How do the laser detect things such as bombs without detonating them?

Question: How do the laser detect things such as bombs without detonating them?
- Keywords:
  equipment,
  laser,
  technology
Asked by to Simon on 12 Mar 2014. This question was also asked by .
- Simon Albright answered on 12 Mar 2014:
  
  I use neutrons rather than lasers to detect bombs etc. When it comes to conventional explosives (C4, TNT) which are based on chemical reactions they always need something specific to make them detonate, sometimes a lot of heat or a smaller explosion which needs a spark. Neutrons don’t produce much heat and don’t create sparks so won’t set off those bombs.
  
  Nuclear bombs are different, a block of uranium the right size and shape blasted with a load of neutrons could potentially explode. But even then the requirements are spurprisingly specific, it would probably be harder to make it detonate thanks to neutrons irradiating it than it would to make it detonate normally. In practice it would take so many neutrons and such a short space of time that I don’t think it could ever happen, though I know some people are working on that to make absolutely sure.

Question: How do the laser detect things such as bombs without detonating them?