Stanislav V. Gordeyev’s scientific contributions

This work presents a comprehensive characterization of a benchtop optical-turbulence simulator system using a Shack—Hartmann (SH) wavefront sensor, an off-axis digital holography (DH) wavefront sensor, and a far-field imaging camera. The system employs two spatial-light modulators (SLMs) to impose turbulent phase screens with prescribed statistics onto a laser beam, simulating atmospheric turbulence. We conduct tests to compare the system’s performance against wave-optics simulations by varying turbulence strength, varying the modeled propagation distance, and using both SLMs to model beam propagation. The results show that the DH wavefront measurements have a root mean square error (RMSE) of 0.02–0.03 µm compared to the simulated wavefronts, while the SH measurements have a RMSE of 0.02–0.05 µm compared to the DH wavefront measurements. We also assess the system’s ability to model beam propagation. Here, we find that the extent of phase disagreement increases with increasing propagation distances. Overall, the results of a Monte–Carlo simulation that models a 25 cm beam along a 1 km path reveal that DH measurements closely match the known turbulence parameters whereas the SH measurements generally underestimate turbulence strength. At large, this work informs system designers of how different wavefront sensors perform in varying optical-turbulence conditions.

This work presents preliminary results on aero-mechanical jitter of a hemispherical optical turret. A simplified geometry with a hemispherical shell and optics-holding canister was designed to reduce degrees of freedom and provide better insight into fundamental physics. Modal analysis of the turret and mounting plate to the wind tunnel, performed using finite element analysis (FEA), revealed significant plate displacements in the lowest frequency modes. Three mounting plate thicknesses (1/4”, 1/2”, and 1”) were tested. Wind tunnel tests at the University of Notre Dame’s White Field Mach 0.6 wind tunnel assessed turret vibrations at speeds from Mach 0.2 to 0.5, using accelerometers and Shack-Hartmann tilt sensors. Two scenarios were tested: one with the turret inside the tunnel exposed to the flow, and another with the turret attached outside of the wind tunnel so that it is only excited by the base motion of the wind tunnel. The 1/4” plate showed tilt measurements ranging from 30 to 190 microradians when exposed to flow, compared to 10 to 50 microradians in the baseline case. The 1/2” and 1” plates exhibited lower tilts and less distinction between flow and baseline conditions. Overall, the simplified turret only had about three vibration modes affecting tilt, with strong spatial agreement between experimental and FEA modal patterns.