Abstract
We report the generation of high energy 2 μm picosecond pulses from a thulium-doped fiber master oscillator power amplifier system. The all-fiber configuration was realized by a flexible large-mode area photonic crystal fiber (LMA-PCF). The amplifier output is a linearly-polarized 1.5 ns, 100 kHz pulse train with a pulse energy of up to 250 μJ. Pulse compression was achieved with (2+2)-pass chirped volume Bragg grating (CVBG) to obtain a 2.8 ps pulse width with a total pulse energy of 46 μJ. The overall system compactness was enabled by the all-fiber amplifier design and the multi-pass CVBG-based compressor. The laser output was then used to demonstrate high-speed direct-writing capability on a temperature-sensitive biomaterial to change its topography (i.e. fabricate microchannels, foams and pores). The topographical modifications of biomaterials are known to influence cell behavior and fate which is potentially useful in many cell and tissue engineering applications.
Highlights
High power light sources emitting at 2 μm are useful for applications in the processing of semiconductors, clear polymers, and water-rich biological tissues and biomaterials[1,2,3]
Amplification of pulses with high peak power in fiber laser systems is limited by nonlinear effects due to the small mode field area (MFA)
We present a fiber master oscillator power amplifier (MOPA) system which consists of an all-fiber amplifier and a compact multi-pass chirped volume Bragg grating (CVBG)-based compressor
Summary
High power light sources emitting at 2 μm are useful for applications in the processing of semiconductors, clear polymers, and water-rich biological tissues and biomaterials[1,2,3]. Fiber lasers are attractive as 2 μm sources offering excellent beam quality. Heat dissipation along long fiber lengths is efficient which enables high output powers. Amplification of pulses with high peak power in fiber laser systems is limited by nonlinear effects due to the small mode field area (MFA). Increasing the fiber core size will effectively increase the MFA but the number of supported waveguiding modes increase as well, leading to beam quality degradation. To circumvent the small MFA limitation whilst preserving the single-mode guidance property, more sophisticated microstructured fibers were devised to substitute conventional step-index fiber designs[4]
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