Axial magnetic field effects on a saturated He-Ne laser amplifier

The behavior of a He-Ne laser amplifier in the presence of an axial magnetic field has been studied experimentally by measuring Faraday rotation and gain for various values of input signal intensity. Two high-gain transitions in the 3.39-μ region were used for study-a to transition and a to transition. Theoretical expressions have been developed, which included the nonlinear effects of saturation strength signals. Experimental results clearly show saturation of Faraday rotation; in addition, for the to transition, a Faraday rotation reversal and a traveling-wave magnetic field dip are seen. These results match the theoretical predictions and provide a method for measuring the upper (3s2) level quadrupole moment decay rate.