Design and fabrication of asymmetric strained layer mirrors for optoelectronic applications

The design of thin‐film mirrors is optimized for strained layer materials systems. It is shown that the use of asymmetric structures produces only minor loss in reflectivity per mirror period, while greatly extending the number of periods that can be grown in a defect‐free mode. As applied to the GexSi1−x/Si strained layer system, the net result is an enhancement of reflectivity, with 1.3 μm mirrors achieving peak values near 75%. The approach is applicable to other materials systems and should yield even higher reflectivities in situations where wider ranges in index of refraction are available.