Mukhzeer Mohamad Shahimin

Electrical behaviour of MEH-PPV based diode and transistor

The potential of organic semiconductor based devices for light generation is demonstrated by the commercialisation of display technologies using organic light emitting diode (OLED). In OLED, organic materials plays an important role of emitting light once the current is passed through. However OLED have drawbacks whereby it suffers from photon loss and exciton quenching. Organic light emitting transistor (OLET) emerged as a new technology to compensate the efficiency and brightness loss encountered in OLED. The structure has combinational capability to switch the electronic signal such as the field effect transistor (FET) as well as to generate light. Different colours of light could be generated by using different types of organic material. The light emission could also be tuned and scanned in OLET. The studies carried out in this paper focuses on investigation of fabricated MEH-PPV based OLED and also OLET via current voltage characteristics. These studies will continue with a view to develop an optimised MEH-PPV based OLET.

Copper ion-exchanged channel waveguides optimization for optical trapping.

Optical trapping of particles has become a powerful non-mechanical and non-destructive technique for precise particle positioning. The manipulation of particles in the evanescent field of a channel waveguide potentially allows for sorting and trapping of several particles and cells simultaneously. Channel waveguide designs can be further optimized to increase evanescent field prior to the fabrication process. This is crucial in order to make sure that the surface intensity is sufficient for optical trapping. Simulation configurations are explained in detail with specific simulation flow. Discussion on parameters optimization; physical geometry, optical polarization and wavelength is included in this paper. The effect of physical, optical parameters and beam spot size on evanescent field has been thoroughly discussed. These studies will continue toward the development of a novel copper ion-exchanged waveguide as a method of particle sorting, with biological cell propulsion studies presently underway.

Surface modification via wet chemical etching of single-crystalline silicon for photovoltaic application

The potential of solar cells have not been fully tapped due to the lack of energy conversion efficiency. There are three important mechanisms in producing high efficiency cells to harvest solar energy; reduction of light reflectance, enhancement of light trapping in the cell and increment of light absorption. The current work represent studies conducted in surface modification of single-crystalline silicon solar cells using wet chemical etching techniques. Two etching types are applied; alkaline etching (KOH:IPA:DI) and acidic etching (HF:HNO3:DI). The alkaline solution resulted in anisotropic profile that leads to the formation of inverted pyramids. While acidic solution formed circular craters along the front surface of silicon wafer. This surface modification will leads to the reduction of light reflectance via texturizing the surface and thereby increases the short circuit current and conversion rate of the solar cells.

Direct optimization of Y-branch silicon nitride optical waveguide for evanescent field biosensor

Evanescent field had been widely used in bio and chemical sensors. However in most cases, evanescent field is not maximized and consequently produced an unoptimized sensor performance. It is the aim of the paper to optimize the design of 1:2 Y-branch splitter optical waveguide through simulation by using FD-BPM. Y-branch splitter are simulated to optimize the power loss. Width of waveguide and effective angle are manipulated in the power loss optimization. The result shows that evanescent field is maximized at optimized thickness and width. The result suggests that Y -branch splitter with width of 25 μm and effective angle of 6.24° is the best design for evanescent field sensor application with both high sensitivity and signal to noise ratio.

Optimization of Silicon Nitride Y-Branch Optical Waveguide for Evanescent Field Biosensor

Evanescent field had been widely used in bio and chemical sensors. However in most cases, evanescent field is not maximized and thus the performance of the sensor is not optimized. It is the aim of the paper to optimize the design of 1:2 Y-branch splitter optical waveguide through simulation by using FD-BPM. Y-branch splitter without taper are simulated to optimize the power loss. Width of waveguide and effective angle are manipulated in the power loss optimization. The result shows that evanescent field is maximized at optimized thickness and width. The result suggests that Y-branch splitter with width of 25μm, effective angle of 6.24° is the best design for evanescent field sensor application with both high sensitivity and signal to noise ratio.

Evanescent field maximization of linear silicon nitride channel waveguide

Sensitivity of evanescent field sensor is highly affected by strength of evanescent field with respect to its penetration depth and intensity. However in most cases, evanescent field is not maximized and thus the performance of the sensor is not optimized. It is the aim of the paper to optimize the silicon nitride linear waveguide through simulation by using 3D FD-BPM. The resultant investigation shows that evanescent field is maximized at TM polarization, 0.9μm thickness and 4μm width waveguide. Besides, result also shows that TM-polarization results in 15.5 times stronger evanescent field at optimized physical dimension compared to TE polarization.

Effect of varied extracting solvent on stability and reliability of DSSCs using natural dyes as photosensitizer

This paper describes fabrication and characterization of several natural dyes in varied solvent. The varied fabrication step is characterized via the stability and reliability study of dyes as photosensitizer. Rosella, Bawang Sabrang, Cherry Barbados, Mulberry, Ardisia, Oxalis Triangularis and Harum Manis mango are used as a dye sensitizer. The dyes are extracted in water and ethanol with the same ratio was employed as nanoparticle titanium dioxide thin film dye-sensitized solar cells (DSSCs). As for Rosella, Bawang Sabrang, Cherry Barbados, Mulberry, Ardisia, Oxalis Triangularis and Harum Manis mango dye sensitized electrode in water solvent, the solar cell yields of energy conversion efficiency is about 0.67%, 1.06%, 0.14%, 0.33%, 2.64%, 0.68% and 0.03%, respectively. In ethanol solvent the conversion efficiency for Rosella, Bawang Sabrang, Cherry Barbados, Mulberry, Ardisia, Oxalis Triangularis and Harum Manis mango is about 0.2%, 0.23%, 0.44%, 0.17%, 0.61%, 0.51% and 0.51%, respectively. Moreover, the stability and reliability of the dyes extracted was also improved by changes the solvent of extracting dyes after 24 hours being stored at room temperature.

Correlation of Brillouin Stokes Signals and Optical-Signal-to-Noise-Ratio in Multi-Wavelength Brillouin Fiber Laser with Additional Fiber Bragg Grating

We experimentally demonstrate unidirectional propagation of multi-wavelength Brillouin fiber laser system with additional fiber Bragg grating. The configuration is arranged in a ring resonator by utilizing five different Brillouin gain mediums. In this experiment, the input Brillouin pump power was varied in order to maximize the generated Brillouin Stokes signals based on the respective fiber lengths. The influence of these controllable parameters leads to the correlation between of Brillouin Stokes signals and optical-signal-to-noise-ratio. In this case, at 10 km of single mode fiber the maximum of 38 Brillouin Stokes signals were generated together with 15.07 dB of average optical-signal-to-noise-ratio when the 17 dBm Brillouin pump power was launched into the ring resonator.

All-Optical XOR Logic Gates: Insights and Comparisons

Three XOR photonics logic gate configurations namely semiconductor optical amplifier-Mach Zender interferometer cross phase modulation (SOA-MZI XPM), SOA-MZI cross gain modulation (XGM) and terahertz optical asymmetrical demultiplexer (TOAD) XOR are analysed and compared in terms of generated power, optical signal-to-noise ratio (OSNR) values and bit error rate (BER) signal quality. The highest generated power is possessed by the TOAD at 23.5 dBm, the SOA-MZI XPM showed the most extinction ratio or OSNR with 109.6 dB whereas the best BER is recorded in the SOA-MZI XGM at 4.42 x 10-22.

Fiber Length Optimization of Ring Cavity Multi-Wavelength Brillouin Fiber Laser Utilizing Fiber Bragg Grating

In this paper, we experimentally investigated the performance of ring cavity multi-wavelength Brillouin fiber laser utilizing fiber Bragg grating which operated in the C-band wavelength region. The combination of stimulated Brillouin scattering and selective wavelengths gave a new invention in the optical fiber communication. Five different lengths of single mode fiber are used in order to get the best gain medium for stimulated Brillouin scattering effect. Up to 33 of Brillouin Stokes signals and 31 of anti-Stokes signals were obtained when 10 km fiber length was used in the laser system. The average value optical signal to noise ratio of 15 dB has been achieved. The broadening bandwidth of Brillouin Stokes signals also occurred at the center wavelength of 1550 nm based on the 3 dB bandwidth of 5 nm fiber Bragg grating.