UNIVERSITY OF BUCHAREST
FACULTY OF PHYSICS

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2024-11-22 1:21
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Conference: Bucharest University Faculty of Physics 2003 Meeting


Section: Optics, Spectroscopy, Plasma and Lasers


Title:
On the optimization of a 3meters active length He-Ne laser.


Authors:
CP II Dr. Marian Ristici, Lector Dr. Ion Gruia


Affiliation:
Faculty od Fisics, University of Bucharest


E-mail


Keywords:


Abstract:
The He-Ne laser is very well known especially for his red line – 633nm wavelength – having many applications. In fact the He-Ne system is able to generate nine visible laser lines. Whose wavelengths range in 730 nm – 543nm. All these lines have the same upper level –3s2- but the lower levels are different on of the 2p level, except 2p9. The 633 nm line operates fot ordinary dielectric laser mirrors, alone – “the winner takes all”. The others laser lines oscillate only if the 633nm oscillation is destroyed. The purpose of our experiment was to develop a laser able to oscillate on all the nine visible wavelengths. Many of them having a low amplification coefficient, to obtain laser oscillation using poor quality laser mirrors, the length of laser tube must be maximum possible. Experimental set-up. The laser tube was realized from pyrex-glass. It has a central duraluminium cathode and two sides tungsten anodes. The inside diameter is 5 mm. The Brewster windows are made from Homosil fused silica especially polished for laser quality. The power supply what we used is able to generate a maximum 150mA current through the tube. We used tree pairs of high reflecting mirrors centered on 700nm, 633nm and 543nm, respectively. The vacuum station was able to generate a vacuum of 10-6torr . The gases where of spectroscopic purity. Results We obtained laser oscillation on eight lines in the deep red, red and orange-yellow spectral region. The green line we did not obtain oscillation, because of the very poor quality of mirrors, we think. We varied the total pressure, partial pressure ratio and discharge current. Maximum laser power we obtained on 633nm line, namely 145mW. For 612nm we obtained 26mW, 5mW for 604,6nm, 5,2mW for 594nm and 15mW for 640,1nm. All other oscillation where weaker. The optimum laser power was obtained for a total pressure 0,8torr, a partial pressure ratio of 9 and a current of 45 mA.