Jingmin Liu

Polarization domain wall pulses in a microfiber-based topological insulator fiber laser

Topological insulators (TIs), are novel two-dimension materials, which can act as effective saturable absorbers (SAs) in a fiber laser. Moreover, based on the evanescent wave interaction, deposition of the TI on microfiber would create an effective SA, which has combined advantages from the strong nonlinear optical response in TI material together with the sufficiently-long-range interaction length in fiber taper. By using this type of TI SA, various scalar solitons have been obtained in fiber lasers. However, a single mode fiber always exhibits birefringence, and hence can support two orthogonal degenerate modes. Here we investigate experimentally the vector characters of a TI SA fiber laser. Using the saturated absorption and the high nonlinearity of the TI SA, a rich variety of dynamic states, including polarization-locked dark pulses and their harmonic mode locked counterparts, polarization-locked noise-like pulses and their harmonic mode locked counterparts, incoherently coupled polarization domain wall pulses, including bright square pulses, bright-dark pulse pairs, dark pulses and bright square pulse-dark pulse pairs are all observed with different pump powers and polarization states.

Tunable and channel spacing precisely controlled comb filters based on the fused taper technology

We propose and demonstrate an adjustable all-fiber comb filter with precisely controlled channel spacing by employing a tapered fiber in one arm of a Mach-Zehnder interferometer (MZI) for the first time. Using fused taper technology to draw the fiber, we can precisely control the optical path difference between the two arms of the MZI, thus realizing a precisely controllable channel spacing. By rotating the polarization controller state in the other arm of the MZI, the transmission spectrum wavelength can be continuously tuned. Comb filters with controllable channel spacings from 0.2 to 3.0 nm have been numerically studied and achieved in experiment. Applications of a filter based on a multi-wavelength tunable all-fiber laser source are also demonstrated.

Fine-structure oscillations of noise-like pulses induced by amplitude modulation of nonlinear polarization rotation

The generation and evolution processes of noise-like pulses (NLPs) in an all-normal-dispersion nonlinear polarization rotation (NPR) mode-locked Yb-doped fiber laser are numerically and experimentally investigated. We demonstrate that the amplitude modulation induced by reverse saturable absorption and the peak-power-limiting effect of the NPR plays a key role in the formation of fine-structure oscillations of NLPs. The width variation of the NLPs is also discussed in detail.

Wavelength Tunable Q-Switched Fiber Laser Using Variable Attenuator Based on Tapered Fiber

We demonstrate a wavelength tunable, Q-switched Er-doped fiber laser using a mixture of gold nanorods and nanospheres as a saturable absorber. The laser has a very low Q-switched threshold pump power of 22 mW, and at a pump power of 47.86 mW, a pulse with a maximum pulse energy of 36.01 nJ, repetition rate of 37.50 kHz, and pulse width of

Duration-controllable square-wave pulse from an L band dissipative soliton fiber laser based on the dispersive Fourier transformation technique

2.74~\mu \text{s}

Research on polarization vector characteristics in a microfiber-based graphene fiber laser

was obtained. In addition, by using a tapered fiber as a variable attenuator (ATT), the central wavelength of the laser could be tuned continuously from 1560.97 to 1554.74 nm. The experimental results further verify that a tapered fiber ATT possesses potential advantages for applications in stable, wavelength tunable, all-fiber laser systems.

Formation of noise-like square-wave pulses in a microfiber based topological insulator fiber laser

We experimentally generated the duration-controllable square-wave pulse from an L band dissipative soliton (DS) fiber laser based on the dispersive Fourier transformation (DFT) technique. The rectangular spectrum emitted from an L band dissipative soliton fiber laser is mapped into a time-domain coherent rectangular waveform through the DFT technique. The duration of the square-wave pulse can be controllable with the adjustments of the pump power. The results demonstrate that it is an effective and flexible way to achieve duration-controllable square-wave pulses by combinating with DFT technique and DS fiber laser.

Research on the broadband operating mode of anisotropic acousto-optic deflector using tellurium dioxide crystal

We experimentally investigated the polarization vector characteristics in an Er-doped fiber laser based on graphene that was deposited on microfiber. A variety of dynamic states, including polarization locked fundamental soliton, and polarization domain wall square pulses and their harmonic mode locked counterparts have all been observed with different pump powers and polarization states. These results indicated that the microfiber-based graphene not only could act as a saturable absorber but also could provide high nonlinearity, which is favorable for the cross coupling between the two orthogonal polarization components. It was worth to mention that it is the first time to obtain the polarization domain wall solitons in a mode locked fiber laser.

Generation of Soliton Bursts With Flexibly Controlled Pulse Intervals Based on the Dispersive Fourier-Transform Technique

We demonstrated the formation of noise-like square-wave pulses in an Er-doped fiber laser, using a microfiber based topological insulator as a saturated absorber (SA). The SA guaranteed both excellent saturable absorption and high nonlinearity. The pulse width can be increased ranging from 0.985 to 5.503 ns by increasing the pump power from 212 to 284 mW with the polarization state fixed. Moreover, with the adjustment of the polarization controllers in the cavity, the pulse width can be adjusted obviously. Worth mentioning, it was the first time that the noise-like square-wave pulse formed in a microfiber based topological insulator fiber laser.

Wavelength-Tunable Burst-Mode Pulse With Controllable Pulse Numbers and Pulse Intervals

Theoretical studies on the broadband operating mode of anisotropic acousto-optic deflector (AOD) using tellurium dioxide crystal are carried out, the operating properties of the bandwidth and the central frequency of the AOD are systematically studied by solving the Dixon equation that characterizes the geometrical relationships of the acousto-optic interaction. The calculation results show that the bandwidth and the central frequency of the AOD are highly depended on the off-axis angle of the ultrasonic vector, which shows linear properties in the operating bandwidth both for the +1 order and -1 order diffractions.