Femtosecond fiber CPA system based on picosecond master oscillator and power amplifier with CCC fiber

Abstract

Results of numerical and experimental investigations of the simple fiber CPA system seeded by nearly bandwidth-limited pulses from the picosecond oscillator are presented. We utilized self-phase modulation in a stretcher fiber to broaden the pulse spectrum and dispersion of the fiber to stretch pulses in time. During amplification in the ytterbium-doped CCC fiber, gain-shaping and self-phase modulation effects were observed, which improved pulse compression with a bulk diffraction grating compressor. After compression with spectral filtering, pulses with the duration of 400 fs and energy as high as 50 µJ were achieved, and the output beam quality was nearly diffraction-limited.

Limits of femtosecond fiber amplification by parabolic pre-shaping

“…Self-similar amplifiers can handle high non-linearity and produce sub-100-fs pulses in a fiber-integrated format, but their rapid spectral broadening coupled with the finite gain bandwidth typically limits them to ≈ 1 μ J [3, 4]. Cubicon amplifiers are scalable to 100 μ J and B ≳ 4 π , but they require specially-engineered input spectra, and reported pulse durations exceed 400 fs [5, 6]. While nonlinear chirped-pulse amplification has been demonstrated at 30 μ J and 240 fs with B ≈ 18 π , its performance drops noticeably if the balance between nonlinearity and third-order-dispersion is disturbed [7].…”

High efficiency, monolithic fiber chirped pulse amplification system for high energy femtosecond pulse generation

“…Most efforts to develop LMA waveguides have focused on approaches such as low NA photonic crystal fiber [20][21][22][23][24][25][26], leakage channel fiber [27,28], chirally-coupled core fiber [29][30][31], large-pitch fiber [32,33], and distributed mode filtering rod fiber [34]. These established approaches all operate in the fundamental fiber mode (LP 0,1 ) which suffers from bendinduced reductions in the mode size and increases in modal instability.…”

Broadband pulse compression gratings with measured 997% diffraction efficiency

“…A drawback of this approach used to be the high losses caused by diffractive optical elements, which, until the latest improvement, suffered from comparatively low efficiencies. In the meantime, the reported values for the diffraction efficiency of reflective grating mirrors have increased continuously and are now typically in the range of 95%-97% [4][5][6][7][8] and even above 99% [9], whereas the diffraction efficiency of transmissive gratings are now commonly in the range of 94%-97% [10][11][12]. Nevertheless, the efficiencies of standard four-pass grating compressors (reflective or transmissive) attained in practice are lower than the theoretically expected value of R DE 4 , where R DE is the diffraction efficiency of the used gratings.…”

“…Recent CPA systems based on reflective gratings are reported with compressor efficiencies ranging from 74% [13] up to 88%-95% [14] (depending on the power level of the laser system) in the best case. For transmissive gratings, reported compressor efficiencies typically range from 75% [11] to 84% [12].…”