3. Continuous operation

The efficiency of the non-linear process is directly related to the intensity of the waves involved. The latter is highly dependent on the duration of the laser pulses. This is why it is common practice to distinguish nonlinear optics applications according to their operating time regime: continuous, nanosecond, picosecond and femtosecond. This distinction is all the more relevant as, unlike laser systems, the pump energy is not stored in the amplifying medium due to the instantaneous nature of the nonlinear interaction. Non-linear gain is therefore highly dependent on how the pump energy is distributed temporally. In this paragraph, we first consider the case of the continuous regime.