Development of a Solid Immersion Lens Microscope for Optical Spectroscopy

Arizona State University, Scottsdale AZ

Investigators

Abstract

This award from the Major Research Instrumentation program supports instrument development at to Arizona State University. The instrument is a solid-immersion lens (SIL) microscope for optical spectroscopy with a spatial resolution of at least 200 nm. The SIL microscope will feature an autofocus system and active control of the SIL-sample separation. These innovations will make optical spectroscopy with nm-scale spatial resolution routinely practicable. The proposed applications will emphasize Raman and fluorescence imaging. SIL-based micro- Raman spectroscopy offers a spatial resolution comparable or better than Near Field Scanning Optical Microscopy. The signal strength for SIL-based spectroscopy increases as the spatial resolution is improved. Furthermore, the SIL microscope makes it possible to collect spectroscopic images directly on a detector by using a global illumination technique. Initial areas of application include carbon nano-tubes, Ge and SiGe quantum dots on silicon, and the optical properties of photosynthetic membranes. The instrument will be build by graduate students who will gain valuable experience in instrument development. This award from the Major Research Instrumentation program supports a project to design and build a Solid Immersion Lens (SIL)microscope for spectroscopic imaging with a spatial resolution of at least 200 nm. There is a critical need for such an instrument because the wavelength of light can be measured with unmatched precision, so that optical spectroscopy is one of the preferred techniques for the study of materials. However, diffraction effects pose a fundamental limit to the spatial resolution of any optical technique, and for conventional instruments this means that it is generally impossible to obtain spatially resolved spectroscopic information from nanoscale objects. An alternative technique to overcome the diffraction limit is the use of optical fibers with nanometer-size apertures. The SIL-microscope will have two fundamental advantages over this approach a much higher light-throughput and the ability to record spectroscopic images without physically scanning a fiber tip over a sample. The instrument will be build by graduate students who will gain valuable experience in instrument development.