Pulse Propagation with Self-Phase Modulation in Nonlinear Chiral Fiber and Its Applications

From Maxwell＇s equations and Post＇s formalism, a generalized chiral nonlinear Schr6dinger equation （CNLSE） is obtained for the nonlinear chiral fiber. This equation governs light transmission through a dispersive nonlinear chiral fiber with joint action of chirality in linear and nonlinear ways. The generalized CNLSE shows a modu- lation of chirality to the effect of attenuation and nonlinearity compared with the case for a conventional fiber. Simulations based on the split-step beam propagation method reveal the role of nonlinearity with cooperation to chirality playing in the pulse evolution. By adjusting its strength the role of chirality in forming solitons is demonstrated for a given circularly polarized component. The application of nonlinear optical rotation is also discussed in an all-optical switch.

Post-compression of high-energy,sub-picosecond laser pulses

The post-compression technique based on self-phase modulation of high-energy pulses leads to an increase in achievable peak power and intensity.Typically,the pulses considered in experiments have been less than 100 fs in duration.Here,the method is applied to the ELFIE laser system at the LULI facility,for a pulse of 7 J energy and an initial measured duration of 350 fs.A 5-mm-thick fused silica window and a 2 mm cyclic-olefin polymer were used as optical nonlinear materials.The 9 cm diameter beam was spectrally broadened to a bandwidth corresponding to 124 fs Fourier-limited pulse duration,and then it was partly post-compressed to 200 fs.After measuring the spatial spectra of the beam fluence,a uniform gain factor of 4 increase in the fluctuations over the studied range of frequencies is observed,due to small-scale self-focusing.

Dynamics of Spatial Dark Solitons Trapped in the Media with Gain and TPA

The propagation of dark solitons in nonlinear media that include gain and Joss described by a nonlinear Schroedinger equation is investigated. Based on the direct approach of perturbation theorv, the width, height and other related quantities of dark solitons are obtained. It is shown that stationarv propagation of dark solitons is found to be possible in the presence of both gain and absorption. The results obtained by means of our analytic method are in excellent agreement with numerical simulations. Our results are helpful for the research into the optical soliton transmission system.

Nonlinear chirped pulse amplification for a 100-W-class GHz femtosecond all-fiber laser system at 1.5μm

In this work,we present a high-power,high-repetition-rate,all-fiber femtosecond laser system operating at 1.5μm.This all-fiber laser system can deliver femtosecond pulses at a fundamental repetition rate of 10.6 GHz with an average output power of 106.4 W–the highest average power reported so far from an all-fiber femtosecond laser at 1.5μm,to the best of our knowledge.By utilizing the soliton-effect-based pulse compression effect with optimized pre-chirping dispersion,the amplified pulses are compressed to 239 fs in an all-fiber configuration.Empowered by such a high-power ultrafast fiber laser system,we further explore the nonlinear interaction among transverse modes LP01,LP11 and LP21 that are expected to potentially exist in fiber laser systems using large-mode-area fibers.The intermodal modulational instability is theoretically investigated and subsequently identified in our experiments.Such a high-power all-fiber ultrafast laser without bulky free-space optics is anticipated to be a promising laser source for applications that specifically require compact and robust operation.

Short mid-infrared watt-level all-fiber nonlinear pulse compressor above 100-MHz pulse repetition rate

We firstly report a 2-μm all-fiber nonlinear pulse compressor based on two pieces of normal dispersion fiber(NDF),which enables a high-power scaling ability of watt-level and a high pulse compression ratio of 13.7.With the NDFbased all-fiber nonlinear pulse compressor,the 450-fs laser pulses with a repetition rate of 101.4 MHz are compressed to 35.1 fs,corresponding to a 5.2 optical oscillation cycle at the 2-μm wavelength region.The output average power reaches 1.28 W,which is believed to be the highest value never achieved from the previous 2-μm all-fiber nonlinear pulse compressors with a high pulse repetition rate above 100 MHz.The dynamic evolution of the ultrafast pulse inside the all-fiber nonlinear pulse compressor is numerically analyzed,matching well with the experimental results.

Dark pulse emission in nonlinear polarization rotation-based multiwavelength mode-locked erbium-doped fiber laser

We experimentally show dark pulse generation in all-normal dispersion multiwavelength erbium-doped fiber laser（EDFL） with a long cavity of figure-of-eight configuration. The EDFL generates a stable multiwavelength laser with 0.47 nm spacing at 24 m W threshold pump power, while the number of lines obtained increases with the pump power. A dark pulse emission is observed as the pump power is increased above 137 m W, with fundamental repetition rate of 29 k Hz and pulse width of 2.7 μs. It is observed that the dark pulse train can be shifted to second-, third-, and fourth-order harmonic dark pulses by carefully adjusting the polarization controller. For the fundamental dark pulse, the maximum pulse energy of 32.4 n J is obtained at pump power of 146.0 mW.

Few-layer MoS2-deposited microfiber as highly nonlinear photonic device for pulse shaping in a fiber laser [Invited]

Two-dimensional（2D） materials have emerged as attractive mediums for fabricating versatile optoelectronic devices. Recently, few-layer molybdenum disulfide（MoS2）, as a shining 2D material, has been discovered to possess both the saturable absorption effect and large nonlinear refractive index. Herein, taking advantage of the unique nonlinear optical properties of MoS2, we fabricated a highly nonlinear saturable absorption photonic device by depositing the few-layer MoS2 onto the microfiber. With the proposed MoS2 photonic device, apart from the conventional soliton patterns, the mode-locked pulses could be shaped into some new soliton patterns, namely,multiple soliton molecules, localized chaotic multipulses, and double-scale soliton clusters. Our findings indicate that the few-layer MoS2-deposited microfiber could operate as a promising highlynonlinear photonic device for the related nonlinear optics applications.

A New Jacobi Elliptic Function Expansion Method for Solving a Nonlinear PDE Describing Pulse Narrowing Nonlinear Transmission Lines

In this article, we apply the first elliptic function equation to find a new kind of solutions of nonlinear partial differential equations （PDEs） based on the ho- mogeneous balance method, the Jacobi elliptic expansion method and the auxiliary equation method. New exact solutions to the Jacobi elliptic functions of a nonlinear PDE describing pulse narrowing nonlinear transmission lines are given with the aid of computer program, e.g. Maple or Mathematica. Based on Kirchhoff＇s current law and Kirchhoff＇s voltage law, the given nonlinear PDE has been derived and can be reduced to a nonlinear ordinary differential equation （ODE） using a simple transformation. The given method in this article is straightforward and concise, and can be applied to other nonlinear PDEs in mathematical physics. Further results may be obtained.

Noise-like pulse generation from a thulium-doped fiber laser using nonlinear polarization rotation with different net anomalous dispersion

A mode-locked thulium-doped fiber laser(TDFL) based on nonlinear polarization rotation(NPR) with different net anomalous dispersion is demonstrated. When the cavity dispersion is-1.425 ps^2, the noise-like(NL) pulse with coherence spike width of 406 fs and pulse energy of 12.342 nJ is generated at a center wavelength of 2003.2 nm with 3 dB spectral bandwidth of 23.20 nm. In the experimental period of 400 min, the 3 dB spectral bandwidth variation, the output power fluctuation, and the central wavelength shift are less than 0.06 nm, 0.04 d B, and0.4 nm, respectively, indicating that the NPR-based TDFL operating in the NL regime holds good long-term stability.

Nonlinear Pulse Compression and Reshaping Using Cross-Phase Modulation in a Dispersion-Shifted Fiber

Nonlinear pulse compression has been demonstrated by cross-phase modulation in a dispersion-shifted fiber. The output is obtained from filtering of the broadened optical spectrum and a pulse width reduction from 61 to 28 ps is achieved.

Intra-Channel Nonlinear Effect on Optical PPM Pulse Transmission

PPM encoded Gaussian pulse sequence shows more immunity than non-PPM schemes on optical fiber intra-channel nonlinearity and demonstrated by a numerical study of IXPM and IFWM effects deploying on 100Gb/s single channelsystem.

Spectral broadening for multi-Joule pulse compression in the APOLLON Long Focal Area facility

Spectral-broadening of the APOLLON PW-class laser pulses using a thin-film compression technique within the longfocal-area interaction chamber of the APOLLON laser facility is reported,demonstrating the delivery of the full energy pulse to the target interaction area.The laser pulse at 7 J passing through large aperture,thin glass wafers is spectrally broadened to a bandwidth that is compatible with a 15-fs pulse,indicating also the possibility to achieve sub-10-fs pulses using 14 J.Placing the post-compressor near the interaction makes for an economical method to produce the shortest pulses by limiting the need for high damage,broadband optics close to the final target rather than throughout the entire laser transport system.