Optical designs for multimodal nonlinear microendoscope for optical biopsy

Linear and nonlinear optical imaging systems are currently being miniaturized to fit endoscopic size requirements of a diameter less than 2 mm. These systems are used for deep imaging and optical biopsy. We report our progress in the development of a multimodal microendoscope based on Gradient Index (GRIN) lenses and double clad fiber (DCF) for femtosecond pulse delivery and signal collection. Four commercial DCFs were identified from the literature and our choice was based on the simulation results for optimal pulse delivery -needed for efficient 2-photon excitation- and optimal fluorescence signal collection. The pulse delivery simulation was done using a GRISM line system for compensating linear and nonlinear effects inside the DCF. The effect of GRIN lens aberration on collection efficiency was estimated by simulation using Zemax. GRIN lenses were also validated for fluorescence lifetime, spectroscopic measurement and mouse tissue imaging.