Research Areas

Note: The majority of my publications are on this topic due to the quick experimental turnaround. However, I have dedicated roughly equal time to all three topics on this page, which share the general themes of interferometry and coupled waves.

The Hybrid Optoelectronic Correlator (HOC) was proposed and demonstrated at LAPT. I was the first to show it is capable of producing shift, scale, and rotation invariant (SSRI) target recognition. The maximum theoretical operating speed is on the order of 5 µs, making it a viable input filter for more resource-intensive image processing systems. I've worked on both the optical and electronic segments to approach this speed limit. The current implementation runs at 720 correlations per second using custom TI DMD spatial light modulators and high-speed cameras, all programmed in C++ with OpenCV. A previous prototype used a Xilinx FPGA with an ONSemi focal plane array.

I proposed a new opto-electronic architecture: the Balanced Joint Transform Correlator (BJTC). This design merges techniques from the HOC and the traditional JTC, achieving SSRI recognition with half the optical complexity of the HOC and orders-of-magnitude higher SNR than a standard JTC. Operating at 720 fps, it is approximately an order of magnitude faster than the current fastest computational image recognition systems. I have also demonstrated a Debiased JTC that further enhances recognition performance in Optics Express (2025). Additionally, I am simulating the use of these correlators as machine learning accelerators — with very promising preliminary results.

The HOC uses optics to perform real-time 2D Fourier transforms of arbitrary images. Magnitudes are captured directly with focal plane arrays; phases are captured using off-axis auxiliary plane waves. These signals are processed electronically — added, subtracted, and multiplied pixel-by-pixel — and the result is sent to an SLM, which produces the 2D cross-correlation via a second Fourier transform. This architecture is inherently shift invariant. Scale and rotation invariance are achieved by incorporating the Polar Mellin transform, which produces unique, geometry-invariant image signatures.

My PQ:PMMA research has focused on fabrication, characterization, and applications of this unique holographic polymer. Unlike most holographic materials, it does not suffer from post-exposure shrinkage and can be manufactured at centimeter-scale thickness — enabling self-sustaining HOEs with extremely high angular and spectral selectivity (Bragg selectivity). I've achieved Δn slightly above 10⁻⁴, among the highest reported for this material. Applications include wavelength division multiplexers and demultiplexers for telecommunications (~1550 nm) and monocular passive ranging (~760 nm). I also designed and constructed a fully automated writing and characterization setup in MatLab to improve repeatability.

Thick HOEs offer very high spectral selectivity but limited angular bandwidth — a fundamental tradeoff. I have been working to broaden the angular field of view. Testing cylindrical HOEs with lensed writing beams yielded a ~100× improvement in angular bandwidth (from ~20 mDeg to ~1 Deg). I am now developing PQ:PMMA samples molded as cylindrical lenses, with simulations indicating spherical lenses are achievable and that spherical and chromatic aberrations can be corrected holographically within the substrate itself.

Analog holograms form when coherent beams interfere inside a photosensitive medium, recording both amplitude and phase in a 3D grating. The grating properties — input/output angles, diffraction efficiency, peak wavelength — are tailored by the writing geometry. Because of high Bragg selectivity, multiple holograms can be spatially multiplexed at the same location; I exploit this for high-density optical image storage in my correlator work.

PQ:PMMA is synthesized as a liquid and cures to a solid, enabling arbitrary substrate shapes at millimeter-to-centimeter thickness. Upon exposure, phenanthrenequinone (PQ) reacts with MMA and PMMA to form oligomers, modulating the local refractive index to create the desired phase grating.

This project is done in collaboration with the Center for Nanoscale Materials (CNM) at Argonne National Laboratory. My research targets an optical system-on-chip in AlGaAs/GaAs, incorporating lasers, detectors, waveguides, isolators, and modulators. I have demonstrated Y-junctions, passive waveguides, ring resonators, Fabry-Pérot and DBR lasers, and detectors on our substrates, along with the custom characterization setups needed to evaluate them. I recently expanded into acousto-optic ring isolators on thin-film LiNbO₃-on-insulator, bypassing the need for magnetic garnet isolators.

Current efforts focus on coupled-wave analysis for LiNbO₃ acousto-optic ring isolator design, while simultaneously evaluating grating coupler designs for efficient chip-to-fiber coupling. A key challenge is combining active and passive components on a single AlGaAs chip: the quantum well structure needed for lasing causes parasitic absorption in passive waveguide regions. I have developed a selective quantum well disordering (QWD) process using an SrF₄ mask prior to rapid thermal annealing, allowing targeted disordering without significantly affecting neighboring active regions.

Colleagues at LAPT have demonstrated fast- and slow-light accelerometers/gyroscopes using Rb atomic transitions, achieving dramatically improved resolution over competing techniques. However, these systems remain bulky and impractical. On-chip integration at the Rb transition wavelengths (~780 nm and ~792 nm) would be transformative. AlGaAs was chosen for its tunability across this range, despite the additional process challenges it introduces (chlorine-based dry etching, aluminum oxidation susceptibility). Three Argonne CNM facility proposals have been accepted to support this work.