Subwavelength structures

Gombert et al. have reported subwavelength structured antireflective surfaces prepared on glass by embossing a nickel master shim on acrylic siloxane layer with UV irradiation (Gombert et al., 1999). Hemispherical reflectance values of <1% are achieved for nonabsorbing planar sheet. 

Lenne, P. F. Etienne, E. Rigneault, H., Subwavelength patterns and high detection efficiency in fluorescence correlation spectroscopy using photonic structures, Appl. Phys. Lett. 2002, 80, 4106 4108... 

Poborchii, V., Tada, T., and Kanayama, T. 2005. Subwavelength-resolution Raman microscopy of Si structures using metal-particle-topped AFM probe. Jpn. J. Appl. Phys. 44 L202-5. 

Liu, C., Chen, N., and Sheppard, C. (2007). Nanoillumination based on self focus and field enhancement inside a subwavelength metallic structure. Appl. Phys. Lett. 90, 011501. 

Ideally, the surface of the transparent cover should have a gradient of the index of refraction ranging from 1.0 for air to the index of refraction of the cover material. For the required very small indices of refraction no materials exist in nature. Such small indices of refraction can only be made by effective media in which the cover material is mixed with air on a subwavelength scale as described in Sect. 1. Subwavelength surface-relief structures with a continuous profile as shown in Fig. 2 form an effective refractive index gradient and are therefore well suited for broadband AR surfaces. This type of AR surface-relief grating is called a moth-eye structure according to the example found in nature on the cornea of... 

The separating layer optical thicknesses were fixed (Fig. 3) about or AqU, where corresponds to the plasmon absorption maximum of a metallic nanoparticle monolayer in the KCl environment. These multilayer structures were fabricated by the thermal evaporation technique followed by deposition of metal and dielectric materials without breaking the vacuum between the evaporation steps. The structures grown by this technique are realized as a sequence of Ag island films separated by KCl intermediate layers of a subwavelength thickness. These data... 

Inhomogeneous media with micro- and nanosized structural features are known to strongly alter the character of various physical processes compared to common homogeneous materials. For example, photonic band gap (PBG) structures and metamaterials can be used for subwavelength light control [1]. Similarly, quantum heterostructures such as quantum dots and quantum wells have shown great promise in nano- and optoelectronics, as well as in quantum computing. 

In 1873, Ernst Abbe established the resolution limit of optical microscopes The minimum distance, d, between two structural elements to be imaged as two objects instead of one is given by d = A/(2 NA), where X is the wavelength of light and NA the numerieal aperture of the objective lens. The physical root for resolution limit is related to optical diffraction and loss of evanescent waves in far-field the evaneseent waves carry high-frequency subwavelength spatial information of an object and decay exponentially with distance from the objeet. With white lights, optical microscope resolution is limited at about 200-250 nm. For about one hundred years, the Abbe criterion was considered the fundamental limit of optical microscope resolution. 

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