NANO-OPTICS LABORATORY

Projects for 2003-2004

James L. Merz, Frank M. Freimann Professor of Electrical Engineering
and Concurrent Professor Physics
Alexander M. Minatirov, Research Professor of Electrical Engineering
Yan Tang, W.M. Keck Postdoctoral Research Fellow
Kai Sun, Research Assistant

1. Composition fluctuations in ternary and quaternary compound semiconductors measured by near-field magnetophotoluminescence
We have measured the clustering of nitrogen in short-period superlattices of InGaAsN and GaAsN using near-field scanning optical microscopy (NSOM) at magnetic fields up to 10 Tesla. Both weak and strong localization effects have been observed. Near-field measurements allow the determination of the density, size, and relative composition of quantum dot formation and larger areas of weak localization.

2. Nanoindentation effects on single and coupled self-assembled quantum dots
We have measured significant high-energy shifts of QD emission induced by pressure applied by the near-field optical fiber probe in physical contact with the surface. Reproducible shifts up to 30 meV, corresponding to pressures as high as 30 kbar, have been observed for single quantum dots, as well as order-of-magnitude increases in the emission intensity. We believe this effect can be used to allow sensitive modulated pressure experiments, and to tune quantum dot emission to resonance with other dots for communications and quantum computer applications.

3. Surface plasmon interactions between the optical field and metal cladding of an optical fiber
This project involves the optimization of the spatial resolution and aperture transmission of the NSOM technique through investigation of these plasmon effects. Magnetic fields and/or nanoindentation techniques, whose effects on fiber transmission have already been observed in our laboratory, will be utilized to enhance NSOM sensitivity and to develop novel devices.

4. Two-dimensional photonic bandgap structures by electron-beam lithography
We are fabricating 2-D photonic bandgap crystals by e-beam lithography and subsequent etching of cylindrical holes in multilayer semiconductor structures containing self-assembled quantum dots. “Defects” (i.e., missing holes) can be placed in these structures in a controlled fashion. These structures have important optical communications applications.

5. Photoluminescence and Infrared spectroscopy of Si/Ge quantum dots
We have used conventional photoluminescence (PL)to study quantum dots grown by our collaborators in the silicon/germanium semiconductor system for application to Quantum Cellular Automata. Our next step is to studies these materials with higher spatial resolution (e.g., micro-PL and near-field PL) , and to study transitions within the conduction band using Fourier transform infra-red spectroscopy (FTIR) of small numbers of these dots.