Fiber-based 1150-nm femtosecond laser source for the label-free virtual optical biopsy (Conference Presentation)

For deep imaging depth and least invasiveness, people commonly use 1100-1300 nm femtosecond laser sources to perform label-free in vivo microscopy. The modalities include reflectance confocal, two & three photon fluorescence, and second & third harmonic generation microscopy. However, most of the laser sources are typically based on bulky oscillators, which are sensitive to environment conditions and less stable for routine clinical use. In contrast, fiber-based lasers have simpler cavity design and potentially compact size for movable use. In this presentation, we demonstrate a fiber-based 1150 nm femtosecond laser source, with 6.5 nJ pulse energy, 86 fs pulse-width, and 11.25 MHz pulse repetition rate. It was achieved by a Bismuth Borate (BIBO) or Magnesium-doped periodically poled Lithium Niobate (MgO:PPLN) mediated frequency doubling of the 2300 nm solitons, generated from an excitation of 1550 nm Er:fiber femtosecond laser pulses on a large mode area photonic crystal fiber. Combined with a laser scanned microscope and a home-build data acquisition card, we achieve a pulse-per-pixel harmonic generation microscopy in vivo at a 30 Hz frame rate. In the future, this solution is potential to be used for label-free clinical virtual optical biopsy.