The impact of crystal birefringence on the performance of diamond Raman lasers has been studied previously at power levels slightly above the threshold. However

the diamond Raman lasers operating far above the threshold usually exhibit different properties. Using the Metripol polarimetry

we obtained the birefringence intensity and fast-axis distribution of a home-made single-crystal diamond. The effects of crystal birefringence on the performance of Stokes laser were then investigated in an external nanosecond-laser pumped Raman cavity with a low Q-factor. When the pump power exceeds 1.5 times the Stokes threshold

the Stokes output performance is significantly affected by birefringence

if the birefringence intensity is high or the fast axis angle is far from the diamond maximum gain angle. In regions where the birefringence intensity is low and the fast axis angle is close to the maximum gain direction

the output is mainly influenced by gain variations. This work can provide valuable insights for the development of single-crystal diamond and polarization-related nanosecond-pulsed diamond Raman laser applications.