Gold-coated silicon nitride mirrors designed for two orthogonal rotations were fabricated. The devices were patterned out of nitride using surface micromachining techniques, and then released by a sacrificial oxide etch and bulk etching the silicon substrate. Vertical nitride ribs were used to stiffen the members and reduce the curvature of the mirrored surfaces due to internal stress in the nitride and the metal layer. This was accomplished by initially etching the silicon substrate to form a mold that was filled with nitride to create a stiffening lattice-work to support the mirrored section. Mirror diameters ranging from 100 mm to 500 mm have been fabricated, with electrostatic actuation used to achieve over four degrees of tilt for each axis.
Experiments were carried out to quantify the contribution of backscattered light and orthogonal polarization to the bias stability of a tactical-grade resonant fiber-optic gyro. The data were found to agree with theory to within 25 percent. It was found that suppressed carrier phase modulation of the light for each input was effective in reducing the backscatter bias error by shifting the modulation frequencies for the counterpropagating signals. The polarization errors could be reduced by adding fiber polarizers at the ring outputs.