Generation of Q-Switching pulse train with topology insulators / Nur Farhanah Zulkipli

This report presents two Q-switched Erbium-doped fiber lasers (EDFLs) utilizing topology insulators (TI) as saturable absorber (SA). The SA was fabricated by embedding Bismuth (III) Selenide (Bi2Se3) or Bismuth (III) Telluride (Bi2Te3) into a polyvinyl alcohol (PVA) film. The first Q-switched EDFL was obtained by incorporating a Bi2Se3 film inside the laser cavity. The laser generates stable pulse train by changing the pump power from 86.1 mW to 116.6 mW with repetition rate that can be tuned from 84.08 kHz to 87.03 kHz. It operated at 1559.8 nm wavelength with an excellent stability. The RF spectrum showed the signal noise to ratio of about 60 dB. The maximum pulse energy of 36.9 nJ and the lowest pulse width of 5.11 μs were obtained at pump power of 116.6 mW. The second Q-switched EDFL was demonstrated using TI Bi2Te3 material. The laser operates at 1558.5 nm with a lower threshold pump power of 25.0 mW. The repetition rate of the laser varies from 38.76 kHz to 77.88 kHz as the 980-nm pump power increased from 25.0 mW to 106.4 mW. The Q-switching operating has the shortest pulse width of 6.56 μs, the maximum pulse energy up to 127 nJ and the peak-to-pedestal ratio of 65 dB for the RF spectrum. These results shows that Bi2Te3 film performed better than Bi2Se3 one in terms of pulse energy and wider tuning range for repetition rate and pulse width. The experimental results also verify that both TI films possess the potential advantage for stable Q-switched pulse generation at 1.5 μm

Passively Q-switched fiber laser tunable by Sagnac interferometer operation

In this paper, a stable passively Q-switched Erbium-doped fiber laser (EDFL) tunable by Sagnac interferometer operation was described by using a graphene oxide saturable absorber (SA) as a Q-switcher. The wavelength operation of the Q-switched EDFL was tunable from 1566.3 nm to 1559.3 nm by increasing the temperature of sagnac loop mirror (SLM) from 30 °C to 70 °C in the figure-of-eight laser configuration. At 1566.3 nm operation, by increasing the pump from the threshold power of 77.3 mW to 126.5 mW, the repetition rate can be increased from 30.7 kHz to 41.5 kHz while the pulse width was narrowed from 10.2 to 7.3 μs. The Q-switching threshold pump power increased with the increase of the temperature, which then shifted the operation to a shorter wavelength. However, the laser efficiency increased at a shorter wavelength operation. At 1561.4 nm operation, the maximum pulse energy of 20.5 nJ was obtained at 161.0 mW pump power

Nanosecond pulse generation with a gallium nitride saturable absorber

A mode-locked nanosecond Erbium-doped fiber laser (EDFL) was demonstrated using gallium nitrate (GaN) in the form of a polished crystal as a saturable absorber (SA). The GaN film exhibited a modulation depth of 2% with a saturable optical intensity of 0.46 MW/cm2. The laser directly produced nanosecond pulses with stable mode-locking operation at a pump threshold of 149.51 mW. The generated output pulses operated at a 1562 nm central wavelength with a pulse duration and a repetition rate of 485 ns and 967 kHz, respectively. The average output power was 3.068 mW at a pump power of 182.34 mW, corresponding to 3.1 nJ single pulse energy. These results indicate that GaN material has a promising application in ultrafast light generation. © 2018 Optical Society of America under the terms of the OSA Open Access Publishing Agreement

Q-Switched Fiber Laser with a Hafnium-Bismuth-Erbium Codoped Fiber as Gain Medium and Sb2Te3 as Saturable Absorber

We successfully demonstrate Q-switched fiber laser with a 20 cm long Hafnium-Bismuth-Erbium codoped fiber (HBEDF) as an active medium in conjunction with Antimony Telluride (Sb2Te3) saturable absorber (SA). The HBEDF has an Erbium ion absorption coefficient of 100 dB/m at 980 nm; thus, the laser setup only requires a very short length of gain medium for lasing in the 1550 nm range. We realize the Sb2Te3 SA obtained by embedding the material into Polyvinyl Alcohol (PVA), and a Q-switched pulse train operating at 1560.7 nm is realized, using only a 20 cm long active fiber, when the prepared Sb2Te3 thin film is integrated into the laser ring cavity. The repetition rate of the Q-switched pulses is tunable from 47.7 to 74.8 kHz as the pump power is raised from the threshold value equal to 69.9 mW to a value of 105.0 mW. The maximum attainable pulse energy is 31.2 nJ. Our results indicate that the Sb2Te3 material is useful as an effective Q-switcher especially for the laser operation in 1.55 mu m range

Generation of Q-switched and mode-locked pulses with Eu2O3 saturable absorber

In this paper, Europium Oxide (Eu2O3) is used as a saturable absorber (SA) to produce Q-switched and mode-locked pulses in an erbium-doped fiber laser (EDFL) cavity. The Eu2O3 was synthesized using casting technique and the resulting Eu2O3 thin film was introduced between two optical fiber ferrule connectors to form a SA. Then the SA was positioned in the EDFL ring cavity. A stable Q-switched operation was achieved by controlling the loss and gain of the cavity. As the pumping power was increased from 84.0 mW to 125.0 mW, the repetition frequency increased from 60.1 kHz to 68.6 kHz and pulse width reduced from 4.5 μs to 3.6 μs respectively. The Q-switched EDFL was operating at the center wavelength of 1568 nm, had a 162 nJ maximum pulse energy and 10.24% slope efficiency. Adding a 100 m SMF in the ring cavity initiated a self-starting mode-locked EDFL and the pulses remained stable within a range of 104.6 to 145.8 mW pump power. At the threshold pump power of 104.6 mW, the mode-locked EDFL operated at a central wavelength of 1565 nm with a repetition rate of 1.8 MHz and a pulse width of 3.51 ps. The results show that Eu2O3 can be deployed as a SA for both Q-switching and mode locking generations. © 2020 Elsevier Lt

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