exchanged the old mirror (T330-HR, T331-AR) by a simple Y1-1025-45P to get more power.
measured laser power : 7.17W
downstream of the new output coupler : 134.6mW
added waveplates & pbs to make the power adjustable. current power through the EOM is 8mW which gives about 4.33V on the RF-PD (Thorlabs PDA10CS, 0dB-setting, 17MHz)