University of Rochester SPIE Student Chapter

Himanshu Shekhar
Electrical and Computer Engineering

Assessment of Cardiovascular Risk with Nonlinear Intravascular Ultrasound Imaging

Tuesday, August 30
12:00- 1:00 PM
Goergen 101

Coronary Artery Disease (CAD) is a leading cause of death in America. It is characterized by the deposition of plaque on the walls of the coronary arteries of the heart. Heart attacks occur when high-risk plaques rupture in the advanced stages of CAD, causing clots that block the oxygen supply to the heart, often resulting in death.

Currently, a significant issue facing cardiologists is that of reliably identifying rupture prone plaque. If plaque vulnerability can be objectively assessed, aggressive drug therapy/ interventional methods can be employed to save those most at risk. However, X-ray angiography, the current clinical imaging technique for coronary imaging, is limited in its ability to assess plaque vulnerability.

My presentation will provide an overview of our efforts towards developing a diagnostic imaging technique to reliably predict the rupture proneness of coronary plaque.

We are adapting Intravascular Ultrasound (IVUS), for the assessment of the functional features of CAD by exploiting the nonlinear acoustic behavior of Ultrasound Contrast Agents. Intravascular Ultrasound uses high frequency ultrasound to generate cross sectional images of the anatomy of the coronary artery with a catheterized transducer. Ultrasound Contrast Agents are stabilized micrometer sized bubbles, which enable the imaging of plaque vulnerability markers, such as neovascularity and perfusion. Nonlinear acoustic backscatter from ultrasound contrast agents enables higher imaging specificity.

My presentation would discuss the advantages associated with nonlinear imaging modes, the dynamics of ultrasound contrast agents and

Dr. Robert Saunders
Program Officer
Roundtable on Value and Science-Driven Health Care
Institute of Medicine of the National Academics

An Overview of Science Policy Careers

Tuesday, August 23
12:15- 2:00 PM
Goergen 108

The term science policy encompasses two disparate concepts: one is considering the policies for the scientific enterprise (such as research funding or stem cell research guidelines), while the second is applying scientific knowledge to pressing public policy questions (such as energy policy or security). While science plays a role in deciding these policies, other factors come into
play as well, including political considerations, economic factors, and values. Given this complexity, what role can scientists play? In addition to considering the role of science in science policy, this talk will also explore career paths in science policy and how students can enter this arena.

Yuzhe Xiao
The Institute of Optics

Adiabatic Wavelength Conversion in Travelling-wave and Resonant Photonic Structures

Tuesday, August 16
12:00- 1:00 PM
Goergen 101

All-optical signal processing, especially wavelength conversion plays a crucial role in modern lightwave systems. Many ways of wavelength conversion use nonlinear effects that require high power and phase matching. Recently, it was found that the spectrum of light can change inside a linear medium whose refractive index changes with time. The term adiabatic wavelength conversion (AWC) is used to describe this optical phenomenon. Methods such finite-difference time-domain (FDTD) simulations and a modal approach, have been used to study this effect. In this talk, we present a new approach for understanding AWC by developing a linear system model for the dynamic photonic structures. The model is first applied to a travelling-wave device to reveal a new physical picture of AWC: a rescaling of transit time by dynamic refractive index changes of the medium. We show that temporal changes in the refractive index not only shift the pulse spectrum but also lead to pulse compression and spectral broadening as well as to phase changes. In the optical resonators, our approach correctly predicts the spectral shift related to AWC. More importantly, it allows us to study the temporal and spectral evolution of an optical pulse that has been ignored so far. Our method is applicable to a broad range of integrated photonic structures, including silicon micro-rings and photonic crystal resonators, and is useful for applications ranging from all-optical signal processing to routing, as well as optical buffering.

Abbie Tippie
The Institute of Optics

Gigapixel Synthetic Aperture Digital Holography

Tuesday, August 9
12:00- 1:00 PM
Goergen 101

In digital holographic synthetic aperture imaging, individual frames from a CCD detector are mosaicked together to form larger array sizes, thereby increasing the effective size of the hologram plane.  The larger aperture allows for an increased numerical aperture and higher frequencies to be detected, thus decreasing the finest resolvable feature size while increasing the space-bandwidth product.

After considering proper propagation and sampling requirements, a high-resolution image was reconstructed using sub-pixel registration algorithms to mosaic together hundreds of arrays of data in combination with phase-error correction algorithms to correct for system instabilities.

Ran Xin
Physics & Astronomy

Directly Chirped Laser Source for Chirped-Pulse Amplification Systems

Tuesday, August 9
12:00- 1:00 PM
Goergen 101

Chirped-pulse–amplification (CPA) is a widely used technique to produce ultra-short optical pulses with high pulse energy. It stretches a pulse before amplification and recompresses it after energy gain to avoid detrimental nonlinear effects in the amplifier, such as self-focusing.  The conventional CPA approach stretches ultra-short optical pulses from a mode-locked laser with a grating-pulse stretcher to produce chirped seed pulses. This approach offers limited flexibility in the control of dispersion without system re-alignment.  The directly chirped laser source (DCLS) produces linearly chirped optical pulses through direct phase modulation in an all-fiber architecture. With a programmable temporal phase profile, DCLS offers improved flexibility and control. It also offers high seed pulse energy and diffraction limited beam performance.

Rebecca Wilson
The Institute of Optics

Multi-Modal Optical Techniques for Intra-Procedural Evaluation of Breast Cancer Specimens

Tuesday, August 2
12:00- 1:00 PM
Goergen 101

A major problem for breast cancer clinicians is evaluating breast cancer at point-of-care during needle core biopsies or lumpectomy surgeries. Patients frequently have to wait days to get a diagnosis, or to find out that some of the cancer was missed (lumpectomies result in a second surgery 30-50% of the time). Microscopy techniques such as confocal and OCT have offered the ability to evaluate such tissues without complicated preparation, but are too time consuming to be clinically useful. I will present research on multi-modal optical techniques to aid clinicians in evaluation of breast lumpectomies and needle core biopsies to allow for rapid intra-procedure microscopic evaluation.

Mehul Malik
The Institute of Optics

High-Dimensional Quantum Key Distribution using Orbital Angular Momentum States of Light

Tuesday, July 26
12:00- 1:00 PM
Goergen 101

Quantum key distribution is a method that utilizes the “non-clonable” property of a quantum state in order to generate a secure key for encryption systems. Traditionally, QKD schemes have relied on polarization states of light to encode information, which are inherently limited to two dimensions. By using a higher dimensional basis set, one can encode more information as well as be more secure against eavesdropping. Orbital angular momentum states of light present an infinite dimensional basis set. Recently, we constructed a QKD system using OAM states of light of up to 8 dimensions.

Davis Glasser
Physics & Astronomy

The Rapidly Generated Motion Aftereffect: Psychophysics and Physiology

Tuesday, July 19
12:00- 1:00 PM
Goergen 101

First documented by Aristotle, the motion aftereffect (MAE) is one of the best-known illusions in vision science. After adapting to a strong moving stimulus (like a waterfall, or the notes in Guitar Hero), subsequently viewed stationary objects seem to move in the opposite direction. In over 150 years of modern investigation, the MAE has typically been studied following tens of seconds of adaptation, which raises some important questions. Can perceptual adaptation be observed at brief, functionally relevant timescales? And if so, how do its properties relate to the rapid adaptation seen in cortical neurons?

In recently published work, we’ve shown that just 25 ms of motion adaptation is sufficient to generate the MAE, even when the motion is too brief to be discriminated. In parallel neurophysiological recordings, we find that brief motion adaptation evokes direction-selective responses to subsequently presented stationary stimuli. A simple model shows that these neural responses can explain the consequences of rapid perceptual adaptation. Overall, we show that the MAE is not merely an intriguing perceptual illusion, but rather a reflection of rapid neural and perceptual processes that can occur essentially every time we experience motion.

Mayukh Lahiri
Physics & Astronomy

Coherence and Polarization Properties of Stochastic Optical Fields

Tuesday, July 12
12:00- 1:00 PM
Goergen 101

All optical fields, whether found in nature or generated in laboratories, have some random fluctuations associated with them. Even though these fluctuations are too rapid to be observed directly, their existence can be experienced by experiments which involve effects of correlations among the fluctuating fields. Coherence and polarization are two basic properties of light, which are manifestations of such correlations.  In this presentation some topics on theories of coherence and polarization of light will be discussed. These theories have been formulated in two different domains, the space-time and the space-frequency domains. We will elucidate the relationship between the theories in the two domains. We will show how the coherence properties of light may play an important role in determining structures of random media. We will also show how the polarization properties of light can be analyzed by quantum theory of electromagnetic fields.