What is a Brewster Window?
. A polarized beam will result only if there is some preference for one polarization orientation inside the laser cavity. This could be due to the lasing crystal characteristics, an optical element like a Brewster plate or window, or an external influence like a magnetic field. For many laser applications, a polarized beam is a requirement. For others, it really doesn’t matter. I don’t know of any cases where a polarized beam would be undesirable except in terms of the additional cost when it isn’t produced automatically (e.g., requiring the addition of a Brewster plate inside the HeNe laser cavity). (Portions from: Brian W. Rich (science@west.net).) Light propagates as a transverse wave. That is, the vibration is sideways to the direction of travel. If the light is polarized, it means that all the waves are vibrating in the same plane.
) so that virtually no energy is lost due to reflections from its surfaces as the beam passes through. Slabs may also be configured in such a way that the laser beam follows a zig-zag path through the slab reflecting back and forth from its flat faces. In both cases, the large surface area of the slab means that it is able to dissipate a large amount of power without damage. The largest pulsed lasers in the world (used for inertial fusion and nuclear bomb research) employ slab type laser amplifiers extensively. See: Lawrence Livermore National Laboratory for more information. Search for “lasers”. • Lasers may be constructed with ‘distributed feedback’ which replaces one of the mirrors with a diffraction grating. See the section: Difference Between Fabry-Perot and DFB Lasers. Adjusting the angle of the grating can be used to select the wavelength of the output in some lasers. (An ‘intra-cavity’ prism can also be used for this purpose.
) so that virtually no energy is lost due to reflections from its surfaces as the beam passes through. Slabs may also be configured in such a way that the laser beam follows a zig-zag path through the slab reflecting back and forth from its flat faces. In both cases, the large surface area of the slab means that it is able to dissipate a large amount of power without damage. The largest pulsed lasers in the world (used for inertial fusion and nuclear bomb research) employ slab type laser amplifiers extensively. See: Lawrence Livermore National Laboratory for more information. Search for “lasers”. • Lasers may be constructed with ‘distributed feedback’ which replaces one of the mirrors with a diffraction grating. See the section: Difference Between Fabry-Perot and DFB Lasers. Adjusting the angle of the grating can be used to select the wavelength of the output in some lasers. (An ‘intra-cavity’ prism can also be used for this purpose.) • Additional optical elements like prisms, modulato
.) The Closeup of Typical Laser Diode shows one that is from a laser printer. It was mounted in a massive module (relative to the size of this laser diode, at least) which included the objective lens and provided the very important heat sink. In some high performance laser printers, a solid state Peltier cooler is used to stabilize the temperature of the laser diode. The low power laser diodes in CD and LD players, and CDROM and other optical drives (at least read-only types) get away with at most, the heat sink provided by the casting of the optical block – and many don’t even need this being of all plastic construction.
