Abstract
We demonstrate highly efficient pulse stretching in Er(3+)-doped femtosecond mode-locked fiber lasers by tailoring cavity dispersion using an intracavity short-pass edge filter. The cavity dispersion is preset at around zero to obtain the shortest pulsewidth. When the cutoff wavelength of the short-pass edge filter is thermo-optically tuned to overlap the constituting spectral components of mode-locked pulses, large negative waveguide dispersion is introduced by the steep cutoff slope and the total cavity dispersion is moved to normal dispersion regime to broaden the pulsewidth. The time-bandwidth product of the mode-locked pulse increases with the decreasing temperature at the optical liquid surrounding the short-pass edge filter. Pulse stretch ratio of 3.53 (623.8 fs/176.8 fs) can be efficiently achieved under a temperature variation of 4 °C.
Highlights
Femtosecond mode-locked fiber lasers (FMLLs) have played important roles in optical coherence tomography imaging, supercontinuum generation, precision sensing, micro/nanomachining, micro/nano-surgery, time resolved spectroscopy, chemical/biological reaction triggering/monitoring, and high speed fiber-optic communications [1,2]
We demonstrate highly efficient pulse stretching in Er3+-doped femtosecond mode-locked fiber lasers by tailoring cavity dispersion using an intracavity short-pass edge filter
When the cutoff wavelength of the short-pass edge filter is thermo-optically tuned to overlap the constituting spectral components of mode-locked pulses, large negative waveguide dispersion is introduced by the steep cutoff slope and the total cavity dispersion is moved to normal dispersion regime to broaden the pulsewidth
Summary
Femtosecond mode-locked fiber lasers (FMLLs) have played important roles in optical coherence tomography imaging, supercontinuum generation, precision sensing, micro/nanomachining, micro/nano-surgery, time resolved spectroscopy, chemical/biological reaction triggering/monitoring, and high speed fiber-optic communications [1,2]. The pulse can be stretched from 176.8fs to 623.8fs (total pulsewidth stretching of 447fs) under a temperature variation of 4°C (from 36°C to 32°C) at the SPEF This high efficient pulse-stretching scheme based on tunable waveguide dispersion is easier than changing the corresponding fiber length in laser cavity. It could be promising for the high power stretched-pulse additive mode-locking lasers since the longer pulse duration, compared with the shorter pulse duration in soliton laser, can support much higher pulse energies before the Kerr nonlinearity is growing strong to cause multi-pulsing instability [16] or to damage the host glass material
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