In this study, high quality ZGP crystals with diameters of 3.85.0 cm have been grown by the ultralow gradient freezing technique in self-made furnaces with growth yields over 95%. The crystal growth efforts and post processing have resulted in ZGP OPO devices with an ultra-low absorption loss (0.015 cm^-1 @2.09 μm) and a size of up to 30 mm×30 mm×40 mm. A high average output power (>100 W) ZGP OPO with only one low absorption ZGP device has been demonstrated, with no obvious limits to further scaling. The results indicate that the combination of large aperture and low absorption losses makes our ZGP crystals extremely attractive for high average power and high energy applications.