Tungsten disulfide saturable absorber for nanosecond pulses generation

We fabricated tungsten disulfide (WS2) based saturable absorber (SA) and use this to passively mode-lock an Erbium-doped fiber laser (EDFL) and produce nanosecond pulses train. The SA was obtained by repeatedly dropping the WS2 solution onto microfiber to form a nanosheets layer after drying process. A stable nanoseconds pulses train operating at 1560 nm was successfully achieved by inserting the developed SA device into a 206.4 m long laser cavity. A stable 409 ns pulse is obtained at repetition rate of 965 kHz as the pump power was raised above the threshold of 150 mW pump power. The maximum pulse energy of 1.79 nJ was obtained at 193 mW pump power. The generated pulses are consistent and stable, which useful in many practical applications. ©2019 Old City Publishing, Inc

Tungsten disulfide coated microfiber as saturable absorber for Q-switched pulses generation

Q-switched fiber laser was demonstrated by using tungsten disulfide (WS2) two-dimensional nanomaterials as a passive saturable absorber (SA) to modulate the loss inside the laser cavity. The SA was produced by repeatedly dropping and drying the WS2 solution onto microfiber to form a nanosheets layer. The WS2 coated microfiber is inserted into the ring laser cavity configured with a 2.4 m long Erbium-doped fiber (EDF) as the gain medium to generate Q-switching pulses train operating at 1568 nm. The Q-switched laser produced a pulse train, which the repetition rate is tunable from 62.0 kHz to 78.0 kHz as the pump power is raised from 151 to 193 mW. The minimum pulse width of 4.72 μs and the maximum pulse energy of 20.5 nJ was obtained at 193 mW pump power. The generated Q-switching pulses are stable and thus it is suitable for use in many practical applications. © 2019, S.C. Virtual Company of Phisics S.R.L. All right reserved

Quantum dot cadmium selenide as a saturable absorber for Q-switched and mode-locked double-clad ytterbium-doped fiber lasers

This paper demonstrates the integration of quantum dot (QD) cadmium selenide (CdSe) nanoparticles, which is embedded into polymethyl methacrylate (PMMA) film into an ytterbium-doped fiber laser (YDFL) cavity to produce Q-switched and mode-locked fiber lasers. The QD CdSe based film functions as a saturable absorber (SA). For Q-switching operation, stable pulse is generated within 970–1200 mW pump power, with tunable repetition rate and pulse width of 24.5–40.5 kHz and 6.8–3.7 µs, respectively. Maximum pulse energy and peak power are obtained about 1.1 µJ and 0.28 W, respectively. As we tune the polarization state of the laser cavity and use a single QD CdSe film, the mode-locking operation could also be generated within 310–468 mW pump power with repetition rate of 14.5 MHz and pulse width of 3.5 ps. Maximum pulse energy and peak power are obtained about 2 nJ and 0.11 W, respectively. These results may contribute to continuous research work on laser pulse generation, providing new opportunities of CdSe material in photonics applications

Q-Switched Erbium-Doped Fiber Laser Using Cadmium Selenide Coated onto Side-Polished D-Shape Fiber as Saturable Absorber

A stable Q-switched erbium doped fiber laser emitting at 1558nm is demonstrated using a cadmium selenide (CdSe) material coated onto a side-polished D-shape fiber as the saturable absorber (SA). By elevating the input pump power from the threshold of 91mW to the maximum available power of 136mW, a pulse train with a maximum repetition rate of 57.44 kHz, minimum pulse width of 3.76 μs, maximum average output power of 7.99mW, maximum pulse energy of 0.1391 μJ, and maximum peak power of 36.99mW are obtained. The signalto-noise ratio of the spectrum is measured to be around 75 dB. This CdSe based SA is simple, robust, and reliable, and thus suitable for making a portable pulse laser source

Nanosecond Pulses Generation with Samarium Oxide Film Saturable Absorber

For an electron-electron collision with characteristic scale length larger than the relative gyro-radius of the two colliding electrons, when the initial relative parallel kinetic energy cannot surmount the Coulomb repulsive potential, reflection will occur with interchange of the parallel velocities of the two electrons after the collision. The Fokker-Planck approach is employed to derive the electron collision term R describing parallel velocity scattering due to the reflections for a magnetized plasma where the average electron gyro-radius is much smaller than the Debye length but much larger than the Landau length. The electron parallel velocity friction and diffusion coefficients due to the reflections are evaluated, which are found not to depend on the electron perpendicular velocity. By studying the temporal evolution of the quantity due to R, it is found that R eventually makes the system relax to a state in which the electron parallel velocity distribution is decoupled from the perpendicular velocity distribution

Passively Q-switched ytterbium-doped fiber laser employing samarium oxide as saturable absorber

The rapid developments in transition metal dichalcogenide materials as saturable absorbers (SAs) have been reported to be efficient materials for generating Q-switched fiber lasers. In this paper, we report on the use of samarium oxide (Sm2O3)saturable absorber (SA) for 1-micron Q-switched fiber laser generation. The Sm2O3 thinfilm SA was constructed in-house through which the Sm2O3 powder was mixed and stirredin polyvinyl alcohol (PVA) solution. It was then integrated into the ytterbium-doped fiberlaser (YDFL) ring cavity, hence producing a sequence of Q-switched pulsed lasers at1062.49 nm wavelength. The stable pulse train appeared from 69.97 to 111.1 kHz betweenthe applied pump power of 57 mW to 96 mW. The signal-to-noise ratio (SNR) of 38.56dB was recorded at the 57 mW pump power, whereas the pulse energy raised until 15.21nJ at 96 mW. These results showed that the Sm2O3 could be a favourable SA material toiniatiate Q-switched ytterbium-doped pulsed fiber laser. ********************************************************************************* Perkembangan pesat dalam bahan logam peralihan dichalcogenide sebagai bahan penyerap boleh larut (SAs) telah dilaporkan sebagai kaedah yang berkesan bagi menjana laser fiber Q-switched. Kajian ini menggunakan samarium oksida (Sm2O3) saturable absorber (SA) bagi menjana laser gentian Q-switched 1-Micron. Filem nipis Sm2O3 SA telah dihasilkan melalui campuran serbuk Sm2O3 ke dalam cecair polivinil alkohol (PVA) dalam persekitaran makmal. Kemudian, ia diintegrasi ke dalam rongga gelang laser gentian dop-ytterbium (YDFL), lalu menghasilkan denyut laser Q-switched stabil pada jarak gelombang 1062.49 nm. Denyutan stabil muncul dari 69.97 kepada 111.1 kHz pada kuasa pam yang dikenakan antara 57 mW hingga 96 mW. Nisbah isyarat-hinggar (SNR) pada 38.56 dB telah direkodkan pada pam kuasa 57 mW, sementara denyut tenaga ditingkatkan kepada 15.21 nJ pada 96 mW. Keputusan menunjukkan Sm2O3 merupakan bahan SA penggalak yang memuaskan bagi menjana denyut laser gentian dop-ytterbium Q-switched

Q‐switching pulses generation with samarium oxide film saturable absorber

Q-switching pulses generation in an erbium-doped fiber laser (EDFL) was demonstrated by using a samarium oxide (Sm2O3) film as a saturable absorber (SA) for the first time. The passively Q-switched EDFL operated stably at 1567 nm with tunable repetition rates, ranging from 47 to 66 kHz with the increase in pump power from 51.0 to 88.1 mW. At 88.1 mW pump power, the maximum pulse energy and the minimum pulse width were obtained at 26 nJ and 5.6 μs, respectively. These results demonstrated that the proposed Sm2O3 SA is viable for the construction of a flexible and reliably stable Q-switched pulsed fiber laser in the 1.5 μm region. © 2019 Wiley Periodicals, Inc

Holmium Oxide Film as a Saturable Absorber for 2 μm Q-Switched Fiber Laser

This work reports on the use of the holmium oxide (Ho2 O3) polymer film as a saturable absorber (SA) for generating stable Q-switching pulses operating in a 2-μm region in a thulium-doped fiber laser cavity. The SA is prepared by diluting a commercial Ho2 O3 powder and then mixing it with polyvinyl alcohol (PVA) solution to form a Ho2 O3 -PVA film. A tiny part of the film about 1 mm×1 mm in size is sandwiched between two fiber ferrules with the help of index matching gel. When incorporated in a laser cavity driven by a 1552-nm pump, stable Q-switching pulses are observed at 1955 nm within the pump power range of 363-491 mW. As the pump power increases within this range, the repetition rate rises from 26 kHz to 39 kHz, as the pulse width drops from 4.22 μs to 2.57 μs. The laser operates with a signal-to-noise ratio of 47 dB, and the maximum output power and the pulse energy obtained are 2.67 mW and 69 nJ, respectively. Our results successfully demonstrate that the Ho2 O3 film can be used as a passive SA to generate a 2-μm pulse laser

Holmium based nanoseconds pulsed fibre laser generation in the 2-micron region

We demonstrate and compare nanoseconds pulse induced by a Holmium oxide PVA film (HOPF, 50 μm thick) and a Holmium-doped fibre (HDF, 8 cm long) saturable absorber (SA) in a Thulium doped-fibre laser (TDFL) cavity. The HOPF SA produced a nanoseconds pulse operating at 1960 nm wavelength, with a pulse width of 57 ns. On the other hand, the HDF SA produced a pulsed laser operating at 1963 nm wavelength, with a pulse width of 53 ns. The HDF SA established a slightly better maximum pulse energy of 0.87 nJ as compared to the HOPF SA with only 0.62 nJ. © 2019 Elsevier Gmb

Q-switched and mode-locked thulium doped fiber lasers with nickel oxide film saturable absorber

A passively Q-switched and mode-locked fiber laser based on thulium-doped fiber laser (TDFL) cavity was demonstrated utilizing nickel oxide (NiO) nanoparticles as a saturable absorber (SA). The NiO synthesis was carried out by using a facile sonochemical method and the prepared NiO thin film was sandwiched between two optical fiber ferrule connectors in the TDFL ring cavity. By controlling the loss and gain in the cavity, stable Q-switching operation was obtained. The repetition rate and pulse width were tunable from 6.71 kHz to 19.58 kHz and from 9.16 μs to 4.24 μs respectively, at different pump powers, ranging from 528 mW to 711 mW. The Q-switched TDFL was centered at 1900.52 nm and had maximum pulse energy and slope efficiency of 0.31 μJ and 2.58%, respectively. On the other hand, self-starting mode-locked TDFL was achieved by employing 10 m scandium-doped fiber into the ring cavity and remained stable within a pump power range of 821–967 mW. The TDFL mode-locked had a central wavelength of 1928.81 nm, at a threshold pump power of 821 mW. The repetition rate and pulse width were 8.10 MHz and 61.27 ns, respectively, while the slope efficiency was measured to be 2.20 %. © 201