Birefringence in electromagnetically induced transparency

(4)He 2 (3)S(1) --> 2 (3)P transitions at 1083 nm were laser probed in the presence of radiation that coupled the 2 (3)P level with the 3 (3)S(1) level in a ladder scheme. The metastable helium that was used was produced in a rf discharge. Significant atomic birefringence was detected, in addition to complete electromagnetically induced transparency. A simple theoretical model explains the experimental results.