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Research
Experience for Undergraduates in Photonics
Summer
2010 Research Projects
Fabrication and characterization of visible and UV LEDs: Wide Bandgap Semiconductor Lab, Prof. Ted Moustakas, ECE, Physics, Division of Materials Science
This research focuses on the study. of both fundamental (structural, transport, optical and recombination) properties and device applications of nitride semiconductors. Device work emphasizes the development of ultraviolet LEDs, UV optical modulators, solar-blind UV-detectors, and green LEDs. The Laboratory is equipped with various deposition systems for the material synthesis (Molecular Beam Epitaxy-MBE and Hydride Vapor Phase Epitaxy-HVPE units) as well as systems for device fabrication and characterization. Intellectual Property (IP) developed in this Laboratory was licensed by the two major manufactures of blue LEDs and lasers (Cree Inc. in the USA and Nichia in Japan). REU students will be involved both in growth and characterization of materials as well as in the fabrication and characterization of devices. This would include working in clean room conditions to prepare and load substrates in the MBE and HVPE systems, management of the deposition, masking and etching cycles, in situ measurements during processing, wafer testing and processing, and finally device measurements.
Nanophotonics for biosensing:
Optical Characterization and Nanophotonics Lab, Prof. Selim Ünlü, ECE
One of the important avenues for biological and chemical sensing is using photonic devices that are very sensitive to surface modification to detect the presence of binding. We propose to involve undergraduate student in the development and testing of these systems. Ring resonators are formed in planar waveguides and then coupled to optical fiber. The surface of the waveguide is coated with biomolecular targets. Sample material flows over the surface and binding events are detected by shifts in the resonant frequency. This technique enables
extremely sensitive measurements. Summer opportunities include the testing of specific protein binding, the development of patterning the surface using PDMS stamps or non-contact optical lithography, and the development of efficient coupling from an external laser into fabricated photonic chips.
Drug Discovery through resonant cavity biosensor :
Magnetic & Optical Devices Lab, Prof. Michael Ruane, ECE
Label-free, high-throughput, real-time imaging of binding events is made possible with a resonant cavity imaging biosensor approach. We are developing an imaging system that comprises a resonant cavity between two reflective surfaces. As biomolecules bind to one coated surface a shift occurs in the resonant frequency that can be detected in real-time. An infrared camera images the cavity, which is patterned with bio-receptors to localize the binding of specific proteins or DNA. Sweeping the illuminating wavelength creates multi-spectral images whose resonant peaks can be used to infer the presence and concentration of biomaterials for genomic or proteomic research, bio-detection, or binding rate experiments. An REU student could contribute to several elements of the project, such as simulation of nanometer sized cavity modifications and their effect on the optical resonance quality and testing; flow cell simulation, especially with micron-sized patterned bio-receptors in the cell; image processing algorithms and massively parallel processing with MATLAB.
Forest canopy/sunlight measurements with sensor networks:
Multimedia Communications Lab, Prof. Tom Little, ECE
This lab is currently focused on technologies and applications of wireless sensor networks, including the integration of photometric sensors with wireless network communications, and using indoor lighting as a means of optical communication. Active research includes the development of foundation techniques for enabling low-power, high-longevity deployments of sensors in the environment. REU students involved in this research will participate in instrumentation design to create a measurement platform capable of capturing a very wide dynamic range of photometric sunlight intensity and spectral characteristics affecting the forest canopy. Equipment will be assembled and deployed for the purpose of recording variations in light and other environmental parameters (temperature, humidity, pressure). Students will be involved in the field, in data collection and analysis supporting the core science.
Graphene: single atomic layer of carbon:
Optical Characterization and Nanophotonics Laboratory, Prof. Bennett Goldberg, Physics
Graphene, a single-atom thick sheet of carbon, is fabricated by micro-cleavage, practiced by literally using Scotch tape to pull off individual layers and stick them back onto a silicon wafer substrate. Recent undergraduates have been active in several areas of graphene research, in particular developing algorithms to calculate reflectivity changes of the single atomic layer on top of various substrates, and then limiting the spectral bandwidth with filters to optimize the contrast and thus ‘count’ atomic layer number through an optical microscope. Because graphene is readily made and easily observed, its unique electronic and optical properties can be quickly accessible by undergraduate researchers. They can fabricate their
own samples, and then perform optical and transport measurements. REU students would explore: (1) Correlation between electronic mobility and atomic vibrations: We have simple flow-through cryostat with optical access, so an undergraduate can experimentally measure the longitudinal (G-band) and defect (D-band) Raman modes simultaneously. (2) Graphene capacitance spectroscopy: Graphene can be both metallic and semiconducting, and can easily form the second plate of a parallel plate capacitor. Almost no research has been done looking at high-frequency capacitance spectroscopy, for which we have the measurement apparatus available in the lab.
Carbon nanotube light emitters:
Optical Characterization and Nanophotonics Laboratory, Prof. Anna Swan, ECE
Two thirds of all nanotubes are semiconducting with a variable gap and therefore should be ideal as nanoscale light emitters. A big challenge that took researchers over a decade to solve was how to isolate the nanotubes so as not to quench the light emission. The first successful attempts were made using surfactants to coat each nanotube, but this alters the color of the emitted light. Our approach is to directly grow individual nanotubes across substrate trenches to be able to measure the intrinsic excitonic bandgap and to correlate the optical and electronic properties with a specific nanotube structure. An REU student could assist in fabricating patterned substrates using photolithography techniques, wet etching and reactive-ion etching, growing carbon nanotubes in ordered arrays using chemical vapor deposition, and in analyzing the samples, optimizing the growth process; and developing software for efficient processing of multi-spectral spectroscopic data.
All optical switching devices using quantum wells:
Optical Processing Facility, Prof. Roberto Paiella, ECE
Our research group is developing all-optical switching devices utilizing intersubband transitions at near-infrared wavelengths in GaN/AlGaN quantum wells. The basic idea is to take advantage of the ultra fast relaxation times and giant optical nonlinearities of intersubband transitions to process information directly in the optical domain, for future ultra-broadband communication networks. Several device configurations are being investigated based on various nonlinear optical interactions, including absorption saturation, the optical Kerr effect, and intersubband Raman scattering. Our REU student will work on the demonstration of near-infrared ridge waveguides based on nitride semiconductors. The design, fabrication, and testing of these waveguides are suitable activities for an REU student. Specifically, the student will carry out the sample photolithography and assist in the reactive-ion etching in our clean room, and simulate and measure the waveguides transmission properties in our lab.
Spectroscopic noninvasive diagnosis of tissue pathologies:
Biomedical Optics Lab, Prof. Irving Bigio, Biomedical Engineering, ECE
REU students in the Biomedical Optics Laboratory will work on the development of optical-spectroscopy and optical interferometry technologies used for minimally-invasive measurements on living systems. These technologies, often mediated by fiber-optic probes, are for noninvasive diagnosis of tissue pathologies, including cancer, and for the measurement of drug concentrations in tissue. Collaborators at medical research centers are testing some of the optical instrumentation we have developed in clinical studies. Other optical methods are being tested in our labs to image nerve activation in real time. REU student(s) will have the opportunity to directly contribute to one or more components of the program by developing and testing experimental elements and/or invoking computational methods for analysis of optical data from laboratory and/or clinical studies.
Physical and analytical chemistry of interfaces:
Surface Plasmon Resonance Spectroscopy Lab, Prof. Rosina Georgiadis, Chemistry
The Georgiadis group uses light to study transient interactions of proteins, nucleic acids and nanoparticles which are important in drug discovery, the mechanism of oxidative stress and cell signaling, nanotoxicology and basic science. We use novel surface plasmon resonance imaging spectroscopy, a powerful label-free method, to make multiple parallel measurements. Reliable quantitative measurements of binding affinities and binding kinetics can help reveal of the mechanism of the biomolecular or nanoparticle binding reaction and may enable prediction of biological response. Collaborations with other faculty in Chemistry and outside the department offer REU students a range of specific projects with emphasis on the physical chemistry aspects of nanoscience, biochemistry, bioinorganic electrochemistry and cancer research.
Ultrafast spectroscopy of semiconductor nanomaterials and photonic structures:
Microphotonics Lab (collaborations at MIT), Prof. Luca Dal Negro, ECE
This new group will be focused on optics and the ultra fast spectroscopy of semi conductor materials and photonic structures.the emphasis will be on experimental optical characterization and engineering of novel materials and photonic structures. Activities will also include electronic structure calculations in nanomaterials and photonic crystals device design. Students with a prevalently computational/theoretical background can work on simulation in direct collaboration with experimental activities. Experimental activities on the optics of nanostructures will include time resolved pump probe light amplification measurements; absolute quantum efficiency measurements; photoluminescence excitation measurements (PLE); single dot spectroscopy; and photon statistics and correlation measurements in gain media. Semiconductor materials deposition and processing will be performed both at BU and in collaboration with the Materials Technological Laboratory at MIT. Computational/theoretical activities include light localization in 2D quasi-periodic arrays, electronic structure calculations in semiconductor nanostructures; semiconductor device modelling; and photonic crystals design.
Nanoelectronic biomolecular field-effect transistor (bioFET) sensors:
Nanotechnology laboratory, Prof. Pritiraj Mohanty, Physics
Optical Biophysics Lab, Prof. Shyamsunder Erramilli, Physics
Ultrasensitive detection of ions in liquid solutions with ion-selective nanoscale electronic sensors is important for medical and healthcare applications. We have recently demonstrated the operation of a nanoscale field-effect pH sensor engineered from a functionalized silicon nanowire made by electron beam lithography. The change in the hydrogen ion concentration or the pH value of a solution can be detected by the corresponding change in the nanowire differential conductance with a resolution of 6 nS/pH. Fabrication of selective side gates on the nanowire sensor allows field-effect control of the surface charge on the nanowire by controlling the accumulation of charge carriers with the side gate voltage. Such local gate is important for the massive individual detection of multiple species. Images of the nanowire sensors are obtained by using a Scanning Near-field Infrared Microscope, using a tunable infrared laser to measure and manipulate biological structures potentially down to single molecule operations. The REU project involves nanofabrication of silicon FET structures, biofunctionalization of the structure with the relevant protein antibodies, and characterization of surface conjugation of the antibody to the silicon surface by atomic force microscopy and fluorescent spectroscopy. The REU student will be learn nanofabrication, wet chemistry/surface conjugation, and atomic force microscopy.
Optical fiber sensors for thermal and biological measurements:
Laboratory for Lightwave Technology, Prof. Ted Morse, ECE
The Laboratory for Lightwave Technology has complete facilities for the design, fabrication, and testing of optical fibers ( modern glass lathes, an 8 m optical fiber draw tower, and characterization capabilities). In addition, there are several other major pieces of equipment: a frequency doubled argon-ion laser for grating writing, high power laser pumps, and numerous optical components relative to work on fiber optic sensors. REU students will learn the basic principles of handling, stripping, and fusion splicing fiber, and focusing light into both single mode and multi mode fibers, help with our draw tower and learn fiber preform preparation. REU participants can use these skills in one of several current projects: development and testing of a high temperature fiber optic probe that is being developed for the measurement of the temperature of the tiles on the space shuttle during re-entry; development of a micro-fluid cell for implementation with a new type of biological sensor; or characterization of a new intra-cavity design for a Q-switched laser using a micro-electromechanical system (MEMS) mirror.
Entangled-photon imaging:
Quantum Optics Lab, Prof. Malvin Teich, ECE
In recent years, optical imaging has undergone enormous expansion as light sources, optical components, detection systems, and computational methods have advanced significantly to measure novel optical properties of a specimen, e.g., absorptivity, refractive index, scattering cross section, fluorescence. In recent years, quantum sources have been developed in which the intrinsic noisiness of light is reduced to allow improvement in the fidelity of optical imaging. One such source of light is generated by splitting the individual photons in a laser beam into pairs of twin photons (called nonlinear parametric downconversion) when a laser beam illuminates a properly oriented nonlinear-optical crystal. Because energy is conserved in the process, the twins are simultaneously produced and each has a wavelength longer than the original. Momentum is also conserved, resulting in a one-to-one correspondence between the direction of travel of a photon in one beam and the direction of its matching photon in the other beam. Because they share the energy and momentum of the original photon, the twin photons are said to be "entangled". Research opportunities are available for REU students to carry out experiments, simulations, and calculations related to the ”entangled” light generation as well as the optics and photonics of the light propagation, management, and imaging.
Nano-electromechanical systems:
Laboratory for Nanometer Scale Engineering, Prof. Kamil Ekinci, Mechanical Engineering
Our laboratory focuses on various aspects of Nano-electro-mechanical Systems (NEMS) using optical techniques to couple into the mechanical motion of high frequency NEMS resonators. In recent experiments and calculations, we have obtained the ultimate limits of optical displacement detection techniques in small structures such as NEMS. We are also trying to improve this sensitivity further by using near field optical techniques. Over the years, a number of REU students have worked on various aspects of the above-mentioned NEMS research. The projects suitable for REU students vary from fabrication projects to helping with various measurement issues. One project that an REU student will pursue is the fabrication and measurement of nanowire NEMS structures. The fabrication steps involve depositing nanowires on previously fabricated trenches in a membrane and clamping the nanowires using electron beam lithography. Measurement will use an optical interferometer that exists in our laboratory.
Studies on ultraviolet imaging spectrographs for astrophysical applications
Center for Space Physics, Prof. Tim Cook, Prof. Supriya Chakrabarti, Astronomy
In Astrophysics a common challenge is to observe faint objects spectroscopically in presence of nearby bright objects in the field. These challenges are even more significant where the reflectivity of common material drops well below 50%. In addition, the transmission of common optical materials below 100 nm is zero. These are exacerbated by the fact that, unlike in the visible, where the quantum efficiencies of detectors approach 90%, they hover around 30% in the ultraviolet. These pose tremendous challenges as well as opportunities for the design of imaging spectrographs in the ultraviolet. In our research we are attacking each technological challenge with our own design of optical system, photon-counting detectors and observation strategies. REU students with an interest in these areas will work to develop specific instrument subsystems or observational strategies to support our research endeavors. Most recently REU students developed a system for characterizing the transmission in UV of multi-layer mirrors.
Confocal fluorescence correlation spectroscopy (cFCS) for non-invasive early diagnostic detection of Alzheimer’s disease in the lens of the eye:
Lee E. Goldstein, MD, PhD., Molecular Aging and Development Laboratory, Boston University School of Medicine
Alzheimer’s disease (AD) is the sixth leading cause of death and the third most costly disease in the US. AD is characterized by Ab peptide accumulation in the brain which begins years before symptoms appear. Early detection of the underlying disease will facilitate clinical testing and early intervention. We previously reported the presence of Ab and distinctive AD-linked amyloid pathology in the lenses of AD patients (Goldstein et al., Lancet, 2003). Here we are developing a non-invasive confocal fluorescence correlation spectroscopy (cFCS)
instrument to quantitatively assess Ab peptide deposition in the lens of the eye as a marker for AD-linked Ab accumulation in the brain. We seek to develop a prototype cFCS instrument using a low-energy pulsed laser for early quantitative detection and monitoring of AD-linked amyloid lens pathology in vivo. REU students will prepare optical bench prototypes of pulsed laser systems and measure their performance using biological (porcine) equivalents of the human lens.
Micro- and nano-lithography:
Microchip Simulation Lab, Prof. Dan Cole, Manufacturing Engineering
This lab concerns techniques for simulating different types of physical processes that occur in micro and nano electronics, including, in particular, micro and nano lithography. Students with good programming skills and physical insight will find a considerable range of projects that are available, from ones that emphasize programming skills, to physics insight, mathematics knowledge, and of course, device engineering design, as well as various combinations of all of these strengths. In some situations, very accurate simulation models are required, while in other cases, simulation speed is far more important. These simulations are used to better control, predict, and optimize real processes in the microchip industry. REU students have worked successfully for several summers in extending a computational model of the interaction of Rydberg atoms with various wavelengths of light, a fundamental question of importance to future nano lithographic innovations.
Microfluidics component engineering for plasmonic-based optofluidic biosensors:
Optofluidics Laboratory, Prof. Hatice Altug ECE
Optofluidic devices hold great promise in a number of areas. Optofluidics is based on the behavior of light in photonic crystals. Light traveling through a photonic crystal gives rise to photonic band structures which effectively eliminate wavelengths of a certain range. Adding impurities in the arrays that form these crystals allows new energy levels to form in the band structure. Placing a single biological particle (a virus, protein, etc.) on such a crystal allows for easy and powerful detection methods via plasmonics. This research deals with engineering a microfluidic chip that allows for capturing these particles. An REU student will work on a pressure-controlled device where a sample in one tube is passed through the microfluidic chip. Under the microfluidic chip will be an array of holes in a gold film which will capture these nano-sized particles. At our current stage, we are developing a mask using photoresist on a silicon wafer, and then we will proceed to make elastomer-based chips from the mask. After constructing the basic pressure device, the student will refine the microfluidic chip and introduce more complex designs (namely valves) for enhanced fluid control.
Funded by the National Science Foundation.
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