February 2000 Meeting

Sensitive Absorption Spectroscopy Using the Quantum Cascade Laser

Professor Ed Whittaker
OSA Eastman Lecturer

The Optical Society of San Diego is pleased to present this year's Eastman Lecturer Professor Ed Whittaker at our February dinner meeting.

In his talk, Whittaker will describe the basic properties and applications of the quantum cascade laser (QCL)-an exciting new semiconductor laser with emissions in the mid- to long-wave infrared, and present results of his sensitive absorption spectroscopy experiments. In 1994 researchers at Lucent Technology announced the successful demonstration of the first quantum cascade laser (QC). The QC laser is a fundamentally new type of laser in which the optical gain occurs as electrons cascade through a series of quantum wells in a semiconductor. The energy levels in the well are determined by the properties of the semiconductor and the well thickness. InGaAs based devices, with wavelengths ranging from 4 to 17 microns, have been demonstrated. Outputs power up to 1 Watt at liquid nitrogen temperature and several milliwatts at room temperature are possible. QC lasers far exceed lead salt lasers in most performance parameters. The high temperature operation is particularly important in terms of the QC laser's potential for use in practical instruments. QC lasers are especially well suited for sensitive laser spectroscopy, remote sensing and free space optical communications.

Information on the QC laser can be found at:

http://www.bell-labs.com/org/physicalsciences/psr/qc/index.html

http://www.bell-labs.com/org/physicalsciences/projects/qcl/qcl.html

http://attila.stevens-tech.edu/physics/People/Faculty/Whittaker/

The first two links are general introductions to the QC laser, and the last to the spectroscopy results.

Biography: Professor Edward Whittaker is the Physics Department Director at Stevens Institute of Technology. He joined the Stevens faculty in 1984 after receiving his Ph. D. in Physics from Columbia University. He has also had visiting research appointments at IBM Research and Bell Laboratories.

 

Review of the February meeting:

"Sensitive Absorption Spectroscopy Using the Quantum Cascade Laser"
by Brian Sullivan.

This year's Eastman Lecture was presented by Dr. Ed Whittaker, professor of physics at the Stevens Institute of Technology. His talk was on the application of quantum cascade (QC) lasers to sensitive molecular spectroscopy. Professor Whittaker's presentation was general in nature and consisted of an overview of quantum cascade lasers and their advantages over other light sources in the near to mid-infrared followed by a discussion of the spectroscopic and communication applications of these devices.

Quantum cascade lasers were recently developed at Lucent Technologies by a team of scientists led by Dr. Federico Capasso. These devices are fabricated by molecular beam epitaxy and depending on layer thickness and materials, these devices can produce infrared light from 4-17 microns. The major advantage over other sources in this wavelength region (primarily the lead salt diode laser), is that they can provide high brightness at near room temperature operation, thus allowing for the development of compact, ground and space based monitoring instruments. They also have narrow linewidth allowing high spectral resolution. Output wavelength can be temperature tuned. The 4-17 micron region is of interest, for there are several atmospheric windows in region, thus allowing for free space optical communication and remote monitoring of atmospheric constituents and pollutants.

Professor Whittaker is a leader in the field of frequency and wavelength modulation spectroscopy and has recently applied these techniques coupled with the use of QC lasers to the sensitive detection of important atmospheric gases. In his talk, Professor Whittaker described these methods in a clear manner and how they were used in the sensitive detection of gases such as nitric oxide (NO) and nitrous oxide (N2O).

The lecture was presented in a personable style and was well received by those in attendance. The talk generated a number of interesting questions and discussions and we thank Professor Whittaker for taking the time to prepare and present this Eastman Lecture.

Editor's note: The Eastman Lecture is an annual event that is sponsored by the Optical Society of America and underwritten by the Eastman Kodak Company. The Lecture includes a travel grant that pays for the travel expenses of the invited speaker.

Brian Sullivan, the February meeting host, invited Professor Whittaker to speak before his recent relocation to the Bay Area. Thanks, Brian, and good luck!