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A passively Q-switched erbium-doped fibre laser was demonstrated by using tris-(8-hydroxyquinoline)aluminium (Alq3) organic material as a passive saturable absorber (SA). The SA was fabricated by a drop casting technique at room temperature and incorporated into a laser cavity by inserting it between two optical fibre ferrules. The Q-switched fibre laser operates at a centre wavelength of 1559 nm with a full-width half maximum of 1 nm. The generated pulse train is stable and has a pulse width decreased from 6.65 to 1.2 I¼s and the pulse repetition rate increased from 31.65 to 144.5 kHz as the pump power increased from 20 to 122 mW. The maximum pulse energy obtained is 63.89 nJ. This work indicates that the Alq3 as SA has a great potential to be utilised for pulsed laser generation. To the best of the authors' knowledge, this is the first time an organic material is utilised as a SA device for generating a stable Q-switched laser pulse. © 2019 Institution of Engineering and Technology. All rights reserved.

A passively mode locked erbium-doped fiber laser (EDFL) operating at center wavelength of 1569.1 nm is demonstrated based on magnesium oxide (MgO) thin film as a saturable absorber (SA) for the first time. MgO SA was constructed using casting solvent method, and it found that it exhibits suitable modulation depth of about 32.4% and saturation intensity of 16 MW/cm2. Self-started mode locked pulse trains with fix repetition rate of 3.5 MHz, short pulse duration of 5.6 ps and high signal to noise ratio (SNR) of 50 dB were achieved at maximum input pump power of 159 mW.

Soft clay is a natural soil that spreads in the south of Iraq and many countries in the world. It is a problematic soil causing trouble for the structures built on it because of, high water content, low shear strength, and high compressibility. This work investigated the geotechnical behavior of soft clay by using mix of Metakaolin (M) and Sugarcane Straw Ash in air (SCSAA).The experimental work contains the following tests: chemical tests, physical tests, Compaction tests and shear test. These tests were carried out on soil samples prepared from soft soil; the replacement materials by weight of dry unit weight for different percentages of M (4%, 6%, 8%, 10%) mix with different percentages of SCSAA (4%, 6%, 8%, 10%). The tests results showed that the best percentage for the plasticity test was M1B4. Also,the percentage which gave the best value for undrained shear strength test was M4B4 (135).Finally, the treatment soil is good sub grade materials and also can be used in highway sub-base material.

We show that the addition of an array of silicon nitride nanowire resonator can boost the absorbance of a monolayer of WS2 from around 5-10% to 62% at the exciton wavelength of 620 nm.

We experimentally demonstrate Q-switched fiber lasers based on Ytterbium-doped fiber laser (YDFL) and Erbium-doped fiber laser (EDFL) cavity using cobalt oxide (Co3O4) nanocubes film as a saturable absorber (SA) to operate at 1043.64 nm and 1560.4 nm respectively. This material is embedded into polyethylene oxide (PEO) film to obtain a high nonlinear optical response that can be used for SA application. The Co3O4 nanocubes film was fabricated by a simple processing technique and it has a modulation depth of 4% and saturation intensity of 56 MW/cm2. By incorporating the Co3O4 nanocubes SA into the YDFL cavity, a stable Q-switched pulse train was generated with repetition rate increasing from 60.3 to 86.66 KHz, by increasing the pump power from 144.4 to 165.4 mW. At the pump power of 147.9 mW the pulse width and pulse energy are 4 µs and 154 nJ respectively. The EDFL generates a stable Q-switched pulses with repetition rate of 119.7 KHz, pulse width of 2.4 µs and pulse energy of 6 nJ at maximum pump power of 141 mW. This results propose that cobalt oxide could be a promising broadband SA for all fiber lasers wavelengths at 1 and 1.5 µm.

Q-switched and mode-locked fibre lasers have been successfully demonstrated in ytterbium-doped fibre laser cavity by taking an advantage of the optical absorption of antimony telluride (Sb2Te3) material. The Sb2Te3 was embedded into polyvinyl alcohol to function as a saturable absorber (SA). A Q-switching pulses train was obtained by incorporating the SA into the laser ring cavity configured with 3 dB coupler. The Q-switching pulse repetition rate increases from 24.4 to 55 kHz as the pump power is increased from the threshold of 75.4–96.2 mW. The maximum pulse energy of 252.6 nJ is obtained at 82.3 mW pump power. On the other hand, by changing the output coupler to 10 dB coupler, a stable self-started mode-locking operation was then generated at pump power range from 47.8 to 89.4 mW with a fixed repetition rate of 24.2 MHz. At 89.4 mW pump power, the maximum output power and pulse energy are obtained to be around 18.6 mW and 0.8 nJ, respectively. The authors results display that the Sb2Te3 material could also be developed as an effective SA for both Q-switched and mode-locked fibre lasers.

In this paper, we report a nanosecond mode locked erbium doped fiber laser (EDFL) using zinc oxide (ZnO) nanoparticles as a saturable absorber (SA) for the first time. Due to its excellent optical properties, in particular a high nonlinear optical response and fast recovery time, ZnO nanoparticles can be used as a saturable absorber device for pulsed laser generation. For easy integration into the laser cavity, the ZnO nanoparticles were imbedded into a polymer film using a seeding solution technique. 400 ns mode locked pulse train was successfully obtained at a relatively low threshold pump power of 45.4 mW. The output laser operates at the fundamental frequency of 1 MHz with a center wavelength of 1558.34 nm. The highest pulse energy and peak power achieved by the laser are estimated at 11.6 nJ and 27.3 mW respectively at the maximum available pump power of 142 mW. The results show that the SA derived from ZnO nanoparticles is capable of producing nanosecond mode locked EDFL for possible applications that require high pulse energy and medium output power.

A high pulse energy Q-switched ytterbium-doped fiber laser (YDFL) based on copper oxide (CuO) nanoparticles as a saturable absorber (SA) is demonstrated. The CuO nanoparticles have been fabricated into a thin film using a liquid-phase exfoliation method then it was integrated into a laser cavity to act as Q-switcher. The proposed Q-switched YDFL operates at a central wavelength of 1035.4 nm with a 3-dB bandwidth of 0.26 nm. The Q-switched laser has a repetition rate range from 57 kHz to 104 kHz by varying the pump power from 179 mW to 226.5 mW, while the pulse width was tuned from 4.5 µs to 2.2 µs. Relatively, high pulse energy around 0.192 µJ was achieved at an average output power of 20 mW. This laser with high pulse energy can be seen as a very promising pulsed laser source in many industrial and optical sensing applications. To the best of our knowledge, this is the first demonstration of a Q-switched fiber laser using CuO-SA in YDF.

This paper demonstrates a few-picosecond and high-peak-power mode-locked fiber laser, using an erbium-doped fiber as a gain medium and zinc oxide (ZnO) element as a new passively saturable absorber (SA). The ZnO element was synthesized using a seeding solution and amended with a polyvinyl alcohol to form a film. The ZnO has been identified as an ideal SA due to its high nonlinear optical response, high sustainability to damage threshold, and fast recovery time. Self-started mode-locked laser pulses have been generated at a relatively low pump power of 42 mW with a fundamental repetition rate and pulse duration of 3.26 MHz and 2.60 ps, respectively. The proposed laser operates at 1599.5 nm with a 3 dB spectral bandwidth of 1.12 nm. A maximum output power, pulse energy, and peak power of about 6.91 mW, 2.12 nJ, and 0.82 kW, respectively, are obtained at a maximum pump power of 159 mW. From these findings, we confirm that the proposed laser can be viewed as a promising light source in the emerging optical communication system.