Denise M. Krol
Professor of Applied Science
Lasers and Nonlinear Optics, Optical Materials
Web: Research Group web-page
Office: 3015 Engineering III
Professor, b. 1954; B. Sc. Chem., University of Utrecht (1976); M. Sc. Chem., University of Utrecht (1977); Ph.D., Physics, University of Utrecht (1980); Research Scientist, Philips Research Labs, Eindhoven (1980-1986); Member of Technical Staff, AT&T Bell Laboratories, Murray Hill, NJ (1986-1994); Visiting Professor, Stanford University (1994-1995)
Teaching and Instructions:
Laser Physics (EAL 265), Nonlinear Optics ( EAL 267), Optical Materials (EAD 169)
My research interests are in optical materials, optical waveguides, nonlinear optics and laser spectroscopy. Currently the research projects in my group revolve around the following two main themes:
Glass-based optical waveguide devices
With the increasing importance of optics in communications (e.g. optical fibers), signal processing and data storage (e.g. CD-ROM, holographic data storage), there is an increasing need for new devices with specifically tailored optical properties. Glasses, which have been historically the optical material of choice, have recently attracted renewed interest for their use in new fiber and nonlinear optical devices, such as fiber lasers, fiber and waveguide amplifiers, fiber Bragg gratings, nonlinear optical switches, and holographic storage materials
In our group we are exploring new ways of making integrated waveguide devices in glass. We do this by adding new functionalities to the glass through a number of different processing techniques. For example, waveguides can be fabricated in glass using the femtosecond laser writing technique. In this technique refractive index changes are induced inside a glass by using femtosecond (fs) laser pulses tightly focused inside the material. Waveguides can be fabricated inside the glass by scanning the glass with respect to the focal point of the laser beam. We have recently fabricated waveguides in fused silica using tightly focused 800 nm, 130 fs laser pulses at fluences between 5 and 200 J cm-2. Other more complex three-dimensional structures have also been fabricated (curved waveguides, splitters, and interferometers). In addition to investigating the properties of such waveguides, e.g. the magnitude of the induced index change as well as the mode structure and loss of the waveguide, we are also interested in understanding the atomic-scale structural changes that take place in the glass as a result of fs-laser modification. We are also developing an electro-optic modulator or frequency doubler in glass by inducing a second-order nonlinearity through electric-field poling. Via proper integration of these new functionalities we can fabricate an integrated frequency doubled waveguide laser in a single glass substrate.
Optical and spectroscopic characterization of optical materials
We have several projects in which we use laser spectroscopy to characterize the optical properties of a number of different materials systems, including laser and nonlinear crystals, nanocrystals and biological systems. We use a variety of spectroscopic techniques, such as Raman and fluorescence spectrocopy, coherent Anti-Stokes Raman scattering and pump-probe techniques. We also can employ these techniques in a confocal microscopy setup, allowing us to perform single molecule spectrocopy.