Browsing by Author "Ahmad, H."

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    Evolution of noise-like pulses to watt-level all-fiber supercontinuum in compact all-normal dispersion fiber laser using nonlinear polarization rotation
    (Academic Press, 2024-07-07) Ahmad, H.; Lutfi, M. A. M.; Ortaç, Bülent; Zaini, M. K. A.; Samion, M. Z.
    Noise-like pulses (NLPs) and supercontinuum (SC) in all normal dispersion (ANDi) fiber lasers are experimentally demonstrated to have excellent characteristics. This all-fiber SC laser source has generated 4.1 W of maximum average optical output with a broad spectrum from 900 nm to 1700 nm. The compact ytterbium-doped fiber ring laser (YDFL) mode-locked was induced by the nonlinear polarization rotation (NPR) mechanism. The YDFL generates NLPs with a pulse energy of 78 nJ, a 3-dB spectral width of 73 nm, and a pulse rate of 13.6 MHz. From the NLPs states, the input power was then increased to generate a supercontinuum with a flat 5-dB spectral width > 320 nm. This compact intracavity SC fiber laser shows its benefits of simple structure, short fiber, low cost, and ease of fabrication, which provide an SC source for multiple practical applications.
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    O-band femtosecond mode-locked laser by using Ni-MOF in praseodymium-doped fluoride fiber
    (Elsevier BV * North-Holland, 2024-09-27) Ahmad, H.; Nizamani, B.; Samion, M. Z.; Mutlu, S.; Yilmaz, S. Savaskan; Arsu, N.; Thambiratnam, K.; Ortaç, Bülent
    This work reports an ultrafast mode-locked fiber laser at the less investigated region of the O-band using a nickel metal-organic framework (Ni-MOF), which works as a saturable absorber (SA). Ni-MOF was prepared using the high-power laser-induced method. A stable mode-locked laser of 450 fs pulse duration was obtained. The repetition rate and signal-to-noise ratio (SNR) were 0.408 MHz and 52.5 dB, while the lasers operate at a wavelength of 1298.1 nm. At the pump power of 88 mW, the mode-locked laser was characterized to have an average output power of 0.69 mW, corresponding to a pulse energy of 1.69 nJ and a pulse peak power of 3.53 kW. Additionally, harmonic mode-locked laser operation was also achieved above the pump power of 88 mW. With the harmonic mode-locked laser operation, the pulse repetition rate increased to 2.45 MHz when the pump power was 125.7 mW. To the author's knowledge, this is the first report of novel MOF material used as an SA in praseodymium-doped fluoride fiber (PDFF) laser.
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    Passive harmonic mode-locking in Tm–Ho doped fiber laser with MoS2–ZnO saturable absorber deposited on the arc-shaped fiber
    (Elsevier BV * North-Holland, 2024-07-10) Ahmad, H.; Arina, M. R. N.; Samion, M. Z.; Ortaç, Bülent; Yusoff, N.
    This work reports a harmonic mode-locked Tm-Ho doped fiber laser (THDFL) using newly fabricated MoS 2 -ZnO as a saturable absorber (SA). It generates harmonic mode-locking (HML) operation with a center wavelength of 1911.4 nm and a 3-dB bandwidth of 3.02 nm. The fundamental repetition rate and pulse width were 14.1 MHz and 2.05 ps, respectively. Based on the radio frequency (RF) spectrum, the observed signal-to-noise (SNR) of the fundamental HML pulse was 67.22 dB. Increasing the pump power with fine-tuning of the polarisation controller (PC), higher order HML pulses were also observed using the MoS 2 -ZnO SA. The highest stable HML frequency was 300 MHz, observed at the 21st HML. The central wavelength and 3-dB bandwidth of the HML pulse were 1915.2 nm and 2.29 nm, respectively. The 21st HML pulses demonstrated a SNR of 40.09 dB. No supermode noise was observed in the RF spectrum, indicating that the 21st HML pulses were relatively stable. With industry demand, this high repetition rate HML with MoS 2 -ZnO SA opens new avenues for comprehension and manipulation of electronic phenomena, paving the way for future innovations in ultrafast lasers.
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    Zn-MOF as a saturable absorber for thulium/holmium-doped fiber laser
    (Institute of Physics Publishing Ltd., 2024-09-19) Ahmad, H.; Chiam, J. W.; Samion, M. Z.; Thambiratnam, K.; Mutlu, S.; Yilmaz, S. S.; Arsu, N.; Ortaç, Bülend
    Metal–organic framework (MOF) is a class of material that is highly porous and modular. Due to their unique properties, MOFs have found applications in gas storage, gas separation, sensing, and supercapacitors. [Zn2(H2L)2(1,2-Bis(4-pyridyl)ethene)4]n, zinc (Zn)-based MOF was used in this work to achieve mode-locked operation in a thulium/holmium-doped fiber laser due to its excellent optical absorption at a wavelength of 1925 nm. The saturable absorber (SA) was fabricated by drop-casting a mixture of Zn-MOF and isopropanol on an arc-shaped fiber. The center wavelength of the mode-locked laser is 1906.75 nm, with a maximum average output power of 3.251 mW. The fundamental repetition rate and the pulse width were 12.89 MHz and 1.772 ps. At the same time, the pulse energy and peak power were 252 pJ and 142 W, respectively. To the authors' knowledge, this is the first time an MOF has been used for mode-locked pulse generation in a thulium/holmium-doped all-fiber laser. This work extends the use of MOF material as a saturable absorber for mode-locking applications in near-infrared fiber lasers.