A heterodyne laser system to study frequency stabilized Zeeman 633 nm He-Ne lasers deficient in temperature steadiness

Abstract

A heterodyne laser system is constructed to study the effect of external transverse magnetic field on the dynamic instability of internal mirror TEM00q He-Ne lasers having temperature instability. The system could provide precise detailed knowledge about the roles of both the temperature and the applied magnetic field separately. Two different internal mirror 633 nm TEM00q He-Ne lasers with frequency stability of 10−6 are studied. The applied transverse magnetic field on He-Ne lasers increased the frequency stability to be in the order of ∼10−10, in spite of temperature instability. In the same time, a single-mode operation with an enhanced laser output power is obtained. The sensitivity of the method showed that the laser exhibits a short-term frequency stability of 4.7×10−10, which after one minute, when mode collapse starts, decreased to 2.6×10−8, over the next four minutes. This increase in the frequency difference of the inter-mode beat signal that affect the stability is attributed to the uncontrolled temperature of the laser tube. The results revealed that the magnetic field plays the dominant role to achieve the maximum frequency stability, while the unsteadiness of temperature of the laser tubes limits the long term single-mode laser operation.