Fiber-Tip TIR Micro-Optics for 3D Optical Trapping
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Solution Overview
Problem
Conventional optical trapping using single-mode optical fibers is limited to 2D trapping due to high or low axial forces, and existing solutions require complex modifications or multiple fibers, making 3D trapping in vivo applications challenging due to light field distortions and limited working distances.
Innovation Solution
A rotationally symmetric dielectric structure is designed on the tip of a single-mode optical fiber, utilizing total internal reflection to split and recombine light paths into a focused annular beam, creating a 3D optical trap with a large working distance and minimizing axial forces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If a single-mode optical fiber is used for optical trapping, then the device size is miniaturized and flexibility is improved, but only 2D trapping is achieved due to high or low axial forces preventing 3D trapping
Solution Approach 1:
The light field emerging from the single-mode fiber is split into multiple separate light paths using total internal reflection surfaces. These segmented light paths are then recombined to form an annular beam, enabling 3D optical trapping while maintaining the miniaturized fiber-based structure.
Solution Approach 2:
The invention transforms the light field from a simple Gaussian beam into a structured annular beam by manipulating light paths in multiple dimensions. This dimensional transformation of the light field enables the generation of optical forces suitable for 3D trapping, overcoming the limitation of 2D trapping in conventional single-mode fibers.
2Illumination intensity
If highly focused beams are generated using additional optics on the fiber tip, then light intensity is improved, but the working distance becomes very small limiting integration freedom
Solution Approach 1:
The invention changes the beam parameter from a highly focused Gaussian beam to a focused annular beam. This parameter change allows the light to be concentrated at a focal point while maintaining a larger working distance, as the annular structure distributes the optical energy differently compared to a conventional focused beam.
3Adaptability or versatility
If conventional high NA microscope objectives are used for optical trapping, then 3D trapping capability is achieved, but light field distortions occur in highly turbid media and access to confined spaces is limited
Solution Approach 1:
The optical fiber acts as an intermediary that guides light to the desired point while preserving it from aberrations and distortions. By using the fiber as the light delivery mechanism rather than direct microscope objectives, the system avoids light field distortions in turbid media while maintaining 3D trapping capability through the structured annular beam generation.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enables miniaturized optical tweezers for in vivo applications, allowing for the manipulation of particles and cells at a distance from the fiber tip while maintaining high light intensity and flexibility, and facilitating the collection of backscattered signals for further analysis.
Implementation Method 1
a rotationally symmetric dielectric structure... utilizing total internal reflection to split and recombine light paths into a focused annular beam
Implementation Method 2
Optical trapping is one of the most important functions in the study of single cells... for trapping and manipulating individual particles and living biological cells
Data Source
AI summary
The present disclosure relates to a rotationally symmetric dielectric structure for optical beam shaping and for trapping and manipulating individual particles and living biological cells in aqueous medium, concentrically mounted on the facet of a single-mode optical fiber, wherein the structure comprises at least three total reflection surfaces configured to split a light field emerging from the single-mode optical fiber into at least two separate light paths and wherein the at least three total reflection surfaces are further configured to bring the separate light paths together as a ring beam in a common focal point.