Preparation of an Exponentially Rising Optical Pulse for Efficient Excitation of Single Atoms in Free Space

We report on a simple method to prepare optical pulses with exponentially rising envelope on the time scale of a few ns. The scheme is based on the exponential transfer function of a fast transistor, which generates an exponentially rising envelope that is transferred first on a radio frequency carrier, and then on a coherent cw laser beam with an electro-optical phase modulator (EOM). The temporally shaped sideband is then extracted with an optical resonator and can be used to efficiently excite a single Rb-87 atom.Comment: 3 pages, 4 figures, small technical not

Doppler-free approach to optical pumping dynamics in the 6S1/2−5D5/26S_{1/2}- 5D_{5/2} electric quadrupole transition of Cesium vapor

The $6S_{1/2}-5D_{5/2}$ electric quadrupole transition is investigated in Cesium vapor at room temperature via nonlinear Doppler-free 6P-6S-5D three-level spectroscopy. Frequency-resolved studies of individual E2 hyperfine lines allow one to analyze optical pumping dynamics, polarization selection rules and line intensities. It opens the way to studies of transfer of light orbital angular momentum to atoms, and the influence of metamaterials on E2 line spectra.Comment: 4 pages, 5 figures, minor updates from previous versio

Development And Implementation of a Novel Code Family for Optical Code Division Multiple Access Systems

Future telecommunication systems and networks are expected to provide a variety of integrated broadband services to the customers. There has been a tremendous interest in applying Code Division Multiple Access (CDMA) techniques to fiber optic communication systems. This technique is one of the multiple access schemes that is becoming popular because of the flexibility in the allocation of channels, ability to operate asynchronously, enhanced privacy and increased capacity in bursty networks. The performance of any Optical CDMA (OCDMA) system strongly depends on the codes properties. In this study we introduce a new code for Optical CDMA namely Double Weight Code family (DW). Double Weight Code (DW) has a basic fixed weight of 2 and exists for every natural number. The DW codes possess ideal cross correlation properties, which have important characteristics in OCDMA systems since these can eliminate multiple access interference (MAI) and reduce noise. Also proposed in this study, a Modified Double-Weight (MDW) code, which is a variation of DW code family that can have a variable weight greater than two. The MDW code possesses ideal crosscorrelation properties and exists for every natural number too. It is shown through simulations, theoretical analysis and partially by the experiments that the transmission performance of DW code family is significantly better than that of existing codes such as Modified Frequency Hopping code (MFH) and Hadarnard code. The performance of DW code family, MFH and Hadamard codes were simulated using commercial simulation software, OptiSystem Version 3.0. The performance of the systems was characterized by referring to the bit error rate (BER) and the eye patterns. DW code family has shown superior performance compared to other OCDMA codes. The simulated eye pattern of one of the four MDW coded carriers running at lOGbps over a cornrnunication-standard fiber shows a good quality transmission at the BER of 10 -12 as opposed to only 1o ' ~an d 1o 4 for Hadamard and MFH codes. In optical CDMA systems, the detection process affects the design of transmitters and receivers. Cross-correlation functions are generated which creates Multiple Access Interference (MAI) and this will degrade the system performance. MA1 can be reduced by using subtraction techniques. The most common subtraction technique is the complementary subtraction technique and also known as balanced detection technique. In this thesis, we also introduce a new approach called AND subtraction technique. This method rejects unwanted signals that interfere with the original signals. Furthermore, the purpose of this new subtraction technique is to reduce the receiver complexity and increase system performance. It has been shown through theoretical analysis, simulation and experimental work, the performance of the system with AND subtraction technique can be improved significantly. Based on the theoretical analysis, BER as good as 10-l2is achieved at the bit rate of 622 Mbps over 70 km distance

BIOMETRICS: FINGERPRINT RECOGNITION

Accurate automatic personal identification is critical in a variety of applications in our electronically interconnected society. Biometrics, which refers to identification based on physical or behavioral characteristics, is being increasingly adopted to provide positive identification with a high degree of confidence. Among all the biometric techniques, fingerprint-based authentication systems have received the most attention because of the long history of fingerprints and their extensive use in forensics. However, the numerous fingerprint systems currently available still do not meet the stringent performance requirements of several important civilian applications. To assess the performance limitations of popular minutiae-based fingerprint verification system, we theoretically estimate the probability of a false correspondence between two fingerprints from different fingers based on the minutiae representation of fingerprints. Due to the limited amount of information present in the minutiae-based representation, it is desirable to explore alternative representations of fingerprints

Excitation of a single atom with exponentially rising light pulses

We investigate the interaction between a single atom and optical pulses in a coherent state with a controlled temporal envelope. In a comparison between a rising exponential and a square envelope, we show that the rising exponential envelope leads to a higher excitation probability for fixed low average photon numbers, in accordance to a time-reversed Weisskopf-Wigner model. We characterize the atomic transition dynamics for a wide range of the average photon numbers, and are able to saturate the optical transition of a single atom with ~50 photons in a pulse by a strong focusing technique. For photon numbers of ~1000 in a 15ns long pulse, we clearly observe Rabi oscillations.Comment: 5 pages, 6 figure

Tailoring optical metamaterials to tune the atom-surface Casimir-Polder interaction

Metamaterials are fascinating tools that can structure not only surface plasmons and electromagnetic waves but also electromagnetic vacuum fluctuations. The possibility of shaping the quantum vacuum is a powerful concept that ultimately allows engineering the interaction between macroscopic surfaces and quantum emitters such as atoms, molecules or quantum dots. The long-range atom-surface interaction, known as Casimir-Polder interaction, is of fundamental importance in quantum electrodynamics but also attracts a significant interest for platforms that interface atoms with nanophotonic devices. Here we perform a spectroscopic selective reflection measurement of the Casimir-Polder interaction between a Cs(6P_{3/2}) atom and a nanostructured metallic planar metamaterial. We show that by engineering the near-field plasmonic resonances of the metamaterial, we can successfully tune the Casimir-Polder interaction, demonstrating both a strong enhancement and reduction with respect to its non-resonant value. We also show an enhancement of the atomic spontaneous emission rate due to its coupling with the evanescent modes of the nanostructure. Probing excited state atoms next to nontrivial tailored surfaces is a rigorous test of quantum electrodynamics. Engineering Casimir-Polder interactions represents a significant step towards atom trapping in the extreme near field, possibly without the use of external fields.Comment: 21 pages, 9 figure

Craniofacial anthropometric norms of Malaysian Indians

Objective: This study was done to establish the craniofacial anthropometric norms of the young adult (18-25 years) Malaysian Indian. Materials and Methods: The study group consisted of convenient samples of 100 healthy volunteers, with equal number of female and male subjects who had no history of mixed racial-parentage. Twenty-two linear measurements were taken twice from 28 landmarks over six craniofacial regions. The methodology and evaluation of indices of the craniofacial region was adapted from Hajnis et al. Results: The minimum measurements are always contributed by the female Indian except for the nose height (n-sn), (left) eye fissure length (ex-en), upper vermillion height (ls-sto), and lower vermillion height (sto-li). There is a gender difference in all the measurements except the (left) eye fissure height (independent t-test; P {\ensuremath{<}} 0.05). The Malaysian Indians exhibit some North American White Caucasian (NAWC) features in all regions. The cephalic index indicates a brachycephalic or relatively short wide head with a tendency towards mesocephaly. From the low nasal index, the Malaysian Indian female have a nose that is narrow or leptorrhin similar to the NAWCs. The lower value of the upper lip height to mouth width index in the Indian female indicates a relatively shorter upper lip height compared to the mouth width, also similar to the NAWC. Conclusion: This study establishes the craniofacial anthropometric norms of the Malaysian Indian over 22 parameters. Male in general has a significantly higher measurement than female. The Malaysian Indians do exhibit some NAWC features

Capacity of public health laws enforcement by health inspectors in state of Selangor, Malaysia

A cross sectional study initiated among the Public Health Enforcement Inspectors in state of Selangor, Malaysia in July 2003 using a self administered questionnaire and universal sampling with the purpose to determine the capacity of public health laws enforcement and factors influencing it. A total of 99 respondents from the Health Districts Ofices and I00 respondents from the Local Municipal Health Departments participated in this study. It was found that the level of enforcement is generally low in all the units except for two units; the Food Unit and Sanitary and Hygiene Units. Factors found to influence enforcement capacity are the units' the enforcers work in and the length of service being in the same unit. Further analysis using multiple logistic regression, showed that respondents from the Food Unit (adjusted odds ratio 22; CI 95% : 7.851, 58.896), enforcers from the middle level category (adjusted odds ratio 5; CI 95%: 1.397, 17.630), duration of service of 4 years and above in the same unit (adjusted odds ratio 6; CI 95%: 2.174, 13.747), past acceptance of formal service rewards from their departments (adjusted odds ratio 3; CI 95% : 1.150, 6.917); low exposure to bribery (adjusted odds ratio 46; CI 95% : 2.336, 1000) and have in the past being oflered bribes while on the field (adjusted odds ratio 3; CI 95% : 1.018, 4.772) are associated with higher enforcement capacity. In conclusion; die attention must be looked into the enforcement organization with respect to the duration of service, acknowledgement via service rewards and monitoring of bribes exposure will help shape a better public health laws' enforcement capacity