A method of constructing optical filters using alternating layers of materials
with "low" and "high" indices of refraction and deposited with atomic layer control.
The multilayered thin film filter uses, but is not limited to, alternating layers
of single crystal, polycrystalline or amorphous materials grown with self-limiting
epitaxial deposition processes well known to the semiconductor industry. The deposition
process, such as atomic layer epitaxy (ALE), pulsed chemical beam epitaxy (PCB
E), molecular layer epitaxy (MLE) or laser molecular beam epitaxy (laser MBE) can
result in epitaxial layer by layer growth and thickness control to within one atomic
layer. The alternating layers are made atomically smooth using a Chemical Reactive-Ion
Surface Planarization (CRISP) process. Intrinsic stress is monitored using an in-situ
cantilever based intrinsic stress optical monitor and adjusted during filter fabrication
by deposition parameter modification. The resulting filter has sufficient individual
layer thickness control and surface roughness to enable 12.5 GHz filters
for next generation multiplexers and demultiplexers with more than 1000 channels
in the wavelength range 1.31-1.62 m.
