Highly efficient frequency doubling of 1700 nm ultrashort pulsed fiber laser in PPLN bulk crystal

We demonstrated efficient frequency doubling of the ultrafast laser system at the wavelength range of 1620 – 1700 nm. The laser system was based on Er3+ fiber laser with Raman soliton self-frequency shift (SSFS) stage. The power of SSFS radiation was up to 110 mW/10.9 MHz with a pulse duration of 125 fs. PPLN crystal with several quasi-phase matching periods was used for efficient frequency doubling in the tuning range. The highest SHG power of 55 mW was obtained at 1675 nm with conversion efficiency of > 50%. The developed laser will be used for bladder cancer diagnosis by multi-photon bioimaging.