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Raman-assisted broadband mode-locked laser.
Shota Kimura1, Shuntaro Tani1, Yohei Kobayashi2
1The Institute for Solid State Physics, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba, 277-8581, Japan.
Scientific Reports
|March 8, 2019
Summary
Researchers developed a new spectral broadening technique using stimulated Raman scattering to shorten femtosecond laser pulses. This method overcomes laser crystal bandwidth limitations, achieving 22 fs pulse durations.
Area of Science:
- Ultrafast optics and laser physics
- Nonlinear optics and spectroscopy
Background:
- Femtosecond mode-locked lasers are limited by the emission bandwidth of laser crystals, restricting achievable pulse durations.
- Extensive research over five decades has focused on broadening the emission gain bandwidth of these lasers.
- Intracavity spectral broadening is essential to overcome current limitations in pulse duration.
Purpose of the Study:
- To propose and demonstrate a novel intracavity spectral broadening method using stimulated Raman scattering (SRS).
- To significantly shorten pulse durations from femtosecond mode-locked lasers by exceeding inherent emission bandwidth limitations.
Main Methods:
- Implementation of a new spectral broadening technique utilizing SRS within the laser cavity.
- Configuration of Kerr-lens mode-locked lasers using Yb:CaGdAlO4, Yb:KY(WO4)2, and Yb:Y2O3 gain media.
- Experimental measurement of spectral broadening and resulting pulse durations.
Main Results:
- Achieved significant spectral broadening exceeding the natural emission bandwidth of the laser crystals.
- Demonstrated substantial pulse shortening, with the Yb:CaGdAlO4 oscillator yielding pulses as short as 22 fs.
- The achieved 22 fs pulse duration represents a one-third reduction compared to unbroadened pulses.
Conclusions:
- Raman-assisted spectral broadening effectively bypasses the limitations imposed by the emission gain bandwidth of laser crystals.
- This novel method enables the generation of significantly shorter pulses from femtosecond mode-locked lasers.
- The findings offer a pathway to further advancements in ultrafast laser technology and applications.
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