Research

Direct Optical Fringe Writing of Computer-Generated Holographic Stereograms in Photorefractive Polymer for Updatable Three-Dimensional Holographic Display

Object-Based Media Group, MIT Media Lab, Massachusetts Institute of Technology
Advisor: Dr. V. Michael Bove
Collaborators: University of Arizona College of Optical Sciences

The current work aims to assess the feasibility of an updatable three-dimensional display based on the direct fringe writing of computer-generated holographic gratings into a novel photorefractive polymer. The photorefractive polymer in question has many attractive properties for the 3-D display application, including long image persistence, rapid erasure, high diffraction efficiency, and large area; however, current display systems based around its use involve optical interference methods that complicate their optical and computational architectures. A direct fringe writing approach may potentially provide similar display performance with reduced system footprint, complexity, and cost as well as improved perceptual quality.

An Updatable Three-Dimensional Display via Direct Optical Fringe Writing of Computer-Generated Holographic Stereograms in Photorefractive Polymer (MIT S.M. Thesis, 2012)
Direct Optical Fringe Writing of Diffraction Specific Coherent Panoramagrams in Photorefractive Polymer for Updatable Holographic Three-Dimensional Display (Paper Presented at the 9th International Symposium on Display Holography, 2012)
Direct Optical Fringe Writing of Diffraction Specific Coherent Panoramagrams in Photorefractive Polymer for Updatable Holographic Three-Dimensional Display (Talk Presented at the 9th International Symposium on Display Holography, 2012)
An Updatable Three-Dimensional Display via Direct Optical Fringe Writing of Computer-Generated Holographic Stereograms in Photorefractive Polymer (MIT S.M. Thesis Proposal, 2011)
An Updatable Three-Dimensional Display via Direct Optical Fringe Writing of Computer-Generated Holographic Stereograms in Photorefractive Polymer (MIT S.M. Thesis Proposal Presentation, 2011)

Consumer Holographic Video

Object-Based Media Group, MIT Media Lab, Massachusetts Institute of Technology
Advisor: Dr. V. Michael Bove

High-fidelity, autostereoscopic three-dimensional video display systems are highly desirable for their vast array of applications in the medical, military, and entertainment arenas. Many current three-dimensional display technologies (e.g., two-view stereoscopic, etc.) are limited, e.g., in the fact that they require the viewer to wear glasses, or in the case of current autostereoscopic displays (e.g., parallax barriers), do not provide all the visual depth cues inherent in real 3-D scenes (e.g., binocular parallax, accommodation, occlusion, and vergence). Holographic video displays can inherently provide all of these depth cues and are therefore viewed as the ultimate development of electronic visual communication systems.

Current work at the MIT Media Lab is focused on the development of novel optical architectures and integrated optical devices for horizontal-parallax only (HPO) holographic video systems and on the development and implementation of multi-view stereographic rendering schemes for real-time computational display holography.

Diffraction Specific Coherent Panoramagrams of Real Scenes (Presented at Practical Holography XXV, SPIE Photonics West 2011)
Depth Perception and User Interface in Digital Holographic Television (Presented at Practical Holography XXVI, SPIE Photonics West 2012)

Optical Modeling and Characterization for Interferometric Displacement Sensor for Micromachined Optical Microphones

Micromachined Sensors and Transducers Laboratory, Georgia Institute of Technology
Advisor: Dr. Levent Degertekin

Recent advances in optical interferometric sensing schemes for acoustic transduction applications have led to the advent of micromachined acoustic sensors with higher scalability than those employing capacitive sensing schemes. A recent diffraction-based optical sensing scheme has been proposed and implemented in a micromachined optical microphone. The acoustic transduction scheme consists of a sensor membrane (i.e., diaphragm) with an integrated diffraction grating. A pulsed vertical cavity surface emitting laser (i.e., VCSEL) is employed as a low-power light source for the sensing scheme. Interferometric sensing of the displacement of the sensor membrane is accomplished through post-processing of the intensities of the diffracted orders as retrieved by a fixed photodiode array. Despite the success of such a structure for highly compact acoustic transducers, there still remains much room for performance improvements in terms of diffraction efficiency (i.e., incident intermediate optical throughput), modulation efficiency, sensitivity, and interferometric resolution.

My research resulted in the development of a modular, flexible, and accurate optical modeling scheme (implemented using MATLAB and ZEMAX) for the overall device. My work on the modeling scheme allowed for the development of requirements and a design for an optical element (i.e., microlens system) to improve the performance (e.g., power efficiency and modulation efficiency) of the overall device.

Integrated Optical Displacement Detection and Electrostatic Actuation for Directional Optical Microphones with Micromachined Biomimetic Diaphragms (Published in //IEEE Sensors//, 2009)
Optical Modeling with Full 2-D Fourier Optics Analysis for Micromachined Acoustic Transducers (Unpublished Paper, 2009)
Optical Modeling for Micromachined Acoustic Transducers (Talk for MiST Seminar Series, 2008)

Volume Holographic Spectrally Dispersive Elements for Diffuse-Source Spectroscopy

Photonics Research Group, Georgia Institute of Technology
Advisor: Dr. Ali Adibi

Highly effective and portable spectrometers are desirable for applications in which the optical source being examined is diffuse in nature. Conventional spectrometers generally operate by employing optical gratings for wavelength dispersion. Spatial filtering for spectroscopy is accomplished in conventional spectrometers by means of a slit-lens collimating setup and is necessary for spatially incoherent light sources. Although spatial filtering in such a manner can effectively increase the output resolution which can be achieved with a grating-based conventional spectrometer, the slit-lens collimator blocks much of the intensity of the original light source.

Because of the resolution-efficiency tradeoff caused by spatial filtering, conventional spectrometers are highly limited when used with diffuse, incoherent light sources, such as those often encountered in biological and environmental sensing applications. Multimodal multiplex spectroscopy (MMS) has been proposed as a method of spectroscopy particularly useful when dealing with diffuse sources. In MMS, an input light source is projected onto a spectral diversity filter (SDF), which converts the input spatial-spectral signal into an output spectral diversity pattern. A general MMS-based spectrometer employs a Fourier-transforming lens and a charge-coupled device for processing and capturing of the intermediate signal achieved by the SDF. Post-processing of the output signal retrieved by the CCD can successfully approximate the spectrum of the input signal.

My research focused on several aspects of the development of a compact and efficient miniature MMS diffuse-source spectrometer using volume holograms as dispersive elements. Most notably, I performed a thorough analysis of the role of the holographic recording geometry on the performance of the volume holograms as spectral diversity filters in the spectroscopic application.

Cylindrical beam volume holograms recorded in reflection geometry for diffuse-source spectroscopy (Georgia Tech B.S. Thesis, 2008)
Spherical beam volume holograms recorded in reflection geometry for diffuse-source spectroscopy (Georgia Tech B.S. Thesis Proposal, 2007)


Nonlinear Optical Characterization of Ferroelectric Thin Films

Quantum and Nonlinear Optics Group, microEP Program at University of Arkansas
Advisor: Dr. Min Xiao

Semiconductor thin films have unique properties that make them especially useful materials for applications in novel integrated optical devices, such as optical modulators and filters, which are more efficient and often times, less expensive, than their conventional counterparts. Particularly, the nonlinear optical properties of certain thin films allow for such effects as optical tunneling of photonic energy to be easily achieved.

My research here focused on the nonlinear optical characterization (e.g., retrieval of chi-2 and chi-3 coefficients) of epitaxial lead-strontium-titanate thin films using a novel prism-coupling technique.

Domain microstructures and ferroelectric phase transition in Pb0.35Sr0.65TiO3 films studied by second harmonic generation in reflection geometry (Published in Journal of Applied Physics, 2006)
Propagating optical modes in epitaxial PbSrTiO3 ferroelectric thin films on (001) MgO substrates (NSF-REU Report, 2006)
Propagating optical modes in ferroelectric PST thin films (Presentation)