How to set the M square In ZEMAX

Normally, in OSLO, There is a function named “Paraxial Gaussian Beam (ABCD)”, we can use this to analysis the Gaussian profile. Even in ZEMAX, there also get this function as “POP”. But in my opinion, this function is just an analysis function. It only can be used once the whole optical system already comes out, then we can set the input and see how is the output. Unfortunately this is not I want.

I want to set up the beam property first. For example I want to design laser optics, and the laser M square is 1.5. So My design will be based on the initial setting of M square =1.5,. But I could find a way to do like this. Can you please point out a way for me to solve this problem?

Basically, ZEMAX get a apodization type setting, we can set the apodization type as Gaussian, and also can give the apodization factor, but this factor is relating between the EPD and beam waist, still get no relationship with M square. so the question is bothering me for a long time.