Lihui Pang

70-fs mode-locked erbium-doped fiber laser with topological insulator.

Femtosecond optical pulses have applications in optical communication, astronomical frequency combs, and laser spectroscopy. Here, a hybrid mode-locked erbium-doped fiber (EDF) laser with topological insulator (TI) is proposed, for the first time to our best knowledge. The pulsed laser deposition (PLD) method is employed to fabricate the fiber-taper TI saturable absorber (TISA). By virtue of the fiber-taper TISA, the hybrid EDF laser is passively mode-locked using the nonlinear polarization evolution (NPE), and emits 70 fs pulses at 1542 nm, whose 3 dB spectral width is 63 nm with a repetition rate and transfer efficiency of 95.4 MHz and 14.12%, respectively. Our experiments indicate that the proposed hybrid mode-locked EDF lasers have better performance to achieve shorter pulses with higher power and lower mode-locking threshold in the future.

Generation of dark solitons in erbium-doped fiber lasers based Sb(2)Te(3) saturable absorbers.

Dark solitons, which have better stability in the presence of noise, have potential applications in optical communication and ultrafast optics. In this paper, the dark soliton formation in erbium-doped fiber lasers based Sb(2)Te(3) saturable absorber (SA) is first experimentally demonstrated. The Sb(2)Te(3) SA is fabricated by using the pulsed laser deposition method. The generated dark solitons are centered at the wavelength of 1530 nm and repetition rate of 94 MHz. Analytic solutions for dark solitons are also obtained theoretically.

Tungsten disulfide saturable absorbers for 67 fs mode-locked erbium-doped fiber lasers

In this paper, we demonstrate 67 fs pulse emitting with tungsten disulfide (WS2) in mode-locked erbium-doped fiber (EDF) lasers. Using the pulsed laser deposition method, WS2 is deposited on the surface of the tapered fiber to form the evanescent field. The fiber-taper WS2 saturable absorber (SA) with the large modulation depth is fabricated to support the ultrashort pulse generation. The influences of the WS2 SA are analyzed through contrastive experiments on fiber lasers with or without the WS2 SA. The pulse duration is measured to be 67 fs, which is the shortest pulse duration obtained in the mode-locked fiber lasers with two dimensional (2D) material SAs. Compared to graphene, topological insulator, and other transition metal dichalcogenides (TMDs) SAs, results in this paper indicate that the fiber-taper WS2 SA with large modulation depth is a more promising photonic device in mode-locked fiber lasers with the wide spectrum and ultrashort pulse duration.

Novel asymmetric representation method for solving the higher-order Ginzburg-Landau equation

In ultrafast optics, optical pulses are generated to be of shorter pulse duration, which has enormous significance to industrial applications and scientific research. The ultrashort pulse evolution in fiber lasers can be described by the higher-order Ginzburg-Landau (GL) equation. However, analytic soliton solutions for this equation have not been obtained by use of existing methods. In this paper, a novel method is proposed to deal with this equation. The analytic soliton solution is obtained for the first time, and is proved to be stable against amplitude perturbations. Through the split-step Fourier method, the bright soliton solution is studied numerically. The analytic results here may extend the integrable methods, and could be used to study soliton dynamics for some equations in other disciplines. It may also provide the other way to obtain two-soliton solutions for higher-order GL equations.

Nanosecond Hybrid Q-Switched Er-Doped Fiber Laser With WS 2 Saturable Absorber

We demonstrate a stable hybrid Q-switched Er-doped fiber (EDF) laser with WS2 as the saturable absorber (SA). The SA device is obtained by depositing WS2 on a tapered fiber using the pulsed laser deposition method. The modulation depth of the SA is 8.0%, the nonsaturable loss is 30%, and the saturation intensity is 200 MW/cm2. By combining the saturable absorption of fiber-taper WS2 and the effect of nonlinear polarization rotation, the Q-switched EDF laser is achieved with a pulse duration of 443 ns and average power of 43 mW. The repetition rate can be adjustable among 235-365 KHz. To our best knowledge, both pulse duration and output power are the best results among Q-switched EDF lasers with transition mental dichalcogenide materials like SAs. These results indicate that the proposed hybrid Q-switched EDF laser performs better to achieve shorter pulses with higher power in the future.

High-order solitons transmission in hollow-core photonic crystal fibers

Hollow-core photonic crystal fibers (HC-PCFs) can be used for the supercontinuum generation. Because the design of HC-PCFs is flexible, the dispersion and nonlinear effects is variable, and the pulses in HC-PCFs can show different transmission characteristics. In this paper, the transmission of high-order solitons in HC-PCFs is studied. Through adjusting the group-velocity dispersion and nonlinear effects of HC-PCFs, we present the different transmission of high-order solitons, and analyze their characteristics. Results are conducive to the applications of HC-PCFs in nonlinear optics and ultrafast optics.

Dynamic solitons for the perturbed derivative nonlinear Schrödinger equation in nonlinear optics

Dynamic solitons for a perturbed derivative nonlinear Schrodinger equation in nonlinear optics are presented for the first time in this paper. The analytic one-soliton solution for the perturbed derivative nonlinear Schrodinger equation is obtained with the Hirota method. The stable transmission soliton is observed and the influences of third-order dispersion and nonlinear coefficients are discussed. The characteristics and properties of solitons are analyzed and the stability analysis for the solitons is made. The salient features of the solitons reveal the possibility for the stable transmission of pulses in nonlinear optics.

Ultra-stability Yb-doped fiber optical frequency comb with 2 × 10^−18/s stability in-loop

We demonstrate a full control ultra-stability Yb-doped fiber optical frequency comb (OFC). The carrier-envelop offset frequency (fceo) and the repetition rate (fr) are locked with the standard phase locked loop (PLL) technique. The fceo is locked to the radio frequency (RF) synthesizer, and the Allan deviation is 1.2 × 10-17/s. The fr is locked to an ultra-stability continuous wave (CW) laser at 972 nm. The beat signal (fbeat) between the Yb-doped fiber OFC and CW laser is obtained with the signal to noise ratio (SNR) of 43 dB at 300 kHz resolution bandwidth (RBW). The time jitter of the fbeat signal is 278 as, which is integrated from 1 Hz to 10 MHz. The long-term stability is 575 μHz in 3 hours, and the corresponding Allan deviation is 2 × 10-18/s, which is the best stability result in Yb-doped fiber OFC. The linewidth is narrowed from 200 kHz to subhertz magnitude limited by the instrument resolution bandwidth.

Study on high coupling efficiency Er-doped fiber laser for femtosecond optical frequency comb

The femtosecond laser is crucial to the operation of the femtosecond optical frequency comb. In this paper, a passively mode-locked erbium-doped fiber laser is presented with 91.4 fs pulse width and 100.8 MHz repetition rate, making use of the nonlinear polarized evolution effect. Using a 976 nm pump laser diode, the average output power is 16 mW from the coupler and 27 mW from the polarization beam splitter at the pump power of 700 mW. The proposed fiber laser can offer excellent temporal purity in generated pulses with high power, and provide a robust source for fiber-based frequency combs and supercontinuum generation well suited for industrial applications.

Multiple refocusing in BK9 glass generated by a loosely focused high-intensity femtosecond pulse

Abstract. Multiple refocusing in BK9 glass induced by a loosely focused high-intensity femtosecond pulse is studied experimentally and numerically. Multiple refocusing and small filament are clearly observed in the sample irradiated by loosely focused 120 fs femtosecond laser pulses with high power, up to 500 times the self-focusing critical power. Up to five refocusing peaks are observed along the direction of the pulse propagation. The dependence of the intensity distribution of the plasma luminescence on the pulse energy is investigated.