An optical thin film stack provides reflection of essentially all light
except for a selected amount of transmission over a selected wavelength
range. Reflecting, rather than absorbing, unwanted light avoids heating
caused by light absorption and allows productive use of the
non-transmitted light in some applications. In some embodiments, reflector
designs are "stacked" on an optical substrate to provide serial optical
reflectors. Stacking dichroic filters provides reduced sensitivity to cone
angle and manufacturing advantages.
