Norazan Mohd. Kassim

Analytical modeling for determination of pull-in voltage for an electrostatic actuated MEMS cantilever beam

A new analytical model has been developed for determining the pull-in voltage of an electrostatic actuated microelectromechanical system (MEMS) cantilever beam. The model takes into account the beam curvature caused by residual stress or stress gradient in the beam material. It can be used to model straight, curled and beam with mixture of straight and curled sections. Modeling result has been compared with published work of other researchers as well as with experimental measurement of this work and is found to be accurate.

Multimode interference optical splitter based on photodefinable benzocyclobutene (BCB 4024-40) polymer

1×2 and 1×3 planar optical splitters based on Benzocyclobutene (BCB 4024-40) polymeric material are demonstrated for the first time. The devices are designed based on symmetric interference and fabricated on BK7 glass substrates with a thin layer of SiO2 as cover. A cost-effective chemical etching technique is used in the fabrication process to take advantage of the photosensitivity of the polymer. The waveguide loss was measured using the cutback method to be 3.5 dB/cm. The splitting uniformity is better than 0.02 and 1.5 dB at 1550-nm optical wavelength for the 1×2 and 1×3 splitters, respectively.

Polymeric Optical Splitter Based on Multimode Interference Mechanism

A 1 times 2 and 1 times 3 planar optical splitter based on BenzoCyclobutene (BCB 4024-40) polymeric material is proposed. The device is designed based on symmetric interference mechanism, utilizing a BK7 glass as a substrate and thin layer of SiO2 as a cover. Simulation results show that the splitting uniformity is better than 0.5 dB at 1550 nm optical wavelength.

Study of effect of microsecond pulsed electric fields on threshold area of HeLa cells

Microsecond pulse electric field (μsPEF) application development substantially affected the development of research process including controlling cell functions by using pulses of electrical fields to create pores through a cellular membrane causes cell lysis and apoptosis commonly known as electroporation. Here we demonstrate the influence of the μsPEF on the threshold area (TA) of human cervical cancer cells (HeLa) membrane. The electric field for μsPEF is 3 kV/cm while the pulse interval is 100 ms. The pulse length and the number of pulses were fixed at 10 μs and 5, respectively. While the cultured skin cells are placed in 9 mm-gap EP electrode chamber for allowing real time observation of membrane permeability changes and cellular physiology. In order to initiate higher cell viability rate, high transfection efficiency, lower sample contamination and smaller Joule heating effect the modification of EP chamber need to be done which can be controlled by pH scale, temperature and humidity. The experiment using high pulse electrical field with simply repetitive pulses shows the threshold area of cell membrane was decreasing gradually to 44.59 μm, and is settled within hundreds of second. We found that the threshold area of cells membrane was affected when exposed to high voltage pulse electric field. The dependence of the threshold area on the HeLa cell membrane might be associated with the electrical impedance of the plasma membrane that begins to fluctuate after the application of a certain level of μsPEF.

WIDE RANGE OF ELECTROSTATIC ACTUATION MEMS FPOTF

By employing Microelectromechanical system (MEMS) technology, Fabry-Perot Optical Tunable Filter (FPOTF) with hybrid tuning mechanism, varying d and altering incident angle is presented. The proposed structure consists of a ∞oating dual membrane FPOTF with capability to be tuned at difierent light incident angles. Three electrostatic cavities have been designed to perform this task independently. This technique is capable to increase the tuning range up to 2/3 of capacitance gap with additional doubly range of incident angle. Optic, mechanic and electrostatic analysis of the proposed structure has been validated by simulation. Analysis in optical performance shows the tuning range enhancement is about 1.92% for §2 - mirror tilting at 6 - initial angle compared to conventional dual beam MEMS FPOTF. This analysis validates the principle of hybrid tuning method.

A Novel 1×2 Thermo-Optic Multimode Interference Switch Structure Based on Photodefinable Benzocyclobutene (BCB 4024-40) Polymer on Silica

A novel 1×2 multimode interference photonics switch structure based on thermal controlling effect is proposed. A ridge waveguide of photosensitive polymer, benzocyclobutene (BCB 4024-40) on silica clad is used as a design structure. A temperature changes as a result of electrode heating are analysed by employing a two-dimensional finite difference thermal model considering both conduction and convection mechanisms. The switching characteristics due to changes in effective index are analysed by the two-dimensional finite difference beam propagation method with transparent boundary condition. The proposed structure works well with low crosstalk level of -28 dB and low switching power relatively to the structural upper cladding thickness.

Single mode rib optical waveguide modeling techniques

A single mode rib optical waveguide is modeled using three distinct methods: the finite difference method (FD); effective index method (EI); two dimensional beam propagation method (2D-BPM). Starting from the fundamental Maxwells equations, the functionalities of the methods in solving the wave equation are discussed. Using a standard rib optical waveguide structure, comparisons between the methods are made in terms of normalized propagation constant values; the obtained results are shown to have good agreement.

Feasibility of Electromagnetic Communication in Underwater Wireless Sensor Networks

Underwater Wireless Sensor networks (UWSNs) comprised of a number of sensor nodes that are deployed to perform collaborative monitoring tasks. Sensor nodes are connected to each other through wireless signals. Acoustic signal is the dominant wave used for UWSNs communications. Acoustic signals face a lot of challenges such as ambient noise, manmade noise, limited bandwidth, multipath and low propagation speed. These challenges become more severe in shallow water environment where a high level of ambient and manmade noise, turbidity and multipath is available. Therefore, Electromagnetic signals can be applied for using as a communication signal for UWSNs. In this work, the performance of electromagnetic communication in the water environment is investigated. The investigation is conducted for fresh and seawater environment. Results show that freshwater environment can permit short range communication while the communication is more difficult for seawater due to the high value of attenuation.

Polymer material for optical devices application

An overview of polymer materials in optical waveguiding technology is presented. This includes a review of the types of polymer being used worldwide in the development of optical devices, the track record and performances of polymer based optical devices successfully being developed as compared to other optical materials and also of the external field control of the polymer material for active devices application. Further discussion then include the current research in polymer based optical waveguiding technology held in our Photonic Research Group together with possible development and commercialization.

Temperature-insensitive photonic crystal fiber interferometer for relative humidity sensing without hygroscopic coating

A novel photonic crystal fiber (PCF) interferometer RH (relative humidity) sensor is proposed and demonstrated in this paper. The sensor is made from a piece of PCF spliced to standard fibers in transmission mode, which has the advantage that it does not require the use of any hygroscopic thin film or layer. In addition, the all-silica nature of the sensing element means the sensor is insensitive to temperature. The sensor has a humidity sensitivity of 60.3 pm/%RH over the range of 60–80% RH and 188.3 pm/%RH in the region from 80 to 95% RH. A response time around ~1 s is observed for a ~2 cm long section of photonic crystal fiber interferometer (PCFI). The sensor exhibits a very low cross temperature sensitivity of around 0.5 pm/°C. The proposed sensor has potential for high humidity monitoring applications, and temperature compensation is not necessary if such a sensor is operated in normal surrounding atmosphere.