Re: Laser light

[pengra@whitman.edu (Jim Pengra)]

> > 4)  What is the purpose of the brewster window and why don't small HeNe
> > lasers have them?

  The Brewster windows were used to get the last smidgin' percentage of
window transmission necessary to cause (allow) the laser to operate when
using external mirrors. For the particular polarization selected by the
Brewster window, the transmission is nearly 100%. Anything less than that
produces unacceptable losses of beam strength due to the reflections from
the window surfaces. Small He-Ne lasers now have internal mirrors. In
consequence, their beams no longer have a definite polarization, which I
always thought was a nice feature.

--Jim(pengra@whitman.edu) Walla Walla, Washinton, USA