Photonic Nanojets

In the geometrical optics description of conventional lens focusing, the focus is the point where all the light rays converge. In Fig. 50, the focusing of a plane wave by a lens is shown. 

The focal point is situated in the middle of a sphere. If the refractive index of the sphere is greater than unity and the sphere is truncated to a hemisphere (part on the right of the dashed line is removed), we end up with a SIL. The key feature of this geometry is that all the rays converge to a point - the focal point. If, instead, the lens is removed from the system such that all parallel incident rays fall directly on the sphere (Fig. 51), then all the rays will not converge to a single point. 

When a nanoparticle is placed in the light path, light is scattered. Assuming that the incident light is a plane wave, the light that radiates back towards the source is termed the backscattered light. When nanoparticles are illuminated by a plane wave, the intensity of backscattered light is small compared with the intensity 

Our study of the C aperture indicates that the resonance wavelength for an aperture of finite length can be shifted from the cutoff 

Summary of near-field transducer NFT) performance. The peak E intensity is normalized by that of the incident beam. 

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Fig. 3 illustrates transport properties of NIMs. The light source was produced directly inside ID colloidal photonic crystal by means of excitation of luminescence in several dye doped globules. Each consecutive sphere acts as a micro-lens and focus light of arbitrary spectrum in a highly distorted and laterally squeezed photonic nanojet [6] at its shadow side close to the intersphere contact point. At these locations the intensity maxima appear in Fig. 3b. 

Fig. 1 Photonic nanojet spatial intensity distribution, /= , inside and outside the 1.0 pm PS particle, illuminated by a laser pulse at A = 248nm, and (a) polarization parallel and (b) perpendicular to the image plane. The maximum intensity enhancement in calculations is about 60 for both regions, (c) Shows the intensity along z-axis. z = 1.0 is the position under the particle, (d) Super-resolution spot in atz=a, the tangent plane right under the particle.

It is noted that theoretically calculated smallest photonic nanojet spot size, roughly between 100 nm and 150 nm when neglecting substrate effect, cannot explain the observed experimental resolution of 50 nm. In practise, the sample is positioned away from the focusing plane, but... 

The outline of this chapter is as follows. In Sect. II we discuss the modeling techniques employed in this study. In Sect. Ill the difference between the near field and the far field is considered and it is argued that any FOM based on far-field quantities is not appropriate for HAMR. Various FOMs are considered in Sect. IV as they relate to HAMR. Several mechanisms that may be employed by NFTs for enhancement of the coupling efficiency are discussed in Sect. V In Sect. VI these mechanisms are studied for a variety of transducer designs and a FOM is used to compare them. Because both antennas and apertures may be useful for HAMR, we discuss the relationship between these different transducer approaches in Sect. VII. The relationship between the far field and the near field, especially in so far as far-field measurements may be used to characterize NFTs, is discussed further in Sect. VIII. Finally, the means for efficiently illuminating the NFT is an important topic which we address in Sect. IX in a discussion on photonic nanojets. 

Figure 52. Two-dimensional photonic nanojet intensity modeled using the FDTD method.

NANOJET-INDUCED MODES IN ONE-DIMENSIONAL COLLOIDAL PHOTONIC CRYSTALS... 

Nanojet-induced modes in one-dimensional colloidal photonic crystals. 

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