Chenchun Ye

Graphene-based passively Q-switched dual-wavelength erbium-doped fiber laser

We demonstrate a compact Q-switched dual-wavelength erbium-doped fiber (EDF) laser based on graphene as a saturable absorber (SA). By optically driven deposition of graphene on a fiber core, the SA is constructed and inserted into a diode-pumped EDF laser cavity. Also benefiting from the strong third-order optical nonlinearity of graphene to suppress the mode competition of EDF, a stable dual-wavelength Q-switching operation has been achieved using a two-reflection peak fiber Bragg grating as the external cavity mirror. The Q-switched EDF laser has a low pump threshold of 6.5 mW at 974 nm and a wide range of pulse-repetition rate from 3.3 to 65.9 kHz. The pulse duration and the pulse energy have been characterized. This is, to the best of our knowledge, the first demonstration of a graphene-based Q-switched laser.

Evanescent-Light Deposition of Graphene Onto Tapered Fibers for Passive Q-Switch and Mode-Locker

We demonstrate the fabrication of graphene-deposited tapered fibers (GDTFs), which can be used as saturable absorbers (SAs) for pulsed lasers. The advantages of GDTF SAs include flexibility, all-fiber configuration, and high optical damage threshold. The fabrication process is based on the interaction of the evanescent field of a tapered fiber with graphene. By in situ monitoring the transmitted power, the deposition process can be controlled, and the GDTF with a desirable level of nonsaturable absorption loss can be fabricated. We also study the dynamic deposition process by employing different waist diameters of tapered fibers and the different deposition powers. The results show that the deposition time can be significantly shortened with stronger evanescent field by decreasing the taper diameter or increasing the deposition power. Furthermore, by exploiting the GDTF as an intracavity passive power modulating element, we demonstrate efficient Q-switched and mode-locked erbium-doped fiber lasers, respectively.

High-energy passively Q-switched 2 μm Tm 3+ -doped double-clad fiber laser using graphene-oxide-deposited fiber taper

We have demonstrated a high-energy Q-switched double-clad thulium-doped fiber laser (TDFL) using a graphene-oxide-deposited tapered fiber (GODTF) device as a saturable absorber operating at a wavelength of 2 μm for the first time. Because of the side-interaction of the graphene-oxide with the evanescent field on the taper waist, the GODTF devices have potential for offering high laser damage threshold. Using a 788 nm laser diode as the pump source, the TDFL generated stable single transverse mode Q-switched pulses with a single pulse energy of 6.71 μJ (corresponding to an average power of 302 mW) at a wavelength of 2032 nm. This is significantly higher than the highest pulse energy/average power from any rare-earth-doped fiber lasers employing a graphene or graphene-oxide based Q-switch so far. The demonstrated TDFL in this paper represents an encouraging step towards the practical applications of graphene or graphene-oxide based Q-switched 2 μm TDFLs.

Graphene-Induced Nonlinear Four-Wave-Mixing and Its Application to Multiwavelength Q-Switched Rare-Earth-Doped Fiber Lasers

We experimentally confirm that graphene within fiber laser cavities can generate four-wave-mixing (FWM) by observing the laser spectral broadening and the transition from the single-longitudinal-mode oscillation to multiple-longitudinal-mode one. Then, by simultaneously exploiting the graphene-induced nonlinear FWM and its super-broadband saturable absorption, we further achieve for the first time to the best of our knowledge, multiwavelength Q-switched Yb3+- or Er3+-doped fiber lasers at 1 μm and 1.5 μm wavebands, respectively. Simultaneous 23-wavelength Q-switching oscillation with a wavelength spacing of 0.2 nm is stably generated at 1.5 μm waveband. The multiwavelength Q-switched pulses have the minimum pulse duration of 2.5 μs, the maximum pulse energy of 72.5 nJ and a wide range of pulse-repetition-rate (PRR) from 2.8 to 63.0 kHz. At 1 μm waveband, we also obtain five-wavelength simultaneous lasing in Q-switching regime with the pulse duration of ~ 3 μs, pulse energy of 10.3 nJ and PRR between 39.8 and 56.2 kHz.

Multiwavelength Dissipative-Soliton Generation in Yb-Fiber Laser Using Graphene-Deposited Fiber-Taper

We propose and demonstrate multiwavelength dissipative soliton (DS) generation in an all-normal-dispersion ytterbium-doped fiber laser based on a graphene-deposited tapered fiber (GDTF) device. Due to the interaction of the graphene with the evanescent field on the taper, the GDTF device possesses the characteristics of both saturable absorption and polarizing effect. Therefore, this device not only initiates the mode-locking operation based on the saturable absorption, but also induces both the special spectral filtering and nonlinear polarization evolution for shaping pulses into DSs. Simultaneous triple-wavelength DS operation around 1035 nm is thus achieved with a pulse energy of 6.4 nJ and pulse duration of 74.6 ps. Moreover, the DS operation is very stable with an RF signal-to-noise ratio of 62.5 dB.

Graphene-Assisted Multiwavelength Erbium-Doped Fiber Ring Laser

We propose and experimentally demonstrate a stable multiwavelength erbium-doped fiber (EDF) ring laser based on four-wave-mixing of atomic few-layer graphene. The compact laser cavity consists of 3-m EDF, an optically deposited ultrathin graphene device, and a polarization-maintaining fiber Sagnac loop filter. The comparison between the ring laser cavity without and with the graphene device shows that the highly nonlinear graphene can be helpful to mitigate the mode competition of EDF laser and stabilize the multiwavelength oscillation. Under the assistance of the graphene device, power-equalized eleven-channel simultaneous lasing with a wavelength-spacing of 0.54 nm is achieved at room temperature. This laser has a very high extinction ratio up to 57 dB and a narrow linewidth per channel of less than 0.01 nm.

Multiwavelength Fiber Optical Parametric Oscillator

We demonstrate, for the first time to the best of our knowledge, a multiwavelength fiber ring laser using a continuous-wave dual-pump fiber optical parametric amplifier (FOPA) as gain medium. In the ring cavity, two high-power pumps are injected into a spool of 1-km highly nonlinear dispersion-shifted fiber to generate the parametric gain, and a superimposed chirped fiber Bragg grating is used as the comb-like filter. Benefiting from the high and flat gain of the dual-pump FOPA, seven lasing lines around 1.55 mum with wavelength spacing of 1 nm have been obtained. Each lasing line has a linewidth of as narrow as 20 pm and an extinction ratio of > 30 dB. The proposed mechanism using a dual-pump FOPA as gain medium is a promising alternative for generating multiwavelength laser.

Stable and spacing-adjustable multiwavelength Raman fiber laser based on mixed- cascaded phosphosilicate fiber Raman linear cavity

A novel multiwavelength Raman fiber laser based on the mixed-cascaded Stokes effects of phosphosilicate fiber is proposed and demonstrated experimentally. By using stimulated Raman scattering of both P(2)O(5) and SiO(2) along 1 km phosphosilicate fiber pumped with a 1064 nm double-clad fiber laser, the mixed-cascaded Raman linear cavity is formed by a pair of fiber Bragg gratings at 1239 nm, a polarization-maintaining fiber (PMF) Sagnac loop filter, and a conventional optical loop mirror. Up to 15-wavelength stable oscillations around 1320 nm are obtained with a wavelength spacing of 0.44 nm and power nonuniformity of less than 4 dB. By changing the length of the PMF in the Sagnac loop filter from 10 to 5.5 m, the wavelength spacing is adjustable from 0.44 to 0.8 nm. The extinction ratio of the laser is more than 30 dB. Excellent stability is also observed with a peak power fluctuation of less than 0.8 dB in 1 h.

Fiber-optic parametric amplifier and oscillator based on intracavity parametric pump technique

A cost-effective fiber optical parametric amplifier (FOPA) based on the laser intracavity pump technique has been proposed and demonstrated experimentally. The parametric process is realized by inserting a 1 km highly nonlinear dispersion-shifted fiber (HNL-DSF) into a fiber ring-laser cavity that consists of a high-power erbium-doped fiber (EDF) amplifier and two highly reflective fiber Bragg gratings. Compared with the conventional parametric pump schemes, the proposed pumping technique is free from a tunable semiconductor laser as the pump source and also the pump phase modulation. When the oscillating power of 530 mW in the EDF laser cavity is achieved to pump the HNL-DSF, a peak parametric gain of 27.5 dB and a net gain over 45 nm are obtained. Moreover, a widely tunable fiber-optic parametric oscillator is further developed using the FOPA as a gain medium.

Stable and wideband L-band erbium superfluorescent fiber source using improved bidirectional pumping configuration

We have proposed and demonstrated a wideband and wavelength stable L-band erbium-doped superfluorescent fiber source (SFS) using an improved double-pass bi-directional (DP-BD) pumping configuration with a segment of un-pumped fiber. The effects of the fiber length and pump power arrangements on the output characteristics of the L-band SFS are examined. Simulations and experiments show that the output characteristics of the L-band SFS are significantly improved by using an un-pumped fiber in the DP-BD pumping configuration. This designed configuration allows a wavelength stable L-band SFS operation with a broadening bandwidth of 52.6nm, an enhanced pumping efficiency of 47.5%, and a mean wavelength of 1580.42nm.