Zhenbao Wang

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.

Super-flat supercontinuum generation from a Tm-doped fiber amplifier

Super-flat supercontinua are generated from a double clad Tm-doped fiber amplifier. Two different laser configurations are investigated and compared. In the direct-output configuration, the long-wavelength edge of the supercontinuum spectra is extended to beyond 2.65 μm with a 10 dB bandwidth of 740 nm. In the passive pigtail configuration, the generated supercontinuum features excellent flatness with an intensity difference smaller than 1 dB in the wide central spectral range from 1.98 μm to 2.41 μm.

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.

Modelling and characteristics of actively Q-switched Er-doped fibre laser with Tm-doped fibre saturable absorber

Abstract A theoretical model concerning FSA-based active Q-switching is developed. And, characteristics of the active Q-switching operation are investigated and compared with the traditional passive Q-switching operation. Numerical results demonstrate that the active control of the repetition rate of FSA-based Q-switching is attainable. And, stable active Q-switching could be obtained from both no lasing state and stable passive Q-switching state.

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.

Stimulated Brillouin scattering suppression in fiber amplifiers with multi-tone amplification

The multi-tone amplification for the purpose of mitigating stimulated Brillouin scattering (SBS) effect is investigated. Different wavelengths and power ratio are considered in the simulation model to achieve optimal results. The numerical simulation results indicate that SBS is effectively suppressed in a fiber amplifier with an output from 53.7W to 96.9W by utilizing this approach.

Theoretical analysis and comparison of Tm-doped fiber lasers with different pump bands

Modeling of Tm-doped fiber lasers pumped with 793 nm, 1.6 μm and 1.9 μm is presented and compared. Output performance of three different pump schemes with active fiber length, pump power and output reflectivity is investigated. Numerical simulation shows that, with 793 nm pump, the cross relaxation process is of vital importance for high efficient operation of Tm-doped fiber laser. And, 1.9 μm pump scheme is more likely to offer even higher output compared with 793 nm pump and 1.6 μm pump.