Sid Senadheera
email: sid.senadheera [at] gmail.com Remove 2 spaces and replace @ in the brackets
* Please note that all contents of this website are intellectual property of the author(s). No material can be copied or used in publications or personal research without consent!
Please see the details in the "ABSTRACT" for all the papers below.
* From a talk (linked) : A four Nanoparticle system that can emulate any RC circuit, with 1/1000000000 the original size of a circuit and increase it's speed 1000X to 100,000 X .....
* Ananlysis of transmission current
(Part -1): http://sidath.senadheera.net/3D-Tunneling.pdf
(Part -2): http://sidath.senadheera.net/Transmission-of-current.pdf
* Magnetic Field Controlled Nanofiber Generation http://sidath.senadheera.net/Magnetization-paper.pdf
*Critical Time to Nucleation: Graphite and Silicon Nanoparticle Generation by Laser Ablation http://sidath.senadheera.net/RZ-theory..pdf
*Pulse shaping effects on nanoparticle generation http://sidath.senadheera.net/dpulse-draft.pdf
*Shielding nano-devices from unwanted electromagnetic radiation by using 3-D nanofiber structure http://sidath.senadheera.net/EMI.pdf
Related - Quantum tunneling analysis of transmissionof a current.. http://sidath.senadheera.net/3D-Tunneling.pdf
*Emission-enhancement of Al and Si nanofibers using dual pulses with varying wavelengths http://sidath.senadheera.net/double-pulse-opexstyle_.pdf
*Nanoparticles emission direction control - using magnetic fields and polarization http://sidath.senadheera.net/Magnetic-Polarization(original-document).pdf
* Electro-mechanical properties of Carbon Nanotubes - REVIEW PAPER [~ 40 pages] http://sidath.senadheera.net/CNT.pdf [paper]
*Size variation due to changing pulse frequencies and pulse-widths on Silicon fractal aggregates : http://sidath.senadheera.net/Size_variations_in_nanoparticles-1.pdf
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papers
* Magnetic Field Controlled Nanofiber Generationhttp://sidath.senadheera.net/Magnetization-paper.pdf
ABSTRACT : It is important to manipulate the density of nanoparticles on a substrate subjected to laser ablation. Although there have been many advances in this area, a modern approach to controlling the nanoparticle trajectories is still required. In this paper we have summarized such an approach for changing the projected paths of nanoparticles by using a static magnetic field. This enables us to control their density in specific locations and their self assembly into nanofibers in these areas. The concentration of nanoparticles can also be redirected towards a quadrupole lens and transported into other applications. From a classical perspective we experimentally showed that the nanoparticle aggregates were concentrated at locations consistent with Lorentz force. We have also explained this phenomenon with a modern approach that gives more accurate estimate for the direction of nanoparticles and where these nanoparticles would create nanofibers. Therefore our findings can be used to understand how nanoparticles react under the influence of magnetic fields from a modern perspective and control their growth in designated areas on a two dimensional substrate.
*Critical Time to Nucleation: Graphite and Silicon Nanoparticle Generation by Laser Ablation
http://sidath.senadheera.net/RZ-theory..pdf [paper]
http://sidath.senadheera.net/seminar1.ppt [slides]
*This paper also has the first fundamental proof of Raizer-Zeldovich theory, 50 years after it's theoretical derivation.
ABSTRACT : Femtosecond laser ablation hydrodynamics has been analyzed numerically. The nucleation process of two materials (silicon and graphite) in an expanding plume produced by a femtosecond laser ablation is analyzed within the framework of the Zeldovich-Raizer theory (RZ theory). RZ theory is the most appropriate theory applicable to an expanding plume created by a femtosecond laser ablation and has been used to estimate the critical times in the evolution of nanoparticle formation. However, there is no experimental result to directly substantiate the theoretical model on a fundamental level. This paper gives an experimental approach to prove theoretical predictions of critical times to nucleation in laser-ablated graphite and silicon plumes. The critical time to nucleation deduced using the RZ theory was found to be in close agreement with pulse frequency at which fibrous nanoparticle aggregates start to formfor both materials.We experimentally showed that the nanoparticle aggregates were produced consistently when the pulse frequency corresponding to the femtosecond laser time interval was shorter than the critical time to begin nucleation. Therefore the nucleation time acts as a threshold time length to begin nucleation.
*Pulse shaping effects on nanoparticle generation
http://sidath.senadheera.net/dpulse-draft.pdf
ABSTRACT : Current research has not fully realized the advantages of pulse shaping in areas such as nanoparticle generation by femtosecond laser ablation. In this paper, we have summarized our findings on how the nanoparticle aggregate generation process is affected by the use of a double pulse ablation and how this process is further manipulated to increase yield by using certain amounts of energy in each pulse. It was found that by using a given ratio of energy for the two pulses can result in a higher amount of nanoparticle generation. Previous scientific research in this area experimentally proved that the ratio of the produced Si+/Si (or Si-II/Si-I) decreases with time. We proved how this ratio decreases with time both theoretically and experimentally. This proof was speculated before by other researchers without enough theoretical explanation.
*Shielding nano-devices from unwanted electromagnetic radiation by using 3-D nanofiber structure
http://sidath.senadheera.net/EMI.pdf
Related - http://sidath.senadheera.net/3D-Tunneling.pdf
Abstract : An introduction to electromagnetic theory is given with emphasis on wave propagation phenomena in free space and inside material. This background is necessary in order to understand the phenomena of penetration of electromagnetic radiation into different media and construct a universal model for electromagnetic shielding at nano-scale. Skin depth of a conductor is defined as the depth that a electromagnetic wave penetrates into. In our research we have shown how the fundamentals of the Faraday cage can also be applied to a system with nano-devices or protect a nano-circuit.
*Emission-enhancement of Al and Si nanofibers using dual pulses with varying wavelengths
http://sidath.senadheera.net/double-pulse-opexstyle_.pdf
Abstract:In this article we report the synthesis of Silicon and Aluminum nanofibers in air as a ambient and at room temperature. Nanofibers are generated by a process of self assembly after the conditions are met for nucleation, inside a plume of plasma created by a femtosecond laser evaporation of the material. They form as interweaving fibrous structures that show certain degree of linear aggregation at high magnification. After experimenting with pulse separation we found that by using two consecutive pulses very close together at two different wavelengths is highly effective when increasing the yield. The creation and the growth mechanism of nanofibers can be explained by the existing theories in hydrodynamics.
*Nanoparticles emission direction control - using magnetic fields and polarization
http://sidath.senadheera.net/Magnetic-Polarization(original-document).pdf
ABSTRACT : It is important to manipulate the density of nanoparticles on a substrate subjected to laser ablation. In this paper we have summarized our approach for changing the projected paths of nanoparticles by using magnetic fields and polarization. This enables us to change the concentration of nanoparticles in specific areas which also enable us to control their density at a given location on the substrate. This concentration of nanoparticles can then be redirected towards a magnetic lens and used in various other applications. We experimentally showed that the nanoparticle aggregates were concentrated at locations consistent with Lorentz force law and highly concentrated towards the direction electric field vector in the polarized case. Therefore our findings can be used to understand how nanoparticles react under the influence of magnetic fields and polarized femtosecond laser ablation.
* Electro-mechanical properties of Carbon Nanotubes - REVIEW PAPER [~ 40 pages]
http://sidath.senadheera.net/CNT2.pdf [slides]
http://sidath.senadheera.net/CNT.pdf [paper]
It was after Iijima’s work in 1991 [1] that global scientific attention was turned to these interesting carbon structures and intense studies on the properties, structure, and applications of these unique materials have been carried out. CNTs are considered to be a rolled-up graphene sheet that forms long concentric cylinders. The properties of nanotubes depend on the structure, morphology, diameter, and length of the tubes. The structure of carbon nanotubes is described in terms of the tube chirality, which is defined by the chiral vector and the chiral angle, Figure (see paper) [1]. The chiral vector indicates the way, in which graphene is rolled-up to form a nanotube.
*Size variation due to changing pulse frequencies and pulse-widths on Silicon fractal aggregates
http://sidath.senadheera.net/Size_variations_in_nanoparticles-1.pdf
Abstract : An analysis is carried out to investigate the influence of pulse frequencies and pulse-widths on the size of nanoparticle aggregates generated by femtosecond laser ablation of bulk silicon. The experiment was carried out at ambient atmosphere at room temperature. The width of Silicon nanoparticle aggregates created by elements were analyzed according to individual nanoparticle sizes and their nanoparticle structure. Most historigical experimental work have been done below 1 kHz pulse frequency, in low frequencies such as 1-100Hz. Research work on the sizes of nanoparticles that make up 3-D nanoparticle fractal aggregates have been rarely done since most researchers collected individual samples of nanoparticles by laser ablation at low pulse frequencies. In our work we analyze the nanoparticle sizes at high pulse frequencies (1 MHz – 13 MHz).
2004-2006 , independent research by Sid Senadheera
* Novel design of a thermo-optic Mach-Zehnder
Interferometer(MZI) with power consumption reduced by one
half.
The US
Patent #20050048409 comes close to this approach. This is a design by the Intel
Corporation group that used this approach to fabricate a Bragg grating. In my
approach, I will apply a different approach to a MZI and a VOA and prove that
the power consumption of these devices can roughly be reduced by one half.
Currently the theory agrees with computer simulations using BeamProp and
FemLab.
* Designing the world's fastest
thermo-optic modulator.
Entire paper : http://sidath.senadheera.net/paper.pdf
Abstract from rough
draft - below I have the URL to the entire paper. This
personal invention has been informally edited by a faculty member. Abstract :
Recently there have been less attention given to thermo-optic Silicon on
Insulator (SOI) Mach-Zehnder Interferometers switches and modulators (MZI's) due
to the their slow frequencies relative to their CMOS fabricated counterparts
working at higher frequencies using the plasma dispersion effect. Although the
speeds of MZI switches and modulators have increased within the last five years
currently they have reached a saturation point due to some physical limitations.
In this paper a research model has been derived for a modulator that could
overcome some of these physical limitations to increase speed and also have the
modulator keep up with increasing modulating frequencies as faster and faster
switches are invented. The model described is estimated to work in lower MHz
frequencies attaining the highest possible modulation frequencies for
thermo-optic modulators while proving that power consumption is lowered
significantly.
* Using
a very robust modulation technique such as PSK ( Phase shift Keying ) in
photonics devices and designing simpler PSK demodulators
This paper will give an outline of the fundamental setup of
a unique modulating and demodulating technique than those currently being
used. Dr. Andrew Knights has informally confirmed the correctness of my
approach, but is not responsible for the details or co-author this publication.
The modulation that has been used in encoding signals to a carrier signal is
almost entirely ASK (or AM) Amplitude modulation. Amplitude modulation is
subjected to electronic noise and other types of defects in the medium that
carries the signal like changes in the index of refraction in the fiber optic
cable. On the other hand PSK is not a function of these defects and noise and
therefore a much stronger signal is received after demodulation with minimum BER
(bit error rate) and high S/N ratio. This same system could be pushed ahead
to QPSK where the phase is not just limited to two, but four different
states while doubling the bandwidth. A prototype this system can be easily
built with inexpensive off the shelf material.
Note: As you will see from the
attached URL below, last year (2005) five researchers from the Intel corporation
built something like this. But they still used AM modulation with their new
modulation technique. PSK modulation has not been used since the demodulating
end is too complex. In my paper I have worked out more technically detailed
information on this approach using a very simplified demodulator for PSK. Paper
from Intel group : Note: The 4th reference in the article below is my
co-supervisor, Andrew Knights
http://www.opticsexpress.org/ViewMedia.cfm?id=82928&seq=0
* Change
polarization to alter the direction of the TE vector by stress /strain and
modulate a signal.
Stress on a piezoelectric material causes polarization
changes. If such a material is continuously made to change the level of stress
in a systematic way, a signal can be created by changing the angle of
electric field vector relative to it's original vertical direction. In other
words flipping the TEoo vector by 0 to 90 degrees the binary numbers (1,0)
can be created. This has already been done in other ways in CMOS fabricated
devices. I will use a novel approach to modulate a similar signal. In
addition since the physical properties of a wave such as phase, polarization,
amplitude are independent of each other, all these three effects can be induced
in the same carrier to form three different modulation schemes at the same time
to carry (3-6) times or more information than what a conventional (ASK or
AM) modulated signal can carry.
* Design of an intermediate
modulation converter from a complex fiber-optic modulation systems to ASK
(AM) operated silicon photonics systems, vice versa.
The next generation of micro-processors and integrated circuits will consist of parts working with silicon photonics. Companies such as Intel will not introduce the first silicon photonics integrated devices with complex modulation schemes. Therefore a transition of a signal modulated under these complex modulation methods that are already being used today such as ASK/ QPSK/ PO-LSK ( Polarization Shift Keying ) from a fiber optics system must be able to be converted to a silicon photonics system, vice versa. This paper will describe why such a conversion is necessary and how such a conversion can be designed with less attenuation of the signal, without lag, introduction of error or noise (or low BER and high S/N).
* All of the first three
applications could be combined.
It is possible to put MZI's in parallel as in # 2 and extend
this configuration to CMOS fabricated MZI's functioning under the plasma
dispersion effect. This could double or quadruple the fastest modulators.
PSK/QPSK can be used to reduce the signal attenuation.
* Using Silicon Photonics interferometry to simplify
Adaptive Optics.
It is a common problem having to demodulate a phase
modulated (Or phase shift induced) signal in fiber optic communications.
The demodulating end is somewhat complex in these systems. Silicon
photonics provides somewhat of an easier solution by using
interferometry. That is, the incoming wave from the guide star is added to
another signal which has the same frequency (Look at Part I in the link above).
Then the intensity of the resultant wave is measured. It can be written as
a function of two phases and amplitude. The added wave must have a similar
amplitude. Or the change in the amplitude as a function of time should be
negligible compared to change in the phase as a function of time. Now the
measured intensity is an addition of two dc offset voltages. One will have
a constant value and the other will be varying (see the end result of PART
II in the link above). By taking the magnitude of the varying voltage at
uniform time intervals gives the change of phase in the incoming radiation.
The alterations done in Shack-Hartman Lenslett array are proportional to these
phase changes.
LINK : gives a crude theoretical
derivation.
email: sid.senadheera [at] gmail.com Remove 2 spaces and replace @ in the brackets
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