The lasing characteristics of a Nd:phosphate glass laser pumped by 514 nm of an $Ar^+$ laser has been investigated. The oscillator consists of a Nd:glass gain medium set at Brewster angle, and two concave mirrors with 1054 nm HR coating and 474 mm radius of curvature, and a flat mirror with a reflectance of 98%. The $Ar^+$ laser pumping beam is focused longitudinally at the beam waist of laser mode for good mode matching. The oscillator is folded by 16°to compensate for the astigmatism caused by the Nd:glass medium set at Brewster angle. Due to poor thermal conductivity of Nd:glass, a mechanical chopper is used to reduce the heat loading. It is found that at the chopping frequency of 100 Hz, the threshold input power of $Ar^+$ laser is 520 mW and the maximum Nd:glass laser output power is 70 mW at 1.5W pumping, resulting the slope efficiency of 7.4%. It was observed that the operating regime of the Nd:glass laser was severely limited by the thermal birefringence.
