Fiber-optic Raman probe couples ball lens for depth-selected Raman measurements of epithelial tissue

In this study, we present a fiber-optic ball lens Raman probe design for improving depth-selected Raman measurements of epithelial tissue. The Monte Carlo simulation results show that tissue Raman collection efficiency can be improved by properly selecting the refractive index and the diameter of the ball lens for the Raman probe design and the depth-selectivity of Raman measurements can also be improved by either increasing the refractive index or reducing the diameter of the ball lens. An appropriate arrangement of the Raman probe-tissue distance can also optimize the collection efficiency for depth-resolved Raman measurements. Experimental evaluation of a ball lens Raman probe design on a two-layer tissue phantom confirms the potential of the ball lens Raman probe design for efficient depth-selected measurement on epithelial tissue. This work suggests that the fiber-optic Raman probe coupled with a ball lens can facilitate the depth-selected Raman measurements of epithelial tissue, which may improve the diagnosis of epithelial precancer and early cancer at the molecular level.