INDEX DATA

Made from two calcite elements cemented together in such way that their optical axes are both parallel to the hypotenuse and to the entrance and exit faces. When compared to other calcite polarizers they present the advantages of maximum refractive index difference between ordinary and extraordinary rays, thus allowing either a larger field angle or a smaller L/A ratio, with uniform and symmetric polarization over all the field. There is no lateral shift of the image for axial objects. Glan-Thompsons present the best extinction coefficient of all polarizers (values of 3x10^-8 have been attained). Due to these advantages they are the preferred polarizers for use with energy density up to 1W/cm², in optical systems such as monochromators, low-power lasers, light sources and precision polarization instruments. These prisms have their entrance and exit faces perpendicular to the prism axis, thus simplifying mounting and alignment. The figure shows the orientation of optical axes and polarized beam in this prism. Glan-Thompsons are made with L/A ratios of 3:1 or 2.5:1, with apertures of 10x10, 15x15 and 20x20mm.

These prisms differ from the Glan-Thomson in being air-spaced instead of cemented and by having their two parts made with optical axes perpendicular to the hypotenuse. As shown in the figure, the extraordinary, linearly polarized beam is transmitted without deviation, while the ordinary beam suffers total internal reflection at the calcite-air interface, being deviated to a side face, where it is completely absorbed. By being air-spaced, these prisms show higher ultraviolet transmission than Glan-Thompsons, with a smaller field. However their field is larger than other equivalent-sized air-spaced polarizers. The cut between the two parts is made near the Brewster angle, further improving transmission. Due to the larger cut angle it is a shorter prism, allowing better calcite yield and consequent cost reduction. They can be used with energy densities up to 5W/cm² (CW) and 10MW/cm² (1ns pulses). Glan-Taylors are made with L/A ratios of 3:1 or 2.5:1, with apertures of 10x10, 15x15 and 20x20mm.

Glan-Laser polarizers are Glan-Taylor prisms optimized to be used with medium to high energy lasers and so are made from scatter-free calcite without any cosmetic defects. As high energybeams reflected at the calcite-air interface will heat the mounting medium, causing degassing and possible damage of the crystal, it is necessary to send these beams outside the prism, which is done by means of two polished side faces, as shown in the drawing. The hypotenuse angle is also optimized to minimize reflection losses and, in order to prevent multiple reflections in Q-switch applications, the entrance and exit faces may be made with a 3 angle relative to the prism mechanical axis, on special request. These prisms may be employed with laser beams of up to 100W/cm² (CW) and 300MW/cm² (pulsed-1ns) in applications such as feedback elimination, pulse extraction and Q-switching. Glan-Laser prisms are made with apertures of 10x10 or 20x20mm.

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