The third class can be called the laser pen light. is some artificial materials, nonlinear optical emission. For example, on the gold surface after etching, and high power laser coupling, the formation of surface plasma, electron flow. Of course not to etching. Once the power high, nonlinear effect will be more significant.
There. This multiphoton effect cannot use single material to evaluate the efficiency of laser pen light, with the increase of power, the higher the efficiency. So the development of this material to see the damage limit where. Now it seems as the semiconductor cathode.
Laser pen light in high field electron tunneling through the emitted electron energy. No surface barrier. High emission tip single degree was very good ah, but life is long. So the guards is imaging class love. Earlier accelerator with metal tungsten, now with silicon, diamond more. Carbon nanotubes in recent years have begun to use.
Laser pen light is not so good control, field emission to produce short bunch, RF gun have special design. The fix became afraid of everyone, ghost worry about the dark current. I’m doing diamond nano tip field emission cathode. I think the future potential is big.