Tunable Bessel Beam Module for High-Speed Volumetric and Multi-Color Multiphoton Imaging

Background

Multiphoton microscopy is a critical technology for observing dynamic biological processes in vivo, particularly in fields like neuroscience and vascular biology. Yet, traditional Gaussian beam-based approaches are limited by shallow depth of focus and slow 3D scanning, making them ill-suited for capturing fast volumetric events across large fields of view. Bessel beam, utilizing their axially elongated Bessel focus and converts a 3D volumetric scan into a 2D frame scan, enabling video-rate volumetric imaging with diffraction-limited resolution.

While advanced beam shaping techniques—such as those based on spatial light modulators (SLMs)—offer some flexibility, they are often expensive, wavelength-specific, and light-inefficient. Other beam shaping techniques that were developed optically for Bessel beam generation only offer limited tenability, and these systems also struggle with axial alignment instability, limiting their utility for simultaneous multicolor imaging or integration with optogenetic tools. This newly developed system is the first optical system that offers full control over generated Bessel beam resolution and length without any focus shift, can be cheaply built and integrated into existing multiphoton imaging systems without the usage of SLMs.

Technology

Technology Description This system is a compact, modular Bessel beam generator designed for plug-in integration with multiphoton microscopes. It utilizes a configuration of three axicons, three lenses, and an iris to precisely generate and control nondiffractive Bessel beams. A standard axicon-lens pair initially transforms a collimated laser into a focused ring. Subsequently, two identical axicons, whose separation can be varied, dynamically adjust the beam’s numerical aperture and lateral resolution without introducing phase errors or axial shifts. An iris positioned at the Bessel beam waist independently fine-tunes Bessel length and suppresses side-ring excitation in real time. This plug-in system enables simultaneous multicolor, high resolution, high-speed volumetric imaging in live samples. The technology stands out by relying on readily available, off-the-shelf optical components instead of expensive and wavelength-specific spatial light modulators. This design choice confers significant advantages, including minimal chromatic aberration, higher light efficiency, and reduced axial motion artifacts. Furthermore, it achieves real-time tunability of beam parameters, allowing for imaging speeds 10 to 100 times faster than conventional Gaussian-based two-photon fluorescence microscopy. Its modular and cost-effective approach enables sub-capillary resolution across millimeter-scale volumes, making it a highly differentiated solution for advanced volumetric imaging.

Benefits

• Enables high-speed volumetric imaging (10-100x faster than conventional methods) with sub-capillary resolution.
• Utilizes cost-effective, off-the-shelf optical components, eliminating the need for expensive spatial light modulators.
• Offers tunability of beam parameters (NA, beam length) without introducing axial shifts or phase errors.
• Provides higher light efficiency and minimal chromatic aberration, supporting simultaneous multicolor imaging.
• Reduces axial motion artifacts, enhancing imaging stability for live samples.

Applications

• Medical diagnostic imaging
• Live biological sample imaging
• Precision material processing
• Microparticle manipulation systems
• Advanced materials analysis

Additional info

This optical module generates and controls tunable Bessel beams for multiphoton microscopy. It employs three axicons, three lenses, and an iris to convert a collimated laser into a focused ring, adjust numerical aperture, length, and control energy confinement. This setup enables high resolution volumetric imaging with high light efficiency, utilizing off-the-shelf components.