Boston Chapter of the IEEE Photonics Society

Abstract:  Colloidal nanocrystals are quantum size-effect tunable and offer an abundance of available surface for electronic and chemical interaction. They can be processed from organic or aqueous solution onto substrates that are rigid or flexible, smooth or rough, flat or curved, inorganic, organic, including biological, crystalline or amorphous, conducting, semiconducting, or insulating.

With the benefit of over a decade's progress in visible-emitting colloidal quantum dot synthesis, physical chemistry, and devices, significant progress has been made recently in infrared-active colloidal quantum dots and devices.

The talk will review the field of infrared colloidal quantum dots, with emphasis on applications and devices and a focus on the research contributions of Prof. Sargent's group in electroluminescence, photoconductive, photovoltaic, nonlinear optical, and optical amplification-based devices. The applications will include monolithic integration of fiber optic and free-space communications photonic components on electronic substrates such as silicon and glass; in vivo biological tagging in infrared spectral bands in which living tissue is optically penetrable to a depth of up to 10 cm; solar and thermal photovoltaics for energy conversion; and infrared sensing and imaging based on non-visible, including thermal, signatures.

The synthesis and properties of quantum dots are first reviewed: luminescence quantum efficiencies greater than 50% are achievable in solution and stable luminescent dots are available in organic and aqueous solvents. Electroluminescent devices based on solution processing and a hybrid solution and small-molecule organic evaporation have been reported with external quantum efficiencies approaching 1%. Photoconductive devices have been realized with greater than 2% internal quantum efficiencies, and a photovoltaic effect recently observed. Electro-optic modulation achieved by either field- or charge-induced modification of the rate of optical absorption has been demonstrated

based both on intraband and intersubband (intraband) transitions. Optical gain from these processible materials with a threshold of 1 mJ/cm2 and an optical net modal gain coefficient of 260±20 cm-1 has been obtained.

Biography:  Prof. Edward (Ted) H. Sargent is the Nortel Networks - Canada Research Chair in Emerging Technologies, Electrical & Computer Engineering Dept., University of Toronto, Canada. Currently he is a Visiting Professor of Nanotechnology and Photonics in the Microphotonics Laboratory at MIT. In 2003 Ted Sargent was named "one of the world's top young innovators" by MIT's "Technology Review." In 2002 he was honored by the Canadian Institute for Advanced Research as one of Canada's top twenty researchers under age forty. In 2002 he won the Outstanding Engineer Award of the Institute of Electrical and Electronics Engineers (IEEE) of Canada for groundbreaking research in applying new phenomena and materials from nanotechnology towards transforming fiber optic communications systems into agile optical networks. He was awarded a Canada Research Chair at the University of Toronto in 2000: "[Ted Sargent] has created a new type of laser that unites many sophisticated optical devices onto a single, integrated photonic chip. His research links the emerging concept of the photonic circuit with the exploding field of fiber optic networks." Ted Sargent's doctoral research on the lateral current injection laser won him the 1999 NSERC Silver Medal. He received the B.Sc.Eng. (Engineering Physics) from Queen's University in 1995 and the Ph.D. in Electrical and Computer Engineering (Photonics) from the University of Toronto in 1998.

Location:  Verizon Laboratories