Hello RRG,

I have not designed an isolator before, but I have used OpticStudio to design retarders. I attach two non-sequential zar files which are perhaps a starting point.

“Quarter wave plate” determines the thickness of birefringent quartz necessary to make a quarter wave retarder. It’s at 550nm, but could be re-optimized for another wavelength.

“Isolator 1_0” uses that quartz thickness. A Source Ellipse launches 1000 rays with random polarization. They go through a polarizer which consists of a Jones Matrix embedded in a window of N-BK7. They then pass through the QWP and strike a window of N-BK7 which represents downstream optics from which we want isolation. Rays that reflect back go through the QWP again and are killed by the polarizer. The polarizer and QWP are AR coated. (The coating could be improved.) There are detectors which measure transmitted and reflected power.

As designed, the reflected detector receives 2.3%. If the QWP is set to Ignore and Hide the reflection increases to 5.7%.  The as-designed reflection could be reduced by improving the AR on the  polarizer and QWP. Path Analysis can be used to explore reflections in detail.