In this study, we propose and experimentally demonstrate a new mode-locked fiber laser configuration in which a large-core erbium-doped fiber (EDF) simultaneously functions as the gain medium and an artificial saturable absorber (SA). A 70 cm-long, highly doped large-core EDF was incorporated into a simple all-fiber ring resonator, eliminating the need for any additional conventional SA device. Stable soliton mode-locking was achieved through nonlinear multimode interference occurring within the large-core EDF. The excitation and interaction of multiple transverse modes under high optical intensity produced intensity-dependent transmission, effectively enabling self-starting pulse formation. The laser generated stable soliton pulses centered at 1564.1 nm with a pulse duration of 330 fs. Mode-locking was maintained over a pump power range from 291.6 to 319.2 mW, demonstrating good operational stability. Owing to the short cavity length—since the same EDF segment serves dual roles as both gain medium and artificial SA—the laser achieved a relatively high fundamental repetition rate of 24.1 MHz. The maximum pulse energy reached 143.5 pJ. This compact and simplified architecture highlights the potential of large-core EDF as a multifunctional nonlinear element for efficient ultrafast pulse generation without relying on discrete SA components.

An optical fiber sensor has shown significant effectiveness for monitoring the refractive index (RI) of liquid analytes, with previous work reporting such sensors for RI detection in a close-proximity setting. In contrast, this work proposed remote monitoring of the RI using bare fiber (BF) and D-shaped fiber (DSF) probes. The optimal DSF structure was simulated using COMSOL Multiphysics to determine the most suitable design parameters. The sensing setup incorporates essential low-complexity components, a 2-km fiber cable connected to an optical time-domain reflectometer (OTDR). This arrangement eliminates the need for a far more complicated sensing setup that requires both ends of the fiber to be utilized as a source and a detector. This simplified architecture allows users to monitor RI changes in hazardous environments, such as nuclear sites, waste treatment plants, and polluted soil. The BF and DSF probes obtained maximum sensitivities of 42.884 dB RIU-1 and 42.089 dB RIU-1, respectively.

This study presents the development and optimization of a multi-D-shaped optical fiber sensor designed for enhanced refractive index (RI) and ethanol detection. The sensor probes were fabricated using a precise side-polishing technique on standard single-mode fiber (SMF-28) to maximize the evanescent field interaction with the surrounding medium. We systematically investigated the influence of the number of D-shaped sensing zones ($N$N = 1 to 5) on sensor performance using glycerin-water solutions (RI 1.357-1.428). The experimental results demonstrate a significant sensitivity enhancement as the number of sensing zones increases, achieving a peak sensitivity of 12.12 dB/RIU with a 4-point ($N$N = 4) configuration. A subsequent performance decline at $N$N = 5 indicated a saturation limit dominated by fundamental mode field distortion and cumulative insertion loss. When applied to ethanol detection (RI 1.333-1.365), the optimized 4-point sensor exhibited a highly linear response (R2 = 0.9828) with a sensitivity of 3.866 dB/RIU. Notably, the sensor demonstrated high wavelength stability with negligible spectral shift across the tested range, confirming its operation as a robust, intensity-modulated device suitable for cost-effective biochemical sensing applications.

This study demonstrates the generation of ultrafast picosecond mode-locked pulses in an erbium-doped fiber laser using a polyaniline–boron nitride (PANI–BN) nanocomposite as a saturable absorber (SA). The PANI–BN nanocomposite exhibits significant nonlinear optical absorption, with a modulation depth of 4.1

In this work, a stable dual-wavelength mode-locked erbium-doped fiber laser (EDFL) incorporating sub-stoichiometric molybdenum trioxide (MoO3-x) as a saturable absorber (SA) is presented. The MoO3-x thin-film SA was prepared by hot-wire chemical vapor deposition (HWCVD) to induce oxygen vacancies and integrated into an all-fiber EDFL cavity. Stable dual-wavelength mode-locking was achieved over a pump power range of 109.1 mW to 164.5 mW, with peak wavelengths at 1532.2 nm and 1558.2 nm, separated by 26.0 nm. The mode-locked pulses exhibited an ultrashort pulse width of 4.44 ps, a repetition rate of 1.277 MHz, and a signal-to-noise ratio (SNR) of 84.32 dB. The maximum output power obtained was 10.07 mW, corresponding to a maximum pulse energy of 7.9 nJ. The stability of the dual-wavelength mode-locking was confirmed by continuous operation over 70 min. These findings demonstrate the potential of MoO3-x as an effective saturable absorber for generating stable dual-wavelength picosecond pulses in fiber lasers.

A polyaniline–boron nitride (PANI–BN) film was demonstrated as a saturable absorber (SA) for domain-wall dark pulse generation in a long-cavity erbium-doped fiber laser (EDFL) operating under net anomalous dispersion. Stable mode-locking was achieved over a pump power range of 129.9–212.1 mW, producing dual-wavelength emission centered at 1532.4 nm and 1557.2 nm. The dual-wavelength operation is attributed to an artificial birefringent filtering effect induced by residual polarization asymmetry from the PANI–BN film and other intracavity components. The generated dark pulses exhibited a repetition rate of approximately 1.30 MHz with a negative pulse width of 189 ns. The pulse formation is explained by domain-wall theory, where dark pulses arise from incoherent nonlinear coupling between two coexisting lasing beams oscillating simultaneously in the cavity. At the maximum pump power of 212.1 mW, the laser delivered an output power of 5.8 mW. A high signal-to-noise ratio of 70 dB at the fundamental frequency confirmed excellent pulse stability, robust mode-locking operation, and low-noise performance. These results highlight the potential of PANI–BN nanocomposites as efficient optical modulators for stable dark pulse fiber laser applications.

Magnesium phthalocyanine (MgPc), a representative material from the phthalocyanine family, has been widely reported to possess strong nonlinear absorption and favorable optical characteristics. In this work, MgPc is utilized as a passive mode-locking element in an L-band erbium-doped fiber laser (EDFL) ring configuration to produce soliton pulses. The MgPc was implanted in a polyvinyl alcohol (PVA) host to form a pulse modulator, yielding a modulation depth of 4.6%. When incorporated into the laser setup, the MgPc-based modulator enabled stable soliton mode-locking with a pulse duration of 5.8 ps. The output spectrum was centered at 1595.6 nm after amplification by a dual-stage amplifier within the ring cavity. The laser operated at a repetition rate of 1.82 MHz, corresponding to the cavity length, and exhibited a high signal-to-noise ratio of 72.2 dB. These results confirm that MgPc is a promising passive modulator for ultrafast mode-locked fiber laser systems operating in the L-band region.

The experimental demonstration of domain-wall dark pulses in an extended cavity mode-locked Erbium-doped fiber laser is presented, employing a Bi2Te3 saturable absorber (SA). Through the incorporation of Bi2Te3 powder into a polyvinyl film, we successfully developed a Bi2Te3 SA with a notable modulation depth of 12.6%. Integrated into a ring EDFL, the Bi2Te3-SA enabled the generation of mode-locked domain-wall dark pulses, exhibiting dual-wavelength emission, capitalizing on its saturable absorbing capability alongside the inherent nonlinear properties of the Bi2Te3 thin film and the extended single-mode fiber spool. The domain-wall dark pulse initiated spontaneously at a pump power of 41.3 mW, emitting at wavelengths of 1562.8 nm and 1564.2 nm. Notably, the dark pulse repetition rate measured at 1.81 MHz, accompanied by a pulse duration of 180 ns and the highest average pulse energy recorded at 1.95 nJ. These results underscore the promising potential of Bi2Te3 as an advanced material for application in pulsed laser systems, particularly due to its exceptional nonlinear properties, positioning it as a fascinating candidate for further advancements in pulsed laser technology.

Fertigation system has been widely used by farmers to automate some processes of crops productions. A conventional system requires workers to prepare a fertilizer mixture, before transferring it into a main storage tank to be mixed with water. Then, electrical conductivity (EC) of the mixture will be measured. The existing fertigation system still relies heavily on workers and is manually operated and prone to human error. Therefore, internet of things (IoT) based fertigation system has been developed to deliver the fertilizer mixture with consistent EC value automatically to the plants. The main system controller is designed using ESP32 development module. The operation of the system can be monitored using an IoT dashboard and farmers can also control the system remotely. Alert will be given to the farmers if the condition of the system or plant does not meet the predefined settings. The values of EC together with temperature and humidity sensors are recorded for further analysis. A testbed is set up to provide fertigation to 120 polybags eggplants. Using the proposed fertigation system, the eggplants have been harvested earlier, therefore reducing the fertilizer usage. The cost of this IoT based fertigation system is lower compared to existing commercial products.

The laser generation was produced at a wavelength of 1562.4 nm with a small spectral bandwidth of 0.4 nm using a short -pulse erbiumdoped fibre laser with unique group delay dispersion. This process was generated by Q -switching, which was accomplished using a vanadium oxide polyethylene glycol (V2O5-PEG) film saturable absorber (SA) within an all -fiber ring cavity arrangement. The laser generated a peak output power of 0.4 mW, a maximum pulse energy of 3.2 nJ, and an astonishingly brief pulse width of 4.7 s. These results highlight the possibility of the V2O5 film as a workable SA substitute for producing pulsed lasers.

Rice is the most consumed food in the world, mainly in Asia and Africa. Malaysia is the second-largest rice importer in Southeast Asia after Indonesia. However, rice yield is limited by water stress. One alternative for a quicker strategy to mitigate water stress is through a combination of foliar spermine application and efficient rice management practices via image monitoring techniques using drone technology. The present study was aimed at evaluating the effects of spermine on rice physiological response and its association with aerial imagery and yield under reproductive during reproductive stage under water stress. The experiment was carried out under greenhouse conditions using a two-factorial randomized complete block design (RCBD), with foliar spermine treatment as the first factor and water stress as the second factor. Physiological parameters showed significantly higher tiller number per pot and photosynthesis rate by 29% and 31%, respectively. Correspondingly, the Normalised Difference Vegetation Index (NDVI) using aerial imagery monitoring showed an increased value in spermine treatments by 2% compared to control. Furthermore, NDVI readings and photosynthetic rate were positively correlated linearly with R2= 0.51. Interestingly, spermine treatments alleviated water stress effects by 40%, 17% and 12% in grain weight per pot, grain number per panicle and percentage filled grain. Biomass partitioning in roots improved by 44% in spermine treatments, even under water stress, due to an efficient translocation of assimilates. In conclusion, spermine foliar application significantly improved growth, grain filling and rice yield production, which was also supported by NDVI values using aerial imagery monitoring.

This paper presents the first demonstration of a Q-switched Thulium-doped fiber laser (TDFL) utilizing our newly developed Thulium-doped fiber (TDF) and a MXene niobium carbide - polyethylene oxide (Nb2CTx-PEO) thin film as a gain medium and saturable absorber (SA), respectively. The TDF core glass contains 6.15wt% Al2O3, 2.2wt% Y2O3, 0.47wt% Tm2O3, 2.12wt% GeO2, 1.57wt% HfO2 and 0.05wt% Bi2O3 with the absorption of 30dB/m at 1550nm. The outcome was the realization of a stable pulsed laser operating at a central wavelength of 1888.3nm. The Q-switched pulses exhibited a maximum repetition rate of 46.7kHz and a minimum pulse width of 1.995 µs at a pump power of 731.41mW. The Q-switched operation maintained a signal-to-noise ratio (SNR) of 45dB, confirming its stability. This breakthrough highlights the laser system's potential for diverse applications, including free-space optical communication, spectroscopy, and medical fields.

Mid-infrared (MIR) fiber lasers are highly demand after for a variety of technological applications, including uses such as laser surgery, frequency metrology, and spectroscopy. This paper demonstrates a stable continuous-wave laser operation in the 2.8 mu m using an Er3+-doped ZBLAN fiber operating in a free space experimental setting. A laser output power of 12.4 mW was attained in a linear cavity when this fiber was pumped at 2.9 W of 980 nm laser diode.

In this paper, Q-switched Thulium-doped fiber lasers (TDFLs) operating near the 2 mu m region were demonstrated, utilizing a newly developed Thulium doped fiber as the gain medium and titanium carbide MXene as the saturable absorber (SA). The Thulium-doped fiber with a composition of SiO2-GeO2-Al2O3-HfO2-Y2O3-Bi2O3, was produced from a preform prepared using the modified chemical vapor deposition (MCVD) process. Two variations of titanium carbide MXene-based SA, Ti3C2Tx and Ti2CTx, were tested and compared, successfully generating Q-switched pulses. When Ti3C2Tx was used, the Q-switched pulse had a center wavelength of 1934.223 nm, a repetition rate of 55.39 kHz and a pulse width and 1.942 mu s. For Ti2CTx, the generated Q-switched pulse has a center wavelength of 1932.229 nm, with a repetition rate of 77.28 kHz and a pulse width of 1.608 mu s. The signal-to-noise ratio (SNR) values were 45.6 dB and 50.2 dB for Ti3C2Tx and Ti2CTx respectively. Based on the experimental results, both Ti3C2Tx and Ti2CTx show promise as SAs for generating Q-switched pulses in the 2 mu m region within the TDFL cavity.

We achieved a self-induced Q-switched erbium-doped fiber laser (EDFL) operating at 1559.4 nm through the integration of a Titanium Aluminum Nitride, Ti4AlN3 MAX phase film as a saturable absorber (SA). The MAX phase was embedded into a polyvinyl alcohol (PVA) matrix, ensuring contamination-free compatibility. The SA film demonstrated a modulation depth of 17% and saturation intensity of 0.5 MW/cm². Integration of the film enabled stable Q-switching, producing pulses with 5.75 µs width at 59.2 kHz repetition rate and 29.9 – 64.7 mW pump power. Parameters included a maximum average output power of 2.34 mW, maximum pulse energy of 39.5 nJ, and highest peak power of 6.87 mW. The RF spectrum exhibited a 63 dB signal-to-noise ratio, indicating high pulse signal quality. This demonstration of Ti4AlN3 MAX phase film Q-switched fiber laser holds promise for applications including biomedicine.

In our study, we employed a Mo2TiAlC2 thin film as a passive saturable absorber (SA) to create a stable pulsed fibre laser at 1564.52 nm. We synthesized a Mo2TiAlC2-PVA thin film with a 6% modulation depth and a 10 MW/cm(2) saturation intensity. This thin film was integrated into the laser cavity between FC/PC fibre connectors, enabling Q-switching over a pump power range of 30 mW to 120 mW. This resulted in an increased repetition rate from 31.1 kHz to 66.83 kHz and a reduced pulse duration from 13.45 mu s to 6.35 mu s. The pulse train's stability was confirmed by a high signal-to-noise ratio (SNR) of 58 dB. The laser achieved a maximum output power of 6.56 mW and a pulse energy of 98.16 nJ. These results demonstrate Mo2TiAlC2 as a viable Q-switching modulator in the 1.55-mu m wavelength range, with promising applications in compact and efficient pulsed fibre lasers.

A new MAX-phase-based saturable absorber (SA) known as Titanium Aluminium Carbonitride, Ti3Al(C0.5N0.5)2 PVA composite film is successfully developed to demonstrate a reliable Q-switched laser in the 1.55-micron region. The Ti3Al(C0.5N0.5)2 composite film with a size of about 1 mm2 is sandwiched between two fibre ferules and integrated into an erbium-doped fibre laser (EDFL) ring cavity. The film SA has a linear absorption of about 5.7 dB at the pulsing region, and a modulation depth of 21%. The Q-switched laser, which is centred at 1561 nm, stably appears at a pump power range of 25 mW-55 mW. The Q-switched laser has the highest repetition rate of 46.3 kHz and the narrowest pulse width of 6.6 µs. The maximum calculated peak power is 1.6 mW, while the highest pulse energy is 10.54 nJ. This demonstration suggests that the Ti3Al(C0.5N0.5)2 can be an alternative SA that may have a good prospect in optical-related applications.

A self-induced Q-switched erbium-doped fiber laser operating at 1563 nm was achieved by integrating a passive modulator based on tantalum aluminum carbide (Ta 2 AlC) MAX phase film embedded into polyynyl alcohol. The modulator, serving as a saturable absorber (SA), established a modulation depth of 9% and a saturation intensity of 0.3 MW cm −2 . Upon integration of the film SA, a stable Q-switched fiber laser was obtained, generating pulses with a minimum width of 7.6 µ s at a repetition rate of 45.1 kHz, within a pump power range of 24.9–59.7 mW. The corresponding maximum average output power, maximum pulse energy, and highest peak power were determined at 1.6 mW, 36.2 nJ, and 4.7 mW, respectively. The RF fundamental spectrum exhibited a good signal-to-noise ratio of 61 dB, indicating excellent pulse signal quality. This demonstration of Ta 2 AlC MAX phase film Q-switched laser may open promising possibilities for scientific applications such as material processing.

An ultrashort pulse erbium-doped fiber laser (EDFL) in anomalous group delay dispersion (GDD) has been proven to produce a soliton wave production at 1596 nm. The mode-locking operation was generated by employing a vanadium pentoxide-polyethylene glycol (V2O5)-(PEG) film as absorber for all-fiber ring setup. Under anomalous dispersion, the soliton mode-locked laser produced a peak wavelength with 2.7 nm spectral bandwidth and Kelly sidebands. Under this condition, we obtained pulse energy of 210 nJ and pulse width of 1.40 ps. The maximum peak electrical power of 150 kW was calculated at the maximum pump power. These findings shows that the V2O5-PEG film can be a good saturable absorber (SA) device in generating stable mode-locking fiber laser at the 1.55- area.

In this work, Molybdenum Titanium Aluminum Carbide (Mo2Ti2AlC2) was examined to function as a reliable saturable absorber (SA) for stable pulse generation in the 1563 nm wavelength. To create the Mo2Ti2AlC2-PVA film, Mo2Ti2AlC2 powder with > 200 nm particle size was dispersed into polyvinyl alcohol (PVA) and dried to form a film. The Mo2Ti2AlC2-PVA film had a linear absorption coefficient of about 1.5 dB at the Q-switched working wavelength. The Mo2Ti2AlC2- PVA film was sandwiched between fiber ferules and analyzed in the Erbium-Doped Fiber (EDF) ring cavity design. Self-started Q-switching was realized with pump power ranging from 20 mW to 55 mW. The pulse width shrunk from 21.7 mu s to 8.9 mu s while the repetition rate increased from 20.45 kHz to 40.40 kHz. The fundamental frequency had a signal-to-noise ratio (SNR) of 61 dB, implying good stability of the pulsed laser. The highest output power and pulse energies are 1.1 mW and 27.2 nJ, respectively. These results demonstrate that Mo2Ti2AlC2 can be a good alter-native passive SA to produce laser pulsing in the 1.55-micron wavelength.