Zian Cheak Tiu

S-band Q-switched fiber laser using molybdenum disulfide (MoS2) saturable absorber

In this letter, a molybdenum disulfide (MoS2) saturable absorber (SA) is fabricated using a simple drop cast method to generate Q-switched fiber laser operating in the S-band region (1460 nm-1530 nm). The MoS2 solution was prepared using the liquid phase exfoliation (LPE) method where MoS2 crystals were added into dimethylformamide (DMF) solvent and subsequently sonicated and centrifuged. They were then repeatedly dripped onto fiber ferrules and dried in an oven. The resultant Q-switched fiber laser starts with some physical disturbance when the pump power was set at 40 mW and continues to operate until the pump power reaches 120 mW. The resultant repetition rate varies with pump power between 27.17 to 101.17 kHz while the changes in pulse widths are from 3.0 to 1.4 μs.

Nonlinear Polarization Rotation-Based Mode-Locked Erbium-Doped Fiber Laser with Three Switchable Operation States

A simple mode-locked erbium-doped fiber laser (EDFL) with three switchable operation states is proposed and demonstrated based on nonlinear polarization rotation. The EDFL generates a stable square pulse at a third harmonic pulse repetition rate of 87 kHz as the 1480 nm pump power increases from the threshold of 17.5 mW to 34.3 mW. The square pulse duration increases from 105 ns to 245 ns as the pump power increases within this region. The pulse operation switches to the second operation state as the pump power is varied from 48.2 mW to 116.7 mW. The laser operates at a fundamental repetition rate of 29 kHz with a fixed pulse width of 8.5 μs within the pump power region. At a pump power of 116.7 mW, the average output power is 3.84 mW, which corresponds to the pulse energy of 131.5 nJ. When the pump power continues to increase, the pulse train experiences unstable oscillation before it reaches the third stable operation state within a pump power region of 138.9 mW to 145.0 mW. Within this region, the EDFL produces a fixed pulse width of 2.8 μs and a harmonic pulse repetition rate of 58 kHz.

Multi-wavelength Q-switched Erbium-doped fiber laser with photonic crystal fiber and multi-walled carbon nanotubes

A simple multi-wavelength passively Q-switched Erbium-doped fiber laser (EDFL) is demonstrated using low-cost multi-walled carbon nanotubes (MWCNTs)-based saturable absorber, which is prepared using polyvinyl alcohol as a host polymer. The multi-wavelength operation is achieved based on non-linear polarization rotation effect by incorporating 50 m long photonic crystal fiber in the ring cavity. The EDFL produces a stable multi-wavelength comb spectrum for more than 14 lines with a fixed spacing of 0.48 nm. The laser also demonstrates a stable pulse train with the repetition rate increasing from 14.9 to 25.4 kHz as the pump power increases from the threshold power of 69.0 mW to the maximum pump power of 133.8 mW. The minimum pulse width of 4.4 μs was obtained at the maximum pump power of 133.8 mW while the highest energy of 0.74 nJ was obtained at the pump power of 69.0 mW.

Application of MoS2 thin film in multi-wavelength and Q-switched EDFL

Abstract Multi-wavelength and Q-switched EDFLs are demonstrated using a MoS2 thin film as stabilizer and saturable absorber, respectively. For a multi-wavelength output, a 50-m-long PCF is incorporated into the cavity to induce unstable multi-wavelength oscillation and a MoS2 thin film is further incorporated into the cavity to achieve stable multi-wavelength. The laser generates 11 lasing wavelengths with constant spacing of 0.47 nm at pump power of 250 mW. In the case of the Q-switched EDFL, MoS2 thin film is utilized as a saturable absorber. Q-switched operation occurrs at a threshold pump power of 28.86–51.48 mW and the spectrum is centered at 1561.15 nm. The pulse repetition rate showed increasing trend from 18.57–30.72 kHz whereas the pulse width decreased from 53.85–32.54 μs in the Q-switched pump power range. The highest pulse energy of 30.73 nJ is obtained at pump power of 51.48 mW.

Generation of mode-locked erbium-doped fiber laser using MoSe2as saturable absorber

Abstract. Mode-locked generation of erbium-doped fiber laser (EDFL) with MoSe2 thin film as saturable absorber is practically demonstrated. Bulk MoSe2 is exfoliated into few-layer MoSe2, which is achieved based on the liquid phase exfoliation technique. The few-layer MoSe2 is mixed with polyvinyl alcohol to become a thin film. Mode-locked occurs between pump powers of 65 and 218 mW. The mode-locked is operated at fundamental frequency of 8.8 MHz, and the spectrum is centered at 1560 nm. The SNR of mode-locked EDFL is more than 50 dB. At pump power of 218 mW, 91.3 pJ of pulse energy is achieved.

Switchable soliton mode-locked and multi-wavelength operation in thulium-doped all-fiber ring laser

A switchable soliton mode-locked and multi-wavelength operation in thulium-doped fiber laser (TDFL) is demonstrated based on nonlinear polarization rotation (NPR) technique. The TDFL produces a soliton pulse operating at 1917.66nm using a 5m long thulium-doped fiber (TDF) as a gain medium as well as nonlinear medium. The solitonic behavior is further identified with two orders of Kelly sidebands in the output spectrum. The mode-locked emission is obtained from threshold pump power of 522–1052mW with consistent pulse repetition rate of 14.7MHz. Maximum pulse energy is calculated as 0.89nJ at pump power of 1052mW, whereas the maximum pulse width is estimated to be approximately 1.36ps corresponding to sech2 pulse profile. By shifting the polarization orientation, the cavity can change to multi-wavelength operation with signal-to-noise ratio (SNR) higher than 53dB. At pump power of 1037mW, three stable peak wavelengths are generated with a power fluctuation and constant spacing of ± 1 dB and 7.4nm, respectively.

Q-Switching Pulse Generation with Thulium-Doped Fiber Saturable Absorber

A simple Q-switched erbium-doped fiber laser (EDFL) is proposed and demonstrated by using a 2-m-long thulium-doped fiber (TDF) as a passive saturable absorber (SA). The EDFL generates a Q-switching pulse operating at 1557.6 nm at a threshold pump power as low as 20.0 mW. The Q-switching operation is maintained before disappearance when the pump power is above 33.7 mW. This is due to the fact that the TDF SA could not fully recover in time after a pulse and less gain population is excited before the next pulsing. With the SA, the laser produces a stable pulse train with repetition rate ranging from 3.9 to 12.7 kHz and the pulse width reduces from 20.6 to 7.4 μs while varying the 1480 nm pump power from 20 mW to 33.7 mW. The maximum pulse energy of 22.8 nJ is obtained at a pump power of 20.0 mW. The laser is perspective for technology processes and medicine.

Single and Double Brillouin Frequency Spacing Multi-Wavelength Brillouin Erbium Fiber Laser With Micro-Air Gap Cavity

Single and double Brillouin frequency spacing multi-wavelength Brillouin Erbium-doped fiber laser based on micro-air gap cavity is proposed and demonstrated. A 6.90-km dispersion shifted fiber is used as Brillouin gain medium to induce stimulated Brillouin scattering in the ring cavity. The micro-air gap cavity is constructed by aligning two polished fiber facets coaxially, and induces strong Fresnel reflection to switch the Brillouin frequency spacing from a double spacing to single spacing regime. Under the Brillouin pump power of 13 dBm and the laser diode pump power of 300 mW, five Stokes with a wavelength spacing of 0.160 nm and six Stokes with a wavelength spacing of 0.084 nm are generated. The fluctuation of the Stokes for both single and double Brillouin spacing regimes in the proposed setup are less than 3 dB throughout a 1-h time span. The variation of the cavity efficiency between the single and double spacing regimes is less than 1.2 dB.

Wide-band, passively Q-switched Yb- and Tm-doped fibre laser using WSSe saturable absorber

ABSTRACT A wide-band, passively Q-switched fibre lasers based on ytterbium- and thulium-doped fibre gain medium are proposed and demonstrated. The lasers employ a transition metal dichalcogenide, tungsten sulphoselenide as a saturable absorber (SA) which is prepared by mechanical exfoliation technique. By integrating the SA in the laser cavities, self-starting Q-switched at 1038 and 1982 nm are obtained. The generated pulses exhibit a microsecond pulse duration with few kilohertz repetition rate. The proposed SA has high potential as a new material to cater to the needs of various scientific, industrial and biomedical applications.

Passive mode-locking in erbium-doped fibre laser based on BN-GO saturable absorber

ABSTRACT A C-band mode-locked fibre laser incorporating a boron nitride-doped graphene oxide (BN-GO)-based saturable absorber (SA) is proposed and demonstrated. The SA is fabricated by depositing multiple layers of synthesized BN-GO nanoparticles onto the polished surface of a side-polished fibre, which is then inserted into an erbium-doped fibre laser cavity to generate the desired pulsed output. The strong nonlinear optical response and light absorption of the BN-GO nanoparticles induces the generation of a highly stable mode-locked pulse at 1567.32 nm with visible Kelly’s sidebands. The pulses have a measured repetition rate of 13.56 MHz and a pulse width of 1.18 ps at the maximum pump power of 280.5 mW. The pulses have a frequency signal-to-noise ratio of ∼53 dB, indicating a highly stable output. The proposed laser would find significant telecommunications applications, particularly for dense wavelength division multiplexing systems.