First Nano-Raman Image

As a physics Ph.D. student, Catherine Jahncke produced the world's first nano-Raman image - an image of strain beneath a semiconductor's surface with nanometer resolution.

Working in the near-field optics laboratory of Professors Hans Hallen and Michael Paesler, Ms. Jahncke built a near-field scanning optical microscope, or NSOM. In her instrument, she guided light down a tapered optical fiber that she had drawn to a sharp point. By then coating the tip with aluminum leaving a small opening at the end, she was able to create a sub-wavelength light source. A coated tip with a 50nm aperture at the tip is shown here.

By using the laser light from the tip to excite a Rubidium doped KTP crystal, Ms. Jahncke directed the scattered light through a spectrometer and then imaged the surface using the inelastically scattered Raman signal. Since the Raman effect is sensitive to stresses, she was able to map the stresses beneath the KTP surface induced by an Rubidium implanted layer. Because imaging was done in an NSOM, the resulting image provided subwavelength resolution. The image below exhibits a region (yellow) of high stress beneath the surface. The image is 2 microns square. It is the first nano-Raman image ever taken.