Lai Liu

Passively Q-switching induced by gold nanocrystals

Passive Q-switching was experimentally demonstrated in an erbium-doped fiber laser (EDFL) by using gold nanocrystals (GNCs). The GNCs were mixed with sodium carboxymethylcellulose (NaCMC) to form GNCs-NaCMC films. The films exhibited a broad absorption band in the range of 400–1750 nm. By placing the GNCs-NaCMC film in an EDFL cavity pumped by a 980 nm laser diode, stable passive Q-switching was achieved for a threshold pump power of ∼30 mW, and 3.2 μs pulses at 1560 nm with a repetition rate of 24.2 kHz were obtained for a pump power of ∼125 mW.

Passively mode-locking induced by gold nanorods in erbium-doped fiber lasers

We demonstrated a passively mode-locked erbium-doped fiber laser by using gold nanorods as a saturable absorber. The gold nanorods (GNRs) were mixed with sodium carboxymethylcellulose (NaCMC) to form GNRs-NaCMC films. By inserting one of the GNRs-NaCMC films into an EDFL cavity pumped by a 980 nm laser diode, stable passively mode-locking was achieved with a threshold pump power of ∼54 mW, and 12 ps pulses at 1561 nm with a repetition rate of 34.7 MHz and a maximum average power of ∼2.05 mW were obtained for a pump power of ∼62 mW.

Gold nanorods as saturable absorbers for all-fiber passively Q-switched erbium-doped fiber laser

A new type of saturable absorber (SA) based on gold nanorods (GNRs) for all-fiber passively Q-switched erbium-doped fiber laser (EDFL) is realized experimentally. The longitudinal surface plasmon resonance (SPR) absorption of GNRs is used to induce Q-switching. By inserting the GNRs SA in an EDFL cavity pumped by a 980 nm laser diode, stable passive Q-switching is achieved with a threshold pump power of ~27 mW, and 4.8 μs pulses at 1560 nm with a repetition rate of 39.9 kHz are obtained for a pump power of ~275 mW.

Coherent mid-infrared supercontinuum generation in all-solid chalcogenide microstructured fibers with all-normal dispersion

We report the coherent mid-infrared supercontinuum generation in an all-solid chalcogenide microstructured fiber with all-normal dispersion. The chalcogenide microstructured fiber is a four-hole structure with core material of AsSe2 and air holes that are replaced by As2S5 glass rods. Coherent mid-infrared supercontinuum light extended to 3.3 μm is generated in a 2 cm long chalcogenide microstructured fiber pumped by a 2.7 μm laser.

Numerical investigation of mid-infrared supercontinuum generation up to 5 μm in single mode fluoride fiber.

We numerically investigate mid-infrared supercontinuum generation in single mode fluoride fiber pumped by 1.56 μm picosecond fiber lasers. To get high energy conversion efficiency in mid-infrared region, the ratio of power generated in 2.5 ~5 μm range to the total input power for supercontinuum generation is optimized by varying the pulse width, peak power and fiber length. The long wavelength edge of the supercontinuum spectrum can be extended to 4.8 μm in a 100 cm long fluoride fiber pumped by a 1.56 μm fiber laser with a pulse width of 4 ps and a peak power of 100 kW, and the corresponding ratio of power generated in 2.5 ~5 μm range to the total input power is about 44.6%. The spectral broadening is mainly caused by self-phase modulation, stimulated Raman scattering and four-wave mixing. The simulated results show that high average power supercontinuum light source in 2.5 ~5 μm range could be obtained in fluoride fibers pumped by 1.56 μm picosecond fiber lasers.

Supercontinuum generation and lasing in thulium doped tellurite microstructured fibers

We report supercontinuum (SC) generation in Tm3+ doped tellurite microstructured fibers (TMFs) pumped by a 1.56 μm femtosecond fiber laser. In comparison with SC generation in undoped TMFs, the SC spectral bandwidth and the spectral intensity in the wavelength region of >1.9 μm are evidently enlarged in Tm3+ doped TMFs owing to the contribution of the combination of linear gain of Tm3+ and the nonlinear optical effects to spectral broadening. Furthermore, a transition from SC generation to 1.887 μm lasing (Tm3+: 3F4→3H6 transition) is observed in Tm3+ doped TMFs by varying the pulse width of the pump laser from 0.29 to 3.47 ps, which gives the evidence of the above spectral broadening mechanism. This is the first observation of the transition from SC generation to lasing, to the best of our knowledge.

Fabrication of all-solid AsSe2–As2S5 microstructured optical fiber with two zero-dispersion wavelengths for generation of mid-infrared dispersive waves

We design and fabricate an all-solid chalcogenide microstructured optical fiber (MOF) with four rods in the cladding, in order to generate mid-infrared (MIR) dispersive waves (DWs). The high-index background is made of AsSe2 glass, and the four low-index rods are made of As2S5 glass. This MOF has two zero-dispersive wavelengths: ~3,720 and 4,230 nm. The propagation loss is ~1.9 dB/m at 2,000 nm, and the nonlinear coefficient is ~4 × 103 km−1 W−1 at 3,000 nm. Using a pulse of ~80 MHz and ~200 fs emitted from an optical parametric oscillator as the pump source, the resulting MIR DWs are investigated at different pump wavelengths.

Broadband amplification and highly efficient lasing in erbium-doped tellurite microstructured fibers

We report broadband amplification and highly efficient lasing in erbium-doped tellurite microstructured fibers. A broad positive net gain bandwidth of 113 nm (1524-1637 nm) is obtained in a 17 cm long erbium-doped tellurite microstructured fiber upon a pump power of 94 mW at 1480 nm. An all-fiber lasing at 1561 nm with maximum unsaturated power of 140 mW and slope efficiency of 53.7% is achieved from the fiber by employing a linear cavity. In addition, the influence of the fiber length on amplification and lasing is investigated and laser oscillation at 1535 nm is realized in a 4.3 cm long fiber.

Coherence property of mid-infrared supercontinuum generation in tapered chalcogenide fibers with different structures

We have numerically investigated the coherence property of mid-infrared supercontinuum generation in tapered step-index chalcogenide fibers with different structures. The pump source is a 4 μm laser with pulse width of 500 fs and peak power of 1 kW. The length ratio is the ratio of transition region length near the laser input to the other transition region length near the output. We calculate the bandwidth and the spectrally averaged coherence of the supercontinuum spectra generated in fibers with different length ratios under the same pumping condition. Numerical results show that as the length ratio increases, the bandwidth decreases from 4.84 μm to 4.11 μm while the spectrally averaged coherence increases from 0.53 to 0.9 and then jitters near the maximum. The length ratio within 1–1.5 is preferable to keep a balance between bandwidth and coherence.

Numerical investigation of mid-infrared Raman soliton source generation in endless single mode fluoride fibers

We numerically investigate Raman soliton generation in a fluoride photonic crystal fiber (PCF) pumped by 1.93 μm femtosecond fiber lasers in order to get widely tunable laser source in the mid-infrared region. The simulated results show that a continuously tunable range (1.93 ∼ 3.95 μm) over 2000 nm is achieved in 1-m-long fluoride PCF pumped by a 1.93 μm femtosecond fiber laser with a pulse width of 200 fs. The power conversion efficiency is also calculated and the maximum efficiency can be up to 84.27%.