Wen-Jun Cao

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.

Polarization-Independent, Multifunctional All-Fiber Comb Filter Using Variable Ratio Coupler-Based Mach–Zehnder Interferometer

A polarization-independent, multifunctional all-fiber comb filter by using variable ratio coupler (VRC)-based dual-pass Mach-Zehnder interferometer is newly proposed and demonstrated. Depending on the dynamic settings of coupling ratios of the fiber couplers, the comb filter provides the channel spacing tunable, multiwavelength switchable, and flat-top spectral responses. Theoretical calculations are verified by the experimental results. Experimentally, a comb filter with the channel spacing tunable from 0.4 to 0.8 nm was obtained. Meanwhile, when the comb spacing was tuned to 0.8 nm, the multiwavelength switchable operation with both the sinusoid and flat-top spectral responses was achieved. The proposed comb filter may find applications in optical communication systems and tunable multiwavelength fiber lasers.

Optical Deposition of Graphene Saturable Absorber Integrated in a Fiber Laser Using a Slot Collimator for Passive Mode-Locking

A compact and efficient intracavity optical deposition of graphene saturable absorber (SA) for a passively mode-locked fiber laser is proposed and demonstrated. The setup for optical deposition is integrated in a fiber ring laser through a slot collimator. By dripping the dimethylformamide (DMF) solution of graphene into the gap of the slot collimator between two fiber ferrules, graphene can be well deposited onto the fiber end to form an SA. The transmission loss of graphene SA is measured. As for application, the fiber ring laser is passively mode-locked with the prepared graphene SA and generates a 1 ps, 13.6 MHz soliton pulse train.

Experimental observation of bright-dark pulse emitting in an all-fiber ring cavity laser

We demonstrate the emission of bright pulse and dark pulse in a simple all-fiber ring cavity laser by using self-pulsing technique. The switching between bright pulse and dark pulse can be realized by properly rotating the polarization controller (PC). Meanwhile, the bright-dark pulse can also be generated in the fiber laser and is experimentally verified to be on two different orthogonal polarization axis of the cavity fiber. Our experimental results show that the bright pulse, the dark pulse or the bright-dark pulse can be obtained in an all-fiber laser by using self-pulsing technique.

Passively Q-switched mode-locking Erbium-doped fiber laser with net-normal dispersion using nonlinear polarization rotation technique

We experimentally demonstrate a passively Q-switched mode-locking (QML) operation in an Erbium-doped fiber ring laser with net normal dispersion by using nonlinear polarization rotation technique. A 2 m long section of dispersion compensating fiber (DCF) with extra large positive dispersion was inserted into the cavity to ensure the fiber laser working in the region of net positive dispersion. By carefully adjusting the polarization controller, both uniform dissipative mode-locking pulses with fundamental repetition rate and QML pulse trains with tunable repetition rate from 71.58 to 98.83 kHz are achieved. It is found that the QML operation is caused by the interaction between the polarization state of the pulse and the intracavity polarizer.

Sub-100 kHz repetition rate erbium-doped fiber laser in anomalous dispersion regime

We propose and demonstrate a simple but efficient way to generate low repetition rate pulses in an erbium-doped fiber ring laser by using self-pulsing technique. About 2.25 km long single mode fiber is used to elongate in the cavity, providing large anomalous cavity dispersion in the wavelength region around 1550 nm. Self pulses at a repetition rate of 85.3 kHz with single pulse energy as high as 110 nJ are efficiently obtained on the nanosecond time scale. The experimental results demonstrate that the self-pulse fiber laser operating in the anomalous dispersion regime can also realize high-energy pulses at a very low pulse repetition rate.

Optical deposition of graphene saturable absorber integrated in fiber laser using a slot collimator for pulsed operation: From Q-switching to mode-locking

An intra-cavity method for optical deposition of graphene saturable absorber (SA) by using a slot collimator is newly proposed. With the fabricated graphene SA, the laser operation regime switched between Q-switching and mode-locking is investigated.