Saturated super-resolution imaging of photonic crystal with negative refraction

Abstract

ABSTRACT This paper reports a new super-resolution, “saturated” imaging method using a flat slab of photonic crystal with negative refraction. The photonic crystal has hexagonal lattice with holes in dielectric material with an index of 3.6. When the operating normalized frequency is around 0.30, the effective refractive index is -1. Such a flat slab lens can tolerate disk deformation of approximately one-wavelength or more while maintaining the same super-resolution as the near-field imaging of the photonic crystal slab. The object distance can be as large as twice the sl ab thickness, and the resolution is about 0.43 . Keywords: Super-resolution, optical imaging, photonic crystal, negative refraction I. INTRODUCTION Higher density of data storage is essential for many applications, such as computing and multi-media. Among different types of data storage, optical data storage (ODS), which uses light for recording and retrieval of information, is the dominate method. However, conventional optical systems used in ODS suffer from diffraction limitation, due to the wave nature of light. Since the resolution of a diffraction-limited optical system is proportional to the wavelength of the light and inversely proportional to the numerical aperture (NA) of the lenses, it is natural to use short wavelength such as blue-violet laser and solid immersion lenses with high NA. There are other alternative ways to overcome the diffraction limit, such as the near-field super-resolution optics (see for example references [1-3]). All the imaging methods use pair-conjugated imaging, that is, one image corr esponds to one object. When object distance changes, the image distance, thus the detector location, must be changed accordingly, in order to have a quality image. To overcome any deformations of the data disk that induce changes to the object-image distance, either large field-depth optics is required, which is contradictory to high-resolution requirement, or a precise servo system is utilized, which involves mechanical movement. This paper reports a new imaging method using photonic crystal (PhC) with negative refraction with super-resolution. It employs the “saturated” imaging region, in which objects within a certain range of distances are imaged to the same location, while the same degree of super-resolution is maintained as for the unrestricted imaging condition. To our knowledge, this is the first report on the saturated imaging of PhC slab which permits an object distance larger than the slab thickness (the shorte st distance between the tw o surfaces of the slab).