Nonlinearity Effect on Multiwavelength fiber laser based on Sagnac loop mirror interferometer

This paper demonstrates a multiwavelength fiber laser (MWFL) with erbiumdoped fiber amplifier (EDFA) as gain medium and Sagnac loop mirror interferometer as filter. Stable and flat lasing spectrum was achieved when highly nonlinear fiber (HNLF) was inserted into the laser cavity. The number of lasing lines and extinction ratio (ER) was directly influenced by EDFA gain where at maximum setting, 14 lasing lines with ER of 19 dB were generated. The stable and flat spectrum achieved spanned about 1.6 nm. This is due to the induced intensity dependent loss mechanism in the cavity by adjusting the half-wave plate of the polarization controller in combination with the HNLF. The MWFL output showed peak power variation of about 2.1 dB within 100 minutes of observation time.

Localized SPR for Pb(II) ion sensing utilizing chitosan/reduced graphene oxide nanocomposite

In this work, a simple and highly sensitive localized surface plasmon resonance (LSPR) technique had been developed for detection of Pb(II) utilizing chitosan/reduced graphene oxide (CS/rGO) nanocomposite as the sensing material. Gold nanoparticles (AuNP) had been incorporated with the nanocomposite material to induce strong LSPR responses. CS/rGO nanocomposite was coated on top of AuNP and had been utilized as active layer for Pb(II) ion sensing. The morphology and physical properties of gold nanoparticle-chitosan/reduced graphene oxide (AuNP-CS/rGO) nanocomposite was studied using field-emission scanning electron microscopy (FESEM), atomic force microscopy (AFM) and x-ray diffraction (XRD) analysis. FESEM exhibits a rough and wrinkle surface of AuNP-CS/rGO after the addition of rGO. AFM shows a higher surface roughness for AuNP-CS/rGO due to the presence of oxygen atoms in rGO where these oxygen atoms provide more sites for adsorption of Pb(II), hence enhance the sensitivity of the sensor. A good sensitivity of the LSPR sensor for detection of Pb(II) utilizing AuNP-CS/rGO was obtained which is 1.544 ppm-1 and the linearity of the sensor are 0.99 and 0.97. In stability study, AuNP-CS/rGO exhibits a good repeatability with relative standard deviation of 2% for 0.01 ppm.

Identification of C-H Bond Vibration Mode Using Absorption Spectroscopy By A Simple Optically Configured Setup

An optical system model for the identification of Carbon-Hydrogen stretching using spectroscopy is demonstrated and applied to the experiment setup. The optical simulation is achieved using simulation software and performed in a two-mirror system. The optical setup covers a wavelength range of 600 nm to 1200 nm which is a new study based on carbon-hydrogen stretch and test with samples from the alkene group. Significant results of the Carbon-Hydrogen stretch from the alkene group at 1149 nm are detected in Dichloromethane and ethanol. This observation is recorded in real-time and applied in a fast diagnostic system. The isosbestic point of water is measured at 970 nm and useful for our system spectral calibration. The result also shows the ability to quantify the chemical bond of a sample based on two peaks of absorption due to the C-H stretching. This gives a better opportunity for Chemometrics to perform accurately.

Continuous Detection of Pb(II) utilizing Chitosan-Graphene Oxide Surface Plasmon Resonance Sensors based on Ag/Au and Au/Ag/Au Nanolayers

This work demonstrates the effect of Ag/Au and Au/Ag/Au nanolayers on the performance of chitosan (CS)-graphene oxide (GO) surface plasmon resonance (SPR) sensors for Pb(II) ion detection. The CS-GO SPR sensors are fabricated on a bi-metallic 40 nm Ag/10 nm Au and tri-metallic 10 nm Au/40 nm Ag/10 nm Au nanolayers. The sensors are tested with Pb(II) ion solution of concentrations 0.1 to 5 ppm using SPR spectroscopy. The results show that the CS-GO SPR sensor on the bimetallic Ag/Au gives a gradual shift in SPR angle from 0.1 to 1 ppm and slightly linear from 3 to 5 ppm. Meanwhile, the CS-GO SPR sensor on the tri-metallic Au/Ag/Au nanolayers provides an extended linearity range from 1 to 5 ppm with the highest shift in SPR angle of 1.8o. Additionally, the tri-metallic CS-GO SPR sensor also exhibits the greatest SNR of 0.25 as compared to 0.15 of the one on the bi-metallic nanolayers. Thus, the studies prove that the tri-metallic Au/Ag/Au nanolayer is an effective and simple approach to improve the performance of a CS-GO SPR sensor for Pb(II) ion detection.

High Sensitivity Temperature Sensor Based on Two-Dimensional Photonic Crystal

In this work, a two-dimensional photonic crystal ring resonator based temperature sensor is investigated. The device consists of a hexagonal array of air holes surrounded by the base material of germanium (Ge). The sensing mechanism is based on the shifting of transmission peak with refractive index changes in Ge induced by variation of temperature. Simulation results are obtained using finite difference time domain method (FDTD). The photonic band gap is studied by plane wave expansion method (PWE). The sensor has high sensitivity of 270 pm/K and high quality factor of 2028.86 with` wide range of temperature detection between 300 K to 800 K. The size of the structure is 112.91 (µm)2 and appropriate for sensing applications in nanotechnology.