Intraluminal FLIm

Intravascular — Design and manufacturing of freeform optics. (a) Simplified representation: a section of ellipsoid reflects and focuses light rays exiting the fiber core. (b) Zemax simulation model used to perform optimization of the reflective surface. (c) Manufacturing process: the coated array is first cut into individual rows (step 1), individual elements are cut from each row (step 2), and polished to the designed length (step 3). (d) The surface sag representation of the curved reflective surface highlights that axial and transaxial directions have different curvature radii, thus enabling astigmatism correction. (e) Individual optics after manufacturing completion.
Adapted from J. Bec et al. Opt Lett, vol. 44 (2019)

Successful implementation of catheter-based optical imaging systems relies on the integration of high-performance miniaturized distal end optics. Established solutions such as GRIN-based optics or ball lens designs present strong limitations for FLIm applications due to high autofluorescence in the UV range and subpar performance when combined with multimode fibers.

To address these issues we developed compact (300 × 300 × 800 μm3) monolithic optics that consists of a fused silica element terminated by a reflective curved back surface that performs beam focusing and reflection. This concept provides high optical performances over an extended wavelength range (near UV-visible-IR) with minimal chromatic aberrations. The design of the optic, fully optimized using standard optical simulation tools, provides the ability to freely determine aperture and working distance. Experimental characterization of the optic demonstrates a good match with simulation results and performances well suited to both optical coherence tomography and fluorescence imaging, thus paving the way for high-performance multimodal endoscopy systems.