Intracavity ranging enabled by a single-frequency self-sweeping fiber laser with a few-longitudinal-mode range.

Self-sweeping fiber lasers have carved out numerous applications such as spectral detection, fiber sensor, etc. In this work, we propose a single-frequency self-sweeping fiber laser with a few-longitudinal-mode range by employing a length of space path to achieve the function of intracavity ranging. Different from the previous design, a fiber collimator and mirror are utilized to act as the reflector, and the distance between them can be adjusted flexibly.

Light localization in defective periodic photonic moiré-like lattices.

Photonic moiré-like lattices, a readily accessible platform for realizing the spatial localization of light, attract intensive attention due to their unique flatband characteristics. In this paper, a periodic moiré-like lattice with embedded defects is proposed theoretically, and the linear propagation of the probe beam in such a system is investigated intensively. The results show that the positions of defects in periodic moiré-like lattices depend on the sublattice rotation angle.

Monitoring local temperature and longitudinal strain along a nonuniform AsSe-PMMA tapered fiber by Brillouin gain-profile tracing.

The local temperature and longitudinal strain at spatial resolution of 0.5% of the pulse-width equivalent length along a nonuniform AsSe-PMMA tapered fiber is investigated by a Brillouin gain-profile tracing method. This scheme uses a 20 ns pump pulse with the pulse-width equivalent length longer than the fiber under test (FUT) of 50 cm nonuniform AsSe-PMMA tapered fiber.

Non-Hermitian mode-locking synthesized by parity-time and anti-parity-time symmetric modulations.

We study the pulse characteristics in a laser mode-locked by active modulators with non-Hermitian driven signals. The signal assembles a parity-time ( ) symmetric and an anti-parity-time ( ) symmetric function with fundamental and harmonic frequencies, respectively, inducing the complex coupling between modes in the frequency domain. A one-dimensional synthetic lattice is used to analyze the spectral mode coupling.

A Review of Sensitivity Enhancement in Interferometer-Based Fiber Sensors.

Optical fiber sensors based on an interferometer structure play a significant role in monitoring physical, chemical, and biological parameters in natural environments. However, sensors with high-sensitivity measurement still present their own challenges. This paper deduces and summarizes the methods of sensitivity enhancement in interferometer based fiber optical sensors, including the derivation of the sensing principles, key characteristics, and recently-reported applications.

Generation of gradient photonic moiré lattice fields.

We designed and generated gradient photonic moiré lattice fields comprising three varying periodic moiré wavefields. Because of the common twisted angles between periodic triangular and hexagonal moiré wavefields, gradient patterns can be easily obtained through coherent superposition of hexagonal-triangular-hexagonal photonic moiré lattice fields. In addition, two specific twisted angles of Δα| and Δα| are proposed, which not only guarantee the periodicity of moiré fields but also provide an additional degree of freedom to control the structural arrangement of the gradient photonic moiré lattice fields.

Generating narrow bandwidth pulses in a hybrid mode-locked fiber laser.

We demonstrate for the first time, to our knowledge, an all-fiber erbium-doped mode-locked laser in which mode-locking (ML) is realized by the combination of nonlinear polarization rotation and a saturable dynamic filtering effect, thereby generating nearly transform-limited ultrashort pulses with a pulse duration and spectral width of 45.2 ps and 0.0775 nm, respectively.

Single-frequency all-polarization-maintaining ytterbium-doped bidirectional fiber laser.

We reported an all-polarization-maintaining single-frequency ytterbium-doped bidirectional fiber laser for the first time, to the best of our knowledge. Single-frequency operation was achieved by a stable dynamic grating in the active fiber of a proper length owing to the bidirectional operation of the laser. The fiber laser possesses a linewidth of 7.

Stable-, period-N- and multiple-soliton regimes in a mode-locked fiber laser with inconsistently filtered central wavelengths.

We systematically study the stable-, period-N- and multiple-soliton regimes in an Erbium-doped fiber laser effectively mode-locked by nonlinear polarization rotation technique. In the stable mode-locked regime, an invariant soliton with 497 fs pulse duration and 6.9 nm optical spectrum are obtained.

Asymmetric localization and symmetric diffraction-free transmission in synthetic photonic lattice with anti-parity-time symmetry.

We study, to the best of our knowledge, the first observations of light propagation in synthetic photonic lattice with anti-parity-time symmetry by tuning the gain or loss of two coupled fiber rings alternatively and corresponding phase distribution periodically. By tuning the phase and the wave number in the lattice, asymmetric transmission of the light field can be achieved for both long and short loops when ≠/2 ( is an integer). Further investigations demonstrate that asymmetric localization of the light field in the long loop and symmetric diffraction-free transmission in two loops can both be realized by changing these two parameters.

Observation of reverse self-sweeping effect in an all-polarization-maintaining bidirectional ytterbium-doped fiber laser.

In this article, we report, to the best of our knowledge, the first observation of the reverse self-sweeping phenomenon in an all-polarization-maintaining bidirectional ytterbium-doped fiber laser. Conventional behaviors, including the dependence of sweeping range, sweeping rate and average pulse repetition rate on the pump power, can be observed in our fiber laser. Two couplers with ratio of 50/50 and 10/90 are respectively employed as the output coupler in fiber laser, which generates the reverse self-sweeping phenomenon for comparison.

Asymmetric localization induced by non-Hermitian perturbations with PT symmetry in photonic lattice.

We study both theoretically and numerically the asymmetric localization of lightwave in a three-layered photonic lattice with non-Hermitian perturbations. The results indicate that the gauge potential for photons can arise from the non-Hermitian perturbations, once the perturbations satisfy parity-time symmetry. Further study shows that the Peierls phase between adjacent waveguides has an important impact on the shapes of the band structures, which result in asymmetric localization of a lightwave in such a system when the wave number and Peierls phase satisfy k=ϕ=±π/2.

Black phosphorus flakes covered microfiber for Q-switched ytterbium-doped fiber laser.

We demonstrate a passively Q-switched ytterbium-doped fiber laser based on black phosphorus (BP) flakes covered microfiber. The BP saturable absorber is fabricated by sandwiching a microfiber between two pieces of polydimethylsiloxane supported BP flakes film, which is prepared by the mechanical exfoliation method. In this case the BP flakes can be well protected from the action of air and moisture.