|Location:||Prysm Inc., 45 Winthrop St., Concord, MA 01742|
|Dinner Reservation Deadline:||April 13, 2015 @ 6pm|
Optical Properties of Two-Dimensional Materials - Graphene and Beyond
Graphene, a single atomic layer of carbon atoms, has attracted great attention worldwide because of its potential for novel science and technology. Recently, this interest has expanded to the much wider class of 2D materials that occur as layers of van-der-Waals crystals. While preserving graphene’s flexibility and tunability by external perturbations, atomically thin layers of this broader set of materials provides access to more varied electronic and optical properties, including semiconducting and insulating behavior.
In this talk, we will discuss some of the distinctive optical properties of this emerging class of atomically thin 2D materials. Graphene has now been investigated across a spectral range from the THz to the UV. The optical properties reveal much interesting physics and also show strong tunability in response by means of external gating. Recently, atomically thin layers of semiconductors in the family of transition metal dichalcogenides (MX2 where M = Mo, W and X = S, Se, Te) have also been prepared and investigated. Although weak light emitters in the bulk, at monolayer thickness these materials emit light efficiently. We will describe some of the surprising properties of these systems.
MEETING SPONSORED BY
|Location:||Rebecca's Cafe, 275 Grove St., Auburndale, MA 02466|
|Dinner Reservation Deadline:||May 11, 2015 @ 6pm|
Compressive phase retrieval
Compressive sensing is a class of image recovery techniques utilizing sparsity priors to recover undersampled signals with high fidelity. This talk is about compressive sensing for phase retrieval from coherent fields and correlation function retrieval from partially coherent fields. For coherent fields, I will discuss in particular the use of intensity priors in the “transport of intensity equation” method, where the phase is obtained by analogy to a lateral pressure potential in a compressible flow. Transport of intensity is especially interesting in the x-ray regime, where standard interferometry is difficult because common sources are spatially partially coherent and beam splitters-combiners are not available; as a convincing example, I will show how the sparsity prior of quasi-constant object density allows successful x-ray phase recovery despite the low coherence. For partially coherent fields, I will describe how by using phase-space (Wigner space) methods and sparsity priors on the number of coherent modes it is possible to retrieve the correlation function, which can still lead to complete characterization of physical objects.
MEETING SPONSORED BY
We are a group of industry professionals and interested individuals promoting the knowledge of Optics including applications and phenomena.
The NES/OSA meets monthly from September to May, generally excluding December, on the third Thursday of each month. Our meetings include a social hour, dinner and talk. These meetings are open to all individuals while members receive the benefits of a monthly mailing, reduced meeting dinner price and voting privileges during council elections. Please sign up online.
The NES/OSA is active in the support of optics education in area schools. The organization sponsors symposia and invited speakers for teachers, teaching grants for optics projects and science fairs.
For information please contact a member of our Executive Council.
If you are interested in becoming a member please see the PDF (10Kbytes) application form.