Zhi-Chao Luo

2 GHz passively harmonic mode-locked fiber laser by a microfiber-based topological insulator saturable absorber

We report on the generation of passive harmonic mode locking of a fiber laser using a microfiber-based topological insulator (TI) Bi(2)Te(3) saturable absorber (SA). The optical deposition method was employed to fabricate the microfiber-based TISA. By virtue of the excellent nonlinear optical property of the proposed TISA, the fiber laser could operate at the pulse repetition rate of 2.04 GHz under a pump power of 126 mW, corresponding to the 418th harmonic of fundamental repetition frequency. The results demonstrate that the microfiber-based TI photonic device can operate as both the high nonlinear optical component and the SA in fiber lasers, and could also find other applications in the related fields of photonics.

Femtosecond pulse erbium-doped fiber laser by a few-layer MoS 2 saturable absorber

We report on the generation of a femtosecond pulse in a fiber ring laser by using a polyvinyl alcohol (PVA)-based molybdenum disulfide (MoS(2)) saturable absorber (SA). With a saturable optical intensity of 34  MW/cm(2) and a modulation depth of ∼4.3%, the PVA-based MoS(2) SA had been employed with an erbium-doped fiber ring laser as a mode locker. The mode-locking operation could be achieved at a low pump threshold of 22 mW. A ∼710  fs pulse centered at 1569.5 nm wavelength with a repetition rate of 12.09 MHz had been achieved with proper cavity dispersion. With the variation of net cavity dispersion, output pulses with durations from 0.71 to 1.46 ps were obtained. The achievement of a femtosecond pulse at 1.55 μm waveband demonstrates the broadband saturable absorption of MoS(2), and also indicates that the filmy PVA-based MoS(2) SA is indeed a good candidate for an ultrafast saturable absorption device.

Femtosecond pulse generation from a topological insulator mode-locked fiber laser

We reported on the generation of femtosecond pulse in a fiber ring laser by using a polyvinyl alcohol (PVA)-based topological insulator (TI), Bi2Se3 saturable absorber (SA). The PVA-TI composite has a low saturable optical intensity of 12 MW/cm2 and a modulation depth of ~3.9%. By incorporating the fabricated PVA-TISA into a fiber laser, mode-locking operation could be achieved at a low pump threshold of 25 mW. After an optimization of the cavity parameters, optical pulse with ~660 fs centered at 1557.5 nm wavelength had been generated. The experimental results demonstrate that the PVA could be an excellent host material for fabricating high-performance TISA, and also indicate that the filmy PVA-TISA is indeed a good candidate for ultrafast saturable absorption device.

Tunable Multiwavelength Passively Mode-Locked Fiber Ring Laser Using Intracavity Birefringence-Induced Comb Filter

A simple configuration for the generation of tunable multiwavelength picosecond-pulse fiber ring lasers by exploiting the intracavity birefringence-induced comb filter is demonstrated. The fiber laser is passively mode locked by using nonlinear polarization rotation (NPR) technique. The polarization-dependent isolator combined with the intracavity birefringence acts as two functions: the tunable comb filter and the mode locker. Up to four-wavelength picosecond pulses were simultaneously obtained in the experiment. The mode competition of the multiwavelength lasing is suppressed by the use of NPR-induced intensity-dependent loss. In addition, the number of the lasing wavelengths, the lasing location, and the spacing between the lasing wavelengths could be flexibly tuned by properly rotating the polarization controllers.

Tunable and switchable multiwavelength erbium-doped fiber ring laser based on a modified dual-pass Mach-Zehnder interferometer

A tunable and switchable multiwavelength erbium-doped fiber ring laser based on what we believe to be a new type of tunable comb filter is proposed and demonstrated. By adjusting the polarization controllers, the dual-function operation of the channel-spacing tunability and the wavelength switching (interleaving) can be readily achieved. Up to 29 stable lasing lines with 0.4 nm spacing and 14 lasing wavelengths with 0.8 nm spacing in 3 dB bandwidth were obtained at room temperature. In addition, the lasing output, including the number of the lasing lines, the lasing evenness, and the lasing locations, can also be flexibly adjusted through the wavelength-dependent polarization rotation mechanism.

Microfiber-based few-layer MoS2 saturable absorber for 2.5 GHz passively harmonic mode-locked fiber laser.

We reported on the generation of high-order harmonic mode-locking in a fiber laser using a microfiber-based molybdenum disulfide (MoS(2)) saturable absorber (SA). Taking advantage of both the saturable absorption and large third-order nonlinear susceptibilities of the few-layer MoS(2), up to 2.5 GHz repetition rate HML pulse could be obtained at a pump power of 181 mW, corresponding to 369th harmonic of fundamental repetition frequency. The results provide the first demonstration of the simultaneous applications of both highly nonlinear and saturable absorption effects of the MoS(2), indicating that the microfiber-based MoS(2) photonic device could serve as high-performance SA and highly nonlinear optical component for application fields such as ultrafast nonlinear optics.

Pulse dynamics of dissipative soliton resonance with large duration-tuning range in a fiber ring laser

The pulse dynamics operating in dissipative soliton resonance (DSR) region is experimentally investigated in a fiber ring laser. With the increase of pump power, the pulse profile transit from sech-like to rectangular shape was observed. The generated pulse in DSR region exhibits the conventional soliton spectrum with sideband generation. The duration-tuning range of the rectangular pulse is up to the cavity roundtrip time. Particularly, during the process of pulse duration broadening it was found that the rectangular pulse would trap a weak pulse generated from cw background. The obtained results may be useful for better understanding the DSR phenomenon.

Dissipative soliton resonance in a passively mode-locked figure-eight fiber laser

The generation of mode-locked rectangular pulses operating in dissipative soliton resonance (DSR) region is demonstrated in an erbium-doped figure-eight fiber laser with net anomalous dispersion. The duration of the wave-breaking-free rectangular pulse broadens with the increase of pump power. At a maximum pump power of 341 mW, the pulse energy can be up to 3.25 nJ with a repetition rate of 3.54 MHz. Particularly, the spectrum of rectangular pulse operating in DSR exhibits conventional soliton sidebands. The observed results show that the formation of pulse operating in DSR region is independent of mode-locking techniques, which may be helpful for further understanding the DSR phenomenon.

Tunable and Switchable Multiwavelength Passively Mode-Locked Fiber Laser Based on SESAM and Inline Birefringence Comb Filter

A tunable and switchable multiwavelength passively mode-locked fiber laser by using a semiconductor saturable absorber mirror (SESAM) and an inline birefringence fiber filter is proposed and demonstrated. By properly rotating the polarization controllers (PCs), up to 7-wavelength mode-locked pulses in 3-dB bandwidth with 3.65-nm channel spacing are obtained. The wavelength switchable operation is determined by the characteristics of the comb filter used in the experiment. Taking advantage of an intensity-dependent loss mechanism caused by the nonlinear polarization rotation (NPR) effect, the mode competition is efficiently suppressed. In addition, the lasing locations of multiwavelength mode-locked pulses can be flexibly tuned via the wavelength-dependent loss mechanism.

Dual-Wavelength Harmonically Mode-Locked Fiber Laser With Topological Insulator Saturable Absorber

Dual-wavelength passively harmonic mode locking (HML) operation is demonstrated in an erbium-doped fiber laser with a microfiber-based topological insulator (TI) saturable absorber. It was found that the dual-wavelength pulse-trains possess different HML orders due to the different cavity nonlinear effects experienced by the two wavelengths. By properly adjusting the cavity parameters, dual-wavelength HML pulses with repetition rates of 388 and 239 MHz were achieved. Moreover, wavelength switchable operation of dual-wavelength HML pulses was also obtained. The experimental results reveal that the microfiber-based TI could indeed be employed as a high-performance dual-function photonic device with the saturable absorption and high nonlinear effects for the applications in fields of ultrafast and nonlinear photonics.