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Abstract The mechanism of laser mode in fibre laser has been a popular talking issue since decades ago. Numerous mode mechanisms are revealed from time to time such as LP and TM. From these modes, fundamental mode and higher-order mode exhibit practical applications such as in fibre laser. Based on this perspective, we employ the mode mechanism in random fibre laser with half open cavity that generates dual-mode output which consists of LP01 and LP11 modes. The investigation on our proposed laser setup is beneficial for developing photonics system that involves the implementation of few-modes mechanism. Highlights • We demonstrated a dual mode output RFL that provides LP01 and LP11 modes simultaneously at 1.55 μ m wavelength region. • First demonstration of random fibre laser in few mode fibre. • A novel solution to generates LP01 and LP11 modes. [ABSTRACT FROM AUTHOR]

A means of supercontinuum (SC) generation is proposed and demonstrated, using femtosecond mode-locked pulses with sub-megahertz repetition rate based on the nonlinear polarization rotation technique. Total cavity length is approximately 522?m, which includes an additional 500?m single mode fiber (SMF) and the fundamental repetition rate obtained is 404.5?kHz. The mode-locked spectrum has a central wavelength of approximately 1600?nm and a 3?dB bandwidth of 16?nm, which falls within the L-band region. The threshold power for the mode-locked operation is achieved at approximately 52?mW. At pump power of 74?mW, the measured pulse width, pulse energy, and average output power are 70?fs, 18.3?nJ and 7.4?mW respectively. The generated pulses are amplified by a 72.44?mW erbium-doped fiber amplifier before being injected into a 100?m long highly non-linear fiber as the nonlinear medium to generate the SC spectrum. The obtained SC spectrum spans from 1250?nm to more than 1700?nm, with bandwidths of 450?nm at a ?70?dBm output power level. For comparison purpose, the 500?m SMF is removed from the setup and similar measurements are then repeated for this case. [ABSTRACT FROM AUTHOR]

An ultra-wide wavelength tuning range, which covers three different band regions consisting of the S-, C-, and L-bands, is proposed and demonstrated for a graphene-based Q-switched erbium-doped fiber laser using a tunable bandpass filter as the wavelength tuning and filtering mechanism. A 3 m length of erbium-doped fiber is used as the gain medium in a ring laser cavity configuration, with absorption coefficients of between 11 and 13 dB m−1at 980 nm and about 18 dB m−1at 1550 nm. The tuning range of the Q-switching pulses covers a wide wavelength range of 58 nm, which spans from 1512.5 nm to 1570.5 nm. In addition, the lasing and Q-switching thresholds are considerably low, with respective values of ∼11.0 mW and ∼18.4 mW. A repetition rate of 55.3 kHz is obtained at the maximum pump power of 100.4 mW, together with pulse width and pulse energy of 1.6 μs and 25.8 nJ, respectively. [ABSTRACT FROM PUBLISHER]

A tunable short-wavelength band Raman fiber laser using a dispersion shifted fiber as the nonlinear medium is proposed and demonstrated. This approach provides an alternative to the common method of using depressed-cladding, erbium-doped fibers as the gain medium in S-band fiber lasers. The proposed laser has a tuning range of 1508 to 1534 nm as well as an average peak power of about −11.3 dBm within the range 1518–1530 nm. A high signal-to-noise ratio of approximately 70 dB is obtained from the system at this range. [ABSTRACT FROM PUBLISHER]

A graphene-based Q-switched erbium-doped fiber laser (EDFL) with a tunable fiber Bragg grating (TFBG) acting as a wavelength tuning mechanism is proposed and demonstrated. The proposed setup utilizes a newly-developed ‘ferrule-to-ferrule transfer’ technique to obtain a single graphene layer that allows for Q-switch operation in the EDFL using a highly doped-gain medium. A TFBG is used as a wavelength tuning mechanism with a tuning range of 10 nm, covering the wavelength range from 1547.66 nm to 1557.66 nm. The system has a wide repetition rate range of over 206.613 kHz from 1.387 kHz to 208.000 kHz with pulse durations of between 94.80 μs to 0.412 μs. The laser output is dependent on the pump power, with energy per pulse of 4.56 nJ to 16.26 nJ. The system is stable, with power and wavelength variations of less than 0.47 dBm and 0.067 nm. The output pulse train is free from self-mode locking and pulse jitters. [ABSTRACT FROM PUBLISHER]

In this paper a tunable single-longitudinal mode (SLM), short-wavelength band (S-band) fiber laser using a conventional erbium-doped fiber (EDF) with a length of 3 m and a step index erbium dopant profile as opposed to the commonly used depressed cladding erbium-doped fiber (DC-EDF) is proposed and demonstrated. The proposed SLM fiber laser has a tuning range of 1496 to 1507 nm in a ring configuration using two 0.15 m of EDF which acts as saturable absorbers (SAs). The highest peak power measured is about −0.6 dBm at a wavelength range of 1502 to 1507 nm. The measured signal-to-noise ratio (SNR) is approximately 74 dB for the same wavelength range. The line-width of the SLM output is measured to be 140 kHz. [ABSTRACT FROM PUBLISHER]

A tunable up frequencies of microwave photonics based on stimulated Brillouin scattering (SBS) for application in radio over fiber is demonstrated. The experimental setup consists of 7.7 km dispersion compensated fiber, which acts as the nonlinear medium for generating the SBS and is pumped by a narrow linewidth (0.015 nm) tunable laser operating in L-band region. The input-modulated RF at 2 GHz is upshifted to new frequencies of 7.71, 7.68, 7.65, 7.62, 7.58, and 7.56 GHz at Brillouin pump wavelengths of 1580, 1585, 1590, 1595, 1600, and 1605 nm, respectively. This system allows certain tunability in the upshifted frequencies by using a tunable laser source. © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.26106 [ABSTRACT FROM AUTHOR]

Abstract: In this paper, we propose and demonstrated a dual wavelength fiber laser (DWFL) based on the use of an erbium doped fiber (EDF) gain medium as well as an 1×24 Arrayed Waveguide Grating (AWG) together with two optical channel selectors (OCS) to provide channel spacing tunability. The output power of the two wavelengths is equalized by controlling the cavity loss in the DWFL using two Programmable Optical Attenuators (POAs). The widest spacing obtained from the DWFL is 18.13nm while the narrowest spacing is 0.8nm. The DWFL has good stability with only minor power fluctuations of less than 1.5dB and a Side Mode Suppression Ratio (SMSR) of approximately 69.1dB with peak fluctuations of less than 2.3dB. [Copyright &y& Elsevier]

Abstract: The switchable multiwavelength fiber laser (SMWLSs) using AWG and broadband FBG with tuning range 11.7nm and 0.75nm spacing are demonstrated. The switchable lasers for every channel shows flatness output power with variation 3.7dBm and peak power around −6.1dBm. The side mode suppression ratio (SMSR) of the laser is significantly improved for every channel when using broadband FBG. The improvement is about 27.7dBm. The laser for every channel also shows the good stability within the 2h operation. [Copyright &y& Elsevier]

• Generation of dual-wavelength mode-locked fiber laser at around 1.56 µm and 1.93 µm. • A graphene saturable absorber was shared among two ring-structured laser cavities. • Mode-locked fiber laser was synchronized at a constant cavity length at 16.4 meters. • The pulse repetition rate was kept constant at 12.905 MHz. Ultrafast pulse with short duration ranging from picosecond to femtosecond has extensive industrial and scientific applications. The laser cavity generates this ultrafast pulse, however, was typically designed to emit the light at wavebands such as at approximately 1.5–1.6 µm or 1.9–2.0 µm. This could be limited by the bandgap of certain saturable absorber material to conduct ultra-broadband laser emission. Graphene, a 2D material with gapless band structure contributes to the optical resonant excitation to emit at any wavelength. The graphene was employed as the saturable absorber and positioned in a laser cavity consisting of both erbium and thulium-doped fiber laser. A synchronized mode-locked fiber laser was generated at a centre wavelength of 1563.5 nm and 1931.9 nm, giving a pulse duration of 700 fs and 1.77 ps at a constant pulse repetition rate of 12.905 MHz. The success of this work will provide a better insight by developing the optimum utilization of a saturable absorber in generating multiple mode-locked lasers with different yet far wavelength in near-infrared red region. [ABSTRACT FROM AUTHOR]

Single longitudinal mode (SLM) erbium-doped fiber (EDF) laser operation using a commercialized ultra-narrow bandwidth optical filter has been demonstrated. A 2-m long EDF with an absorption coefficient of 24 dB m −1 at the pump wavelength is used as gain medium. The ultra-narrow tunable filter is used for selection of a single longitudinal mode from the available spectrum of multiple modes, which originally exist in the FBG's reflection spectrum. Our approach provides a relatively simple and direct method for realization of SLM operation. A high-resolution optical spectral analyser with a resolution of 0.16 pm is used to observe the output spectrum. To verify the SLM operation, the delayed self-heterodyne method is used, giving a measured laser linewidth of 61.5 kHz. [ABSTRACT FROM AUTHOR]

A semiconductor optical amplifier (SOA) based linear cavity L-band dual wavelength fiber laser (DWFL) with a switchable output is proposed and its operation demonstrated. The DWFL is configured as a linear cavity, with a 1 × 24 arrayed waveguide grating together with two optical switches providing channel spacing tunability. An L-band SOA, with a central operating wavelength of 1580 nm and an operation bandwidth of 1500–1640 nm serves as the gain medium of the proposed laser cavity. The DWFL is able to generate a dual-wavelength output, with the widest spacing obtained being 18.7 nm and the narrowest spacing being 0.8 nm. The generated output is highly stable, with only minor power fluctuations of less than 2 dB as well as having a signal-to-noise ratio of 42 dB. The proposed setup would have numerous uses, particularly for sensor applications. [ABSTRACT FROM AUTHOR]

Abstract A tunable, passively Q-switched fiber laser using titanium dioxide (TiO 2) as saturable absorber (SA) is proposed and demonstrated. The TiO 2 SA has an insertion loss and modulation depth of 2.6 dB and 19.1 % respectively. The generated laser output has a repetition rate of 83.3 kHz and pulse-width of 0.08 μ s at a maximum pump power of 270.0 mW. On the other hand, tuning the operational wavelength from 1534.0 nm to 1570 nm while fixing the pump power at 70.0 mW varies the repetition rate and pulse width from 50.5 to 22.2 kHz and 1.3 to 2.7 μ s respectively. The results indicate that TiO 2 could be an inexpensive and efficient SA for generating passively Q-switched fiber laser. Highlights • Tunable passively Q-switched fiber laser. • Titanium Dioxide (TiO 2) as saturable absorber. • Repetition rate of 83.3 kHz and pulse-width of 0.08 μ s at maximum pump power of 270.0 mW. • Tuning the operational wavelength from 1534.0 nm to 1570.0 nm. • Varies the repetition rate and pulse width from 50.5 to 22.2 kHz and 1.3 to 2.7 μ s respectively. [ABSTRACT FROM AUTHOR]

Abstract A passively Q-switched thulium/holmium fiber laser with a gallium selenide (GaSe) saturable absorber (SA) is proposed and demonstrated for the first time. The GaSe based SA is prepared by mechanical exfoliation and inserted into the proposed laser cavity to generate Q-switched pulses. Stable Q-switching operation is achieved at 1986.0 nm, with output pulse repetition rates ranging from 22.9 kHz to 32.3 kHz over a pump power range of 112.0 mW to 235.0 mW. The generated Q-switched pulses have a maximum pulse energy of 120.3 nJ and minimum pulse width of 6.9 μs. The proposed thulium/holmium fiber laser with GaSe SA will be able to cater to multiple applications requiring pulsed laser outputs in the 2.0 μm region. [ABSTRACT FROM AUTHOR]