Zhixu Jia

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.

Gold nanorod saturable absorber for passive mode-locking at 1 μm wavelength

Gold nanorods (GNRs) were used as a saturable absorber (SA) for passive mode-locking at 1 μm wavelength. The GNR-SA film was fabricated by mixing GNRs with sodium carboxymethylcellulose. The longitudinal surface plasmon resonance absorption of GNRs was used to induce mode-locking. By using the GNR-SA film, stable passive mode-locking at 1039 nm was experimentally demonstrated in an ytterbium-doped fiber laser cavity pumped by a 980 nm laser diode. The laser produced ~440 ps pulses with a repetition rate of 36.6 MHz and an average output power of ~1.25 mW for a pump power of ~82 mW.

Holmium-doped fluorotellurite microstructured fibers for 2.1 μm lasing

Holmium (Ho3+)-doped fluorotellurite microstructured fibers based on TeO2-BaF2-Y2O3 glasses are fabricated by using a rod-in-tube method. By using a 1.992 μm fiber laser as the pump source, lasing at 2.077 μm is obtained from a 27 cm long Ho3+-doped fluorotellurite microstructured fiber. The maximum unsaturated power is about 161 mW and the corresponding slope efficiency is up to 67.4%. The influence of fiber length on lasing at 2.1 μm is also investigated. Our results show that Ho3+-doped fluorotellurite microstructured fibers are promising gain media for 2.1 μm laser applications.

Tapered fluorotellurite microstructured fibers for broadband supercontinuum generation

Fluorotellurite microstructured fibers (MFs) based on TeO2-BaF2-Y2O3 glasses are fabricated by using a rod-in-tube method. Tapered fluorotellurite MFs with varied transition region lengths are prepared by employing an elongation machine. By using a tapered fluorotellurite MF with a transition region length of ∼3.3  cm as the nonlinear medium and a 1560 nm femtosecond fiber laser as the pump source, broadband supercontinuum generation covering from 470 to 2770 nm is obtained. The effects of the transition region length of the tapered fluorotellurite MF on supercontinuum generation are also investigated. Our results show that tapered fluorotellurite MFs are promising nonlinear media for generating broadband supercontinuum light expanding from visible to mid-infrared spectral region.

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.

All-fiber widely tunable mode-locked thulium-doped laser using a curvature multimode interference filter

We demonstrated a widely tunable mode-locked thulium doped fiber laser (TDFL) by using a homemade multimode interference filter (MMIF). The MMIF had a structure of single mode fiber (SMF)-multimode fiber (MMF)-SMF and three main transmission peaks at 1901.2, 1957.2 and 2043.2 nm. By mechanically bending the MMIF, the three main transmission peaks were tuned in the range of 1860-2024 nm due to multimode interference effect. By inserting the MMIF into a passively mode-locked TDFL cavity pumped by a 1570 nm fiber laser, a tunable mode-locked TDFL with a tuning range of 1919.6-2014.9 nm was achieved by adjusting the MMIF. To the best of our knowledge, such a tunable range is the largest among all-fiber tunable mode-locked TDFLs.

Coherent supercontinuum generation from 1.4 to 4 .MU.m in a tapered fluorotellurite microstructured fiber pumped by a 1980 nm femtosecond fiber laser

Coherent supercontinuum light expanding from 1.4 to 4 μm is generated in a 4 cm long tapered fluorotellurite microstructured fiber (MF) pumped by a 1980 nm femtosecond fiber laser. The spectral broadening in the tapered fluorotellurite MF is caused by self-phase modulation, the Raman soliton, and red-shifted dispersive wave generation. Our results show that tapered fluorotellurite MFs are promising nonlinear medium for generating coherent broadband mid-infrared supercontinuum light.

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.

Optical waveguide amplifiers based on NaYF 4 : Er 3+ , Yb 3+ NPs-PMMA covalent-linking nanocomposites

NaYF4: Er3+, Yb3+ nanoparticles (NPs) were synthesized by using a high temperature thermal decomposition approach. Under a 980 nm laser excitation, intense emission at 1.53 μm from NaYF4: Er3+,Yb3+ NPs was obtained. NaYF4: Er3+, Yb3+ NPs-PMMA covalent-linking nanocomposite was prepared by copolymerization of the oleic acid-modified NaYF4: Er3+, Yb3+ NPs and methylmethacrylate(MMA). In this case, the doping mass concentration of NPs in the polymer matrix could be up to 1%, which is 10 times larger than previously published results. We constructed optical waveguide amplifiers with a structure of embedded waveguide using the NPs-PMMA nanocomposite as the core material. For an input signal power of 0.14 mW and a pump power of 400 mW, a relative optical gain of 7.6 dB was obtained at 1540 nm in a 15 mm-long waveguide.