Abstract: Beam shaping plays a crucial role in microscopy by improving spatial resolution and imaging performance. Conventional beam shaping relies on refractive and diffractive optical elements. Recent advances in ultrathin meta-optics have expanded beam-shaping capabilities and enabled the generation of complex structured light fields. Light-sheet microscopy (LSM) has recently emerged as a complementary alternative to conventional epi-illumination techniques. In this geometry, excitation and detection paths are arranged orthogonally, reducing photodamage and improving optical sectioning. In LSM, Gaussian beams provide a limited field of view due to their low depth of focus (DoF). Bessel beams offer an extended DoF and are therefore attractive for light-sheet illumination. However, their strong sidelobes cause unwanted excitation in the sample and reduce image contrast. Meta-optics enable the realisation of arbitrary phase functions, allowing the design of Bessel beams with reduced sidelobes. This capability provides a promising route for improving light-sheet imaging performance.

In this work, the generation of sidelobe-suppressed Bessel beams (SSBBs) for LSM is demonstrated using dielectric metasurfaces. Silicon and silicon nitride metasurfaces are designed to generate the SSBBs at near-infrared (1064 nm) and visible wavelengths (520 nm and 642 nm). The design and fabrication of the metasurfaces are systematically investigated, including key challenges in the fabrication process. The generated beams are implemented in an LSM setup, and imaging of onion epidermal cells is demonstrated. The performance of the SSBB-based light sheet is compared with that of a conventional Bessel-beam-based light sheet. To further enhance imaging performance, additional strategies are explored. Structured illumination using SSBBs is experimentally demonstrated using metasurface-generated beam arrays. Furthermore, the applicability of SSBBs to the stimulated emission depletion (STED) principle in a light-sheet geometry is investigated. In this context, zeroth-order and first-order SSBBs for excitation and depletion are experimentally generated, while the resulting super-resolution light needle is demonstrated through simulations.

The metasurface-generated zeroth-order SSBBs exhibit 50-57% suppression of the first sidelobe compared to conventional Bessel beams in both silicon and silicon nitride platforms. The DoF of the SSBB is about 1.7 times that of a Gaussian beam with a comparable beam size. The light sheet created by scanning the SSBB also shows a substantial reduction in sidelobes compared with a Bessel-beam-based light sheet. Imaging of onion epidermal cells using SSBB light sheet demonstrates a 55% improvement in image contrast compared to a Bessel beam. Structured illumination using SSBB is further demonstrated, where five nearly equal-intensity copies of the SSBB are generated using a metasurface. In addition, first-order SSBB is generated as the depletion beam for STED light-sheet microscopy, exhibiting 45% reduction in the first sidelobe compared to a first-order Bessel beam.

These results demonstrate that SSBBs improve light-sheet imaging by reducing sidelobes and enhancing image contrast. Although the DoF of the SSBB is lower than that of a conventional Bessel beam, it exceeds that of an equivalent Gaussian beam, thereby extending the usable field of view. The realisation of SSBBs using meta-optics enables their implementation in LSM using ultra compact optical elements. Furthermore, the additional strategies presented in this work, including structured illumination using SSBBs and the incorporation of the STED principle within a light-sheet geometry, provide further routes for improving LSM performance.

                                                                                                        All are cordially invited.

Event Details
Title: Meta-optics Beam Shaping for Improved Bessel Light Sheets
Date: May 18, 2026 at 10:00 AM
Venue: Google Meet (https://meet.google.com/mmt-qmgx-otg)
Speaker: Mr. Jerin Geogy George (EE20D029)
Guide: Dr. Shanti Bhattacharya
Type: PHD seminar

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