Guoliang Chen

Square-wave pulse with ultra-wide tuning range in a passively mode-locked fiber laser

We report the generation of ultrawide tunable square-wave pulse in an erbium-doped mode-locked fiber laser. The pulse width can be tuned in an ultrawide range of more than 1700 ns by simply increasing the pump power. The pulse-width tuning is 5.1 ns/mW. To the best of our knowledge, this is the widest pulse-width tuning range of any square-wave pulse in an all-fiber passively mode-locked fiber laser. Experimental results show that the fiber nonlinearity plays an important role in the tuning range of the output pulse width. The high nonlinearity helps to increase the tuning range of the pulse width.

Width and amplitude tunable square-wave pulse in dual-pump passively mode-locked fiber laser

We have proposed and demonstrated a figure-8 dual-pump passively mode-locked fiber laser to generate square-wave pulse tunable by both width and amplitude. Just by simply adjusting the power of the pumps, both the amplitude and width of the output square-wave pulse can be tuned independently and continuously. One pump is used to tune the output pulsewidth while the other is used to tune amplitude.

Mode-locked all-fiber laser producing radially polarized rectangular pulses

We propose and demonstrate a radially polarized mode-locked fiber laser through the use of a figure-8 cavity in combination with cascade fiber Bragg gratings (FBGs). The mode-locked laser emits rectangular pulses with width tunable from 2.8 to 23 ns under an increasing pump power at 1056.3 nm with 0.2-nm 30-dB linewidth. A polarization purity as high as 96% for the output transverse mode has been achieved simultaneously.

Ultra-High Repetition Rate Harmonic Mode-Locking Generated in a Dispersion and Nonlinearity Managed Fiber Laser

Stable pulses with a 22.132-GHz repetition rate are successfully obtained by managing the dispersion and nonlinearity in a passively soliton erbium-doped single-mode fiber laser, which is as high as the 2192nd order of the fundamental frequency of 10.096 MHz. The super-mode suppression ratio beyond 40 dB is observed under only 485 mW pump power.

Simulation of nanosecond square pulse f iber laser based on nonlinear amplifying loop mirror

A nanosecond square pulse fiber laser based on the nonlinear amplifying loop mirror (NALM) is numerically analyzed by the nonlinear Schr¨odinger equation. The fiber cavity with a NALM has a tendency to provide pulse shaping effect with nonlinearity increasing in the NALM, and the nanosecond square pulse is generated by the pulse shaping effect. The numerical results show that the stable square pulse can be obtained when the parameters of the NALM are chosen appropriately. The generated square pulses have flat top and no internal structure.

Square shape spectrum in 1550 nm and 1060 nm bands in passive mode-locked fiber laser

Square shape spectrum is observed in passively mode-locked fiber laser both in 1550 nm and 1060 nm band, the spectrum is broad and flat, the bandwidth is up to 28 nm in 1550 nm band.

Experimental investigations on spectrum width of square-wave pulses in passively mode-locked figure-8 fiber laser

We have proposed and demonstrated a nanosecond square-wave fiber laser working in the 1060nm band. The passively mode-locked fiber laser based on the nonlinear optical loop mirror has a peak power clamping effect which leads to the generation of nanosecond square-wave pulses. To investigate the spectrum width of the nanosecond square-wave pulse laser, we added couplers with different coupling ratio to the bidirectional ring of the figure-8 fiber laser and analyzed the laser output. The results show that a higher output coupling ratio leads to stronger peak power clamping effect, and the peak power of the square-wave pulse gets lower and the corresponding spectrum band width is narrower.

Investigations of mode-locked fiber laser based on CVD fabricated graphene saturable absorber

A stable mode-locked fiber laser employing graphene as a saturable absorber is presented. One monolayer graphene can obtain mode-locking when the cavity is around 12m, but when the cavity decreases to 6m, no stable pulses can be formed. In order to solve this problem, cascade of two monolayer graphenes is used and stable mode locked pulses with a frequency of 44.53MHz, a bandwidth of 2.4nm, a pulse width of 43.89ps and an average power of 19.10mW have been directly obtained from the laser. Our results show the atomic-layer graphene may be a promising satrurable absorber for stable pulses formation of fiber laser.

Radially polarized mode-locked fiber laser based on few-mode FBG

We demonstrate a figure-8 fiber laser emitting radially polarized, mode locked pulses based on few-mode fiber Bragg grating. The laser emits mode-locked pulses with 7-ns duration and 1.21 MHz repetition and operates at 1054 nm with 0.62 nm 30 dB linewidth. The polarization purity of the output is more than 96%.

High repetition rate passively mode-locked fiber laser with a composite cavity structure for repetition rate control

We have demonstrated a passively mode-locked fiber laser with a composite cavity structure for repetition rate control. An optical delay line is used to control the length so that the lengths of the main cavity and the sub-ring cavity are accurately co-prime. Using this method we have obtained 46th harmonic pulses with a fundamental repetition of 17.39MHz. The fundamental mode-locking is substantially suppressed. The SNR of rf spectrum is higher than 45 dB. Stable 800MHz repetition rate mode-locked pulses in duration of 14.27 ps are generated. The detuning phenomenon appears when two cavity’s lengths are not matched. A larger pump power is required to maintain the oscillation.