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.

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Hardware Startups 101:   Entrepreneurship for Engineers

Considering striking out on your own to commercialize a product that has optical, electronic, or otherwise tangible elements? Curious or worried about: fundraising, early product development, term sheets, or sales? Gregg Favalora, entrepreneur in optical systems since 1997, will layer the case study of (3-D display pioneer) Actuality Systems and its eventual exit with lessons and context in key topics that may be new for career engineers. Topics in this high-density talk will be addressed from the standpoint of electro-optical entrepreneurship, and will be a rapid introduction to key topics for further inquiry: what startups are *really* like, frugal prototyping, product definition, getting to First Customer Ship, financing and the basics of Term Sheets, publicity, equity budgets, the Whole Product, accelerators, and Characters to Be Wary Of. You will also be provided with resource lists for useful meetings, books, and key people to “follow.” 

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Half a century of laser weapon development

DARPA launched the Pentagon’s first laser weapon program in early 1959, when it issued a million-dollar contract to TRG Inc. to try to build a laser based on Gordon Gould’s patent application. Ever since, the military has been trying to scale lasers to weapon-level powers. In the early 1960s, they tried to scale laser rods into laser logs, only to run into thermal problems. As that program wound down, AVCO Everett Research Laboratory developed the gas-dynamic CO2 laser, the first laser to produce tens of kilowatts CW. Chemical lasers followed, and MIRACL reached 2 megawatts CW, for a few seconds at a time, by the early 1980s. “Star Wars” produced the Alpha chemical laser, which also reached multi megawatt powers, and was supposed to be scalable to an orbiting laser battle station. The Airborne Laser followed, and for a while it looked like it really would really work. Now a dark horse, the fiber laser, has been shooting down targets at relatively short ranges in the Persian Gulf. This talk will cover the long road to this promising success, why it looks like it might work, and what its limits are.

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The Shockley-Queisser Limit and Its Discontents

In 1961, Shockley and Queisser proved that single-junction solar cells cannot be more than ~34% efficient, under certain assumptions. Many researchers have viewed this theoretical efficiency limit as a challenge to overcome, and have proposed a dizzying variety of techniques to surpass that limit: multijunctions, concentration, multi-exciton generation, intermediate bands, hot electrons, upconversion, downconversion, anisotropic re-radiation, etc.

In the first part of the talk, Dr. Byrnes will give a tutorial on the Shockley-Queisser limit, explaining the steps and assumptions. Then, for each of those limit-surpassing techniques, he will explain how it works, why it can (in principle) beat the S-Q limit, and whether he thinks it is promising for real-world solar cells.

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