Scientific & Technological Research
Femtosecond optical pulses are the shortest controlled bursts of energy yet produced, and enable the highest laboratory peak-power densities ever generated. These two characteristics have opened up access to a number of new fields of research not previously available to basic science and applied technology. In the original establishment of the Center, it was pointed out that “ultrafast optical science is an inherently interdisciplinary effort … [requiring] the collaboration of scientists and technologists working on laser and optical physics, atomic and condensed-matter physics, chemistry, optical fibers, and electronics. The field requires all of their efforts and, in turn, rewards each with otherwise unattainable opportunities of discovery in their own fields.” The remarkable growth and success of CUOS has amply demonstrated the truth of that statement. The Center now includes researchers in all of those fields, as well as in plasma physics, accelerator physics, materials science, biophysics, and medicine, all working closely with scientists developing new ultrafast laser sources and measurement techniques – in short, in a “center mode” of research.
The inception of the Center coincided with the rapid development of mode-locked solid-state lasers, and one of the most significant early contributions of CUOS was the invention and development of high-repetition-rate Ti:sapphire amplifiers based on chirped-pulse amplification (CPA). Both the millijoule, kilohertz-repetition-rate class amplifiers and the microjoule, 250-kHz-repetition-rate systems that are now found in nearly every major ultrafast optics lab worldwide were first pioneered at CUOS. With white light continuum generation and ultrafast parametric amplifiers, femtosecond pulses can be readily produced across the visible and near-infrared spectrum, enabling researchers to study “electron-volt” physics and chemistry. For example, a continuing theme of CUOS research has been the study of ultrafast processes in semiconductors and optoelectronic devices, such as quantum dots, semiconductor lasers, and high-mobility quantum transport structures. The generation and applications of terahertz (THz) radiation is also enabled by ultrafast lasers, opening up imaging and spectroscopy in the far-infrared region of the spectrum.
A major thrust of CUOS has been and continues to be the development of CPA systems to achieve the highest possible peak power. This has led to the establishment of “high field science” – the fundamental interaction of light at extreme intensities with matter – where the relevant electron energies are kilo-electron-volts to even giga (billion) electron volts. The impact of our CPA development on both peak intensity and average power is illustrated in Figure 1. High-field laser interactions with plasmas have opened up a world of possibilities in short-wavelength generation, so that now ultrashort pulses are available from the terahertz to the exahertz region of the spectrum.
Access to an interdisciplinary center-type environment is not only fruitful for research, but also for education and technology transfer. The environment of the Center is stimulating and challenging for both undergraduate and graduate students. The Center places a high priority on transferring technology into the marketplace. CUOS pursues active collaborations with companies through SBIR and STTR programs, as well as through informal exploratory collaborations. Several companies have spun off from the Center, and numerous patents and licensing arrangements provide a further avenue for technology transfer.
At the core of ultrafast optical science is our ability to generate, manipulate, and amplify femtosecond pulses. The motivations to do so are both scientific and technological. Indeed, this dual motivation gives rise to the structure summarizing the Center’s main themes:
• High-Field Science is based on the creation of extremely high peak-power levels by squeezing pulses with modest energy levels into ultrashort time frames. When focused, these pulses create electric field strengths far exceeding those that bind the inner-most electrons of an atom to its nucleus, and electron motion becomes relativistic. The fundamental physics of laser-plasma interactions at these extreme intensities and their applications to particle acceleration and short-wavelength generation are the main themes.
• Ultrafast and High Power Fiber Lasers concerns the fundamental aspects of ultrashort pulse generation and amplification in fiber lasers.
• Ultrafast Science applies ultrashort-pulse lasers to the study of high-speed dynamics, with a focus primarily on condensed matter systems of importance to emerging electronic and optoelectronic technology.
• Terahertz Optoelectronics refers to the development of novel single- or few-cycle far-infrared (mm or sub-mm wave) radiation. Applications include sensing, spectroscopy, and imaging.
• Ultrafast Biomedical Optics concerns the application of femtosecond lasers to biomedical problems. These include highly controlled laser ablation, enabling sub-cellular manipulation (“surgery”), fabrication of nanoscale channels for “nanofluidics,” the use of multiphoton excitation for in vivo sensing (e.g. in vivo flow cytometry), coherent control for selective imaging, etc.
• Materials Science concerns micromachining, nanomorphing (generation of nanoscale structure in a controlled way), laser-induced breakdown spectroscopy, and materials characterization with ultrafast x-rays.
The mission of the Center is to investigate that fundamental science and applied technology which “pushes the envelope” of ultrafast optics. The field is intrinsically interdisciplinary, as it involves coupling state-of-the-art laser optics with applications in far-flung fields which often have no apparent (or prior) connection to optical science. By following the links under “research,” you will find general overviews of the areas of research active at CUOS in each of these areas, as well as more detailed information representative of specific programs.
The Center’s most important educational role is the training of graduate students, skilled in interdisciplinary research, who will be highly sought after by industry and academia. CUOS provides a unique interdiscplinary research training environment, in which students from a wide variety of backgrounds work together on projects applying state of the art femtosecond laser technology to problems in basic science and technology in other fields (examples are materials science, biomedical engineering, nuclear engineering and plasma physics, semiconductor electronics, and imaging). CUOS has trained well over 100 PhD’s in ultrafast science and technology, and approximately twenty students are engaged in research in CUOS labs at the present time. CUOS students often participate or collaborate with other University of Michigan research centers, such as FOCUS, MNF, and M-NIMBS.
The Center has consistently participated in active industrial collaboration ever since its creation. Translation of ultrafast optical technology into the commercial sector has been and continues to be a high priority for CUOS. Industrial interactions take several forms, as described below. Collaborations using CUOS facilities. CUOS faculty and staff actively seek collaborative research with industry. Ultrafast lasers with a wide range of operating parameters (wavelength, pulse energy and duration, and average power) are available at CUOS for collaborative work. Working relationships may range from simple informal exploratory collaborations to contractually binding agreements. Laboratory time may be made available for specific periods of time, to explore solutions to problems or test new products. When work that is performed at CUOS is of proprietary interest to individual associates, appropriate contractual agreements are made to safeguard these interests. In many cases, joint publication of scholarly work results from the interaction. It is explicitly understood that corporate associates will move developing ultrafast technology into their commercial product and process lines. The university’s interest, if any, is represented through published works and agreements that are executed through it Technology Management Office and/or its Division of Research and Development Administration. Industrial participation in CUOS is predicated on a balanced contribution of financial and in-kind support. This typically consists of a combination of cash, professional labor time in collaborative research or student mentoring, and equipment loans or donations. Parties interested in collaborative research should contact the CUOS Director, who will identify potentially interested CUOS personnel.
Industrial research using CUOS facilities on a recharge basis. As above, CUOS laser facilities may be made available for industrial research on a recharge basis, subject to availability. Interested people should contact the Director.
SBIR/STTR programs. CUOS has participated and continues to participate in numerous SBIR and STTR collaborations. These have proved a very effective means of developing new commercial applications of ultrafast optical technology. Present STTR activity includes collaborations with Picometrix on THz generation and imaging.
Spin-offs. CUOS has an established record of generating spin-off companies. Five companies have their origins in the Center, with four started by former CUOS scientists: Picometrix (fast detectors and THz instrumentation, S. Williamson and J. Valmanis), Clark-MXR (scientific lasers and micromachining, P. Bado), Translume (waveguide optics, P. Bado) and Intralase (precision surgery, R. Kurtz and T. Juhasz). Most recently Arbor Photonics was founded by CUOS Prof. Almantas Galvanauskas to develop high power fiber laser technology.
Patent and licensing activity. Patents are key to technology transfer both to startups and to established companies. The Center has had a continuous flow of patents that are applied for through U-M’s Technology Management Office (TMO). From this group of patents, licenses have been sold and others are under negotiation. An example of the process is provided by Intralase, based in Irvine, CA. The application of femtosecond lasers to corneal surgery was developed at CUOS, and Intralase was formed to commercialize the process under patents developed at CUOS through TMO. Intralase was granted FDA approval for its Femtosecond Laser Keratome System in January 2000, and the company has seen rapid growth based on the extraordinary success of the procedure.