Diffractive tunable lens for remote focusing in high-NA optical systems.

Area of Science:

• Optical microscopy
• Diffractive optics
• Super-resolution imaging

Background:

• Remote focusing enables 3D focus control in scanning microscopy without moving the objective lens.
• This technique is crucial for maintaining sample stability and integrating with adaptive optics.
• Existing methods face limitations with high numerical aperture (NA) objectives.

Purpose of the Study:

• To develop and demonstrate a novel remote focusing method compatible with high-NA optics.
• To achieve significant axial translation of the focal spot while preserving focus quality.
• To compare the performance of this new method against conventional lens designs.

Main Methods:

• Utilized a pair of diffractive elements acting as a tunable auxiliary lens.
• Adjusted the mutual rotation angle between the diffractive elements to control focus position.
• Employed a NA = 0.95 air objective (equivalent to NA = 1.44 oil immersion).

Main Results:

• Achieved an axial translation of the focal spot exceeding 140 µm.
• Demonstrated largely maintained focus quality throughout the translation range.
• Showcased superior wavefront performance compared to parabolic and achromatic lens doublets for focus shifting.

Conclusions:

• The novel diffractive element-based remote focusing system effectively enables extended axial focus control for high-NA microscopy.
• This method offers a robust solution for 3D imaging applications requiring precise and dynamic focal adjustments.
• The demonstrated performance highlights the potential of diffractive optics in advancing microscopy capabilities.