The feedback mechanism uses mirrors with reflectivity and alignment described as what?

• A. 75% reflective and misaligned
• B. 90% reflective and misaligned
• C. 50% reflective and parallel
• D. 99.7% reflective and aligned optically parallel

Answer: (D)

The idea being tested is how an optical feedback loop relies on two things: how much light the mirrors reflect and how precisely they are aligned. When the mirrors are extremely reflective and kept optically parallel, most of the signal is reflected back into the system with the correct phase. That high reflectivity (about 99.7%) minimizes loss per pass, and the parallel alignment ensures the returning wave stays in phase and stays directed into the cavity. Together, these conditions create strong, stable feedback necessary for the intended operation.

If the mirrors were only moderately reflective, much of the signal would be lost instead of fed back, weakening the loop. If the mirrors were misaligned, even a high-reflectivity setup would fail to couple the reflected light back properly, causing phase errors or misdirection that disrupts the feedback. A lower reflectivity along with misalignment compounds these problems, making effective feedback unlikely.