Brewster angle laser window

Figure 4.2 Layout of a typical HeNe laser (and other gas laser) resonator. Normally, the laser tube is sealed by Brewster-angle-oriented windows in short-length HeNe alignment lasers, the resonator mirrors are directly attached tothelasertube...

Also relying on light reflection to polarize light are Brewster angle windows based on the effect discussed in section 1.6. This type of window is also used in most laser cavities... 

FIGURE 9.6 Overview of the experimental apparatus for measuring laser-induced fluorescence and photodissociation action spectra of gas phase ions stored in a 3-D quadrupole ion trap. Optical component abbreviations Lenses (L1-L4) P-BaBj04 crystal (BBO) Mirrors (M1-M8) Shutter (Sh) Irises (Irl-lr2) Pinholes (PH1-PH2) Brewster-angle windows (BWl-BW2) Neutral density filter (ND) Long-pass filter (LP). L3 is inside the ring electrode (see Figure 9.7). 

The first concave mirror in Figure 20 is not essential, but in many experiments the energy density is increased by placing the experimental cell in a spherical concentric Fabry-Perot cavity. The windows of the experimental cell must be tilted at the Brewster angle to reduce the losses in the cavity. The length of this cavity is piezoelectrically locked on the Laser frequency, to maximize the signal transmitted throug it. 

A very high degree of linear polarization can be obtained for a laser with low losses in one direction of oscillation and high losses in the perpendicular direction. For a laser with a gas as the active medium this is accomplished by placing the windows of the gas container at the Brewster angle to the optical axis of the laser (Fig. 8.5). For other lasers some other type of polarizer can be placed inside the cavity. 

Brewster window A flat optical window tilted at an angle such that light whose electric vector is polarized parallel to the plane of the window is 100% transmitted. Light polarized perpendicular to the window is partially reflected. It is used on the ends of a laser to produce light whose electric field oscillates perpendicularly to the long axis of the laser. 

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