In the process of researching high-energy, high-power lasers, with the pump power raised, the threshold will raise, the efficiency will reduce, the refractive index distribution will be non-uniform.

It's proved that the cause of high threshold of thulium laser is the heat-distribution particle at low laser energy level.

But solid explosives are high-energy metastability materials, when encountered external stimulation to the reactive threshold, a strong chemical reaction will occur.