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A broadband continuously tunable SESAM all-fiber laser based on optical parametric generation (OPG) for Coherent anti-Stokes Raman Scattering (CARS) imaging applications is presented in this article. This laser structure is built on allpolarization maintaining fibers yielding high environmental stability. The OPG is based on PM photonic crystal fiber as parametric gain pumped by a wavelength-tunable (1025 nm to 1055 nm) and repetition rate-tunable (3 MHz to 500 KHz) Ybdoped pulsed fiber laser. The all-fiber structure features free polarization adjustment in slow-axis tunable operation with a wavelength range from 770 to 940 nm for signal radiation and 1225 to 1510 nm for idler radiation. The pump and signal pulses (CARS-Stokes and CARS-pump respectively) are intrinsically overlapped, both spatially and temporarily, due to the four-wave mixing (FWM) generation and emitted from a single fiber end. The CARS-Stokes and CARS-pump pulse duration vary between 25 to 32 ps and 21 to 24 ps respectively in the whole band, ensuring a good overlap of the generated signals, and both exhibit a Gaussian profile with high spatial beam quality. The frequency conversion allows to obtain a frequency difference between the generated signals from 1100 to 3300− . The reported low-cost laser source is ideal for bio-imaging applications, especially in CARS imaging, due to its compactness, simplicity, robustness and ease of handling. A patent has been filed based on this technology.

An ultra-long, low-threshold and high-stability Random distributed feedback fiber laser (RDF-FL) based on Erbium-doped fiber (EDF) to provide the gain medium, and single mode fiber (SMF) as a distributed mirror in combination with fiber-brag grating (FBG) to form the cavity is proposed in this paper. Typical random laser radiation for a SMF length of 50 km with a low-threshold of 10 dBm and high-stability (~0.1 dB) is achieved, thanks to the design of the cavity and the high-gain from the pumped erbium-doped fiber. Besides, 200 km quasi-losses random laser due to the distributed mirror and the FBG reflector is demonstrated.

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