at
around 5 mW. I'm guessing black balloons are used because they
absorb more of the light energy and therefore heat faster. A debate
on the YouTube page argues between melting or air heating causing the
balloon to burst. My money is on local melting since it would take a
long time to heat the air inside enough to expand enough to cause the
popping.