How to Build a Laser Death Ray
If a laser emits a pulse of light so intense that it causes matter it is incident upon to violently explode, I will call it a blaster. A single pulse can carve a crater out of the surface. If the pulse is fast enough and its energy is large enough, the subsequent blast can cause damage similar to that of the detonation of a high explosive. Alternately, the blaster can emit a very rapid burst of pulses, so fast that they land on top of each other. Each pulse enters into the hole dug out by its predecessors, allowing the blaster to drill deeply to reach vital components or organs.
It is likely that to acheive this performance, each pulse will have to be less than a nanosecond in duration. Some modern lasers can emit pulses that are picoseconds or femptoseconds in duration, so this is not a technological limit. The energy density of matter irradiated by these pulses can be higher than the fissioning core of an exploding nuclear weapon, or the fusioning core of a sun. This energy is so high that no matter held together by chemical bonds can withstand it. However, modern lasers deliver pulses that have an energy too low to cause much damage. They blast out only a very small amount of material - suitable for drilling small holes or producing a small flash of thermal x-rays but not for use as a weapon. To use a blaster for deep penetration against active targets, it is likely the pulses in a burst will need to be spaced only microseconds or less apart, and will all need to be delivered within a few milliseconds or less.
The extreme intensity of a blaster pulse can cause odd effects. Normal linear optical properties of matter, such as reflectivity or transparency, cease to apply - any condensed matter will absorb the pulse and explode. The pulse can also affect the air it travels through in odd ways, producing non-linear effects such as self focusing and fillamentation.
Technical Note - While the energy density of the irradiated material can be higher than the core of a sun, you cannot say that the temperature is higher. Temperature is an equilibrium phenomena, and the laser flash occurs so quickly that the illuminated matter does not have time to come to equilibrium (or, in fact, for the atoms composing it to even move) so that it does not even have a temperature during this process.