Over the past decade, the ultimate fusion of optical engineering, ultrafast laser physics and nonlinear optics, materials science, biophysics, biochemistry and biology gave rise to a vast new field of biomedical photonics that emerged as one of the most active frontiers of interdisciplinary scientific research. One of the key areas of biomedical photonics research is focused on the direct visualization and rapid detection of living biological specimens at cellular and molecular levels. The recent booming success in the area of optical biomedical imaging techniques was driven by advances in optical sciences, particularly owing to the advent of ultrashort pulse laser technologies. Ultrafast nonlinear optics was another field that played a crucial role and provided an excellent platform for stimulating new achievements in optical microscopic imaging and molecular diagnostic techniques for biological and medical applications.

Our research program continues to expand the frontiers of ultrafast photonics and biophotonics. The main objective of our Group is the research, development, evaluation and application of novel optical biotechnologies. Our activities can be roughly divided into three main research areas:

Advanced ultrafast laser sources for biomedical applications.

Such laser devices are capable of generating ultrashort light pulses, also termed ultrafast. These pulses are so short (10-13 – 10-15 s or simply femtoseconds), that during this time even light with its enormous speed of 3×108 m/s manages to travel only some microns! This means that all energy carried by the pulse is contained within extremely short period of time, giving rise to high electric field intensities. In other words, ultrashort pulses can have very high peak powers which can be used for biomedical imaging and other applications.

As advanced as ultrafast laser technology is today, there is still plenty of room for new developments and continuing improvements. Emerging and challenging imaging requirements in biological and medical sciences demand innovative solutions, for which laser-based techniques appears to be well suited. Compactness, reliability, efficiency, shorter pulses, wavelength tunability, new active gain media and higher output powers provide for a few examples of our application-oriented research directions in the field of laser technology. Ultrafast laser sources are one of the key enabling technologies in biomedical sciences.

Novel microscopic imaging techniques.

Interaction of ultrashort light pulses with matter can result in many different optical effects, such as generation of second harmonic (a new optical frequency which is twice higher than the incident one). This is caused by the nonlinear behavior of matter at high field intensities provided by the femtosecond pulses. Such effects are unique because they can happen only at the focal spot of a lens, where the intensities are the highest. Since light can be focused to a very small spot, typically less than a micron, this enables high-resolution point-by-point imaging of samples by detecting the intensity of the produced nonlinear signal. To obtain a 3D image of an object, laser beam can be scanned across and within the sample. In studying of live cells the best part of it is that we can obtain images without any special chemical preparation of the sample. This is a usual practice with other imaging techniques and can disturb or influence normal cell functioning.

Each nonlinear effect can provide some specific information about the sample and our Group is exploring the ways to apply them to demonstrate new modalities in microscopic biomedical imaging. These advanced techniques will enable investigations of various biological structures and processes at the molecular and cellular levels which can contribute, for example, to the understanding of wide range of diseases.

Nonlinear spectroscopy of biomedical and optical materials.

Ultrafast nonlinear spectroscopy, like a nonlinear microscopy, plays and will continue to play a crucial role in biological and physical sciences. The availability of ultrashort pulse lasers has stimulated numerous advances in the fields of the nonlinear optical properties of materials, structures and reaction dynamics of complicated biomolecules.

Since nonlinear optical properties are frequency dependent, detailed spectroscopic investigations are required to elucidate the origin of processes as well as the optimal conditions for their excitation or even control. Such fundamental knowledge is invaluable and can provide us with helpful feedback in interpreting our results from microscopic imaging. Spectroscopic studies can also aid in improvement or development of new imaging modalities. For example, two-photon excitation, second harmonic generation or coherent anti-Stokes Raman scattering are all well-known spectroscopic techniques that were later adopted for nonlinear optical imaging.

Our Group is also interested in optical properties of various crystals and glasses. These materials are important for the design of more efficient and reliable laser sources.

Representative publications:

  1. Download PublicationA. Major, R. Cisek and V. Barzda, “Femtosecond Yb:KGd(WO4)2 laser oscillator pumped by a high power fiber-coupled diode laser module”, Optics Express, Vol. 14, No. 25, pp. 12163-12168 (2006)
  2. Download PublicationA. Major, P. Piunno, S. Musikhin, U. Krull and V. Barzda, “An extended cavity diode-pumped femtosecond Yb:KGW laser for applications in optical DNA sensor technology based on fluorescence lifetime measurements”, Optics Express, Vol. 14, No. 12, pp. 5285-5294 (2006)
  3. Download PublicationA. Major, R. Cisek, C.A. Greenhalgh, N. Prent, B. Stewart and V. Barzda, “A diode-pumped high-power extended cavity femtosecond Yb:KGW laser: from development to applications in nonlinear biological microscopy”, SPIE Proceedings, Vol. 6343, pp. 634345-1 – 8 (2006)
  4. Download PublicationA. Major, F. Yoshino, J.S. Aitchison, P.W.E. Smith, D. Zigmantas, V. Barzda, “Picosecond z-scan measurements of the two-photon absorption in beta-carotene solution over the 590-790 nm wavelength range”, SPIE Proceedings, Vol. 5724, pp. 269-276 (2005)

Project funding:

Our research projects are currently funded by the University of Manitoba, Western Economic Diversification Canada, Natural Sciences and Engineering Research Council of Canada and Canada Foundation for Innovation.

NSERC CFI Dr. Arkday Major WED