Energy-Efficient Photonics: Computing Applications and Fundamental Limits

Academic papers have routinely reported power per bit numbers in the low pJs for several years.  It may be reasonable to assume as an upper limit that deployed systems may achieve the one to two orders of magnitude improvement to reach 0.5 pJ/bit within the next 5 years.  These optimistic electrical link estimates still fall short of energy performance required by advanced microprocessors.  Here we demonstrate that the current state of photonic devices integrated in foundry CMOS foundry processes are competitive with existing and next generation on-chip power dissipation numb

Ultrafast Coherent Optical Signal Processing using Stabilized Optical Frequency Combs from Mode-locked Semiconductor Diode Lasers

The development of high speed communications, interconnects and signal processing are critical for an information based economy. Lightwave technologies offer the promise of high bandwidth connectivity from component development that is manufacturable, cost effective, and electrically efficient. The concept of optical frequency/wavelength division multiplexing has revolutionized methods of optical communications, however the development of optical systems using 100’s of wavelengths present challenges for network planners.

Nanostructured Energy Devices: Phonons, Electrons and Photons on the Nanoscale

Supplying the world with sustainable energy is one of the most pressing issues in modern society. Dramatically improved control over heat, electricity and solar energy is essential to create a new energy paradigm. Nanomaterials with carefully tailored properties (such as interface, geometry) can be used to manipulate the flow of phonons, electrons and photons, to enable novel energy devices in an unconventional manner. In this talk, I will present three examples of nanostructure-enabled energy devices.

Interfacial Charge Transfer in Nanomaterial Based Light Harvesting Devices

We purposefully design and study “molecular-like” interfacial interactions between the multidimensional nanometer-scale building blocks that compose larger-scale functional light harvesting devices. Using time-resolved optical spectroscopy, we aim to understand the nature of discrete interfacial electronic states and their role as crucial intermediates promoting efficient interactions between extended systems (e.g., charge transfer).

Using Asymmetric Crystals for New Functionality: Moving Spins with Heat Using Spin-Orbit Coupling and Dopant-less Diodes Using Polarization Charge

The lack of inversion symmetry in certain crystals leads to interesting properties. Two such properties, the spin-orbit effect and polarization charge, can be exploited for new thermoelectric and optoelectronic devices. In the first part of the talk, I will introduce the heat/spin conversion phenomenon, the spin-Seebeck effect. Phonons interact with the magnetic moments in a material driving them away from equilibrium inducing a diffusive spin current, which can be converted in a neighboring material into an electric voltage.

Dielectric and Molecular "Multipole Antennas" for Energy Sciences and Technology

Solid-state lighting and solar photovoltaic devices typically employ optical materials comprising isotropic assemblies of atomic and molecular electric dipoles. Many nanomaterials, however, exhibit optical properties that are inconsistent with these simple models. In this talk we discuss novel optical phenomena arising from oriented “multipole antenna” resonances in organic materials and dielectric nanostructures.

Sustainable Buildings Research: Opportunities in Design and Operation

Gregor Henze has been involved in building sciences research for 20 years, both in the United States and Europe. This seminar will offer a discussion of case studies of sustainable energy research applied to commercial buildings and an outlook on the need for future advances. The first part of the seminar will discuss low-exergy building systems for new building design.

How to Freeze Silicon: A Many-Splendored Problem

Since the first use of silicon in electronic devices, the crystallization of silicon into useful forms for device processing has been a constant subject of both fundamental research and commercial development. To make suitable substrates for ever-smaller devices, companies have perfected the Czochralski crystal growth process for sizes up to 450 mm in diameter, with ingots up to 300 kg in weight. For use in photovoltaic applications, up to six different crystallization methods have been in production at different companies at the same time.