An all-fiber dumbbell-shaped dual-amplifier mode-locked Er-doped laser that can function in dissipative soliton resonance(DSR)regime is demonstrated.A nonlinear optical loop mirror(NOLM)and a nonlinear amplifying loop mirror(NALM)are employed to initiate the mode-locking pulses.Unlike conventional single-amplifier structure,the output peak power of which remains unchanged when pump power is varied,the proposed structure allows its output peak power to be tuned by changing the pump power of the two amplifiers while the pulse duration is directly determined by the amplifier of nonlinear amplifying loop mirror.The entire distribution maps of peak power and pulse duration clearly demonstrate that the two amplifiers are related to each other,and they supply directly a guideline for designing tunable peak power DSR fiber laser.Pulse width can change from 800 ps to 2.6 ns and peak power varies from 13 W to 27 W.To the best of our knowledge,the peak power tunable DSR pulse is observed for the first time in dumbbell-shaped Er-doped all-fiber mode-locked lasers.
Generation of noise-like rectangular pulse was investigated systematically in an Er–Yb co-doped fiber laser based on an intra-cavity coupler with different coupling ratios.When the coupling ratio was 5/95,stable mode-locked pulses could be obtained with the pulse packet duration tunable from 4.86 ns to 80 ns.The repetition frequency was 1.186 MHz with the output spectrum centered at 1.6μm.The average output power and single pulse energy reached a record 1.43 W and1.21μJ,respectively.Pulse characteristics under different coupling ratios(5/95,10/90,20/80,30/70,40/60)were also presented and discussed.
Picosecond pulse pumped supercontinuum generation in photonic crystal fiber is investigated by performing a series of comparative experiments. The main purpose is to investigate the supercontinuum generation processes excited by a given pump source through the experimental study of some specific fibers. A 20-W all-fiber picosecond master oscillator-power amplifier (MOPA) laser is used to pump three different kinds of photonic crystal fibers for supercontinuum generation. Three diverse supercontinuum formation processes are observed to correspond to photonic crystal fibers with distinct dispersion properties. The experimental results are consistent with the relevant theoretical results. Based on the above analyses, a watt-level broadband white light supercontinuum source spanning from 500 nm to beyond 1700 nm is demonstrated by using a picosecond fiber laser in combination with the matched photonic crystal fiber. The limitation of the group velocity matching curve of the photonic crystal fiber is also discussed in the paper.
Theoretical and experimental research on the effect of initial chirp on near-infrared supercontinuum generation by a nanosecond pulse in a nonlinear fiber amplifier is carried out. The complex Ginzburg-Landau equation is used to simulate the propagation of the pulse in the fiber amplifier and the results show that pulses with negative initial chirp produce the widest supercontinuum and pulses with positive initial chirp produce the narrowest supercontinuum when the central wavelength of the pump lies in the normal dispersion region of the gain fiber. A self-made line width narrowing system is utilized to control the initial chirp of the nanosecond pump pulse and a four-stage master oscillator power amplifier configuration is adopted to produce a high power near-infrared suppercontinuum. The experimental results are in good agreement with simulations which can provide some guidance on further optimization of the system in future work.
We demonstrate efficient supercontinuum generation extending into mid-infrared spectral range by pumping a twomode As2S3 fiber in the normal dispersion regime. The As2S3 fiber is fusion spliced to the pigtail of a near-infrared supercontinuum pump source with ultra-low splicing loss of 0.125 dB, which enables a monolithic all-fiber mid-infrared supercontinuum source. By two-mode excitation and mixed-mode cascaded stimulated Raman scattering, a supercontinuum spanning from 1.8 μm to 4.2 μm is obtained. Over 70% of the supercontinuum power is converted to wavelengths beyond2.4 μm. This is the first experimental report with respect to the multimode mid-infrared supercontinuum generation in a step-index two-mode chalcogenide fiber.
Pumped by rectangular-shaped dissipative soliton resonance(DSR)pulses at 1030 nm,selective excitations of Raman Stokes lines of up to third order with extinction ratios of 8 d B and fifth order with extinction ratios of 4 dB are demonstrated experimentally.The rectangular DSR pulses are generated from a dual-amplifier ytterbium-doped figureof-eight mode-locked laser constructed using all 10μm-core-diameter large-mode-area fibers.By varying the two pump powers,the peak power of the output DSR pulses can be continuously tuned from 10 W to 100 W and from 30 W to200 W,respectively,for two different lengths of the nonlinear amplifying loop mirror inside the cavity.High-frequency components are found to correspond to parts of the pulse in the trailing edge when two bandpass filters are used to separate the propagated pulse.Consequently,it provides an all-fiber technique to achieve selective excitation of the Raman shift by adjusting the peak power of the DSR pulse.
