Abstract
The possibilities and limitations of linear compression of positively chirped pulses in the negative-dispersion region of a step-index large mode-area single-mode optical fibre are investigated for the first time. Analytical formulae for critical values of radiation power are found, below which pedestal-free pulse compression is possible down to the Fourier limit. It is demonstrated that at radiation powers exceeding these critical values, there exists an optimal compressing fibre length, over which laser pulses reach the minimum of the time-bandwidth product, and beyond which irreversible pulse deformation occurs. The modelling results agree well with the experimental data.
Highlights
IntroductionOne of the most frequently used ways to generate ultra-short laser pulses is linear dispersion compression (by means of external dispersion elements) of pulses with nearly monotonic frequency chirp coupled out of a laser cavity or an optical amplifier
One of the most frequently used ways to generate ultra-short laser pulses is linear dispersion compression of pulses with nearly monotonic frequency chirp coupled out of a laser cavity or an optical amplifier
We explore for the first time both theoretically and experimentally possibilities and limitations of linear compression of positively chirped pulses in the negativedispersion region of a step-index single-mode optical fibre with core size of 25 μm, which is close to the physical limit for single-mode operation [22]
Summary
One of the most frequently used ways to generate ultra-short laser pulses is linear dispersion compression (by means of external dispersion elements) of pulses with nearly monotonic frequency chirp coupled out of a laser cavity or an optical amplifier. Within the spectral domain around 1.5 μm, linear temporal compression of positively chirped pulses may be done with a conventional single-mode optical fibre (for instance, SMF-28) having negative chromatic dispersion and close to linear group-velocity dispersion slope in this spectral range This possibility was earlier experimentally demonstrated using a singlemode optical fibre with a standard mode area [6,7,8,9,10,11,12]. We explore for the first time both theoretically and experimentally possibilities and limitations of linear compression of positively chirped pulses in the negativedispersion region of a step-index single-mode optical fibre with core size of 25 μm, which is close to the physical limit for single-mode operation [22] Interest in this type of temporal pulse compression stems from the fact that step-index LMA-fibre-based linear compressor complies with the concept of all-fibre configuration and may be welded to the output fibre of an all-fibre master oscillator or fibre amplifier. We discovered that at power levels exceeding the critical value, there exists an optimal fibre length over which laser pulses reach a minimum ( not the physically possible minimal value) of the time-bandwidth product (TBP), thereafter undergoing an irreversible deformation
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