Optics and Electronics Seminar

OSA/SPIE Seminar: Computational Optics for Multidimensional Nanoscale Imaging of Single Fluorescent Molecules

Topic: 
Computational Optics for Multidimensional Nanoscale Imaging of Single Fluorescent Molecules
Abstract / Description: 

Visualizing the dynamic movements and interactions between biomolecules remains a challenge, motivating the development of new optical technology and computational algorithms for imaging at the nanoscale. We have built two technologies for multidimensional imaging of single molecules (SMs): the Tri-spot point spread function (PSF) and the Robust Statistical Estimation (RoSE) algorithm. The Tri-spot PSF measures each second moment of SM orientation with near-uniform sensitivity, thereby capturing the orientation and rotational diffusion of SMs using just one camera frame. For 3D imaging, we developed RoSE to minimize the vectorial localization errors in super-resolution microscopy that result from both the structure of the sample and the PSF itself. By estimating the likelihood of a blinking event to be present in each imaging frame, RoSE localizes molecules accurately and minimizes false localizations even when images overlap.

Date and Time: 
Thursday, June 7, 2018 - 4:15pm
Venue: 
Spilker 232

OSA/SPIE Seminar: Noninvasive diffuse optical imaging of breast cancer risk and treatment response

Topic: 
Noninvasive diffuse optical imaging of breast cancer risk and treatment response
Abstract / Description: 

Diffuse optical spectroscopy and imaging (DOSI) is a class of non-invasive near-infrared imaging techniques based upon measuring the wavelength-dependent absorption and (reduced) scattering optical properties of living tissues. In the far-red to near-infrared optical therapeutic window, these optical properties provide information about deep (several cm) tissue composition, structure, and oxygen metabolism. In particular, DOSI is capable of quantifying tissue concentrations of the physiologically relevant molecules oxyhemoglobin, deoxygenated hemoglobin, lipid, and water, as well as structural parameters including cellular size and density (obtained from scattering spectra). The significance and applicability of these and other DOSI biomarkers collected with research devices have been demonstrated in numerous clinical studies of oncology, cardiovascular assessment, exercise physiology, and neuroscience.

In this presentation, I will discuss how DOSI has shown promise in the field of breast oncology for risk assessment, screening, differential diagnosis of benign and malignant lesions, and predicting and monitoring response to chemotherapy treatment. DOSI biomarkers vary significantly in abundance and molecular state between breast cancer and normal tissue and unique cancer-specific absorption signatures have been observed. Finally, I will demonstrate how we are working to translate this promising technology to clinical practice and my vision for the future.

Date and Time: 
Thursday, April 19, 2018 - 4:15pm
Venue: 
Spilker 232

Optics & Electronics Seminar: The Physics and Applications of high Q optical microcavities: Cavity Quantum Optomechanics

Topic: 
The Physics and Applications of high Q optical microcavities: Cavity Quantum Optomechanics
Abstract / Description: 

TBA

Date and Time: 
Monday, May 14, 2018 - 4:15pm
Venue: 
Spilker 232

Light-field-driven currents in graphene

Topic: 
Light-field-driven currents in graphene
Abstract / Description: 

The ability to steer electrons using the strong electromagnetic field of light has opened up the possibility of controlling electron dynamics on the sub-femtosecond timescale. In dielectrics and semiconductors, various light-field-driven effects have been explored, including high-harmonic generation and sub-optical-cycle interband population transfer. In contrast, much less is known about light-field-driven electron dynamics in narrow-bandgap systems or in conductors, in which screening due to free carriers or light absorption hinders the application of strong optical fields.

Graphene is a promising platform with which to achieve light-field-driven control of electrons in a conducting material because of its broadband and ultrafast optical response, weak screening and high damage threshold. We have recently shown that a current induced in monolayer graphene by two-cycle laser pulses is sensitive to the electric-field waveform, that is, to the exact shape of the optical carrier field of the pulse, which is controlled by the carrier-envelope phase, with a precision on the attosecond timescale. Such a current, dependent on the carrier-envelope phase, shows a striking reversal of the direction of the current as a function of the driving field amplitude at about two volts per nanometre. This reversal indicates a transition of light–matter interaction from the weak-field (photon-driven) regime to the strong-field (light-field-driven) regime, where the intraband dynamics influence interband transitions.

We show that in this strong-field regime the electron dynamics are governed by sub-optical-cycle Landau–Zener–Stückelberg interference, composed of coherent repeated Landau–Zener transitions on the femtosecond timescale. Time permitting, we will show another type of quantum path interference in multiphoton emission of electrons from nanoscale tungsten tips, where the admixture of a few percent of second harmonic radiation can suppress or enhance the emission with a visibility of 98%, depending on the relative phase of fundamental and second harmonic.

Date and Time: 
Monday, April 9, 2018 - 4:15pm
Venue: 
Spilker 232

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