
158 OPTICS FOR ENGINEERS
resulting in a reection of the input polarization as shown in Equation 6.22. Likewise a quarter-
wave plate to convert linear polarization to circular according to Equation 6.24 requires
δφ
qwp
=
π
2
= k
n
yy
−n
xx
n
yy
−n
xx
=
λ
4
. (6.81)
For example, in quartz at a wavelength of 589.3 nm,
n
yy
−n
xx
= 1.5534 − 1.5443, (6.82)
and a quarter-wave plate must have a thickness of 16.24 μm. Normally, this birefringent mate-
rial will be deposited onto a substrate. It is easier to manufacture a thicker wave plate, so
frequently higher-order wave plates are used. For example, a ve-quarter-wave plate, 81 μm
thick in this example, is quite common, ...