title: A diffraction-limited scanning system providing broad spectral range for laser scanning microscopy.
abstract: Diversified research interests in scanning laser microscopy nowadays require broadband capability of the optical system. Although an all-mirror-based optical design with a suitable metallic coating is appropriate for broad-spectrum applications from ultraviolet to terahertz, most researchers prefer lens-based scanning systems despite the drawbacks of a limited spectral range, ghost reflection, and chromatic aberration. One of the main concerns is that the geometrical aberration induced by off-axis incidence on spherical mirrors significantly deteriorates image resolution. Here, we demonstrate a novel geometrical design of a spherical-mirror-based scanning system in which off-axis aberrations, both astigmatism and coma, are compensated to reach diffraction-limited performance. We have numerically simulated and experimentally verified that this scanning system meets the Marechal condition and provides high Strehl ratio within a 3 degrees x 3 degrees scanning area. Moreover, we demonstrate second-harmonic-generation imaging from starch with our new design. A greatly improved resolution compared to the conventional mirror-based system is confirmed. This scanning system will be ideal for high-resolution linear/nonlinear laser scanning microscopy, ophthalmoscopic applications, and precision fabrications.
authors: Department of Physics, National Taiwan University, 1, Sec. 4, Roosevelt Rd., Taipei 10617, Taiwan.
authors: Jiun-Yann
authors: JY
authors: Yu
authors: Chien-Sheng
authors: CS
authors: Liao
authors: Zong-Yan
authors: ZY
authors: Zhuo
authors: Chen-Han
authors: CH
authors: Huang
authors: Hsiang-Chen
authors: HC
authors: Chui
authors: Shi-Wei
authors: SW
authors: Chu
mesh_terms: D018613:Microscopy, Confocal / Q000295:instrumentation*; D055620:Optical Phenomena; D015203:Reproducibility of Results; D012542:Scattering, Radiation