Hyper-NA Optical Systems and Applications in Sample Measurement

Abstract

In this dissertation, vector effects of hyper-NA (NA>1) optical systems are investigated. Several applications of hyper-NA optical systems in sample measurement are demonstrated. Simulation techniques for hyper-NA imaging are developed to illustrate illumination artifacts due to the vector effects in such systems. Several prototypes of solid immersion lens (SIL) microscopes are developed to verify the phenomena observed in simulation and demonstrate hyper-NA optical systems’ applications in sample measurement. A surface plasmon microscope is designed to measure the oxygen saturation (SO₂) of red blood cells (RBCs). Vector effects of hyper-NA optical systems are studied by both simulations and experiments with off-axis polarized monopole illumination. A model based on rigorous coupled wave theory (RCWT) is used to simulate image profiles for dielectric, semiconductor and metal gratings with different monopole locations and polarization states. A solid immersion lens (SIL) microscope is used to image different types of samples, and the experimental images are in good agreement with simulation results. Several prototypes of hyper-NA optical systems are developed to demonstrate the applications. First, a SIL is described with NA=2.64 that is fabricated from a twostep process using a large BK7 glass hemisphere and a small gallium phosphide (GaP) hemisphere. This two-step SIL can be used in next generation ODS systems to increase the capacity to 150GB/layer. Second, a near-field subsurface (100μm) microscope with numerical aperture (NA) =2.45 is developed for integrated circuit (IC) inspection by using a silicon solid immersion lens (SIL). With the illumination light at 1.2μm, a lateral resolution of better than 300nm is experimentally demonstrated. Third, a SIL microscope system is introduced to image Blu-ray disc (BD) samples without removing the protective cover layer. Sub-surface imaging simulation is achieved by using rigorous coupled wave theory (RCWT), partial coherence, vector diffraction and Babinet’s Principle. Last, a SPM is designed to measure the oxygen saturation of red blood cells (RBCs) by measuring the refractive indices of RBCs at three wavelengths. SP images with different angles are simulated, and threshold irradiance and calibration curves are used to indicate refractive index of RBCs. Modulation transfer function (MTF) characteristics are also studied for the SPM.