Simple and effective frequency stabilisation for HeNe lasers at 1.52μm

An extremely simple, but highly effective method of frequency stabilisation of HeNe is demonstrated. It allows production of frequency stabilities in the sub-(parts in 10⁹) region without external optical resonators, and without modulation signals to determines relative extrema of the laser output signal (Lamb dip). The principle of regulation is explained, and measured data are presented, which were obtained by heterodyning two independently ´self´-frequency-stabilised HeNe lasers at 1.52μm.