A. R. Muhammad

Q-Switching Pulse Operation in 1.5-μm Region Using Copper Nanoparticles as Saturable Absorber

We demonstrate a passively Q-switched erbium-doped fiber laser (EDFL) using a copper nanoparticle (CuNP) thin film as the saturable absorber in a ring cavity. A stable Q-switched pulse operation is observed as the CuNP saturable absorber (SA) is introduced in the cavity. The pulse repetition rate of the EDFL is observed to be proportional to the pump power, and is limited to 101.2 kHz by the maximum pump power of 113.7mW. On the other hand, the pulse width reduces from 10.19μs to 4.28μs as the pump power is varied from 26.1mW to 113.7mW. The findings suggest that CuNP SA could be useful as a potential saturable absorber for the development of the robust, compact, efficient and low cost Q-switched fiber laser operating at 1.5-μm region.

S-band Thulium-doped fiber amplifier enhancement using ASE suppression

A new method for gain enhancement in S-band Thulium-doped fiber amplifier (TDFA) co-doped with Aluminum is demonstrated using a photonic crystal fiber and macro-bending approach. The photonic crystal fiber and macro-bending methods suppresses both amplified spontaneous emissions (ASEs) at 800 nm and 1800 nm band and thus increases the population inversion in S-band region. Gain enhancements of about 5~8 dB are obtained at the wavelength region between 1420 and 1470 nm.

Generation of soliton and bound soliton pulses in mode-locked erbium-doped fiber laser using graphene film as saturable absorber

We report an observation of soliton and bound-state soliton in passive mode-locked fibre laser employing graphene film as a passive saturable absorber (SA). The SA was fabricated from the graphene flakes, which were obtained from electrochemical exfoliation process. The graphene flakes was mixed with polyethylene oxide solution to form a polymer composite, which was then dried at room temperature to produce a film. The film was then integrated in a laser cavity by attaching it to the end of a fibre ferrule with the aid of index matching gel. The fibre laser generated soliton pulses with a 20.7 MHz repetition rate, 0.88 ps pulse width, 0.0158 mW average output power, 0.175 pJ pulse energy and 18.72 W peak power at the wavelength of 1564 nm. A bound soliton with pulse duration of ~1.04 ps was also obtained at the pump power of 110.85 mW by carefully adjusting the polarization of the oscillating laser. The formation of bound soliton is due to the direct pulse to pulse interaction. The results show that the proposed graphene-based SA offers a simple and cost efficient approach of generating soliton and bound soliton in mode-locked EDFL set-up.

Gain-shift induced by dopant concentration ratio in a thulium-bismuth doped fiber amplifier

This paper details the effect of Thulium and Bismuth concentration ratio on gain-shift at 1800 nm and 1400 nm band in a Thulium-Bismuth Doped Fiber Amplifier (TBDFA). The effect of Thulium and Bismuths concentration ratio on gain shifting is experimentally established and subsequently numerically modeled. The analysis is carried out via the cross relaxation and energy transfer processes between the two dopants. The energy transfer in this process was studied through experimental and numerical analysis of three samples with different Tm/Bi concentration ratio of 2, 0.5 and 0.2, respectively. The optimized length for the three samples (TBDFA-1, TBDFA-2 and TBDFA-3) was determined and set at 6.5, 4 and 5.5 m, respectively. In addition, the experimental result of Thulium Doped Fiber Amplifier (TDFA) was compared with the earlier TBDFA samples. The gain for TBDFA-1, with the highest Tm/Bi ratio, showed no shift at the 1800 nm region, while TBDFA-2 and TBDFA-3, possessing a lower Tm/Bi concentration ratio, shifted to the region of 1950 and 1960 nm, respectively. The gain shifting from 1460 nm to 1490 nm is also observed. The numerical model demonstrates that the common 3F4 layer for 1460 nm emission (3H4→3F4), and 1800 nm emission (3F4→3H6)inversely affects the 1460 nm and 1800 nm gain shifting.

All-fibre Q-switching YDFL operation with bismuth-doped fibre as saturable absorber

Abstract We demonstrate the generation of a passively Q-switched ytterbium-doped fibre laser (YDFL) using a bismuth-doped fibre (BDF) as a solid-state fibre saturable absorber (FSA) in a ring cavity. The BDF used has a wide and low absorption band of 5 dB/m at the 1.0 μm region due to the ion transition of that occurs around the region. When introduced into a YDFL laser cavity, a stable Q-switched pulse operation was observed and the pulse repetition rate was proportional to the input pump power. It was limited to 72.99 kHz by the maximum power that the laser diode could supply. Meanwhile, the pulse width decreased from 12.22 to 4.85 μs as the pump power was increased from 215.6 to 475.6 mW. The finding suggests that BDF could be used as a potential SA for the development of robust, compact, efficient and low cost Q-switched fibre lasers operating at 1 micron region.

1.9~2 μm gain shifted TBDFA employing different Tm-Bi concentration ratio

A gain shift in the 1.8 μm band of Tm-Bi co-doped fiber amplifier was achieved by varying both the Tm and Bi concentrations. The effect of energy transfer in this process was studied through experimental results of three samples with different Tm/Bi ratio of 2, 0.5 and 0.2. The gain at TB-1, with highest Tm/Bi ratio showed no shift, while TB-2 and TB-3, with lower Tm-Bi concentration ratio shifted to 1950 and 1960 nm, respectively.