Using ultra-short light pulses
Femtosecond lasers produce ultra-short light pulses that can be used in a variety of applications. Ultra-short light pulses ranging from 10 to 500 femtoseconds (10-15 second) produce very different effects on materials than standard nanosecond (10-9 second) light pulses. Femtosecond light pulses deposit energy on a time frame which is faster than the characteristic time of many fundamental processes in the target, leading to qualitatively different outcomes than obtained with longer pulse lasers.
"When you use extremely short light pulses, you're putting the energy into the sample so quickly that there is negligible heat flow during the absorption of the light pulse, and material has not started to ablate from the surface during the pulse," explained Harold Haugen, Professor in the Department of Physics and Astronomy and the Department of Engineering Physics at McMaster University.
Ultra-short light pulses are used in a number of fundamental scientific endeavours in physics, chemistry, biology, and other disciplines. In addition, the ultrafast laser technology is deployed in a variety of areas, including for example, micromachining and micromodification of materials, and in novel forms of high-resolution optical imaging.
Dr. Haugen's group is involved with a range of projects aimed at the micromodification and nanomodification of materials. In one thrust, in collaboration with the silicon photonics group, his group has been working on a variety of experiments related to silicon-based optoelectronics, as well as fundamental laser-solid interaction studies.
Fine nanostructuring is also possible with femtosecond light pulses, which can slightly alter the surface of a wide range of materials, such as synthetic diamond and silicon. Micromachining and nanomachining techniques allow for the removal of very small amounts of material. "One can achieve a high degree of precision with these extremely short light pulses, a precision we wouldn't obtain with the standard long nanosecond light pulses," said Haugen.
Haugen’s research activities on laser ablation and materials modification have involved a close interaction with the Canadian Centre for Electron Microscopy (CCEM) under the Brockhouse Institute for Materials Research. In addition to a suite of standard analytical facilities, the CCEM hosts cutting-edge capabilities in electron microscopy which enable specialized and unique investigations of the final state of target materials after ultrashort pulse interactions.
In addition his group has worked on selected applications of Terahertz (THz) radiation. With a frequency in the range of 1012 Hertz, it is also known as far infrared radiation. THz radiation can be utilized as a sensitive probe of the properties of materials, and in the study of time dependent processes, opening the door for a host of novel experiments in basic physics. THz beams are also of interest for a broad range of applications. For example, they can be deployed like x-rays to see through the walls of a container or to detect concealed weapons.
Haugen described his research group as an interdisciplinary team composed of students who are interested in continuing their careers in research after completing graduate degrees, or in other cases, finding employment in high-tech industry. The nature of the research in the Haugen group lends itself well to students taking either of these paths after graduation.
Femtosecond Laser Ablation and Micromachining, Electron Microscopic Studies of Ytterbium-Doped Optical Fibres, Applications of THz Radiation
Department of Physics & Astronomy
Dear Prospective Graduate Student,
My work is in the area of laser physics and applications of lasers, with a particular emphasis on ultrashort pulse (femtosecond) science and technology. I am cross-appointed between the Department of Physics and Astronomy in the Faculty of Science and the Department of Engineering Physics in the Faculty of Engineering, and my students typically come from both departments. Our research activities are housed within the Photonics Research Laboratories (PRL), jointly run by Dr. John Preston and myself, under the Brockhouse Institute for Materials Research. One or two openings for a graduate student are expected over the coming year.
My current research covers areas of laser-based micromodification and nanomodification of materials; femtosecond optics; as well as unique electron microscopic studies of doped optical fibres. The materials modification projects often utilize the analytical capabilities of the Canadian Centre for Electron Microscopy, including high resolution transmission electron microscopy of sub-surface regions of the laser-modified target materials. Projects vary from scientific studies to more engineering oriented work. (http://www.physics.mcmaster.ca/optics/.)
My philosophy regarding research is to provide students early on with a broader experience in the laboratory and not to select a narrow and well-defined project from the very outset. In the PRL, we truly are at the boundary between the two departments and individual students can choose a project which may be either more fundamental or applied. The interaction between the students from both areas, as well as with other PRL-related faculty, has proven to be a valuable aspect for learning and development of technical expertise in the research laboratory environment. A rather special aspect of my group is the possibility for students to conduct part of their research in another laboratory selected to provide a broader experience as well as a unique research opportunity, including groups located in foreign institutions.
If you would like more information on our activities, please do not hesitate to contact me at email@example.com.