Chuanfei Yao

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.

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.

Self-Q-switching behavior of erbium-doped tellurite microstructured fiber lasers

We reported self-Q-switching behavior of erbium-doped tellurite microstructured fiber (EDTMF) lasers and further demonstrated a self-Q-switched EDTMF laser with a high repetition rate of more than 1 MHz. A 14 cm EDTMF was used as the gain medium. Upon a pump power of ∼705 mW at 1480 nm, output pulses with a lasing wavelength of ∼1558 nm, a repetition rate of ∼1.14 MHz, and a pulse width of ∼282 ns were generated from the fiber by employing a linear cavity. The maximum output power was ∼316 mW and the slope efficiency was about 72.6% before the saturation of the laser power. Moreover, the influence of the fiber length on laser performances was investigated. The results showed that self-Q-switching behavior in our experiments was caused by the re-absorption originated from the ineffectively pumped part of the active fiber.

Supercontinuum generation from 437 to 2850 nm in a tapered fluorotellurite microstructured fiber

We demonstrated supercontinuum (SC) generation in a tapered fluorotellurite microstructured fiber (MF) with a sub-micrometer core diameter. Fluorotellurite MFs based on TeO2–BaF2–Y2O3 glasses were fabricated by using a rod-in-tube method and a tapered fluorotellurite MF with a minimum core diameter of ~0.65 µm was prepared by employing a tapering system. A 1560 nm femtosecond fiber laser was used as the pumping source. With increasing the peak power of the launched pump laser to ~11 kW, SC light expanding from 437 to 2850 nm was generated in the tapered fluorotellurite MF. In addition, relatively strong blue-shifted dispersive wave at ~489 nm was also observed from the tapered fluorotellurite MF.

Mid-infrared dispersive waves generation in a birefringent fluorotellurite microstructured fiber

Tunable mid-infrared dispersive waves are generated in a birefringent fluorotellurite microstructured fiber (FTMF) pumped by a 1560 nm femtosecond fiber laser. The FTMF have two zero-dispersion wavelengths (ZDWs) for each polarization axis. The second ZDWs for the fast and slow axes of the FTMF are 2224 and 2042 nm, respectively. As the pump laser is polarized along the fast (or slow) axis of the FTMF, tunable mid-infrared dispersive waves from 2680 to 2725 nm (or from 2260 to 2400 nm) are generated in the FTMF when the Raman soliton meets the second zero-dispersion wavelength of the fast (or slow) axis with increasing the pump power. Our results show that the designed FTMFs are promising nonlinear media for generating tunable mid-infrared light sources.

Amplification of wavelength-shifting soliton in active photonic crystal fibers

We demonstrate the amplification of a wavelength-shifting soliton in an active photonic crystal fiber (PCF). When a redshifting soliton experiences optical gain in a certain spectral range in the active PCF, in addition to its amplification, the redshifting speed of the soliton is increased dramatically and the corresponding pulse width of the soliton can also be reduced down dramatically. The dramatical increase in the redshifting speed is due to the amplification and large pulse compression. Large pulse compression arises because of the self-reinforcing feature of the fundamental soliton during amplification. Furthermore, gain-induced deceleration of the optical soliton causes the collision between the soliton and its corresponding dispersive wave and the generation of the temporal analog of reflection of optical beams. Our experimental results coincided with the simulated results partly.

Enhancement of phase-matched third harmonic generation via soliton self-frequency shift cancellation in a fluorotellurite microstructured fiber

We report the enhancement of phase-matched third harmonic generation (THG) via soliton self-frequency shift cancellation (SSFSC) in a fluorotellurite microstructured fiber (FTMF) pumped by a 1560 nm femtosecond fiber laser. The FTMF has two zero-dispersion wavelengths of 891 and 2012 nm for its slow axis. As the pump laser is polarized along the slow axis of the FTMF, phase matched THG at 629 nm is observed in the FTMF when the Raman soliton red-shifts to 1913 nm and the effective index at 1913 nm for the fundamental propagation mode matches with that at 629 nm for the high order propagation mode for a pump power of ∼25.2 mW. Interestingly, the THG at 629 nm is enhanced very much when the Raman soliton meets the second zero-dispersion wavelength of the slow axis and further SSFSC occurs with increasing the pump power. Such an enhancement is due to the unchanged operating wavelength of the Raman soliton with an increase in the pump power when SSFSC occurs and the resulting increase in the interaction lengt...

4.5 W supercontinuum generation from 1017 to 3438 nm in an all-solid fluorotellurite fiber

All-solid fluorotellurite fibers are fabricated by using a rod-in-tube method. The core and cladding materials are TeO2-BaF2-Y2O3 (TBY) and AlF3-based glasses, respectively. Since the refractive index (∼1.46) of AlF3-based glass is much lower than that (∼1.84) of TBY glass, the zero-dispersion-wavelength of the fabricated fiber can be tuned from 2145 to 1507 nm by varying the fiber core diameter from 50 to 3 μm. By using a 0.6 m long all-solid fluorotellurite fiber with a core diameter of ∼7 μm as the nonlinear medium and a 2 μm femtosecond fiber laser as the pump source, 4.5 W supercontinuum (SC) generation from 1017 to 3438 nm is obtained for a launched pump power of ∼10.48 W. The corresponding optical-to-optical conversion efficiency is about 42.9%. In addition, no any damage of the fluorotellurite fiber is observed during the operation of the above SC light source. Our results show that all-solid fluorotellurite fibers are promising nonlinear media for constructing high power mid-infrared SC light sou...