Raman imaging of patterned silicon using a solid immersion lens

We show an enhanced spatial resolution using a solid immersion lens by directly imaging the Raman scattered light from silicon masked by periodic metal lines. A glass hemisphere solid immersion lens with an index of refraction $n=1.868$ at 488 nm is used in conjunction with a 100×0.8 numerical aperture objective to obtain the enhanced spatial resolution. The increased numerical aperture is demonstrated by a direct line scan over the periodic metal lines. Compared with near-field optical microscopy, the solid immersion lens technique overcomes the difficulty of limited excitation power obtainable with tapered fibers, while providing excellent spatial resolution which in principle could be extended to the 0.1 μm range.