Abstract
We demonstrate an all-fiber mode locked laser based on hybrid structure of multimode fiber saturable absorber (SA) that can realize both conventional soliton and stretched-pulse states. Stable 16.44 MHz conventional soliton pulses are achieved by injecting 80 mW threshold pump power. By increasing the incident pump power to 420 mW, the laser evolves from soliton operation into stretched-pulse mode locking state. 310 fs stretched-pulse are obtained with the same repetition rate as the soliton pulses. The center wavelength and its 3 dB spectrum bandwidth are 1603 nm and 14.2 nm, respectively. For the first time, we experimentally confirm transition between conventional soliton and stretched-pulse in 1.5 μm mode-locked fiber laser by introducing multimode optical fiber SA. Moreover, the maximum single pulse energy of nearly 1 nJ is achieved. Such all-fiber mode-locked lasers based on hybrid structure of multimode fiber are attractive for practical applications without damage and the limitation of life time.
Highlights
Ultrafast pulse fiber lasers have attracted extensive attentions due to their merits of compactness, high stability and reliability[1]
The ratio of LG00 mode-field diameters coupling to graded-index multimode fiber (GIMMF) and the excited ones is adjustable
By raising injected pump power to 80 mW, soliton pulses with 1.0 ps pulse width are obtained at 16.44 MHz fundamental repetition rate
Summary
Ultrafast pulse fiber lasers have attracted extensive attentions due to their merits of compactness, high stability and reliability[1]. The merit of soliton pulses is that its shape is maintained during transmission, the information transmitted is more accurate These soliton fiber lasers are at the core of optical communication, sensing, optical frequency comb, nonlinear optics and so forth. Compared with mode-locked soliton pulses, wider spectrum bandwidths and shorter pulse durations can be realized These stretched-pulse fiber lasers with high output pulse energy have a wide range of applications in the domains of optical amplification, spectroscopy and optical frequency doubling. Contributed by the GIMMF, the laser can work at soliton pulse or stretched-pulse mode locking state via changing the pump power. It is attractive to operate this high energy ultrafast soliton and stretched-pulse switchable mode locking fiber laser for a range of applications in practice
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