Laser-assisted atom probe tomography (La-APT) is a powerful tool for condensed matter analysis at the level of individual atoms. Application of high voltage (kV) potential to the specimen under investigation results in desorption and acceleration of surface atoms. Precise detection of the time of flight (ToF) gives information about the initial position of any atom and its mass to charge ratio. Long enough ToF distance improves the accuracy of the method. For La-APT the electric field is chosen to be about 5-10% below the desorption threshold and sub-picosecond laser pulses of low intensity with high repetition rate are used to stimulate atom evaporation. In the latter case, the evaporation rate may be of the order of 0.01 per pulse. Different mechanisms such as electron-hole pair recombination or inverse bremsstrahlung absorption can be involved in this process. Continual or statistical models fail in the description of these effects.