Pengling Yang

Experimental demonstration of an Er-doped fiber ring laser mode-locked with a Tm-Ho co-doped fiber saturable absorber

Mode-locking operation of an Er-doped fiber laser with a Tm?Ho co-doped fiber saturable absorber is demonstrated for the first time. Q-switching, Q-switched mode-locking and CW mode-locking operation modes are observed sequentially with increase of the pump power. In the mode-locking operation mode, a repetition rate at the fundamental cavity frequency of 9.05?MHz is obtained with a pulse duration of 46.3 ns. By rotating the polarization controller, a repetition rate up to 887?MHz is achieved, and the pulse duration is shortened to 0.548?ns.

Tm-Ho co-doped fiber-based high repetition rate passive Q-switching of an Er-doped fiber laser

An all-fiber Q-switched Er-doped laser is built with a ring cavity. Stable Q-switching is demonstrated with a Tm–Ho co-doped fiber saturable absorber. The maximum repetition rate of the laser system reaches 42 kHz, which is much larger than that with Tm singly doped fiber saturable absorbers. Analysis shows that interaction between thulium and holmium ions is the main reason for this high repetition rate operation.

A Tm–Ho codoped fiber based 38 nm wideband wavelength tunable passively Q-switched Er-doped fiber laser

Exploiting a piece of 0.2 m long Tm–Ho codoped fiber as the saturable absorber, we demonstrate a wideband wavelength tunable passively Q-switched Er-doped fiber laser. The Tm–Ho codoped fiber has a wide absorption band around 1550 nm, promising wideband Q-switching of Er-doped fiber lasers. With a Fabry–Perot tunable filter, stable passive Q-switching is observed in a wide wavelength range from 1535 to 1573 nm. The repetition rate of the laser system is tunable with both the pump power and the lasing wavelength in the range between 0.5 and 50 kHz.

Modeling of Tm-Ho codoped fiber saturable absorber based passive Q-switching of an Er-doped fiber laser

A theoretical model concerning the Tm–Ho codoped fiber saturable absorber based passive Q-switching of an Er-doped fiber laser is established. Comparison with the Tm-doped fiber saturable absorber is described and discussed. Numerical results indicate that, compared with a Tm-doped fiber saturable absorber, the Tm–Ho codoped fiber saturable absorber shortens the lifetime of the 3F4 energy level and improves the operation of the laser system.

Gain-switching and gain-switched mode-locking operation of a Tm/Ho co-doped fiber laser

Pumped by a 1550 nm fiber laser, a gain-switched Tm/Ho co-doped single-clad fiber laser is built with a linear cavity. Stable gain-switching is achieved with the repetition rate ranging from 2 to 150 kHz. The highest peak power is 11.1 W with a pulse duration of 130 ns. Increasing the pulse energy of the pump, gain-switched mode-locking is attained with a sub-pulse repetition rate of 20 MHz and a pulse duration of about 10 ns; the peak power of the gain-switched envelope is about 4.6 W.

Experimental investigation of gain-switched Tm?Ho Co-doped single clad fiber lasers

Gain-switched Tm?Ho Co-doped single clad fiber lasers are investigated with in-band pumping. The output ratio and cavity length are varied to investigate their impacts on the output pulses. The shortest pulse is 83.4?ns with a peak power of 10.5?W generated from the 3?m long laser cavity with 50% output ratio. At high pump pulse energies, gain-switched mode-locking operation is observed with a mode-locking repetition rate of tens of MHz, determined by the cavity length. The duration of the mode-locked pulse is no longer than 10?ns.

Cross Relaxation in Tm-doped Fiber Lasers

Cross relaxation (CR) process in thulium ions is described. Performance of Tm-doped fiber lasers with different dopant concentrations is evaluated numerically with and without CR. Simulation shows that CR process can not only improve the slope efficiency and output of the laser system, but also lower the lasing threshold and extend the growth momentum of the laser performance. Backward LD-clad-pumped Tm-doped fiber lasers are built with Tm-doped fibers of different doping levels. A maximum output of 35.3W around 2μm is obtained with a slope efficiency of 47.2% from the 4.5wt.%- doped fiber laser while a higher slope efficiency of 54.1% was achieved from the 6.8wt.%-doped fiber laser. And, modeling shows that these laser systems are much more efficient than that without CR process.

A highly efficient 57 pm Tm-doped fiber laser with two multimode fiber Bragg gratings

An LD-clad pumped Tm-doped fiber laser is built with two multimode double-clad fiber Bragg gratings (FBGs) to generate narrow linewidth output around 2??m. The slope efficiency of this laser system is 43.1% with respect to the launched pump power, corresponding to a quantum efficiency of 109%, which means that at least 9% of the doped thulium ions take part in the two-for-one cross relaxation process. Exploiting two multimode FBGs and wrapping the fiber onto an aluminum spool, a single peak narrow linewidth spectrum is generated. A 3?dB linewidth of 57?pm centering at 1996.2?nm is obtained at an output of 3.6?W.

Q-switched and mode-locked erbium-doped fiber laser based on graphene saturable absorber

A compact passively Q-switched and mode-locked erbium-doped fiber laser based on graphene saturable absorber was reported in this paper. A fiber ferrule, which had graphene deposited on the core region, was used as the saturable absorber. The Q-switched operation was initiated with a low pump threshold of about 50 mW at 974 nm and the repetition rate can be widely tuned from 14 kHz to 70 kHz along with the increase of the pump power. Moreover, the mode-locking state working at 1559.7 nm with a 0.4nm spectral bandwidth and about 3 ns pulse duration was also demonstrated in the same ring cavity when the pump power increased to about 150 mW. This is, to the best of our knowledge, the first report of the fiber laser, which had the both Q-switched operation with so wide repetition rate and mode-locking operation in the same ring cavity based on the same graphene saturable absorber.

Diagnostic technology for temporal-spatial distribution of far-field high power laser beam profile

Measuring far-field laser beam profile is an effective way to study the atmospheric transmission effects of high power laser in a long distance and evaluate the technical performance of high power laser system. Diagnostic technologies for measuring the far-field high power laser beam profile are summarized and their applicable scopes are described. The measuring method based on spatial sampling discrete detector arrays is mainly introduced. Finally, two types of laser beam profilers based on detector array are presented, which are developed by our group recently, and they are respectively suitable for measuring far-field continuous wave high energy laser and high repetition rate pulsed laser.