Enhancement of second harmonic generation in DPSS laser

High-power diode-pumped compact visible lasers have attracted much attention. A diode-pumped solid-state laser (DPSSL) with high efficiency, high output power, a good spatial beam profile, and good stability is highly desired for use in a lot of applications such as material processing holography, range finding, target illumination and designation, satellite and lunar ranging, thermonuclear fusion, plasma experiments, and in general for scientific work requiring high power densities such as pumping other laser crystals. Laser diode with 808 nm wavelength is the key component in the development of diode pumped solid state laser (DPSSL). Much higher pumping intensity can be achieved using laser diodes instead of flashlamps as pump sources for solid-state lasers because of laser diode high spatial and spectral brightness. The main advantages of diode lasers over flashlamps as pump sources are overall laser efficiency and extended pump-source lifetime. The increase in efficiency is due to improved use of the optical pump radiation. Solid state laser like Nd:YVO4 has optical absorption only in relatively narrow wavelength bands; thus only small portion of the broadband flashlamp energy passes can be absorbed and the rest just passing through the material without being absorbed. On the other hand, diode laser output is narrowband; thus most of it is absorbed and utilized

Z-transform method for optimization of add-drop configuration system

This paper presents the new approaches of optimization the add-drop configuration system by using Z-transform method. Dark soliton was chosen as the input signal and Gaussian beam was chosen as the control signal for the model proposed. The incident light was said to achieve the maximum resonance with the ring resonator when the phase shift, f=2nm. The derivation, analyzation, and optimization of the system are typically very important especially for the communication technology

Influence of coating thickness of polyimide for moisture sensing

This work focused on the effect of existence of polyimide coated fibre Bragg grating (FBG) for moisture sensing in stingless bee. The moisture sensitive material namely polyimide (PI) was used to improve the sensitivity of the fibre optic sensor. By taking the benefits from amine groups in 3-(aminopropyl) triethoxysilane (APTES), PI is coated onto the segment of FBG through covalent interaction. Different thickness of PI coated FBG as well as determination and optimization of the designated sensor has been done. 3 layers of polyimide coating were used to improve the sensitivity of moisture sensing, and the sensitivity of coated fibre been analysed

Temperature sensing with Fibre Bragg Grating and No-Core Fibre

In this paper, optical fibre Bragg grating (FBG) and no-core fibre (NCF) sensors have been investigated for their performance in the temperature range 30–100 �C. The change in Bragg and NCF wavelengths with temperature changes was used to determine the performance and sensitivity of the sensors. The gradient of D kFBG and kNCF versus temperature leads the sensitivity of the FBG and NCF sensors as 23.97 and 20.08 pm/�C, respectivel

Influence of coating thickness of polyimide for moisture sensing

This work focused on the effect of existence of polyimide coated fibre Bragg grating (FBG) for moisture sensing in stingless bee. The moisture sensitive material namely polyimide (PI) was used to improve the sensitivity of the fibre optic sensor. By taking the benefits from amine groups in 3-(aminopropyl) triethoxysilane (APTES), PI is coated onto the segment of FBG through covalent interaction. Different thickness of PI coated FBG as well as determination and optimization of the designated sensor has been done. 3 layers of polyimide coating were used to improve the sensitivity of moisture sensing, and the sensitivity of coated fibre been analysed

Geometrical analysis of light-emitting diode for enhancing extraction efficiency

A non-uniform current spreading in the current spreader can greatly reduce the effciency of the light-emitting diode (LED). The effects of the electrode contact area to the spreading layer towards extraction effciency of LED chips is analysed in analytical simulations. Length of current spreading and light extraction effciency is analysed for variation of contact area. The contact area value is varied by changing the shape of the electrode and the value of width of contact area. The increase in contact area decreases light extraction effciency as more light are absorbed by the bottom electrode surface. The effective current spreading length for Indium Tin Oxide (ITO) of thickness 300nm is 36.44µm. The 6 strips ‘fork’ design is the most optimum. The design has the most area for photons produced in active region to escape without reducing the area cover with current density. This enables the chip to has more extraction effciency with more uniform current spreading

Carbon ion characterization in arc discharge plasma

The objective of this study is to determine the energy of carbon ion in different environment and pressures. The purpose of determination the energy of carbon ion is to get better knowledge regarding on the fabrication of different type of carbon nanostructures. Carbon nanostructures become more useful due to their unique carbon elements. They can form ball-shaped, fullerenes and cylindrical nanotubes. The energy of carbon ion can be obtained by measuring the ion track sizes on the CR-39 target. Solid state nuclear track detector (SSNTD) was used to track the charged nuclear particles, such as alpha particles or fission fragments. In this study, arc discharge plasma generated by graphite electrode were chosen to produce carbon nanostructures and the CR-39 were exposed to energetic carbon ion under different environment and pressures. The energetic carbon ion was etched by 6.25 M of NaOH solution for 8 hours. The temperature was maintained at (72±1) °C to ensure the etching process going smoothly. The ion tracks was observed under optical microscope and the diameter of ion track were measured. The energy was determined from the diameter obtained by using the related formula. The energy of carbon ion is influenced by the diameter ion track. High values of carbon ions energy are observed in hydrogen ambient environment as compared to air ambient environment under same ambient pressures and the energy of carbon ions decrease with increase in the ambient pressure

Trapping of gold nanoparticle and polystyrene beads by dynamic optical tweezers

Gold nanoparticles and polystyrene beads are very important to use in advanced nanoscopic optical trapping techniques to probe any biological system of interest. Multiple trapping of these particles with different diameters can be performed by an optical tweezers system employing dark soliton controlled by Gaussian pulse within a particular configuration of microring resonators. By controlling some parameters and input power of the system, dynamics of the tweezers can be tuned. Radiation pressure acting on the particles including gradient and scattering forces were theoretically measured as a function of normalized position from the center of the laser beam. In this work, the highest output signal in the form of potential well is recorded at 112.80 W corresponding to 1.6 pm wavelength. Sizes of the tweezers are found within the range of 20 nm and the highest value of the optical force is recorded at 895.70 pN. We have demonstrated that the gradient force component is dominant over particle size within Rayleigh regime, thus a good agreement with theory is found

Glucose and sucrose analysis in daucus carota extract using optical tapered fibre sensor with GOU-AuNP composite layer synthesization

Tapered single-mode fibre (SMF) immobilized with glucose oxidase enzyme (GOD) and gold nanoparticles (AuNP) for the recognition of glucose and sucrose elements have been proposed. A tapered fibre was fabricated using a flame heating technique to improve the sensitivity of the fibre-based sensor. By taking advantage of amine groups in 3-aminopropyl triethoxysilane (APTES), GOD and AuNP are functionalized onto the tapered region of SMF through covalent interaction. The developments of the immobilized tapered fibre sensor for the analysis of glucose and sucrose concentration in different concentrations of the solution and types of carrots extracts were discussed in this paper. The solution concentrations of 0.1, 0.2, and 0.3 g/ml of glucose and sucrose were used to analyze the sensitivity of the fibre sensor. The extracts of baby carrots, imported carrots, and organic carrots were used to determine the existence of glucose and sucrose in these carrots. We demonstrated the sensitivities of GOD-immobilized fibre for 0.00672, 0.00722, 0.00902, and 0.00921 a.u/nm in terms of their glucose solutions, baby carrots, imported carrots, and organic carrots, respectively. Meanwhile, the sensitivities of AuNP-immobilized fibre were found to be 0.000030, 0.000026, 0.000012, and 0.000024 a.u/nm, respectivel

Integrating vernier spectrum with fano resonance for high sensitivity of an all-optical sensor

Vernier and Fano resonances are promising approaches for enhancing the sensitivity of an all-optical sensor. A theoretical analysis was performed to integrate a Fano-like resonance shape with a Vernier resonance by considering the presence of partially reflective end facets at a double microring resonator waveguide. The system was developed based on scattering matrix and optical transfer function. The all-pass racetrack microring resonator (ARMRR) and the double racetrack microring resonator (DRMRR) were compared with and without the end facet at the waveguide to analyze the dynamic change of the output resonance spectrum. The spectrum was analyzed based on the free spectral range and resonance pattern. The resonator systems were applied to a refractive index-based sensing protocol, which was operated by a resonance wavelength shift with a refractive index change. The sensitivity was optimized by varying the configuration parameters such as the radius of the ring, the distance between the end facet, and the coupling coefficients. Integrating Vernier spectrum with Fano resonance improved the sensitivity for ARMRR configuration by 5.16% and the sensitivity for DRMRR configuration by 6.31%. The recorded limit of detection (LOD) of the DRMRR was 3.30 × 10-