Laser having two modes at different frequencies
AssigneeSociete d'Applications Generales d'Electricite et de Mecanique Sagem
InventorsFabien Bretenaker, Albert Le Floch
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Abstract
A laser for use in all fields of measurement using a heterodyne effect delivers two waves at different frequencies, having mutually orthogonal linear polarizations. It comprises a lasing medium placed in a laser resonating cavity defined by mirrors and a birefringent crystal placed on the path of the two waves. The lasing medium is located in the resonating cavity in a zone where the two waves are separated spatially. Two quarter wave plates, one of which has neutral lines at substantially 45.degree. from the polarization axes of the birefringent means, are placed in the common path of the two waves so as to give a helical polarization to the two waves between the plates.
Claims9
Laser for delivery of two waves having different frequencies and mutually orthogonal linear polarization directions, comprising:
- a laser resonating cavity defined by two mirrors;
- a lasing medium located in only a portion of said laser resonating cavity for being traversed by light reflected between said two mirrors;
- birefringent means located outside said portion and traversed by said light for separating said light into two waves having parallel paths when said light is in a first direction and recombining the light from said two paths into a common path when said light is in an opposite direction, said portion being so located with respect to said birefringent means that the light is separated in two parallel paths throughout said portion;
- and
- two quarter-wave plates located for being traversed by said light along said two paths, one of said quarter wave plates having neutral lines at approximately 45.degree. from the polarization axes of the birefringent means, whereby the two waves are helically polarized between the two quarter-wave plates.
Dependencies are inferred from the claim text.