Time-resolved microscopy of laser

Time-resolved microscopy of laser microchemistry

Dana D. Dlott (personal home page)

David M. Dlott (personal home page)

Some of the most important practical applications of laser chemistry are found in the lithography and graphic arts industry. Recently a great deal of attention has been devoted to utilizing laser microchemical processes in high resolution graphic arts applications. In the last few years, the Dlott group has become a leader in developing a fundamental understanding of the mechanisms of laser photothermal imaging processes used in the graphic arts industry, thanks to financial support from Presstek, Inc., Optodot, Inc., and the US Army Research Office.

"Presstek, Inc., founded in 1987, has developed a patented proprietary non-photographic, toxic-free, digital imaging and printing plate technology for the printing and graphic arts industries on a worldwide basis. PEARL's thermal laser diode system is capable of imaging various types of Presstek printing plates either off-press or on-press to produce high quality, full-color lithographic printed materials. Presstek is also engaged in the development of additional products and applications that incorporate its proprietary PEARL technologies and consumables, including both computer-to-plate and other direct-to-press applications." ----From a Presstek press release

“Pioneering research at Optodot, by leading experts in organic semiconductor and microporous materials, is producing scientific discoveries that meet the needs of a progressively interdependent world. Optodot: Energy and Security solutions through nanotechnology”—Optodot web page.

In the Presstek project we are trying to understand the fundamental mechanisms of computer-to-plate imaging processes, and trying to develop a theoretical model which will predict the response of imaging materials to various types of laser pulses.

In the Optodot project we are trying to understand the fundamental mechanisms of laser writing of invisible print used for security coding applications.

A powerful tool used in these studies is our ultrafast time-resolved microscopy apparatus (see at right) which is used to study the physical and chemical processes occurring in micron sized volumes of multilayer thin film materials. A movie made by Dr. Serguei Koulikov seen at right shows how an imaging material with a silicone rubber imaging layer, developed by Presstek, Inc. responds to short laser pulses.

These projects involve studies of solid-state chemistry of rather complicated imaging materials, which consists of micro and nano fabricated thin film multilayer composites made of different polymers and metals. Since modern digital images are generated as a series of "dots", and each "dot" is just a few micrometers in diameter, this work involves studies of laser chemistry in micron domains, i.e. laser microchemistry. Besides time-resolved microscopy, other techniques including laser spectroscopy are used to study these materials. Imaging media developed by many different companies, including 3M, Rexham Graphics, Scitex, Anitec, Mitsubishi Chemical, Presstek, Optodot, MeadWestvaco and others have been studied in our labs.

This project is ideal for students who want to experience an in-depth collaborative relation with dynamic industrial partners, and who are attracted to projects which involve fundamantal studies with immediate practical applications.

REPRESENTATIVE PUBLICATIONS

"Fundamental mechanisms of lithographic printing plate imaging by near-infrared lasers", David E. Hare, Stuart T. Rhea, Dana D. Dlott, Richard J. D’Amato, Thomas E. Lewis, J. Imag. Sci. Technol. 41, pp. 291-300 (1997).

"Pulse duration dependence of lithographic printing plate imaging by near-infrared lasers", David E. Hare, Stuart T. Rhea, Dana D. Dlott, Richard J. D’Amato and Thomas E. Lewis, J. Imag. Soc. Tech. 42, pp. 187-193 (1998).

“Focus fluctuations in laser photothermal imaging”, Serguei G. Koulikiov and Dana D. Dlott, J. Imag. Sci. Technol. 44, pp. 1-12 (2000).

“Effects of energetic polymers on laser photothermal imaging materials”, Serguei G. Koulikiov and Dana D. Dlott, J. Imag. Sci. Tech. 44, pp. 111-119 (2000).

“Time-resolved microscopy of laser photothermal imaging”, Serguei G. Koulikov and Dana D. Dlott, Optics and Photonics News 11, pp. 26-32 (2000).

“Ultrafast microscopy of laser ablation of refractory materials: ultra low threshold stress-induced ablation”, Serguei G. Koulikov and Dana D. Dlott, J. Photochem. Photobiol. A: Chemistry 145(3), pp. 183-194 (2001).

“Time-resolved Microscopy Analysis of Laser Photothermal Imaging Media”, Hyunung Yu, Dana D. Dlott, F. Richard Kearney, J. Imag. Sci. Tech. (submitted 7/05).

Artist's conception of laser microchemistry

Ultrafast optical microscopy apparatus

Block diagram of microscopy apparatus

Schematic diagram of some imaging materials studied in our lab

Movie (4 ms duration) of laser micro-chemistry in a silicone thin film with nitro-cellulose undercoa ting, using a 100 ns laser pulse. The diameter of the imaged spot is about 30 mm. The imaging medium is at left and the laser pulse comes in from the right.