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In this research, refractive-diffractive hybrid design is proposed for micro-lens used in optical scanning system. For refractive design of the lens, optimization method with reducing transverse ray aberration is used for target focal length with minimized aberration. Diffractive efficiency considering depth and period of Fresnel edge pattern is calculated by RCWA, and then the proper depth and minimum period of the Fresnel edge pattern can be determined for high efficiency. In the lens geometry, machining limit of V-shaped diamond tool must be applied, because the tool determines limit of the micro-pattern size and possibility of the machining so that it determines the whole size of the lens. With the process, the refractive lens can be optimized for 300 μm focal length and minimum aberration, the depth of Fresnel edge is determined to 0.94 μm by the diffractive design of PMMA (index 1.4985) lens, and also the maximum diameter of the hybrid lens is determined to 423.4 μm when considering machining limit. This designed lens is fabricated by 5-axis ultraprecision machine with nanometer resolution for low surface roughness. Then, the lens is imprinted by hot embossing process. The result of measuring focal length is 336 μm and NA is calculated to 0.63. Also, imaging test of the lens is investigated, and the lens can be used in optical scanning system by the result.

A gradient-index solid immersion lens is fabricated to approximate a distribution of refractive index matching derived from transformation optics. The simulation result has shown reduction of the ghost image and increase of the magnifying area.

Immersion lithography has been proposed as a method for improving optical lithography resolution to 45 nm and below. The premise behind the concept is to increase the refraction index in the space between the lens and wafer by insertion of a high refractive index liquid in place of the low refractive index air that currently fills the gap. During the scanning and exposure process, immersion liquid is injected into the space between wafer and lens with certain inlet pressure and angle. Because the liquid will act as a lens component during the lithographic process, it must maintain high uniform optical quality. Air bubbles in immersion liquid will decay the optical quality of the fluid and must be concerned. In this paper, some preliminary experimental results are included. Four types of bubble formation during lithographic process are defined and discussed, and the corresponding preventive means are also proposed.

We have already reported a high density near field readout system with a GaN blue laser of 405 nm wavelength and an optical pick-up of an effective numerical aperture (NA) of 1.4. A readout performance of the near field readout system depends on the optical parameters, namely the NA of a solid immersion lens (SIL) and the laser wavelength. With a relative high refractive index glass material, we can design a SIL with higher NA. In this study, by using a glass with the refractive index of 2.08, we developed the optical pick-up with the effective NA of 1.8. We could observe a clear eye pattern for 50 GB capacity ROM in a /spl phi/120 mm single side disc.