Enhancement of thulium– ytterbium doped fiber laser efficiency using dual-pumping method

Performance enhancement of laser acquired from a newly developed double-clad Yb31/Tm31 codoped fiber (YTDF) is demonstrated using dual-pumping scheme. The laser uses a 2 m long YTDF fiber with a core dopant concentrations (in wt%) of 2.00 Yb2O3, 0.5 Tm2O3, 1.0 Al2O3, and 3.00 Y2O3 as a gain medium in conjunction with a pair of fiber Bragg grating in a linear cavity resonator to generate lasing at 1901.6 nm. The best efficiency of 2.9% and the highest output power of 27 mW are obtained by combining 927 nm pump with 905 nm pump. As compared to a single pumping scheme using 927 nm pumping source, about 0.43% increment in efficiency is observed with no evidence of rollover at the highest output power. The best combination is to use 200 mW of 800 nm pump with 927 nm pump, wherein only a total pump power of 1900 mW is required to generate 20 mW of 1.9 lm laser output

Finite element simulation of miniaturized ZnO/Si SAW sensor for rapid detection of dichloromethane gas

Air quality control is very crucial as poor air quality can lead to chronic respiratory organ diseases. Hence, detection of numerous toxic and hazardous gas is utmost significance. A low cost and high sensitivity gas sensor is crucial to monitor the excessive presence of the dangerous gas that can harm human’s health. In recent years, various type of gas sensors have been developed for various applications such as medicine, industry, automotive and environmental monitoring. One of the harmful gas is the dichloromethane gas. Dichloromethane (DCM) gas, CH2Cl2 is widely used in industry due to its organic characteristics. However, the excessive of the amount of the gas could bring harm to human’s health. Hence, a lot of sensing devices have been developed including surface acoustic wave (SAW) gas sensor. This paper presents the 2D finite element simulation of miniaturized ZnO/Si SAW gas sensor for rapid detection of DCM gas. Using a powerful finite element analysis software known as COMSOL Multiphysics, the gas sensor is modelled according to the specific criteria using 2D approach. The effect of different thickness of ZnO thin film as piezoelectric layer is investigated on the SAW propagation characteristics. The resonance frequency of simulated ZnO/Si SAW gas sensor is 300 MHz with wavelength of 11.67μm. The shift in frequency is the measurement used to measure the changes occured to sense the presence or absence of DCM gas. The shift of resonance frequency is observed in the absence and presence of dichloromethane gas. This work has high potential to realize single chip gas sensor due to its silicon compatibility for rapid detection of harmful gas for environmental monitoring

Degradation of InGaN LEDs by proton radiation

Light-emitting diodes (LEDs) made of nitride are appealing because they can withstand high temperatures and be used in harsh environments. The degradation behaviour of the device performance on Indium Gallium Nitride (InGaN) LEDs (light emitting diodes) irradiated by 2-MeV protons with the fluence of 1x 1013 cm-2 is studied. The electrical and optical characteristics of three commercially available LEDs, VLHW4100, OVLAW4CB7 and VAOL-3GWY4, were compared before and after radiation. The results show a considerable degradation in the LED electrical performance. After irradiation, the reverse leakage current increases in all three devices. The degradation in OVLAW4CB7 is for the entire reverse bias voltage range, while the degradation is prominent at lower reverse bias voltages for the other two devices. However, while calculating the increase in dark current at a reverse bias voltage of 5 volts, it is found that the dark current increases the most in VAOL-3GWY4, which is around 22 times. The traps and the bulk defect are believed to contribute to the increased leakage current. The forward Current-Voltage and the Capacitance-Voltage characteristics do not change much after radiation. The optical intensity corresponding to different wavelengths is obtained for the device's optical characterization. The results show that the optical intensity of the devices increased after radiation. This increase is because of the increase in carrier lifetime in the active region after radiation and radiation-induced annealing of defects. In this research quantum well LEDs are used. When using these devices based on InGaN in harsh conditions or open spaces, the degradation characteristics described in the present study can assist scientists and engineers in making well-informed decisions, as little is known about the degradation of InGaN LEDs after proton radiation

Silicon carbide schottky diodes forward and reverse current properties upon fast electron radiation

This paper investigates on the reaction of 10 and 15MGy, 3MeV electron irradiation upon off-the-shelves (commercial) Silicon Carbide Schottky diodes from Infineon Technologies (model: IDH08SG60C) and STMicroelectronics (model: STPSC806). Such irradiation reduces the forward-bias current. The reduction is mainly due to the significant increase of the series resistance (i.e. Infineon: 1.45Ω at before irradiation → 121×103 Ω at 15MGy); STMicroelectronics: 1.44Ω at before irradiation → 2.1×109 Ω at 15MGy). This increase in series resistance gives 4.6 and 8.2 orders of magnitude reduction for the forward-bias current density of Infineon and STMicroelectronics respectively. It is also observed that the ideality factor and the saturation current of the diodes increases with increasing dose (i.e. ideality factor- Infineon: 1.01 at before irradiation → 1.05 at 15MGy; STMicroelectronics: 1.02 at before irradiation → 1.3 at 15MGy | saturation current- Infineon: 1.6×10-17A at before irradiation → 2.5×10-17A at 15MGy; STMicroelectronics: 2.4×10-15A at before irradiation → 8×10-15A at 15MGy). Reverse-bias leakage current density in model by Infineon increases by one order of magnitude after 15MGy irradiation, however, in model by STMicroelectronics decreases by one order of magnitude. Overall, for these particular samples studied, Infineon devices have shown to be better in quality and more radiation resistance toward electron irradiation in forward-bias operation while STMicroelectronics exhibit better characteristics in reverse-bias operation

Design and simulation of film bulk acoustic wave resonator (FBAR) gas sensor based on ZnO thin film

The interest in miniature device has led to the development of thin film bulk acoustic wave resonator (FBAR). The function of a resonator to gain a high resonant frequency value of an equipment make FBAR is suitable to act as sensor and filter for wide range of applications. The success of FBAR in providing a reduction of cost and power consumption make it an applicable device. It can be integrated with carbon nanotubes and oscillator circuit to enhance its performance as a gas sensor. Some of the chosen piezoelectric thin film are zinc oxide (ZnO) and aluminum nitride (AlN). This paper focuses on implementing FBAR as gas sensing application to monitor a person's health using breath analysis. The establishment of FBAR sensor to detect acetone gas as breath marker for diabetic disease through breath analysis is emphasize in this paper. A thin film FBAR is modelled using finite element simulation to evaluate its performances in term of coupling coefficient, sensitivity and resonance frequency. Zinc oxide was chosen as the piezoelectric thin film, aluminum as electrodes and silicon as substrate. FBAR sensor with ZnO thickness of 4.4 μ m demonstrated the highest coupling coefficient of 0.0643 at 472.65 MHz resonance frequency. The result is comparable to other previous works on FBAR sensor. Hence, this work indicates that FBAR has high potential for breath analysis. It can detect which type of gases exhaled by patient based on the different mass sensitivity value and different type of diseases can be identified

Reliability study of silicon carbide Schottky Diode with fast electron irradiation

The impact of fast electron exposure upon the performance of commercial silicon carbide Schottky diodes has been studied. Under 3 MeV electrons, absorbed dose of 10 and 15 MGy at room temperature, the forward current density-voltage characteristic of INFINEON and STMICROELECTRONICS devices have been decreased by 4.6 and 8.2 orders of magnitude respectively. The reduction is associated with the significant rise in the series resistance (INFINEON: 1.45 Ω to 121×103 Ω; STMICROELECTRONICS: 1.44 Ω to 2.1 × 109 Ω) due to the irradiation-induced defects. Besides that, the reverse leakage current density in INFINEON increased by one order of magnitude while reverse leakage current density in STMICROELECTRONICS decreased by about one order of magnitude. We have also observed an increase in ideality factor (INFINEON: 1.01 to 1.05; STMICROELECTRONICS: 1.02 to 1.3) and saturation current (INFINEON: 1.6×10-17 A to 2.5×10-17 A; STMICROELECTRONICS: 2.4×10-15 A to 8 × 10-15 A) as a result of electron irradiation. Overall, for particular devices studied, INFINEON have better quality devices and more radiation resistance compared to STMICROELECTRONICS

Performance configuration of Raman-EDFA hybrid optical amplifier for WDM applications

A hybrid configuration of Raman amplifier and erbium-doped fiber amplifier (EDFA) is proposed to obtain a better performance in term of gain, noise figure and flat gain. It is based on the optimum parameter configuration of a singly-based Raman amplifier and EDFA. The best parameter for both amplification has been analyze in terms of its input signal power, pump power and their fiber length whereas the best erbium ion density has also been analyze in EDFA setup. All the parameters are varied to some values to get the optimum result. The simulation is done by using Optisystem 14.0 software. The hybrid amplifier consists of Raman amplifier with multi-pump power set up and bidirectional pump power of EDFA with the pump wavelength of 980 nm is designed and simulated in order to obtain higher gain and lower noise figure. From the simulation of the hybrid configuration, the optimum output has been achieved. The hybrid configurations exhibit the average gain of 46 dB and average noise figure of 3 dB. The flat gain obtained is between 1530 nm to 1600 nm which include C-Band and L-Band frequency with the gain bandwidth of 70 nm.

Influence of electron irradiation on the electroluminescence spectra of white InGaN light emitting diodes

We analyze the influence of electron irradiation on the electroluminescence spectra of white light emitting diodes (LEDs) based on indium gallium nitride. Three different irradiation fluences, 9.90×1015 , 1.32×1016 and 1.98×1016 cm-2 , are studied. For all 27 samples of LEDs of the commercially available models VAOL-5GWY4, VAOL-10GWY4 and OVL-3321, we observe a significant decrease in the emission light intensity after the irradiation. Degradation of the overall light intensity is believed to be due to irradiation-induced defects which act as nonradiative recombination centres. We also study the emission intensities and the central wavelengths of the LED samples subjected to electron irradiation under conditions of different injection currents. After irradiation with the fluence 1.98×1016 cm-2 , the blue peak located at 453 nm experiences severe degradation, so that only the yellow luminescence at 590 nm remains. This yellow band is related to radiative transitions from donor bands to the levels associated with gallium vacancie

Optical fiber coated Zinc Oxide (ZnO) nanorods decorated with Palladium (Pd) for hydrogen sensing

A novel hydrogen (H-2) sensor was developed using acid-etched optical fiber coated with zinc oxide (ZnO) nanorods. The sensing performance was done by comparing the acid-etched fiber coated with ZnO nanorods with and without decorated Palladium (Pd). The conventional optical single-mode fiber (SMF) with a diameter of 125 mu m has been modified as a transducing platform by etching it to 11 mu m diameter using hydrofluoric acid (HF) to enhance the evanescent field of the light propagates in the fiber core. The etched fiber was coated with ZnO nanorods via hydrothermal process by using seeding and growth solution method. The sensing layer was characterized through Scanning Electron Microscopy (SEM), Energy Dispersive X-Ray (EDX) and X-Ray Diffraction (XRD) to verify the properties of ZnO. Catalyst Palladium (Pd) was sputtered onto the ZnO nanorods to improve H-2 detection. The developed sensor operating temperature was found to be 150 degrees C that produces 6.36 dBm increase in response towards the 1% concentration of H-2 in synthetic air. It was then tested with different concentration of H-2. The sensor decorated with Pd has better performance in sensing compared to non-decorated Pd based on the output power versus time. The sensor best response and recovery times is 6 and 5 min respectively, for acid-etched optical fiber coated with ZnO nanorods decorated with Pd for 0.75% of H-2 concentrations at 150 degrees C. The results indicate the optical fiber sensor might improve the performance towards H-2 as oppose to the conventional electrical sensor

Dual-wavelength thulium ytterbium Co-doped fiber laser

We report on the generation of dual-wavelength fiber laser peaking at 1990.64 and 1998.92 nm with a simple ring cavity setup. The lasers are demonstrated using a fabricated silica-based nanoengineered octagonal shaped double-clad Thulium-Ytterbium co-doped fiber (TYDF) as a gain medium in a simple all-fiber ring configuration. By using 980 nm multimode laser, a stable dual-wavelength laser is generated at a threshold pump power of 1500 mW due to the non-polarization rotation (NPR) effect occurred in the cavity. The effect has been self-controlled by a suppression of mode competition in the gain medium. The result shows that the slope efficiency of the generated dual–wavelength laser is measured to be 27.23%. This dual-wavelength TYDF laser operated steadily at room temperature with a 34 dB optical signal-to-noise rati