Effects of exciton-polariton on Mach-Zehnder interference devices

A new optoelectronic device based on excitonpolariton was studied. In particular a Mach-Zehnder interference device fabricated by using a GaAs quantum well was studied. We simulated the output characteristics of Mach-Zehnder interference device by using a Finite Difference Time Domain (FDTD) method. Then we compared them with the experimental results measured in a low-temperature. After that we obtained the numerical values of electro-optic effect coefficients. Those were as large as 105×10-11 m/V for 4.5 K, while 74×10-11 m/V for 77 K. Therefore this estimation is considerably large, showing 57 (4 K) and 41 (77 K) times larger than conventional KDP crystal. This effect is probably caused by the excitonpolariton effect. Furthermore, we performed a photocurrent experiment to understand the transmitted light phase change characteristics, causing such large electro-optics effect at a comparatively higher temperature. Temperature dependence of photocurrent showed that the absorption edge and exciton peak remained constant up to 77 K, and then shifted to lower energy as the temperature increased. This probably explains how the large electro-optic effect can be obtained at a comparatively high temperature, i.e., 77 K

ZIGBEE-BASED SMART FALL DETECTION AND NOTIFICATION SYSTEM WITH WEARABLE SENSOR (e-SAFE)

Fall is one of the serious health issues among elderly population in Malaysia. In the event of a fall, a strong impact may be inflicted on the elderly causing severe injuries or even death. Another research by the National Institutes of Health found that 67% of elderly who fall and fail to seek help within 72 hours are unlikely to survive. Current Personal Emergency Respond System (PERS) often employs the use of a manual emergency button. However this approach may not be useful if the fall victim become unconscious or even not be able to move to reach the emergency button. In addition, such as this approach also requires more time and inadequate to notify and seek for immediate help. This paper attempts to design and implement a smart fall detection system for real time notification known as e-SAFE. This system will automatically detect a fall and notifies the incident instantly to internal and external correspondence. The e-SAFE equipped with a wearable accelerometer sensor, microcontroller, ZigBee transceiver module and Global System for Mobile communications (GSM) device. The in-house correspondence will be notifies though the ZigBee technology, meanwhile the external correspondence will be notified through GSM. Once a fall has been detected by e-SAFE system, a Short Message Service (SMS) and an E-mail will be sent to predefined contacts which is stored in the system. This system will provide a path toward independent living for the elderly while keeping them save

COMPARATIVE STUDY ON SINGLE- AND DOUBLE-PASS CONFIGURATIONS FOR SERIAL DUAL-STAGE HIGH CONCENTRATION EDFA

A comparative study on a single- and double-pass configurations for Erbium-doped fiber amplifier (EDFA) are demonstrated using a gain media of high concentration Silica-based erbium doped fiber (EDF). The amplifier has two stages comprising a 1.5 m and 9 m long EDF optimized for C-band and L-band operations respectively, in a single-pass and double-pass configuration s. The CFBG is used at the end of EDF stage to allow a double propagation of signal and thus increases the attainable gain in both C- and L-band spectra. At an input signal power of -30 dBm, a flat gain of 22 dB is achieved with a gain variation of ±3 dB within a wide wavelength range from 1530 to 1600nm (C- and L-band) in double-pass configurations. The corresponding noise figure varies from 4 to 8 dB within this wavelength region. The flat gains for single-pass configuration only amplify within 1555 nm to 1600 nm (L-band)

An Enhancement of RTS/CTS Control Handshake in CSMA/CA Based MAC Protocol for an Efficient Packet Delivery over Multihop Wireless Mesh Network (WMN)

The Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA) based Medium Access Control (MAC) protocol uses a short request-to-send (RTS) and clear-to-send (CTS) control packets prior of actual data packet transmission. The function of the CSMA/CA based MAC protocol in wireless communication is to facilitate wireless nodes (i.e. laptop, PC, smart phones and etc) to access a wireless medium efficiently. Besides, it is also efficiently manage the wireless medium when more wireless nodes involving in transmission activity in the network. This protocol allows all wireless nodes in the network to communicate between each other without collision. Since collisions may only occurred on the RTS control packets thus it can reduce the actual data collision on the medium. The RTS/CTS control handshake provides better performance and reduce the duration of collision especially when long data packets are transmitted over wireless medium. However, even though the CSMA/CA based MAC protocol working effectively and provides better throughput performance over single hop communication but it performance degrade significantly when directly applied in multihop Wireless Mesh Network (WMN). The reason behind this poor performance is due to the inefficient packet delivery of CSMA/CA based MAC protocol in multihop network. The exchange of RTS and CTS signaling that required at each hop throughout the multihop network eventually will cause the large overheads and subsequently degrade network throughput. Therefore, in this paper, an enhancement of RTS/CTS handshake has been proposed in order reduces the signaling overheads and ultimately allows a smooth packet delivery in the multihop network without any collision. In this work, the multihop network performances are evaluated analytically in terms of throughput and overhead. It is proven that the new method of RTS/CTS handshake provides significant improvement in throughput and overhead

THREE BIT SUBTRACTION CIRCUIT VIA FIELD PROGRAMMABLE

This project is about to design the software and hardware simulator for a Three Bit subtraction Circuit via Field Programmable Gate Array (FPGA). The three bit subtraction circuits are involved in performing the subtraction for each bit by performs operation the arithmetic and logic unit, called the Arithmetic Logic Unit (ALU). All this operation is to be displayed at seven segment using FPGA board by using Verilog language. A FPGA is a semiconductor device containing programmable logic components called "logic blocks", and programmable interconnects. Logic blocks can be programmed to perform the function of basic logic gates such as AND, and XOR, or more complex combinational functions such as decoders or simple mathematical functions such as additional, subtraction, multiplication, and divisions (+, -, x, ÷). In conclusion, three bit subtraction circuit via FPGA has been successfully designed and developed. In order to have a complete system that is design by our own, one of the recommendation to enhance the possibility of this thesis is to develop the hardware equip with wireless technology

Graphene oxide film as a passive q-switcher in an erbium-doped fiber laser cavity

All-fiber passively Q-switched fiber lasers have been demonstrated by using a graphene oxide (GO) Q-switcher for possible applications in telecommunication, laser processing, fiber sensing and medicine. The GO material was obtained through a modified Hummers method from expanded acid washed graphite flakes and was embedded into a polyvinyl alcohol (PVA) film to form a saturable absorber (SA) device. The Q-switched pulse operates at 1563.3nm with a repetition rate that can be tuned from 44.33kHz to 61.77kHz as the pump power changes from 39mW to 96mW. The highest repetition rate of 61.77kHz is achieved at a pump power of 96mW and it is observed that the Q-switched pulse produced a maximum pulse energy of 0.054nJ and pulse width of 5.57 mu s at 96mW pump power

NEODYMIUM OXIDE (ND2O3) AS PASSIVE Q-SWITCHER FOR PULSED FIBER LASER GENERATION IN C-BAND REGION

his work demonstrate Neodymium Oxide (Nd2O3) film as a passive saturable absorber (SA) for pulse generation within C-band region. The saturable absorber was fabricated from Nd2O3 powder, and polyvinyl alcohol (PVA) was used to form a film. The all-fiber ring cavity configuration was used in the experiment. The Q-switching operated with the pump power from 60 mW to 120 mW. The repetition rate increases from 52 kHz to 77 kHz, while the pulse width shown decrement of 7.4 µs to 5.3 µs. The signal-to-noise ratio obtained of the fundamental frequency is 64 dB. The maximum output power and pulse energy are 3.6 mW and 4.6 nJ respectively. The maximum peak power obtained is 0.87 mW

Q-Switched And Mode-Locked Thulium Doped Fiber Lasers With Nickel Oxide Film Saturable Absorber

A passively Q-switched and mode-locked fiber laser based on thulium-doped fiber laser (TDFL) cavity was demonstrated utilizing nickel oxide (NiO) nanoparticles as a saturable absorber (SA). The NiO synthesis was carried out by using a facile sonochemical method and the prepared NiO thin film was sandwiched between two optical fiber ferrule connectors in the TDFL ring cavity. By controlling the loss and gain in the cavity, stable Q-switching operation was obtained. The repetition rate and pulse width were tunable from 6.71 kHz to 19.58 kHz and from 9.1

Modelling of Swarm Communication

Swarm communication is a communication process of sending data within a certain area via agents.. Data will be sent to all the agents in this process. This is also closely related to the way of broadcasting via “short communication” as a way to find out the data among their agents. This field involved an in -depth study of the behaviour of the agents and by using a homogeneous approach, inspect the process of sending data. This includes investigation of independence of agents and the characteristics of sending and receiving data for a random process in a swarm. In this paper, techniques useful for swarm implemented bit-communication behaviour will be presented. There are two approaches that are used to send and receive signals. The reverse approach is where data can be resend to the sender for the next cycle, where the program randomly selects the nearest agents t o send data to. While for the nonreversing approach data is not able to return to the sender in the previous cycle. The non -reversing approach can improve system performance and efficiency. This paper presents the development of a swarm communication mode l and how it can be used to illustrate the communication process