Research Experience for Undergraduates in Photonics

Summer 2008 Research Projects

Fabrication & Characterization of Visible & UV LEDs: Wide Bandgap Semiconductor Lab

Prof. Ted Moustakas, ECE

The Wide Band-gap Semiconductor Lab has two molecular beam epitaxy (MBE) machines, various other fabrication systems, and extensive characterization equipment for materials and devices.  The lab has been a world-leader in GaN semiconductor ultraviolet  (UV) and blue laser and detector development, including key patents used by Nichia for blue laser manufacturing and extensive work on solar-blind detectors and UV sources.  New recent funding has supported the development of visible light emitting devices (LEDs) for architectural lighting, an area of immense implication for energy conservation.

The REU student will be involved with the fabrication and characterization of visible and UV LEDs made of GaN semiconductors.  They will work as a junior member of a team, mentored by Ph.D. students, post-docs and staff. This would include working in clean room conditions to prepare and load MBE or evaporator substrates, management of the deposition, masking and etching cycles, in situ measurements during processing, wafer testing and processing, and finally device measurements.  A particular project would be to apply a specific fabrication innovation, say variation of the thickness of the substrate lattice matching layer, preparation of an LED structure on the substrate, and optical and electrical characterization of the resulting LED.  A particular objective might be to improve quantum efficiency while maintaining a smooth and broad spectral output.

Nanophotonics for Biosensing: Optical Characterization & Nanophotonics Lab

Prof. Selim Ünlü, ECE,BME,PHY

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. The project has several summer opportunities, including 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 the external laser into the fabricated photonic chips.  Students with biochemistry, optics, engineering or software background can contribute to this work.  There is potential to collaborate with colleagues abroad in Lausanne or Istanbul.

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 have developed and are refining 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.  A synthesizer can print patterned DNA structures in the cavity. 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 undergraduate student from Biomedical Engineering completed her senior research project in this lab recently, simulating and building a flow cell resonant cavity and characterizing its fluid and optical properties.  Another BS/MS student developed a DSP tool on the Analog Devices Sharc dual processor for implementing the image capture and processing algorithms, to make the device more portable.

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; or the transfer of algorithms to dedicated DSP hardware connected to the detector camera and ancillary sensors.

Communications, networking, and sensing technologies for activity and ecological monitoring: Multimedia Communications Lab, Prof. Tom Little, ECE

This lab is currently focused on technologies and applications of wireless networking in personal activity monitoring using body area networks and in ecological applications employing video sources.  The lab is also investigating free-space optical networking as a communications medium for pervasive computing.  Active research includes the development of foundation techniques for enabling low-power, high-longevity deployments of sensor systems. REU students involved in this research will participate in instrumentation design, analysis, and data collection using one or more of (a) body area devices and PDAs, (b) video cameras enabled with low-power embedded microcontrollers running Linux, deployed as an array of cameras, or (c) development of prototype systems for bridging wired or wireless RF to optical networking.

Spherical Samples for Resonant Scattering Experiments: Optical Characterization and Nanophotonics Laboratory

Prof. Bennett Goldberg, Physics

For a decade researchers have studied the optical properties of quantum dots, both self-assembled and colloidal structures made from semiconductor systems. Yet because of the geometric restriction that the incoming light is largely co-linear with the scattered light, we have not been able to engage in a whole series of experiments similar to those performed in atomic physics. These are broadly referred to as resonant scattering experiments and have the geometric requirement that the incoming and scattered light occupy orthogonal paths. We have recently developed solid immersion microscopy using spherical lenses, and as an offshoot, have developed ideas to place quantum dots inside spheres of semiconductor hosts. Using a simple two axis spinning grinder we plan to engage undergraduate REU summer researchers in building spheres, measuring their sphericity with a special interferometer, and determining the efficiency for resonant scattering of quantum dots.

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.

There are several areas in this project where the REU student could be involved, for example in fabricating patterned substrates using photolithography techniques and wet etching and  reactive-ion etching, growing carbon nanotubes in ordered arrays using chemical vapor deposition, and to analyze the samples and optimize the growth process; and developing software for efficient processing of multi-spectral spectroscopic data.  The necessary clean room training and supervision in the Optical Processing Facility would be given by graduate students and Photonics Center staff.

All Optical Switching Devices Using Quantum Wells: Optical Processing Facility

Prof. Roberto Paiella, ECE

Our research group is currently 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.  At the same time, we are also pursuing the development of III-nitride near-infrared quantum cascade lasers, given their potential for ultra-high-speed direct current modulation and all-optical switching with gain. 

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 very suitable activities for an undergraduate research experience.  Specifically, we will have the student carry out the sample photolithography and assist in the reactive-ion etching, as well as to simulate and measure the waveguides transmission properties (in the Wide Bandgap Semiconductor Lab).  In the process he/she will learn a set of very valuable skills, and will also contribute to our research by providing a detailed characterization of propagation and coupling losses versus waveguide design. 

Spectroscopic Noninvasive Diagnosis of Tissue Pathologies: Biomedical Optics Lab

Prof. Irving Bigio, Biomedical Engineering (BME), ECE

REU students in the Biomedical Optics Laboratory will work on one of various aspects of the development of optical-spectroscopy and optical interferometry technologies, which are 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.  Biomedical optics research is highly interdisciplinary and provides learning experiences in optical engineering, computer controls, optical properties of tissue, cellular biology and physiology, and mathematical/computational methods of data analysis and experimental simulation.  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, Chemisrty

Our research focuses on the development and use of novel label-free detection methods based on surface plasmon resonance (SPR) spectroscopy. Current projects are focused around the development of novel label-free DNA microarray technologies. Areas of study include: Electric field effects at interfaces: rapid mismatch discrimination by electric field induced denaturation. DNA/protein interactions: screening methods for anti-tumor aptamers as tumor targeting reagents. DNA/drug interactions: kinetics of binding novel platinum anti-tumor drugs with oligonucleotides. We have previously had REU and UROP students working in our group.

An REU will be assigned to a particular label-free microarray application.  They will learn to prepare the materials for screening, to use the surface plasmon spectroscopy apparatus, and to interpret the resulting data.

Ultrafast Spectroscopy of Semiconductor Nanomaterials and Photonic Structures: Microphotonics Lab (collaborations at MIT)

Prof. Luca Dal Negro, ECE

Research activities in computation in this new group will be focused on electrodynamics modeling of complex photonic devices, such as photonic crystal structures and nano-plasmonics components. The main computational techniques are:  Finite Difference Time Domain (FDTD), Finite Elements (FEM), Mie scattering codes, Discrete Dipoles and Coupled Dipoles codes, and a variety of ad hoc computational schemes for the solution of more specialized research problems.  The first problem area involves Ultrafast Nanostructure Optics: a) ultrafast emission spectroscopy; b) optical gain relaxation dynamics; c) nonlinear optical characterization of semiconductor nanostructures, novel bio-compatible materials, photonic and plasmonic nano-devices. Implemented Optical techniques include: picosecond fluorescence lifetime spectroscopy, time-resolved variable stripe length and pump-probe gain techniques, emission quantum efficiency and photon statistics, Z-scan nonlinear characterization, second harmonic generation (SHG).  The second involves Luminescence: the steady-state optical spectroscopy of semiconductor nanostructures, bio-compatible materials and plasmonic devices. Implemented Optical techniques include: Broad-band Photoluminescence Excitation Spectroscopy (PLE), Emission lifetime measurements under steady state (CW) excitation, CW photoluminescence (PL), CW Quantum efficiency.

Nanoelectronic Biomolecular Field-Effect Transistor (bioFET) Sensors: Nanotechnology Laboratory,Prof. Pritiraj Mohanty, Physics

Optical Biophysics Lab, Prof. Shyamsundar Erramilli, Physics

Ultrasensitive detection of biological and chemical species is fundamental to a number of fields. In particular, the ability to detect 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 trained on nanofabrication, wet chemistry for 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.  The equipment includes several 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 participate in many of the activities of the laboratory along-side graduate and post-doctoral students.  Undergraduate will learn the basic principles of handling, stripping, and fusion splicing fiber, and focusing light into both single mode and multi mode fibers.  They can help with our draw tower and learn fiber preform preparation basics. 

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 & Prof. Bahaa Saleh, ECE

For hundreds of years, the microscope and telescope have allowed us to peek into domains invisible to the naked eye.  Developed by Galileo in the early 1600's, these remarkable instruments continue to serve us nobly today.  In recent years, optical imaging has undergone enormous expansion as light sources, optical components, detection systems, and computational methods have advanced significantly.  Moreover, a dazzling array of new techniques have come to the fore that take advantage of different optical properties of a specimen, e.g., absorptivity, refractive index, scattering cross section, fluorescence.   

However, all of the instruments that have been developed to date rely on sources whose light particles (called photons) arrive randomly in time and position.  The light is noisy.  This is true of both natural and artificial sources: skylight, sunlight, starlight, incandescent light, fluorescent light, laser light.  Indeed, every kind of light that comes to mind. In recent years, new kinds of light (quantum sources) have been developed in which the intrinsic noisiness is reduced in one way or another.  This attendant reduction of noise can, if harnessed properly, improve 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.  As unlikely as it seems, this process (called nonlinear parametric downconversion) takes place 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" with each other. Entangled-photon optical-imaging systems are being developed in the Quantum Imaging Laboratory. Research opportunities are available for undergraduate students to carry out experiments, simulations, computer interfacing, and calculations related to the quantum optics of the light generation as well as the optics and photonics of the light propagation, management, and imaging.

Studies on Ultraviolet Imaging Spectrographs for Astrophysical Applications: Center for Space Physics

Prof. Tim Cook & 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 short ward of 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, instrument software, or observational strategies to support our research on balloon-based and spacecraft instrumentation.

Detection of Pathogens via Dye Affinity Targeting: Photochemical Processes Lab

Prof. and Chair Guilford Jones, Chemistry

Development of spectroscopically based methods and instruments for the rapid detection of bacteria is an important goal. Recent progress, made in our laboratory has led to the identification of dyes that provide differentiating signature absorption or fluorescence, when they are bound to bacterial cells or spores. The system is designed to identify unusual (above background) concentrations of microorganisms. The rapid method (ca. 20 min) requires the reading of very small quantities of sample using a micro titer plate reader. Analysis is carried out on standard arrays (e.g., 96 microwells), arranged as multianalyte test panels of distinct chemical reactions that require no microbe sample amplification. The spectral profiles obtained allow  preliminary quantitation and typing of pathogen-related bioparticles --- in particular, priority classes of spore-forming bacteria such as  //B. subtilis //at amounts greater than 1000 CFU per cc of sample  (colony forming units). Currently, a small number of dyes have been identified that show a special affinity for spore coats of various //Bacilli//. An REU student would work to expand this panel by synthesizing analogues of current lead compounds, in order to optimize the fluorescence fingerprint that is read from microtiter panels. The long range goal of the research is the development of a working prototype of a field deployable chemistry-spectroscopy kit or  mini-laboratory.

Micro- & Nano-Lithography: Micro- and Nano-Electronics 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.

As an example, an undergraduate recently worked to help develop the java based simulations of particle-tracking.  This project is essentially a visualization demonstration of an electrodynamics problem involving charged particles and applied electromagnetic radiation (light).  Other typical projects involve detailing the equations governing the physical process of interest, and using that knowledge to simulate and to better control the process.

Funded by the National Science Foundation.