Power characteristics of a helium-neon laser in a transverse magnetic field

Abstract

Most of the numerous investigations of the effect of a magnetic field on the emission of a gas laser [1][2][3] relate to the case of an axial field. This is probably due to the fact that the magnetooptic effects in the two cases have several features in common [1] and the production of an extended transverse magnetic field presents some difficulty. Yet the transverse Zeeman effect in a gas laser is of definite interest. We know [2], for instance, that in a transverse magnetic field, laser emission continues to higher values of H than in an axial field. The presence of three Zeeman components in the emission leads to interesting polarization effects [3].Little attention has been given so far, however, to the investigation of the power characteristics in a transverse field, although this question is important both from the viewpoint of increasing the output power of a gas laser and, for instance, variation of the frequency of a laser by a magnetic field. These characteristics have not been considered at all in the case of laser emission on competing transitions.Finally, in most investigations the laser has beenexcited by a high-frequency field. The use of tubes excited by a glow discharge in a transverse magnetic field, i.e., the use of crossed electric and magnetic fields, can lead to specific plasma effects. An investigation of these effects will enable us to select the best operating conditions for a laser in a transverse magnetic field.The effect of a magnetic field on the power characteristics of a laser may be qualitatively different for lasers which differ in the factor by which the gain of the active medium exceeds the loss factor of the system. In view of this we used in our work several laser tubes with different output powers. They had a length l = 43-45 cm and were closed at the ends by quartz Brewster-angle windows. Tube No. 1, with internal diameter d = 3 mm, operated on an apparatus with a pumping system which allowed variation of the pressure and ratio of gases in the mixture. Tubes Nos. 2, Po, 3, and 4, with internal diameter d = 3.5 mm, had standard tel. units filling and different loss levels. The discharge was excited by adc supply. 80The transverse magnetic field was produced by electromagnets with pole pieces 30 and 35 cm long, which provided fields of up to H = 2000 Oe with a nonuniformity of not more 0 Fig. 1. Po = f(H): 1-4) A = 0.63t~; 1'-4') A= 3.39#; 1,1') I d = 35; 2,2') 50; 3, 3') 70; 4, 4') 90 mA. than 5% along the poles. The electromagnets could be powered from a stabilized direct voltage supply or from a VSA-11 pulsed voltage supply (pulse rate 50 Hz).The measurements were made with mirrors of two types -for the lines 0.63 p and 1.15 t~. In both cases we observed simultaneous emission on 3.39 t~. The length of the "piano-concave" resonator could be varied from 50 to 150 cm.The radiation receiver was an FI~U-28 photomultiplier for the 0.63 p and 1.15 g lines and a thermocouple for the