Optra, Inc. is company that used to manufacture what is called a "Two-Frequency HeNe Laser". Very little info is available about Optra's lasers beyond their original U.S. Patent #4,823,348: Laser Stabilization Device. They seem to be designed for applications in metrology similar to those using lasers, optics, and electronics from HP/Agilent, Zygo, Excel, and others.
The Optra Optralite is an axial Zeeman two-frequency HeNe laser like those from HP/Agilent, but it operates with a much lower split frequency (250 kHz). Much more information on these lasers can be found in the chapter: Commercial Stabilized HeNe Lasers of Sam's Laser FAQ.
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