Tuning Curves of 70 MHz Frequency Differences for HeNe Standing-Wave Lasers

Two experiments are reported on measuring the variation of the frequency differences for the standing wave lasers with tuning the cavity length. The frequency difference is caused by an intracavity quartz crystal plate (laser mode splitting technology,). The relative variation of the frequency difference during the tuning are about 10^-3 order from the edge to the centre of lasing bandwidth. The difference between the largest and the smallest frequency differences is two orders as large as that of ring lasers.