Nonlinear gain in a SHG crystal

kiviuq

I'm not a native English speaker so I need some clarification about the term "nonlinear gain" concerning a laser experiment.

In detail I'm working on a lab report where I'm supposed to estimate the nonlinear gain of a KTP crystal in a Nd:YAG LASER using the intracavity second harmonic generation technique.

We measured the output power of the fundamental wavelength of the Laser (1064nm) [tex]P_\omega(P_{\mathrm {diode}})[/tex] and the output power of the SHG (523 nm) [tex]P_{2\omega}(P_{\mathrm {diode}})[/tex] where [tex]P_{\mathrm {diode}}[/tex] is the Laser diode pump power.

The "non linear" gain must be expressed in units of %/W

Thanks for your help!