Highly Efficient Frequency Doubling of Ultrashort-Pulse Fiber Laser at 1700 nm in PPLN Bulk and Waveguide Crystals

An early-stage cancer diagnosis is one of the key points in reducing the mortality of cancer patients. However current standard techniques of care to treat some cancers are not for early-stage cancer cases. Intensively developing multi-photon imaging is one of the most promising techniques which can provide valuable information about the intrinsic properties of the biological samples which can be employed in diagnosis applications. Multi-photon imaging commonly used green fluorescent proteins, which can be excited by ultrafast lasers at 700-900 nm [1, 2]. Ti:sapphire lasers cover this spectral range however, they are bulky, expensive, and susceptible to environmental perturbations. The alternative is fiber lasers with nonlinear stages which are not so expensive and more suitable for the clinical environment due to compactness and alignment-free [3]. In this paper, laser system at the Ti:Sa spectral region based on frequency doubling of radiation at 1625 - 1700 nm was demonstrated.