2004 Bowman Scholars
Division of Engineering and Weapons
- 1/C Matthew A. Beasley
- Major: Electrical Engineering
- Title: Packaging for Satellite-based Microelectromechanical Systems
- Advisor: Assistant Professor Samara L. Firebaugh, Electrical Engineering Department Abstract
Packaging for Satellite-based Microelectromechanical Systems
The goal of this project is to successfully design, build, and test a package for a microelectromechanical variable emissivity radiator to launch on the Naval Academy satellite, MIDSTAR I. Microelectromechanical Systems (MEMS) are microchips with moving parts. Utilizing integrated circuit fabrication technology, these micro-scale devices offer the advantages of reduced mass, greater efficiency and bulk fabrication.
While much of MEMS research is focused on device design, there is a vital step required to link the laboratory with the real world that receives much less attention. MEMS packaging is equally important as the device it will support. Unlike integrated circuits, MEMS require protection from external elements but must also interact with the environment. This requirement makes packaging complex and difficult to standardize.
A research team at the Johns Hopkins University Applied Physics Laboratory (JHU/APL) is currently designing and fabricating a MEMS-based thermal control device for satellites. The device has two layers: a thermally emissive outer layer and a layer in contact with the satellite. When a voltage is applied, the top layer contacts the bottom layer, allowing heat to radiate from the satellite.
Through research and laboratory testing, this research will involve designing and fabricating the package for this device. Doing so will require extensive characterization of the first generation device alone, as well as testing of the device and package for expected levels of vibration, radiation, and temperature. This will ensure the device and package can survive space launch and orbit for the life of a satellite. The package is specifically being designed to allow testing on the next Naval Academy satellite, MIDSTAR I. In addition to protecting the device, the package must also provide connections to the satellite’s onboard computer and power supply, and include sensors to verify operation.
This research work will provide valuable feedback to the APL research team, as the development of the package should reveal device design changes that will increase overall system performance. The research completed in this project will also become part of the foundation for future work in space packaging for MEMS, and aid future defense applications as the military continues to look toward space for the answers to modern communications and intelligence problems.
- 1/C Kevin J. Behm
- Major: Electrical Engineering
- Title: The Integration of a Nuclear Acquisition System with Wireless Communications Technology
- Advisor: Professor Martin E. Nelson, Mechanical Engineering Department
- Advisor: Commander Thaddeus B. Welch, III, USN, Electrical Engineering Department Abstract
The Integration of a Nuclear Acquisition System with Wireless Communications Technology
Nuclear threats can be detected by measuring the neutron and gamma radiation that is emitted by nuclear material. Such data can be collected in the field by portable data acquisition systems (DAQS) that could be mounted within a wide variety of platforms, such as unmanned aerial vehicles (UAV’s). These DAQS collect large arrays of data using multi-channel analyzer technology. More sophisticated analysis can be performed if the data is analyzed remotely on more powerful computers than if analyzed in-situ. To accomplish this advanced analysis, the data must be transferred remotely using wireless communications technology. However, currently very limited work has been performed on the integration of nuclear DAQs with this technology.
The goal of this project is to integrate and then successfully demonstrate that a nuclear DAQ can wirelessly transfer data to a laptop computer using internet protocol (IP). To accomplish this, a number of interface issues, including proper data formatting and stopping and starting of data acquisition, must first be resolved. This project will be broken down into three successive phases.
Phase one, the building phase, will work to create a point to point transfer of data between two laptops using peer to peer networking. This phase of work shall serve as the base for the rest of the project, and will reference the work of Ensign DeForge, Class of 2003, who built and worked on this phase of the project last year.
During the second phase of this project, the wireless phase, the IP code written in phase one will be altered to create a wireless network. This network will adhere to one of the wireless standards set forth in the wireless networking standard IEEE 802.11.
The third and final phase of this project will give the nuclear DAQ the capabilities to send its data to an IP ready phone. This should represent the most challenging phase of the project, but also the most applicable, since it has such wide-ranging capabilities.
Upon successful completion of the final phase of this project, the system will be demonstrated by using a neutron source and a neutron sensitive nuclear DAQ, both of which are located in the nucleonic laboratory in Rickover Hall to collect data.
After collection, this data will be sent wirelessly to another laptop, and an IP ready phone. Both the neutron source and the nuclear DAQ were undamaged by the recent flooding in Rickover Hall.
Practical Uses of the Project Results
This project could serve as a useful tool for the United States to help regulate its rigid force protection measures. Gate guards and other members responsible for force protection could benefit from the wireless capabilities and mobility of such a system. Also, UAV’s could use this technology to perform radiation sweeps miles into enemy territory. If the radiation detectors could be made small enough to fit onto a cell phone, this system could represent the most comprehensive radiation detection network ever created, as it would be maintained by the users. In this system, every cell phone could identify, and report possible radiation sources to proper authorities.
- 1/C Ryan J. Corcoran
- Major: Systems Engineering
- Title: Assessment of a DC Stability Toolbox Application to a Shipboard Nonlinear Integrated Power System
- Advisor: Assistant Professor Edwin L. Zivi, Weapons & Systems Engineering Department
- Advisor: Associate Professor John. G. Ciezki, Electrical Engineering Departmen Abstract
Assessment of a DC Stability Toolbox Application to a Shipboard Nonlinear Integrated Power System
The power system of the Navy’s future electric warships will supply approximately 100 MW of power for critical operations such as propulsion, ship’s service, and weapons. These interdependent, automated systems need to be efficiently managed under dynamic conditions including large power transients from the use of energy weapons, damage control operations, and battle induced casualties. As mobile energy sources for a future electric naval force, these ships need to respond quickly to faults and disturbances so they can remain online to continuously carry out their missions.
In order to fully develop and test electric warships, additional research is required to accurately model and control the nonlinear power systems aboard these ships. Concurrently, an effective nonlinear analytic design tool to confidently design a nonlinear stabilizing controller for a shipboard Integrated Power System (IPS) may be years away. This research aims to explore the range of applicability of existing impedance-based tools to determine nonlinear system stability. Recently, a MATLAB-based DC Stability Toolbox, developed by Sudhoff et al, has provided promising results. This model approximates nonlinearities and uncertainty through specified variations in parameter values. Essentially, the nonlinear system is linearized with respect to an equilibrium point. However, this implicit small signal assumption may limit the validity for stability analysis of large-scale transients and disturbances. This investigation will examine the range of the DC Stability Toolbox’s effectiveness for the nonlinear system beyond the linearized neighborhood of particular operating points. If the DC Stability Toolbox cannot effectively model the complete nonlinear system, other stability methods can be investigated. In particular, it may be possible to extend the applicability of the DC Stability Toolbox by decomposing large-scale nonlinear transients into a sequence of smaller steps. Assuming that the nonlinearities are sufficiently smooth, the linear analysis will be applicable within a finite neighborhood of a particular operating point. The analysis can then be applied to an overlapping sequence of neighborhoods completely describing the nonlinear behavior. Several tools are available to investigate these possibilities. Two separate time-domain simulations and experimental hardware results will serve as a comparison to the predictions of the Stability Toolbox.
- 1/C Adam S. Fisher
- Major: Electrical Engineering
- Title: A Bidirectional Wavelength Multiplexed Fiber Ring Network
- Advisor: Associate Professor R. Brian Jenkins, Electrical Engineering Department
- Advisor: Captain Robert J. Voigt, USN, Electrical Engineering Department Abstract
A Bidirectional Wavelength Multiplexed Fiber Ring Network
There is much untapped potential in the use of fiber optic technology. Its advantages, including greater bandwidth and higher data rates, are currently used most effectively in large-scale network backbones. While used to connect continents and cities, optical fiber still has yet to be widely integrated into small-scale applications, such as local area networks. The aim of this research project is to build a working eight-node optical fiber ring network that functions as a precursor to such a local area network. The network uses four wavelength division multiplexed (WDM) frequency channels and eight bidirectional add-drop multiplexers to route mixed types of data signals (digital and analog) between the individual nodes.
In WDM communications, information is transmitted on multiple optical frequencies. In this project, the specific frequencies are routed to different nodes in a bidirectional manner, minimizing the number of nodes a message must through in order to reach its destination. Eight add-drop multiplexers (ADM), one for each node, perform the routing function. The ADMs used in this network allow information on multiple wavelengths to propagate through them in both directions. Each ADM adds (drops) two wavelengths to (from) the ring network. The bidirectional capability is achieved using thin film filter technology, in which filtered wavelengths are reflected in a direction opposite that of the transmitted wavelengths.
The project is comprised of integrating each ADM into the network, addressing performance issues such as crosstalk between frequencies, bit error rates, signal to noise ratio, and reliability using different data formats. The practicality of the small-scale network is also examined, considering issues such as security and fault-tolerance.Successful completion of the project will further harness the benefits of optical fiber. Ships, campuses, office buildings, even whole neighborhoods could be connected with the high bandwidth associated with fiber optic networks. If it can be shown that local area networks can operate at high data rates in a single fiber ring, while maintaining scalability and modularity, the possibility of installing smaller scale optical fiber networks would be significantly enhanced.
- 1/C Brandon R. Monaghan
- Major: Electrical Engineering
- Title: Signal Filtering using the Hilbert-Huang Transform
- Advisor: Commander Charles B. Cameron, USN, Electrical Engineering Department
- Advisor: Professor Antal A. Sarkady, Electrical Engineering Department Abstract
Signal Filtering using the Hilbert-Huang Transform
The objective of this research project is to use the Hilbert-Huang Transform (HHT) to analyze signals with non-stationary, non-linear characteristics. Dr. Norden Huang et al. of NASA’s Goddard Space Flight Center proposed that the HHT algorithm could be used to understand time-series signals of this kind. This project has potential in naval applications in the detection of distant or quiet submarines. The sounds that submarines generate are often signals whose amplitudes and frequencies both vary with time. Propagation through the ocean environment affects those signals in a non-linear fashion. There are more traditional algorithms such as the Fourier Transform that detect stationary, linear signals in the presence of random noise. However, they are less successful with signals that are not stationary and linear, but, rather, vary in frequency, amplitude, or both and behave in a non-linear fashion.
Implementation of the HHT algorithm will require sifting the time-domain data with cubic-spline interpolation functions. Two cubic-spline functions will be calculated, one for the upper envelope and one for the lower envelope of the signal. An iterative process entailing subtracting the mean of the two cubic-spline functions from the data will generate a series of intrinsic mode functions (IMF). Once the set of IMF has been calculated, the Hilbert Transform of each of them can be computed. The Hilbert Transform will provide the amplitude and frequency of each IMF as functions of time. During the course of this project, different methods for calculating the cubic splines will be used and compared in order to compare their performance.
- 1/C Alan R. Van Reet
- Major: Systems Engineering
- Title: Active Based Electrical Training Equipment
- Advisor: Assistant Professor Matthew G. Feemster, Weapons & Systems Engineering Department Abstract
Active Based Electrical Training Equipment
This Bowman Scholar project involves an investigation of the feasibility and advantages of replacing free-weight exercise equipment in the shipboard environment with electrically-actuated, resistive-based training equipment. Though electrically based equipment is currently available from a variety of manufacturers, the overall goal of this research is the application of recent advances in the area of nonlinear, adaptive/observer based control strategies to the electrically actuated fitness training equipment in order to improve the overall quality of training.
With the removal of the free weights, the planned unit will be lighter than existing weight stack units making rearrangement and loading into ships easier. The removal of a sliding weight stack and cable system will reduce noise from weight movement and slamming. The reduced noise should allow use of the equipment by crew or SEALs without compromising the submarine’s covert transit.
In an effort to reduce the number of independent sensors, the proposed controller will track a desired resistance/assistance trajectory (time varying or constant) utilizing measurements of only actuator electrical current. Two nonlinear observers for actuator position and speed will be employed to promote stability within the system as well as offering an alternative to direct measurement (i.e., an encoder or resolver is not required to be integrated into the mechanical mockup).Prior to experimental verification of the proposed control strategy, an electrically actuated exercise test bed will be developed. The electric actuator (e.g., separately excited direct current motor) will be controlled via a real-time PC based control environment that will allow for on-line performance monitoring, safety features, and variable resistance trajectory generation to accurately mimic free-weight motion. Actuator current will be measured via Hall based sensor technology and digitized for control calculations within the PC by a commercially available PCI or ISA bus I/O card.
- 1/C Alexis B. Wise
- Major: Systems Engineering
- Title: Militarizing Commercial Automation for Warship Command and Control
- Advisor: Assistant Professor Edwin L. Zivi, Weapons & Systems Engineering Department Abstract
Militarizing Commercial Automation for Warship Command and Control
Automation technologies are essential to achieve future warship survivability despite increased threat and decreased manpower. Commercial technology can perform the tasks required for automation, however, they lack the dependability, system integrity, and fault tolerance a military platform requires in unpredictable battle environments. For this research, automation involves the transfer of functions from man to machine within the existing shipboard command and control structure. The technical challenge is to extend commercial control technology to provide increased survivability. Viable commercial technologies exist for the engineering and damage control automation systems. Therefore, these systems will be the focus of this research. Furthermore, automation of these systems becomes increasingly important when damage to the ship threatens to interrupt normal operation.
The research sequence will begin with a quantitative definition of survivability in terms of continuity of service with respect to combat induced disruptions. Based on the definition of survivability, a promising commercially available automation technology solution will be selected for computer aided design and simulation using Matlab and Simulink. The research will conclude with the development of a small-scale prototype proof of concept demonstration.
- 1/C Gregory A. Woelfel
- Major: Systems Engineering
- Title: Autonomous Planing Craft
- Advisor: Associate Professor Bradley E. Bishop, Weapons & Systems Engineering Department Abstract
Autonomous Planing Craft
The purpose of this Bowman Scholar research project is to develop a control system for a small planing craft or drone that will be capable of maneuvering in an autonomous manner to prosecute a threat or patrol a seaway. The ship will be capable of detecting a threat, or receiving commands to move in such a way as to render the threat ineffective. This will involve the development of a control suite that may use GPS, radar, and visual sensors to determine the appropriate guidance commands. These commands will be interpreted by a single board computer that will command the physical control surfaces of the craft. Work will be done to ensure the effectiveness of these control surfaces in achieving the most efficient performance for a planing hull based on power usage and ship dynamics. This portion of the design will also involve the use of movable ballast and trim tabs to support autonomous control in the dynamic marine environment.
The attack on the USS Cole and other terrorist attempts on surface ships have demonstrated the vulnerability of surface fleet when in port or in transit of high traffic littoral areas. Surface drones provide a ship with the ability to deal with unidentified ships or hostile craft at a safe distance, limiting exposure of the high value unit.Surface Drones have been demonstrated successfully using commercial JETSKIs, Boston Whalers, and inflatable RIBs. The objectives of this project include successful demonstration of the control concept and integration of commercial off-the-shelf components to decrease cost. The test hull has been supplied by the Naval Architecture and Ocean Engineering Department.
Division of Math and Science
- 1/C Dang V. Duong
- Major: Physics
- Title: Nonlinear Acoustic Detection of Plastic Landmines
- Advisor: Professor Murray S. Korman, Physics Department Abstract
Nonlinear Acoustic Detection of Plastic Landmines
The purpose of this Bowman Scholar project is to explore an acoustic, nonlinear scheme to detect plastic landmines. Using acoustic-to-seismic coupling, airborne sound couples into the ground and vibrates the top plate of the buried landmine case. Then, the soil surface vibrations are modified in the presence of the mine.
The soil-plate oscillator is an apparatus that represents a good physical model of two inert anti-tank plastic landmines, the VS 1.6 and the VS 2.2. The apparatus consists of a thick-walled cylinder filled with the sifted, homogenous soil resting on a thin elastic plate that is clamped to the bottom of the column.
Two nonlinear experiments have been performed using this apparatus. First, using an amplifier and loud speakers, a tuning curve experiment has been performed. The vibration amplitude vs frequency of the soil-loaded plate was detected by a geophone placed on the soil-air interface. The data was displayed using a sweep spectrum analyzer. Second, a two-tone test experiment was carried out with two amplifiers and two electronically driven speakers to generate two different acoustic frequencies that insonify the soil surface and excite the soil-plate oscillator. Combination frequencies were then measured.
Linear acoustic techniques to detect landmines are susceptible to false alarms caused by the resonance of soil layers covering objects such as buried roots, rocks, concrete and metal debris. During a wave cycle, the compressible plastic surface of the mine oscillates together with the soil through the first half of the cycle but separates from the soil during the second half, causing a nonlinear oscillation. On the other hand, a rock for example is relatively incompressible, so that the soil resting against it will linearly oscillate throughout the whole cycle. Thus, the nonlinear acoustic technique offers a clear advantage in the detection of plastic landmines since false alarms are eliminated.
Although, some metallic landmines are readily detectable using a metal detector, the successful detection of plastic mines proves to be a challenge. This experiment will aid in refining the process to accurately detect plastic landmines by analyzing the nonlinear experiments. The success of this project could ultimately result in saving hundreds of thousands of lives from becoming potential victims to these indiscriminate killers. In addition, our military forces would benefit greatly from this method that makes possible the successful clearing of plastic landmines.
- 1/C Eric C. Eckstrand
- Major: Computer Science
- Title: High Energy Laser Modeling and Simulation Framework Evaluation
- Advisor: Associate Professor Donald M. Needham, Computer Science Department Abstract
High Energy Laser Modeling and Simulation Framework Evaluation
High Energy Lasers offer the potential of technological and operational superiority in terms of combat fighting capabilities. The High Energy Laser Joint Technology Office (HEL-JTO) has funded considerable research in terms of the modeling, simulation, and construction of high energy laser devices. A wide variety of end-to-end High Energy Laser simulations exist, and the development of these simulations could greatly benefit from modularizing the software architecture under which these simulations are developed. In this manner, one component of a software simulation framework, such as a laser’s propagation component, could be modified or replaced without disturbing the rest of the simulation framework. Such a modification to the component model must be efficient in terms of ease of use of the modeling framework as well as in minimizing the restrictions placed on the component undergoing modification. Changing a particular portion of a simulation should only require modifying the component which held that particular part, rather than having to modify the whole simulation. A group modifying the simulation framework to support the inclusion of a new propagation code would not need a perspective of the entire simulation, but rather only the perspective of their particular module and its interaction with the surrounding modules necessary to develop their component. The goal of this Bowman Scholar project is to contribute to the HEL-JTO effort by incorporating an existing laser propagation model into the Northrup Grumman High Energy Laser Simulation (HELSEEM). This project focuses on the feasibility of incorporating legacy laser propagation codes into the HELSEEM framework. The incorporation process will be detailed, with particular attention given to problems likely to be encountered by developers of subsequent laser propagation codes. Lessons learned from the incorporation process, as well as recommendations for the improvement of the process, will be identified.
- 1/C Michael C. Graham
- Major: Physics
- Title: Impedance Analysis of Nafion Impregnated SiO2 Aerogels
- Advisor: Professor John J. Fontanella, Physics Department Abstract
Impedance Analysis of Nafion Impregnated SiO2 Aerogels
This Bowman research project seeks to investigate the electrical properties of a SiO2 aerogel coated with Nafion, a well known proton conductor. Aerogels show great promise as a material for use in nanobatteries and nanofuel cells. Due to their extremely porous structure they have very high surface area and show potential for use in a variety of electrochemical devices. For example, a hypothetical nanobattery might use an aerogel as an electrode, a polymer coating applied to the aerogel as the electrolyte, and a metal as the second electrode.
However, many problems remain to achieving a working device. Aerogels are delicate materials both to fabrication and use. Work still remains to find a suitable polymer to serve as an electrolyte.
This project will characterize the performance of a candidate polymer in an aerogel. A SiO2 aerogel will be fabricated using established techniques. The aerogel is made by first mixing tetramethyl orthosilicate (TMOS), water, methanol, and ammonium hydroxide. After stirring, the mixture is poured into molds and allowed to gel. The gel is washed in ethanol and acetone a total of seven to ten times. The gels must then be dried using a carbon dioxide critical point dryer. Finally the dry gels are densified by heating to 900°C.
After the aerogels are dry, they will be immersed in a Nafion solution to coat the surface of the aerogel with the Nafion polymer. After drying the response of the SiO2-Nafion material will be characterized using impedance analysis techniques.A separate experiment will be performed to analyze the performance of Nafion films on different substrates. Nafion coatings of various thicknesses will be applied to flat, solid Teflon and aluminum oxide (sapphire) surfaces. The impedance results will be compared to the Nafion impregnated aerogel. Similarities between the two sets of impedance results will allow characterization of the conduction process in the aerogel and the effect of Nafion on conduction.
- 1/C Derek M. Jennings
- Major: Mathematics (Honors)
- Title: A Mathematical Approach to Finding Ship Berthing Capability
- Advisor: Associate Professor John F. Pierce, Mathematics Department Abstract
A Mathematical Approach to Finding Ship Berthing Capability
This project will attempt to produce a calculator which will determine whether or not there is ample berthing space in our Continental United States (CONUS) homeports for all of our non-forward deployed naval vessels. The researcher will explore a number of mathematical techniques in an attempt to optimize the physical pier/quay space available at each CONUS homeport. This data will then be used to determine how many of each naval vessel can be accommodated at each naval base. The goal is to create a computer program which will take a number of physical parameters (such as: number in ship class, ship length, draft, beam, etc.) and indicate whether or not such a configuration is possible. An interactive capability allowing the user to subtract or add additional pier/quay space would also be desirable. This calculator may be used in conjunction with further (unrelated) analysis to determine the readiness and capability of the U.S. Naval fleets.
- 1/C Keith G. Labbe
- Major: Computer Science
- Title: Virtual Environment (VE) Collaboration
- Advisor: Major Mark J. Lennerton, USMC, Computer Science Department Abstract
Virtual Environment (VE) Collaboration
The research undertaken in this proposal is a joint venture between the U.S. Naval Academy (USNA) and the Naval Postgraduate School (NPS). It will entail establishing a secure virtual private network (VPN) connection with NPS. This connectivity will provide and serve as a test bed in determining VPN functionality in meeting the needs for continued collaborative virtual environment (VE) and information technology (IT) research. A commercial off the shelf (COTS) desktop VE will initially be used to test issues such as bandwidth requirements/availability, latency, and barriers to collaborative communication and coordination. Once established, customized and scaled, bicoastal collaborative sessions will be connected to explore performance in pursuit of collaborative goals. The specific objectives of this research are to:
a. Explore networked VEs and the difference associated with LAN and WAN implementations.
b. Install and test a COTS VPN connection between designated NPS and USNA IP addresses.
c. Gain an understanding of human factors associated with of VEs.
d. Gain an understanding of the types of VEs and their employment in pursuit of individual and collaborative training.e. Hands on migration from COTS desktop VEs to wrap-around VEs under development. The researcher will have the opportunity to write C++ and OpenGL code as well as utilize VE application software (MultiGen Paradigm's Vega).
- 1/C Joshua M. Mueller
- Major: Physics
- Title: Complex Impedance Studies of Electrospray Deposited Proton Conductors
- Advisor: Associate Professor Charles A. Edmondson, Physics Department Abstract
Complex Impedance Studies of Electrospray Deposited Proton Conductors
The focus of this project is to study the material properties of electrospray deposited polymers for use as proton conducting membranes in fuel cells. The ultimate goal of the project is to provide critical insight into the behavior of the proton conductors so as to provide feedback for improving the next generation of fuel cells. The primary polymer in question will be an electrospray deposited Nafion, which has long stood as a benchmark material in proton conducting fuel cells. The properties that will be tested include conductivity as a function of water content, temperature, pressure and material swelling. If time permits, studies of mechanical properties will also be conducted. The results from this research will be shared with Hunter College, where NMR data will be taken on the materials, and Virginia Commonwealth University, where the polymers are chemically engineered.
This project is in keeping with the Office of Naval Research’s Grand Challenges for the 21st Century, specifically, the development of new, safe, effective, and non-petroleum based sources of power and power generation. Hydrogen powered fuel cells are an area of focus for potential use as an energy storage mechanism in the future. At the heart of the fuel cell is a membrane electrode assembly (MEA) composed of two catalyst contacts sandwiching a proton exchange membrane. Electrospraying is a deposition process in which the material is passed through a charged syringe and accelerated towards a grounded drum, thus producing the layered MEA. The goal of this method of fabrication is to be able to quickly and inexpensively mass produce the MEA.
- 1/C Jeffrey C. Payne
- Major: Physics
- Title: Optical Limiting in Single-mode Waveguide Systems
- Advisor: Assistant Professor James J. Butler, Physics Department Abstract
Optical Limiting in Single-mode Waveguide Systems
The objective of this research project is to study the optical properties of single mode waveguide systems that exhibit an absorption that increases with intensity of the light that is incident upon them. In this way these devices limit the transmission of optical energy and are referred to as “optical limiters”. Such systems are of great value to both the military and the telecommunications industry because of their ability to protect sensitive equipment from exposure to high intensity light. This work is being done in conjunction with researchers at the Naval Research Laboratory where many of the materials under investigation are being developed.
Experiments will be performed using very small glass capillaries that are filled with materials that exhibit a nonlinear absorption, that is these materials absorb a greater amount of incoming light as the intensity of that light increases. These systems act as waveguides where light is confined to the small “core” region where the nonlinear material resides. Furthermore, only one intensity profile (or “mode”) is allowed if the index of refraction of the core is very close to that of the surrounding glass. In this case, the waveguide is called “single mode”. This situation will be realized by controlling the temperature of the waveguide since the index of refraction of the core materials that will be used in this study depend strongly on temperature. Lasers that emit pulses of light in visible and near infrared wavelengths will be coupled into the waveguides and input and output intensities will be measured.
After characterizing optical limiting in a single waveguide filled with a nonlinear material, a subsequent study will be pursued to analyze the optical properties of two such waveguides that are placed very close to one another. It is known that when light is coupled into one waveguide, a portion of its electric field will extend into the neighboring waveguide. This provides a pathway for energy to be coupled from one waveguide to the other. Optical limiting in a system of two coupled, nonlinear waveguides will be characterized.