| Abstrakt: |
We review our development of wavelength tuneable, high average power, picosecond-pulse, mid-infrared sources in the three micron widow for proposed application in tissue ablation studies and with the objective of source simplification and exploring the potential of all-fiber integration. Initial systems were based on difference frequency generation (DFG) of two synchronous master oscillator power fiber amplifier (MOPFA) schemes. The generated idler was tuneable over the range 3.28–3.45 m, delivering greater than 3 W of average power, with a maximum pump to total DFG power conversion efficiency of 78 . By simplifying the seed sources through synchronised in-line modulation of cw diode laser sources, more than 6 W was generated 3.31–3.48 m with similar efficiency and with near diffraction limited beam quality (). In an improved and significantly simplified experimental configuration a source emitting around 3 m was developed employing a novel cascaded nonlinear conversion architecture. Picosecond pulses from a 1.064 m mode-locked Yb:fiber pump laser were used to generate 1.65 m signal pulses through based four-wave mixing in a polarisation preserving photonic crystal fiber (PCF). The output of the PCF was then directly focused into a periodically poled lithium niobate crystal, generating idler radiation around 3 m, with peak powers of 0.5 kW, via -based three-wave mixing between the pump and signal pulses. [ABSTRACT FROM AUTHOR] |
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