Dynamic wavefront distortion in resonant scanners

Abstract

Dynamic mirror deformation can substantially degrade the performance of optical instruments using resonant scanners. Here, we evaluate two scanners with resonant frequencies > 12 k H z with low dynamic distortion. First, we tested an existing galvanometric motor with a novel, to the best of our knowledge, mirror substrate material, silicon carbide, which resonates at 13.8 kHz. This material is stiffer than conventional optical glasses and has lower manufacturing toxicity than beryllium, the stiffest material currently used for this application. Then, we tested a biaxial microelectromechanical (MEMS) scanner with the resonant axis operating at 29.4 kHz. Dynamic deformation measurements show that wavefront aberrations in the galvanometric scanner are dominated by linear oblique astigmatism (90%), while wavefront aberrations in the MEMS scanner are dominated by horizontal coma (30%) and oblique trefoil (27%). In both scanners, distortion amplitude increases linearly with deflection angle, yielding diffraction-limited performance over half of the maximum possible deflection for wavelengths longer than 450 nm and over the full deflection range for wavelengths above 850 nm. Diffraction-limited performance for shorter wavelengths or over larger fractions of the deflection range can be achieved by reducing the beam diameter at the mirror surface. The small dynamic distortion of the MEMS scanner offers a promising alternative to galvanometric resonant scanners with desirable but currently unattainably high resonant frequencies.

Acousto-optic Scanning Spatial-switching Multiphoton Lithography

“…However, serial scanning MPL is unfortunately too slow to be a valuable solution for many practical applications. Although attempts at multi-foci parallelization increase the printing throughput of the scanning MPL, the printing speed is still limited by the inertia of the scanning mirrors [36][37][38][39], and it can only print periodic structures [28,[40][41][42][43][44], resulting in a loss of nanomanufacturing flexibility. Therefore, it remains a serious challenge to take advantage of both scanning and projection methods while avoiding their shortcomings to achieve arbitrary complex 3D structures with high throughput, high accuracy, and broad material applicability.…”