April 28, 2000

"Polarization Measurements: Ellipsometry and Polarimetry"
Shankar Krishnan
Containerless Research, Inc.
Evanston, Illinois

Measurement of the polarization state of light is important in numerous fields including materials science, optics, optical engineering, communications, and astronomy. A review of polarization measurement techniques and specific applications in ellipsometry and polarimetry will be presented. Recent efforts to achieve time-resolved measurements of the polarization state of light will be described.

Bio Sketch

Dr. Shankar Krishnan received his undergraduate degree in materials science from the Indian Institute of Technology in 1984 and his doctoral degree in Materials Science from Rice University in 1989. He was employed from 1989-1993 at Intersonics, Inc. and from 1993-Present at Containerless Research, Inc. where he has developed instrumentation and techniques that exploit measurements of the polarization state including time-resolved ellipsometry and polarimetry, spectroscopic ellipsometry, and Mueller-matrix ellipsometry.

Report of SMSI meeting of April 28, 2000

The meeting was called to order by Bill Mikuska at 7PM. Several announcements, including a reminder that the annual picnic would be held in York Woods South in Oak Brook on June 10th, preceded the introduction of Dr. Shankar Krishnan of Containerless Research Inc. of Evanston as the evening's guest speaker. Dr. Krishnan prefaced remarks about his work at Containerless Research with a description of measurement of the four Stokes parameters which provide a complete description of polarized light. With the aid of a diagram of a Poincare sphere Dr. Krishnan explained how ellipsometers measure the elliptical states of polarized light reflected from or transmitted through a material surface.

By studying the interface induced changes, specifically the phase differences, in the material / polarized light interactions, one can measure many useful properties of physical systems. In the world of Nature, bees and butterflies, for example, have been shown by recent studies to use biological polarized light detectors to guide their navigation. Potential technical applications of high speed ellipsometric measurement devices, utilizing the rapid modulation and demodulation of lasers, can provide a window of opportunity for time measurements on a one half microsecond scale.

A promising line of inquiry at Containerless Research may lead to the application of spectroscopic ellipsometry in the field of thin film measurements. Applied in situ, this technique could potentially lead to revolutionary cost savings in the semiconductor industry by detecting flaws in the construction of silicon wafers at an early stage as opposed to current practice, which locates problems only when it is too late to take corrective action and an expensive investment must be scrapped. In a very different direction, ellipsometry, as a nitrogen detection device, has potential to help reduce overuse of nitrogen fertilizers in agriculture and thereby reducing pollution of the Gulf of Mexico.

Technical know-how and imagination appear to be the guides for Dr.Krishnan and his colleagues at Containerless Research Inc.

Report submitted by John Macdonald, Recording Secretary.