GB1075185A - Improvements in or relating to optical masers - Google Patents

Abstract

1,075,185. Lasers. WESTERN ELECTRIC CO. Inc. Sept. 24, 1964 [Sept. 30, 1963], No. 38923/64. Heading H1C. A laser includes a gaseous active medium, and an auxiliary gas containing a significant proportion of He<SP>3</SP>. The active medium may be neon, xenon, or mercury vapour. The ratios of the partial pressures of the helium and neon may be between 3 to 1 and 50 to 1, preferably about 7 to 1. It is stated that the laser tube may be substantially smaller than in lasers using He<SP>4</SP>, a length of two inches and a diameter of one millimetre being possible. An arrangement for selecting weak modes from the laser consists of the provision of a dispersive reflecting element as one of the terminal elements of the optical cavity. The other end of the cavity may consist of a spherical mirror or a second similar dispersive element. The dispersive reflecting member in one embodiment (Fig. 5, not shown) consists of a prism having a plane refracting surface (59) upon which the laser radiation falls at the Brewster angle (#), and a reflecting surface (60) upon which a selected wavelength falls normally. The reflecting surface (60) may be coated with dielectric reflecting layers (61). In a second embodiment (Figs. 6A, 6B, not shown) the prism has a spherically curved reflecting surface and a cylindrically curved refracting surface (71), the laser radiation again being incident at the Brewster angle. The radius of curvature of the cylindrical surface is made equal to S -, where S is the radius of curvature of n cos # the spherical surface, n is the refractive index of the prism and # is the Brewster angle, whereby astigmatism is avoided.