Search

A Q-switched erbium-doped fiber laser integrating graphene-based polymer composite is reported. Electrochemical exfoliation was used to synthesize graphene by immersing two graphite rods in solution containing 1% of sodium dodecyl sulfate (SDS) in de-ionized water. The supply for the electrochemical process is 20 V and the process took around 5 hours to produces suspension containing graphene flakes. The suspension is then mixed with chitin bio polymer composites to develop graphene-chitin film based passive Q-switcher. A small portion of the fabricated film was then integrated in erbium doped fiber laser in ring cavity for pulse laser generation. Pulsed laser with repetition rate of 67.39 kHz with 2.24 μs pulse width was generated. The laser output also has high pulse energy of 108.38 nJ with instantaneous peak power of 45.48 mW.

Graphene/MoS 2 has been widely used in optoelectronic devices due to its unique optical properties. First principles calculation on the properties of graphene/MoS 2 have been performed by using density functional theory (DFT) with a plane wave basis set as implemented in the CASTEP computer code. Electronic and optical properties were further discussed comprehensively to explain the electron transfer mechanism in atomic structure of graphene/MoS 2 . The results reveal the opening in graphene’s band gap at the k-point of the Brillouin zone when MoS 2 layer is introduced in the structure. The excellent absorption characteristic in the visible to ultraviolet region demonstrates the graphene/MoS 2 as a promising candidate material for broadband operation wavelength.

An Erbium-doped fiber laser with a 3D printer filament based aluminium polymer composite SA is reported. A free standing film was fabricated using chitin as host polymer for ease of integration. A Q-switched lasing was generated with repetition rate and pulse width of 20.06 kHz and 9.64 μs, respectively. A high pulse energy was produced at 7.18 nJ with respective instantaneous peak power of 699.97 μW.

We report the effect of depth on fabrication of nanopore on silicon substrate by utilizing one-step focused ion beam (FIB) milling. The conical shaped of nanopores were successfully fabricated by optimizing the milling parameters of FIB system. The milling depth, base diameter and tip diameter of the resulting nanopores were characterized using field emission scanning electron microscope (FESEM). The minimum diameter of the conical shaped nanopore was found to be 66.51 nm. Moreover, when aspect ratio is less than unity, the redeposited material will land on the tip of the nanopores and adhere at the sidewall for high aspect ratio. This result will be beneficial towards the new generation of nanopore-based DNA sequencing.

A wavelength-tunable passively Erbium-doped mode-locked fiber laser by residing single-walled carbon nanotubes (SWCNTs) embedded in polyethylene oxide (PEO) based saturable absorber (SA) is demonstrated. The mode-locker is fabricated by solution casting method of single-walled carbon nanotubes embedded in polyethylene oxide as host polymer. The fabricated nanotube based mode-locker is resided in Erbium doped fiber laser in ring cavity. In this experiment, tuning is performed using a tunable Mach-Zehnder filter (TMZF) for the tuning of output wavelength continuity of 20 nm (from 1544 nm to 1564 nm). The tunable pulse duration is range from 300 fs to 435 fs, maximum output power of 0.91 mW and signal to noise ratio (SNR) of 40 dB.

An optical fiber tip sensing probe coated with graphene is proposed for nitrate-sensing application. The sensor was coated with graphene using dip-casting method to detect nitrate at different concentrations ranging from 0 to 50 ppm. The graphene-coated fiber tip sensor was highly sensitive in detecting nitrate ion. When the concentration of the nitrate solution was dropped onto the sensing region, the reflected optical power decreased as the nitrate concentration increased. Without the graphene layer, the uncoated fiber tip sensor only had a sensitivity of 0.0076 dBm/ppm. However, the coated sensor's sensitivity was significantly enhanced to 0.0624 dBm/ppm, eight times higher than the uncoated fiber tip sensor, mainly due to the adsorption of nitrate on the graphene surface. This graphene-coated optical fiber tip sensor has a high potential to be used in nitrate-sensing applications.

This paper presents the fabrication and thickness analysis of TiO 2 on Fluorine-doped Tin Oxide (FTO) glass for Dye-Sensitized Solar Cell (DSSC). The TiO 2 layer was deposited on the cleaned FTO glass using doctor blade technique and the thickness of the TiO 2 were controlled by with different layers of adhesive tape. This results showed that the two-layer with thickness 15.09 μm of adhesive tape achieved the highest efficiency of 4.73 %, and followed by three-layer and one-layer at 3.64% at 2.32 % respectively.

The rapidity of producing good material for electronic use is really beneficial to the wireless communication technology especially in material engineering field. Research works are on-going to find potential material that has the ability to replace the limitation of conventional material. Related to this work, fifth generation (5G) antenna will be completed with high data rate and low interference besides welcoming the advantages of the coming new material in terms of aesthetic value. Since there are some limitations using conventional material for higher frequency, then this paper proposes graphene to be used as radiating or receiving element in antenna design. An antenna with CPW-fed chamfer-shaped with rectangular slot made by graphene at 15 GHz is proposed. The antenna is designed for single and array in which the array has 8 elements with inter-element spacing at 0.71λ. The antenna has large bandwidth with more than 1 GHz and achieve high gain with more than 12 dBi.

This paper discuss the measurement of resistive type pressure sensor namely FlexiForce from Tekscan. The important parameters of the sensor such as linearity, hysteresis, settling time and sampling time have been investigated and a measurement system with graphical user interface has been developed. The analysis results of 80 calibrated sensors show that the developed measurement system is highly practical and easily blended in with standard pressure sensor calibration procedures. The measurement data of each sensor can be used for calibration of the sensors.

This paper reports the fabrication and analysis of flexible photoanode on titanium (Ti) foil for back-illuminated dye sensitized solar cells (DSSCs). Performance comparison with the solid state FTO glass based DSSC using the back-illumination and frond-illuminated techniques were also carried. During the fabrication process, the surface of Ti foil., had been treated with H 2 O 2 and doctor blade method was applied for deposition of the photoanode on substrates. The measurement results show that the fabricated DSSC with flexible photoanode has power conversion efficiency of 1.00% under back illuminated solar radiation of 1.5 A.M while DSSCs with solid state photoanodes have power conversion efficiency of 0.53% (back-illuminated) and 2.22% (front-illuminated)., respectively. The DSSC with flexible photoanode has better power conversion efficiency than the DSSC with solid-state photoanode under back-illumination condition. However., it is comparatively low from front illumination DSSC due to platinized counter electrode partially reflects light., while iodine in the electrolyte absorbs photons affects the performance.

Doppler Laser Velocity measurement by selfmixing effect using direct modulation laser diode is proposed to distinguish the direction of the object movement. In order to distinguish the movement direction, assembling the frequency shift device such as an acoustic optic cell in the optical system is imperative. However, the self-mixing scheme does not have the ability to satisfy this condition due to its simple system. Therefore, triangular-wave modulation current with repetition frequency of 250Hz is applied directly to the laser diode. The emission produced a wavelength of 780nm. Target speed of 0.1 - 0.4 cm/s was measured and its movement direction was distinguished successfully. Both the velocity and moving direction of the target were obtained.

For the future optical sensing application, a simple, fast and cost-effective method to achieve exposed core is required for a good mass production and commercialization. Hence, this paper proposes sensing application with exposed core technology using Self-Written Waveguide (SWW) method. The SWW method uses a UV-curable resin and enables fabrication of an optical channel waveguide. SWW is known as an attractive and useful technique in optical interconnection. This SWW is passively aligned between two fibers from the end of the optical fiber under irradiation UV light. This makes the technology is a reliable exposed core technology for sensing application. A SWW with length of 800 micrometers is fabricated from the end face of the multi-mode optical fiber under irradiation with UV light. Experiment is done under several testing materials with different refractive index. The output optical power is decreasing as the refractive indexes of testing materials are increasing. Simulation is also done using ray-tracing method. From these results, it seems possible to apply this SWW using UV-curable resin in sensing application.

The conduction properties of materials such as copper and aluminum is most known often and exploited in electricals and electronics developments. In photonics and fiber lasers, the properties of material's conductivity and its effects on pulsed laser performances have not yet been investigated and characterized. For this purpose, silver-based saturable absorber, as the best in its class in terms of conductivity properties, have been fabricated on a Kapton substrate using the technologies from Kushen Hisense Electronics. The silver ink particles is deposited onto the Kapton taped through 128 nozzles in vacuum before it is annealed at 120 °C for 5 minutes. Upon annealing, the formerly grey ink changes to silver color. The proposed experimental works generated high peak power and pulse energy of about 35 mW and 155 nJ, respectively. The pump power when increased from 51.6 mW to 151.46 mW, generates a maximum of 111.11 kHz of repetition rate with shortest pulse width of 4.09 μs. Signal-to-noise ratio of 59 dB is observed from the radio frequency spectrum, indicating pulse stability.

Recently, the importance of the optical fiber is increasing particularly in sensing application. Thus, this paper proposes optical sensing by exposed core fiber technology using Self-Written Waveguide (SWW) method. SWW method is fabrication of an optical channel waveguide using a UV-curable resin. As a UV light irradiated, A SWW with length of 800 micrometers is aligned between two fibers from the end of the multi-mode optical fiber. A several testing materials with different refractive index are being tested on the SWW. The output optical power is decreasing as the refractive indexes of testing materials are increasing. From these results, this makes the SWW technology is a reliable exposed core technology for sensing application.

A relative humidity sensor based on Multi Walled Carbon Nanotubes (MWCNTs) doped with polymer Poly(methyl methacryate) was proposed in this paper. The fabrication technique applied in this paper is a simple direct drawing method that was able to produce a uniform waist microfiber with a minimum diameter of 5 μm with a length of 5 mm. This microfiber was tested on a different range of relative humidity from 45% to 80%. Performance of the fabricated sensor were then analyzed, focusing at the sensitivity of undoped and MWCNTs-doped polymer microfiber. Based on the results, MWCNTs-doped polymer microfiber exhibits higher sensitivities and better resolution compared to undoped polymer microfiber, with sensitivity and resolution obtained at 0.3341 dBm/% and 1.649% respectively. Indeed, the sensor exhibited a high reliability as well as repeatability. Therefore, this study provides a good platform for enhancing the concept of doping nanomaterials like MWCNTs into PMMA for a chemical and biosensor application.

Readout circuit integrated with large scale sensors array is important for improving the effectiveness of data acquisition system. However to design such system, it will require a variety of additional components which contributes to the increment of power consumption. In this paper we proposed an improved method of readout topology for resistive sensor array to reduce the measurement error. A new equation is also proposed to obtain the resistance value. A simulation has been done on 8x8 matrix sensor array represented by 64 fixed resistors and 8 standard reference resistors. The results show that the optimum reference resistance is 510 Ω for the value range between 100 Ω and 100 kΩ, and the improved percentage error is kept to be lower than 5%.

We successfully demonstrated a simple, compact and low cost passive Q-switched Thulium doped fiber laser (TDFL) at long wavelength of 1854.3 nm regions in conjunction with 1552 nm pump excitation. A stable pulse has been generated using graphene film based saturable absorber (SA). The graphene is synthesized by electrochemical exfoliation of graphite at room temperature in 1% sodium dodecyl sulphate (SDS) aqueous solution. Graphene flakes obtained from the process are mixed with polyethylene oxide (PEO) as the host polymer to produce free standing composite thin film which acts as a passive Q-switcher in the TDFL ring cavity. The SA is fabricated by sandwiching the graphene thin film between two fiber connectors. At 1552 nm pump power of 498 mW, a stable pulse train has been observed with a repetition rate of 6.51 kHz and pulse duration of 11.51 μs. The high performances of Q-switched laser suggest that the new type of saturable absorber based on electrochemical exfoliation in conjunction with all-fiber ring cavity configuration is suitable for a Q-switcher near 1900 nm wavelength.

Rotational inverted pendulum (RIP) is widely used as a benchmark system in evaluating various control strategies, as it is an ideal test bed that represents under-actuated plants. Although a proportional-integral-derivative (PID) controller is popular and relatively simple in structure, its use in balancing the RIP is usually not recommended due to the difficulties in finding the suitable PID controller parameter values for the RIP system, which has two unstable open-loop poles. Therefore, this paper presents an investigation on a PID tuning problem for stabilizing the RIP using a variant of multi-objective Genetic Algorithm (GA), called the Global Criterion Genetic Algorithm (GCGA). Simulation work has shown that GCGA is capable in tuning the PID controller gains to balance the RIP. Compared to the standard single objective GA, the solutions found in GCGA have better control performances. The optimization results have then been applied to the real RIP in order to validate the results in the real-time environment.