RICHARD K. CHANG
Henry Ford II Professor of Applied Physics
Professor of Physics and of Electrical Engineering
Ph.D. 1965, Harvard University
E-mail: richard.chang@yale.edu
Phone: 1 (203) 432-4272
Fax: 1 (203) 432-4274
Office: Becton Center, Room 407


Our groups research focuses on two related topics. 

The first is the detection, characterization, and deflection of ambient airborne aerosols (in the respiratory size range, 1-10mm). To distinguish bioaerosols from the ambient background, we detect the entire fluorescence spectrum of each particle that flows through the desired focal volume and is excited by the UV laser or an array of UV LEDS. The entire back-scattered angle-resolved distribution is recorded for each lasing firing. Should the fluorescence and angular scattering distribution satisfy preset-profile characteristics, the particle is aerodynamically deflected (by puffer) so that the deflected particles cab be biochemically analyzed.

Our second research topic is the design of semiconductor microcavities (2mm high micro-pillars with a variety of 2-d cross-sectional shapes) that will exhibit two properties: (1) the pillar sidewalls, through total-internal reflection, provides necessary feedback for lasing through the quantum wells; and (2) the pillar geometry provides an optimal amount of output coupling for a unidirectional output beam. At Yale, we are using selectively shaped optical beam to pump the micro-pillars; our industrial partners are using selectively shaped electrodes for injection pumping. We are working on micro-pillar lasers that could emit radiation in the UV; this could do away with distributed Bragg reflectors that are difficult to grow with low defect density for the A1GaN system. UV laser diodes may be able to replace UV LEDs which are barely able to induce the fluorescence needed in the detection (with good signal-to-noise ratio) and characterization of ambient aerosols.

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Selected Publications
"Uni-directional lasing from InGaN multiple quantum-well spiral-shaped micropillars," G.D. Chern, H.E. Tureci, A. Douglas Stone, R.K. Chang, M. Kneissl, and N.M. Johnson, Appl. Phys. Lett. (in press 2003).

"Single-Particle Fluorescence Spectrometer for Ambient Aerosols," Y-L. Pan, J. Hartings, R.G. Pinnick, S.C. Hill, J. Halverson, and R.K. Chang, Aerosol and Science Technology (in press 2003).

"Characterizing and Monitoring Respiratory Aerosols by Light Scattering," Y-L. Pan, K.B. Aptowicz, M. Hart, J.D. Eversole, and R.K. Chang, Opt. Lett., 28, 589 (2003).

"Highly efficient prism coupling to whispering gallery modes of a square m-cavity," Y-L. Pan, R.K. Chang, Appl. Phys. Lett,. 82, 487 (2003).

Updated: 5/19/03


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