Acoustic Optic Modulator (AOM): Effect of the polarizer and lense

I tried to put the polarizer after the AOM. In input to the Polarizer there are both beam of order 0 and 1.
I did some measure:

Without Polarizer:
Plaser = 1,22 W (out AOM...order 0 + order 1)
P(order 0) = 0,225 W
P(order 1) = 0,894 W

With Polarizer:
Plaser = 1,22 W
P(order 0) = 0,246 W
P(order 1) = 0,750 W




We can see the effect of the polarizer on the order 1. This can means that the AOM introduces a change of polarization in particular on the order 1 (see also last topics on the efficiency of the AOM).

I tried also to see if was changed tha bragg angle using the polarizer: the bragg angle doesn't change.

Moreover i tried to put the lense first the AOM for better the efficiency and focusing the beam. I observed a changing of the efficiency (to the fixed angle): from a minum to a maximum. Never i had the efficiency that i had without the lenses (around 75 %), with the lense the efficiency seems decreasing to the fixed angle. But if change the angle the efficiency change...So, this can means that with the lense the bragg angle change.
I observe that changing the angle and using the lenses the efficiency is around 75 %.
With the lense we can improve a bit the efficiency but we can change the bragg angle.